Reports of 
Experiments Referred to at 
Hearings on Ice Cream 
Before Dr. G. L. Alsberg 
Chief of the Bureau of Chemistry 
United States Department 
of Agriculture 
Subject: 
The Bacteriology of Ice Cream 
Published by 
THE RATIONAL ASSOCIATION OF 
ICE CREAM MANUFACTURERS 
C v-- 'v ■ 
October, 1914 FOREWORD 
In June, 1914, the National Association of Ice Cream 
Manufacturers published the Report of the hearing’s held 
before Dr. C. L. Alsberg on the use of colloids as stabi- 
lizers in ice cream, the butter fat standard for ice cream 
and the bacteriology of ice cream, and in that part of the 
report which relates to the bacteriology of ice cream it 
appears that at the hearing Professor Gordon, Professor 
Prescott, Dr. Heinemann and Dr. Pease repeatedly re- 
ferred to experiments which they had made and upon 
which they based their testimony. The National Asso- 
ciation of Ice Cream Manufacturers now makes public 
the reports of these experiments for the benefit of those 
engaged in the ice cream industry and others interested 
in the subject. 
These reports should be read in connection with the 
testimony above referred to. 
Walter Jeffreys Carlix. 
5 JOHN GORDON, graduate of the University of Missouri, formerly 
assistant Professor of Bacteriology, lowa State College. Worked on 
dairy farms in Missouri, lowa, Illinois and New York. Operated 
bottling plant for the Walker-Gordon Milk Co. Since 1911 in charge 
of the sanitation work of a number of plants in New York State, pur- 
chasing several million pounds of milk yearly. Author of a number 
of papers on the subect of sanitation of dairy plants, etc. 
SAMUEL C. PRESCOTT, Professor of Industrial Micro-biology, 
Massachusetts Institute of Technology. Graduate of the Massachu- 
setts Institute of Technology, class of 1904. Formerly Assistant 
Chemist and Bacteriologist of the Worcester Sewerage Works. 
Studied in Denmark and Germany, devoting time especially to bac- 
teriology and fermentation in food. Since 1905 director of the Boston 
Bio-Chemical Laboratory. Joint author of work on bacteriology and 
also a book dealing with canning. Connected with the Journal of 
Bacteriology and author of numerous papers dealing with scientific 
subjects. Member of the Society of American Bacteriologists and 
Fellow of the American Society for the Advancement of Science and 
member of the American Chemical Society, the British Society of 
Chemical Industry, American Public Health Association and the 
Boston Society of Medical Sciences. 
P. G. HEINEMANN, Bachelor of Science. Doctor of Philosophy, 
University of Chicago. Instructor in Bacteriology, University of 
Chicago, and Serum Expert of the Memorial Institute for Infectious 
Diseases, Chicago. Publisher of many pamphlets dealing with differ- 
ent phases of the milk question, also a book on bacteriology. Re- 
viewer of important scientific papers for the German publications on 
bacteriology. Editorial writer for the Journal of the American 
Medical Association. For two years examiner and inspector for the 
Chicago Medical Milk Commission. 
HERBERT D. PEASE, Doctor of Medicine, University of Toronto. 
Post-graduate student and fellow-in pathology, Johns Hopkins Uni- 
versity. For one year resident bacteriologist and pathologist of the 
Thomas Wilson Sanitarium for Sick Children. For four years First 
Assistant Bacteriologist of the Bureau of Health of the City of Phila- 
delphia. For two years bacteriologist of the New York State Patho- 
logical Laboratory. For one year instructor in bacteriology in the 
Sheffield Scientific School, Yale University. For nine years director 
of the Hygienic and Antitoxin Laboratory of the New York State 
Department of Health. At present and for four years past director 
of the Department of Bacteriology of the Lederle Laboratories of 
New York City. At present and for three years past sanitary expert 
of the Board of Water Supply of the City of New York. 
6 Report on Ice Cream Ex- 
aminations Outlined in 
Washington Hearing of 
Ice Cream Manufacturers 
JOHN GORDON REPORT ON ICE CREAM EXAMINATIONS OUT- 
LINED IN WASHINGTON HEARING OF 
ICE CREAM MANUFACTURERS. 
John Gordon. 
The experimental work as set forth herein was carried 
on with a view of obtaining exact information as to the 
factors which influence the bacteria content of ice cream as 
manufactured in commercial plants. The raw materials 
for ice cream manufacture were followed from the place 
of origin, the farm, through the creamery and condensory 
into the ice cream factory. In the creamery and condens- 
ory the effect of the handling consequent to the ordinary 
factory routine involved in the receiving, separating, pas- 
teurizing, condensing, etc., of milk upon the bacteria con- 
tent of the raw materials was considered. In the ice 
cream factory the effect of all routine operations upon 
the bacteria content of the ice cream up until the time of 
delivery to the retailer were considered. 
Methods. 
The agar employed in all experiments reported herein 
was prepared after the method recommended by the 
American Public Health Associations’ Committee on 
Standard Milk Analysis. All plates were incubated at 
37° C. for a period of 48 hours. 
Since most of the ice cream experiments were made on 
semi-hard ice cream, samples were taken directly from 
the freezers in sterile bottles holding seventy cubic centi- 
meters, which were stoppered and carried immediately to 
the laboratory of the Wheat’s Ice Cream Company, 
wherein most of the work was done. 
When it was necessary to sample hard ice cream in the 
containers, this was done by forcing a sterile butter trier 
down through the ice cream in the can. After the core 
thus obtained was withdrawn, it was broken with n sterile 
spatula and except for a thin section on the top was 
9 placed in a sterile wide-mouthed sample bottle, holding 
seventy cubic centimeters. 
After the samples had reached the laboratory, they 
were in all cases melted by placing the bottles in a dish 
containing warm water. After melting, the routine pro- 
cedure of an ordinary milk analysis was followed. 
Many of the tables given are a fractional part of the 
data on that particular subject, being the results of the 
routine tests of a large commercial ice cream manufac- 
tory. Naturally, nothing would be gained by printing the 
results of a great many routine tests where a few will 
depict average conditions satisfactorily. 
Tests on Farm Milks Received At a Creamery Supplying Several 
Ice Cream Factories. 
THE BACTERIAL CONTENTS OF FARMERS’ MILKS AT TIME OF 
DELIVERY TO CREAMERY ON SUCCESSIVE DAYS. 
Sample Patron Bacteria Content Per C.C. 
1 No. 170 1,700,000 
2 “ 61 6,100,000 
3 “ 154 15,400,000 
4 “ 285 90,000 
5 “ 285 55,000 
6 “ 77 32,500 
7 “ 77 2,500,000 
8 “ 265 2,850.000 
9 “ 265 280;000 
10 “ 15 950,000 
11 “ 15 155,000 
12 “ 15 1,250,000 
13 “ 266 7,000,000 
14 “ 266 28,000 
15 “ 215 2,000,000 
16 “ 281 960,000 
17 “ 281 3,000,000 
18 “ 224 700,000 
19 “ 224 110,000 
20 “ 224 450,000 
21 “ 292 480,000 
22 “ 292 10,000,000 
23 “ 292 1,800,000 
24 “ 66 820,000 
25 “ 101 95,000 
26 “ 101 120,000 
27 “ 288 360,000 
28 “ 288 1,750,000 
29 “ 288 200,000 
The above table is used merely to show the general run 
of bacteria contents of farmers’ milk as received at an 
ice cream creamery. It represents only a few of the tests 
made, but the printing of more would be needless, as it 
shows that one farmer may bring milk of high bacteria 
10 content one day and milk of low bacteria content the 
next. 
The Bacteria Content of Milk, Cream, and Condensed Milk, Used 
For Ice Cream Manufacture As Received At 
Several Ice Cream Plants. 
The following two tables depict the condition in which 
cream arrives at the average ice cream factory from the 
average country creamery: 
BACTERIA CONTENTS OF PASTEURIZED CREAM FROM CREAMERY A AT 
TIME OP DELIVERY TO ICE CREAM PLANT IN 
ROCHESTER, NEW YORK. 
Date Bacteria Content Per C.C. 
I, cr 21st Can 1 26,100,000 
-lst “ 2 9,500,000 
“ 3 51,600,000 
Aug. 21st 
4 52,500,000 
5 27,400,000 
1 11,500,000 
Ayi cr 93rd “ 1 11,500,090 
Aug. -ora .. 2 11,000,000 
a vjcr 94+h “ 1 22,500,000 
Aue. -am .. 2 19,600,000 
A lie-. 29th “ 1 29,000,000 
All" 29th “ 1 29,000,000 
Aug. _9tn . „ 2 31,100,000 
3 20,000,000 
4 22,800,000 
«pr)t 1.,!- “ 1 1,600,000 
Sept, ist „ 2 1,450,000 
1 1,300,000 
BACTERIA CONTENTS OF PASTEURIZED CREAM FROM CREAMERY B 
SHIPPING TO THE ROCHESTER PLANT. 
Date Bacteria Content Per C.C. 
9th Can 1 5,000,000 
Aue. ym t( 9 10,000,000 
“ 3 4,300,000 
\Uo- 24th “ 1 5,100,000 
Aue. -iin „ 2 15,200,000 
“ 3 15,000,000 
“ 4 1,500,000 
Rent 2n<l “ 1 1,060,000 
bept. -na „ 2 1,760,000 
Since I was convinced that the high counts obtained 
on the pasteurized cream from the creameries A and B 
were due not to faulty methods of pasteurization but to 
poor storage facilities since they, like the great bulk of 
creameries, relied upon the ice tank method of storage, I 
had one of the creameries ship cream to the ice cream 
factory directly after pasteurization and cooling and not 
hold it in the ice tank until the next day as was the usual 
custom. The ordinary method of pasteurization was fol- 
lowed, no unusual precautions being taken. 
11 BACTERIA CONTENTS OF PASTEURIZED CREAM PROPERLY COOLED 
AFTER PASTEURIZATION AND SHIPPED IMMEDIATELY. 
Date Bacteria Per C.C. 
Sept. 2nd Can 1 39,000 
“ 2 21,000 
“ 3 71,000 
“ 4 39,000 
“ 5 33,000 
“ 6 70,000 
“ 7 35,000 
“ 8 64,000 
“ 9 26,000 
turer may when he purchases pasteurized milk be obtain- 
ing milk of much higher bacteria content than raw milk. 
The milk in this case was sweet and apparently good but 
it required a bacteriological analysis before the enormous 
The following table shows that the ice cream manufac- 
bacteria content was revealed: 
BACTERIA CONTENTS OF PASTEURIZED MILK SOLD TO AN ICE CREAM 
COMPANY BY A DAIRY CONCERN. 
Can 1 60,000,000 Bacteria per C.C. 
“ 2 420,000,000 “ “ “ 
“ -3 21,000,000 “ “ “ 
“ 4 100,000,000 “ “ “ 
THE BACTERIA CONTENTS OF HOMOGENISED CREAM FROM CREAMERY 
C AS RECEIVED AT AN ICE CREAM FACTORY ON DIFFERENT DAYS. 
Date Sample Bacteria Per C.C. 
Aug. 3 1 4,800 
“ 4 2 6,500 
3 3 8,000 
6 4 15,500 
7 5 5,000 
‘ 8 6 3,400 
9 7 80,000 
10 8 250,000 
11 9 125,000 
12 10 30,000 
Since the process of homogenization as followed at this 
creamery required a temperature of 180° F., it followed 
that the bacteria content would be low. Only a very small 
percentage of ice cream manufacturers have homogen- 
izers, however, therefore homogenizers cannot be a factor 
in reducing the bacteria content of ice cream. 
BACTERIA CONTENT OF CONDENSED MILK FROM TWO CREAMERY AND 
CONDENSERIES. 
Date 
July 
July A 2,940,000 
A 50,000 
. A 53,000 
Aug. A 10,000 
A 35,000 
A 80,000 
B 5,000,000 
B 180,000 
B 2,000.000 
Condensery Bacteria Per C.C. 
12 The foregoing shows that the bacteria content of the 
type of condensed (unsweetened whole milk) used in ice 
cream manufacture fluctuates after the fashion of normal 
milk or cream. The condensing temperature (120° F.) 
kills only a portion of the bacteria, nor is the superheat- 
ing temperature (180° F.) sufficient to dispose of the en- 
tire number. Numerous factors can increase the bacteria 
content of condensed milk, temperature being the chief 
one. If the condensed milk is not cooled to a low enough 
temperature after being drawn from the condensing pan,, 
the bacteria content will increase to enormous propor- 
tions. Unsweetened condensed milk must he cared for 
with the ordinary care awarded normal milk. The best 
possible storage conditions must obtain for its successful 
storage. 
The Increase In Bacteria Contents of Raw Materials During 
Shipment By Rail. 
It is not customary for railroads to provide ice for the 
preservation of milk in transit. In the hot summer 
weather enormous increases of the bacteria content of 
milk and much actual souring of milk results from the 
faulty methods of transportation in use. 
The following table does not depict average conditions,, 
because the creamery mentioned in the experiment is 
equipped with artificial refrigeration and consequently 
secures much lower temperatures prior to shipment than 
the average creamery can secure: 
TABLE SHOWING INCREASE OE TEMPERATURES AND BACTERIA IN FIVE- 
HOUR SHIPMENT PERIOD OF MILK FROM AKRON. N. Y., TO 
ROCHESTER, N. Y., ON A COOL DAY IN AUGUST, 
MAXIMUM TEMPERATURE 76° F. 
Temperature Temperature Increase in 
Akron, N. Y. Rochester, N. Y. Temperature 
Can 1 43° F. 55° F. 12° F. 
“ 2 44° “ 55° “ 11° “ 
“ 3 44° “ 52° “ 8° “ 
“ 4 42° “ 53° “ 11° “ 
“ 5 44° “ 55° “ 11° “ 
“ 6 43° “ 53° “ 10° “ 
“ 7 45° “ 55° “ 10° “ 
“ 8' 46° “ 54° “ 9° “ 
“ 9 45° “ 54° “ 9° “ 
“ 10 45° “ 55° “ 10° “ 
13 BACTERIA CONTENTS OF FOREGOING CANS OF MILK AT STARTING AND 
FINISHING POINTS OF SHIPMENT. 
At Akron, N. Y. At Rochester, N. Y. Increase 
Bacteria Per C.C. Bacteria Per C.C. 
Can 1 140,000 230,000 90.000 
“ 2 117,000 250,000 133,000 
3 96,000 300,000 204.000 
4 107.000 210,000 103,000 
5 97,000 225,000 128,000 
6 85,000 330.000 265.000 
7 170,000 265,000 95.000 
8 225,000 320,000 95,000 
9 130.000 420,000 290,000 
“ 10 120.000 850.000 730,000 
Average Bact. Aver. Bact. Aver. 
Content 127,000 Content 342,000 Increase 210,000 
The above demonstrates that even on a cool day milk 
shipped at a low initial temperature will very materially 
increase, in fact almost double in bacteria content. 
Storage of Ice Cream Materials. 
A SIX DAY TEST ON THE BACTERIAL GROWTH IN UNPASTEURIZED 
CREAM STORED AT 32° F. IN THE COLD ROOM OF AN 
ICE CREAM PLANT. 
First day Can 1 12,000,000 
“ 2 10,500,000 
“ 3 12,500,000 
Third day “ 1 12,800.000 
“ 2 10,800,000 
“ 3 13,000,000 
Fourth day “ 1 12.000,000 
“ 2 9,000,000 
“ 3 10,000,000 
Fifth day “ 1 14,800,000 
“ 2 10,000,000 
“ 3 14,500,000 
Sixth day “ 1 17.800,000 
“ 2 12,200,000 
“ 3 13,500,000 
Bacteria Per C.C. 
The above table shows a material increase in bacteria 
in unpasteurized cream in storage at 32° F. starting on 
the sixth day. This is a longer period than cream is com- 
monly stored in the ice cream factory. 
It‘should be borne in mind that only a small percentage 
of ice cream manufacturers have artificial refrigeration, 
therefore, the best temperature of storage obtainable by 
manv ice cream factories is 40° F. to 50° F. and their 
14 milk and cream storage facilities are confined to ice tanks 
or ice boxes. 
The Bacteria Contents of Other Ice Cream Materials. 
The following gelatine analyses were made by weighing 
out one gram of gelatine on a sterile filter paper, which 
was afterwards nsed funnel fashion to pour the gelatine 
into a 99 cubic centimeter water blank which had been 
warmed up slightly. After the warm water had taken the 
gelatine into solution the bottle was considered to contain 
a 1-100 dilution and the test proceeded with accordingly: 
BACTERIA CONTENTS OF RAW GELATINE AS RECEIVED FROM 
MANUFACTURER OR JOBBER. 
Bacteria Content Bacteria Content 
Sample Per Gram Sample Per Gram 
1 1,150,000 14 29,000,000 
2 2,050,000 15 1,600.000 
3 2,850,000 16 20,000,000 
4 45,000 17 28,500,000 
5 2,370,000 18 25,000,000 
6 200 19 11,000,000 
7 3,500 20 16,000.000 
8 4,000 21 600 
9 20,000,000 22 1,200 
10 30,000,000 23 14,000 
11 75,000 24 200 
12 30,000 25 200 
13 200,000 26 100 
The last six samples are table gelatines. The preceding 
samples are ice cream gelatines. 
The Preparation of Raw Gelatine For Use In Ice Cream. 
This is properly done by bringing the desired amount 
of water to the point where it boils vigorously and then 
shutting the steam off. The gelatine should then be 
poured into the cooker. A large part of it will immedi- 
ately dissolve and a slight stirring will cause the rest to 
do the same. The gelatine is immediately poured into the 
ice cream. This process, which is followed in the modern 
plants, secures very satisfactory results and renders cer- 
tain the almost complete destruction of the bacteria in the 
raw gelatine. The bacteria content of gelatine prepared 
in this fashion is rarely over 2,000 bacteria per cubic cen- 
timeter. 
Analyses of sugar secured from several ice cream 
Bacteria Content of Sugar. 
15 plants were practically negative in that they contained 
practically no bacteria. Molds, however, were occasion- 
ally present. 
Sample Bacteria Per C.C. Sample Bacteria Per C.C. 
1 1,800 3 100 
2 UOO 4 2,000 
Effect of Mixing And Freezing Processes on the Bacteria Content 
of Ice Cream. 
BACTERIA CONTENT OF VANILLA. 
It is a generally recognized fact that agitation of a 
milk sample produces an apparent increase of bac- 
teria in the same, due to the breaking up of clumps, 
which, had they remained intact, would have produced 
only one colony when plated. In cream there is an added 
incentive toward the clumping of bacteria and a conse- 
quent uneven distribution, owing to its heavy, viscid 
nature. 
Experiments made at the lowa Experiment Station 
while the writer was working on the effect of freezing on 
Lactic Acid bacteria in “Lacto,” a frozen product made 
of clabbered milk, and originated at that Station, revealed 
an enormous apparent increase in these bacteria in the 
frozen lacto as compared with the unfrozen material. 
Much of the increase I ascribed to the breaking up of 
clumps of coagulated milk, although prior to freezing, the 
mixed material was carefully strained through a very fine 
meshed strainer. How much of the increase was due to 
the breaking up of aggregates of bacteria, I would not 
attempt to say. 
After noticing on many occasions a marked increase in 
the bacterial content of the frozen ice cream as made in 
commercial plants over the mixed materials, I concluded 
that the increase was due to the agitation received in the 
mixer or in the freezers. 
INFLUENCE OF MIXING PROCESS ON BACTERIAL CONTENT OF ONE 
HUNDRED AND SEVENTY-FIVE GALLONS OF ICE CREAM MIXTURE. 
Exnerimont Average Number of Bacteria Average Number of Bacteria 
Experiment before Mixing after Freezing 
1 22,500,000 14 goo 000 
3 non 20’,000’,000 
3 25,500,000 26.500 000 
4 30,000,000 28,000000 
5 39,000,000 38,000:000 
16 From these tests it can be concluded that the agitation 
of the paddles in the mixer is not sufficient to create an 
apparent bacterial increase in the materials being mixed. 
This condition, however, can he hronght ahont by holding 
the materials in the mixer for a much longer period of 
time than is usually the custom. 
Effect of Agitation In Freezer on Bacteria Content of Ice Cream. 
All the experiments following were made under prac- 
tical conditions except that the hopper from which the 
unfrozen sample was taken and the freezer through which 
the cream passed were made practically sterile by the use 
of boiling hot water. The time of freezing (six to eight 
minutes) and the freezing temperature (10° F.) were not 
changed from the daily routine. All results are the aver- 
ages of the results on two or more samples. 
Bacteria Per C.C. Bacteria Per C.C. Increase of Decrease of 
in Unfrozen Mix. in Ice Cream Bact. Per C.C. Bact. Per C.C. 
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The above results readily prove that the rapidly re- 
volving dashers in the ice cream freezer, by their action 
upon clumps of bacteria produce an apparent increase in 
the total number of bacteria in the frozen ice cream. 
17 Increase Experiment In Which All the Materials of 
Ice Cream Were Tested Prior to Mixing. 
Batch of 
Bacteria Per C.C. 
10,000,000 
MILK. 
Bacteria Per C.C. 
Can 1 
6,000,000 
9,000,000 
Can 4 
“ 5 
10,000,000 
140,000,000^ 
CREAM 
Can 1 
“ 2 
“ 3 
Bacteria Per C.C. 
40,000,000 Can 4 
2,000,000 “ 5 
2,700,000 “ 6 
Bacteria Per C.C. 
6,000,000 
1,500,000 
Bacteria Per C.C. 
CONDENSED MILK. 
Bacteria Per C.C. 
10,000,000 
Can 1 
“ 2 
40,000,000 Can 3 
7,000,000 “ 4 
OTHER MATERIALS. 
Gelatine—1,000 bacteria per cubic centimeter. 
Sugar—No bacteria; a few molds. 
Vanilla—100 bacteria per cubic centimeter. 
BACTERIAL CONTENT OF MIXED MATERIALS IN MIXER. 
Average of two samples—2s,soo,ooo bacteria per cubic centimeter. 
BACTERIAL CONTENT OF MIXED MATERIALS TAKEN FROM HOPPER 
ON TOP FREEZER. 
Freezer No. 14 Freezer No. 15 
26,500,000 26,000,000 
BACTERIAL CONTENT OF THE FROZEN ICE CREAM 
Freezer No. 14 Freezer No. 15 
Freezer No. 15 
40,500,000 46,500,000 
EFFECT OF STORAGE TEMPERATURES ON BACTERIAL CONTENT OF 
ICE CREAM MADE IN ABOVE EXPERIMENT IN FREEZERS 14 AND 
15 FROM TESTED MATERIALS. AVERAGE STORAGE 
TEMPERATURE, ZERO FAHRENHEIT. 
Freezer 14 Free 
Freezer 14 „ Freezer 15 
Storage Bacteria Per C.C. Storage Bacteria Per C.C. 
Ist day 40,500,000 Ist day 46,500,000 
3rd “ 42,000,000 3rd “ 39,500,000 
4th “ 18,500,000 4th “ i^OOO.OOO 
5th “ 21,500,000 5th “ 26,000,000 
6th “ 35,000,000 6th “ 28,000,000 
8th “ 36,000,000 . ... 
10th “ 37,000,000 10th “ 
14th “ 21,800,000 14th “ 14,700,000 
20th “ 16,500,000 
Disregarding the rise and fall of the number of bac- 
teria from day to day due to unequal distribution, it can 
be seen that there is a gradual decline of the number of 
bacteria in the stored ice cream beginning with the first 
day of storage. 
18 EXPERIMENT SHOWING EFFECT OF ZERO FAHRENHEIT STORAGE 
TEMPERATURES ON ICE CREAM OF LOW BACTERIA CONTENT. 
Ist Day Bth Day 
Can 1 53,000 52,000 
“ 2 49,000 42.000 
“ 3 55,000 48,000 
A slight steady decline in the numbers of bacteria is 
apparent in the above results. 
BACTERIAL CONTENTS OF VARIOUS SAMPLES FROM THE CONTENTS 
Distribution of Bacteria In Ice Cream. 
OF TEN-GALLON ICE CREAM FREEZERS. 
Freezer 1 Freeze 
Freezer 1 Freezer 2 
Sample Bacteria Per C.C. Sample Bacteria Per C.C. 
1 20,000,000 1 21,400,000 
2 24,000,000 2 25,500,000 
3 14,000,000 3 29,600,000 
4 23,000,000 4 27,000,000 
5 16,500,000 5 25,000,000 
6 20,000,000 6 24,000,000 
7 31,000,000 
8 23,700,000 
9 29,500,000 
10 27,600,000 
BACTERIA CONTENTS OF SAMPLES FROM VARIOUS PORTIONS OF A 
CAN OF ICE CREAM. 
Can 1 Can 2 
Sample Bacteria Per C.C. Sample Bacteria Per C.C. 
1 7,600,000 1 14,500,000 
2 9,500,000 2 21,000,000 
3 13,500,000 3 16,000,000 
4 17,500,000 4 18,500,000 
5 9,000,000 5 14,000,000 
Widest Variation Widest Variation 
9,900,000 Bacteria Per C.C. 7,000,000 Bacteria Per C.C. 
The results in this and the preceding table show that 
the distribution of bacteria in ice cream is markedly 
uneven. 
The following bacteriological analyses of the product of 
a large commercial ice cream plant operated in a most 
cleanly fashion, show that such plants turn out ice cream 
of high bacteria content despite their many precautions. 
It can also he seen that the bacteria content of the ice 
cream varies greatly, both on the same day and succeed- 
ing days: 
It can safely be said that of the numbers of bacteria 
recorded in the following table that only an infinitesimal 
percentage were due to the utensils in the ice cream plant. 
19 The ice cream was positively manufactured under the best 
conditions obtainable in the ice cream industry to-day: 
BACTERIA CONTENTS OF ICE CREAM MADE ON SUCCESSIVE DAYS IN A 
SANITARY ICE CREAM PLANT. 
Date Sample Bacteria Per C.C. 
Ansrust lltb 1 11,000,000 
AUgUST 1-LIU i i Aaaa AAA 
2 10,000.000 
3 14,000,000 
4 16.000.000 
6 20,000.000 
12th 1 5,000,000 
5 15,000,000 
2 20.000.000 
3 15.000.000 
13th 1 1,600,000 
2 2,500,000 
4 19,000,000 
4 3,000,000 
14th 1 10.000,000 
3 1,500,000 
2 12,000.000 
3 11.000.000 
4 16,000,000 
5 2,500.000 
6 1,500,000 
7 3,000.000 
15th 1 1,260,660 
4 1,000.000 
6 3,000.000 
16th 1 
2 10,000.000 
4 5.000.000 
5 5,000.000 
18th 1 20.000,000 
7 11,000.000 
2 17,000,000 
4 16,000,000 
6 13.500.000 
7 14,000,000 
8 15,500.000 
19th 2 10.000.000 
3 20.000.000 
4 18.000.000 
7 14.000.000 
20th i 12,500,000 
2 25,000.000 
4 18.000.000 
5 20.000,000 
6 22,000,000 
7 17.000.000 
8 15,000.000 
22nd 3 4,606.000 
4 5.000.000 
5 5.500.000 
6 6,000.000 
7 4.000.000 
Given raw materials of low bacteria content it can be 
said in absolute assurance that the ice cream manufac- 
turer can produce with great ease ice cream of low 
bacteria content. 
20 21 Report on Ice Cream 
Examinations 
S. C. PRESCOTT PROF. S. C. PRESCOTT’S REPORT. 
Boston, March 4, 1914. 
Walter J. Carlin, Esq., 
2 Rector St., New York City. 
Dear Sir.—Attached hereto are the figures for the 
examination of two lots of ice cream—one a very high 
grade product, obtained from one of our best caterers, 
the other a commercial sample manufactured by one of 
the largest ice cream dealers in the city. These have 
been examined with reference to the number of bacteria 
developing at room temperature and body temperature 
upon several different media as indicated, and we have 
used in this investigation two different lots of media, 
made in exactly the same way and differing only in that 
one of them has been kept in storage in our ice-chest for 
a period of a week longer than the other. The age at 
the time of use was for the media marked “old” ten 
days, and for the media marked “new,” three days. 
The examinations have been carried out in three differ- 
ent dilutions in order to observe what variations, if any,, 
may be traced merely to difference in dilution of the 
sample. ] 
The plots following the tables are in each case, I 
believe, self-explanatory, and have been made using the 
figures in each case which judgment would dictate to 
be the most reliable—namely—those dilutions which give 
from 25 to 200 or 300 bacteria per plate. The samples 
marked A 1? A 2, A3 were all taken from the same general 
23 location, and might be regarded as each forming a frac- 
tion of the top portion of the freezer. The sample 
marked B was taken from a point lower down in the 
freezer; C from a still lower layer, and D from the 
bottom. In this way we can determine differences, if 
any exist, in the portion of the freezer used. I think 
yon will note both from the tables and the plots that it 
would he practically impossible to select any particular 
spoonful which could he taken as representing the whole 
mass, and you will also find that the age of the medium 
sometimes reacts one way and sometimes the other, hut 
that in general the age is largely in favor of the newer 
or fresher medium. 
Very truly yours, 
Samuel C. Prescott. 
24 EXAMINATION OF VANILLA ICE CREAM; LOT 1, CATERER. 
Determination of Effect of Different Media, Different Dilutions and Different 
Temperatures of Incubation on Numbers of Bacteria. 
SAMPLE Al. 
Dilution 
Bacteria per c.c. 
Dilution Dilution 
New Meat agar....... 37° 51 
Medium Temp. 1:10,000 
1:100,000 1 -.1,000,000 
4 0 
78 
20° 192 
121 
Old Meat agar 37° 52 
spr. 2 
21 6 
19 1 
61 
20° 184 
2 0 
4 3 
29 spr. 
19 3 
240 
New Extract agar. ...37° 46 
53 
20° 136 
3 0 
2 2 
164 
Old Extract agar, ...37° 32 
24 2 
25 3 
1 0 
128 
New Casein agar 37° 19 
38 
20° 138 
0 3 
16 3 
23 2 
23 
Old Casein agar 37° 22 
2 0 
2 16 
6 17 
New Dextrose 37° 40 
Litmus agar spr. 
Old Dextrose 37° 11 
Litmus agar 3 
New Lactose 37° 12 
Litmus agar 2 
Old Lactose ....37° spr. 
Litmus agar spr. 
New Bile 37° 5 neg. 
Old Bile 37° 5 neg. 
Acid Acid Acid 
40 1 1 spr. 
0 0 
11 4 4 spr. 
5 5 
3 10 spr. 
11 0 0 0 
2 spr. 0 spr. 
0 0 0 O 
37° 5 neg. 
0 0 10 
5 neg. 5 neg. 
5 neg. 5 neg. 
SAMPLE A 2. 
Medium Temp. 1 :10,000 
Dilution 
1 :100,000 1 :1,000,000 
Bacteria per c.c. 
Dilution Dilution 
New Meat agar 37° spr. 
7° 
20° 360 
6 spr. 
10 0 
199 
Old Meat agar 37° spr. 
spr. 4 
20 8 
9 2 
145 
New Extract agar....37° 63 
71 
20° 224 
108 2 
32 3 
26 3 
20° 184 
237 
Old Extract agar 37° 52 
6 o 
7 1 
29 6 
156 
20° 171 
169 
New Casein agar 37° 29 
spr. 7 
3 l 
7 2 
18 6 
22 2 
10 5 
25 
Old Casein agar 37° 62 
0 1 
2 0 
2 1 
New Dextrose 37° 25 
Litmus agar . 32 
Old Dextrose 37° 55 
Litmus agar spr. 
New Litmus 37° 24 
Lactose agar 19 
Old Litmus 37° 22 
Lactose agar 35 
New Bile 37° 5 neg. 
Old Bile 37° 5 neg. 
Acid Acid Acid 
25 spr. .. o 
32 9 9 1 ' i 
55 4 4 0 0 
o o i 
20 5 5 0 0 
3 3 11 
19 3 3 0 0 
22 3 1 2 0 
23 8 7 1 l 
37° 5 neg. 
5 neg. 5 neg. 
5 neg. 5 neg. 
25 SAMPLE A3. 
Dilution 
1 ;100,000 1:1,000,000 
Bacteria per c.c. 
Dilution Dilution 
New Meat agar 37° 63 
spr. 
20° 151 
284 
Medium Temp. 1 :10,000 
8 spr. 
8 4 
spr. 5 
40 spr. 
27 4 
Old Meat agar 37° sp^r. 
20° 315 
16 8 
30 6 
34 5 
, spr. 
New Extract agar....37° 27 
46 
3 0 
o 0 
27 3 
Old Extract agar 37° 30 
20° 156 
130 
20° 132 
28 6 
4 3 
8 0 
27 7 
spr. spr. 
11 2 
New Casein agar 37° 74 
56 
Old Casein agar 37° 43 
55 
5 8 
Acid Acid ' Acid 
2 O 
9 44 
New Litmus 37° spr. 
35 3 3 0 0 
2 2 2 1 
Dextrose agar 36 
Old Litmus 37° spr. 
Dextrose agar 73 
spr. . . spr. 
73 5 5 spr. .. 
78 9 7 0 0 
New Litmus 37° 79 
Lactose agar 69 
Old Litmus 37° 63 
68 3 1 0 1 
60 4 3 0 0 
40 14 14 2 2 
Lactose agar _ 49 
New Bile 37° 4 neg. 
1 pos. 15 p. c. 
Old Bile 37° 5 neg. 
1 pos. 5 p. c. 1 pos. 5 p. c. 
4 neg. 4 neg. 
5 neg. 5 neg. 
SAMPLE B. 
Dilution 
Bacteria per c.c. 
Dilution Dilution 
New Meat agar 37° 61 
Medium Temp. 1 ;10,000 
1 ;100,000 1 :1,000,000 
8 5 
7 4 
spr. 
Old Meat agar 37° spr 
20° 215 
25 spr. 
30 spr. 
spr. 1 
20° spr. 
216 
spr. 7 
spr. 5 
10 11 
New Extract agar 37° 5 
6 10 
Old Extract agar 37° 35 
20° 140 
156 
23 1 
16 6 
5 6 
20° 141 
135 
44 3 
24 7 
26 7 
New Casein agar 37° 60 
Old Casein agar 37° 37 
10 5 
16 11 
7 1 
New Litmus 37° 47 
Acid Acid Acid 
47 7 7 2 0 
4 2 
Dextrose agar 56 
Old Litmus'’ 37° 32 
Dextrose agar 54 
New Litmus 37° 
56 4 4 1 1 
31 6 6 1 0 
54 5 5 0 0 
Lactose agar 
Old Litmus 37° 23 
Lactose agar 29 
New Bile 37° 5 neg. 
20 1 1 0 0 
10 0 0 
2 0 4 0 
Old Bile ..' 37° 5 neg. 
28 0 0 0 0 
5 neg. 5 neg. 
5 neg. 5 neg. 
26 SAMPLE C. 
Bacteria per c.c. 
Medium Temp. 1 :10,000 
Dilution 
Dilution Dilution 
1 ;100.000 1 :1,000,000 
New Meat agar 37° 51 
66 
20° 175 
spr. 1 
spr. 0 
169 
Old Meat agar 37° 73 
71 
20° 74 
19 1 
19 2 
2 0 
6 1 
66 
New Extract agar....37° 20 
10 3 
7 0 
17 
20° 134 
16 2 
6 0 
4 0 
149 
Old Extract agar....37° 12 
9 
20° 112 
17 2 
0 spr. 
3 2 
spr. 
New Casein agar 37° 5 
16 1 
10 1 
4 3 
Old Casein agar 37° 10 
4 1 
1 4 
6 2 
New Litmus 37° spr. 
Dextrose agar 22 
Old Litmus 37° 23 
Dextrose agar 20 
New Litmus 37° 6 
Lactose agar 8 
Old Litmus 37° 12 
Lactose agar 12 
New Bile 37° 5 neg. 
Acid Acid Acid 
-L JL 1 U 
22 1 0 0 0 
1110 
23 1 0 0 0 
20 0 6 spr. 
6 10 0 0 
4 0 0 0 0 
10 0 0 0 0 
11 1 1 0 0 
-Dlie Ol O Deg. 
Old Bile ..37° 5 neg. 
5 neg. 5 neg. 
5 neg. 5 neg. 
SAMPLE D. 
Bacteria per c.c. 
Medium Temp. 1 -.10,000 
Dilution 
Dilution Dilution 
1 :100,000 1 :1,000,000 
New Meat agar 37° 59 
spr. 
20° 199 
2 0 
2 1 
19 1 
172 
Old Meat agar 37° spr. 
82 
20° spr. 
27 2 
6 1 
spr. 
New Extract agar..... 37° 19 
spr. 2 
spr. 3 
22 spr. 
20 
20° 161 
24 1 
1 4 
7 0 
126 
Old Extract agar 37° 5 
12 
20° 99 
44 3 
spr. 0 
0 1 
122 
New Casein agar 37° 11 
10 2 
11 1 
5 5 
5 
Old Casein agar 37° 9 
8 2 
1 6 
1 5 
New Litmus 37° 16 
Dextrose agar 12 
Old Litmus 37° spr. 
Acid Acid Acid 
16 1 0 2 2 
12 1 0 0 0 
Dextrose agar 22 
New Litmus 37° spr, 
Lactose agar 27 
Old Litmus 37° 4 
Lactose agar 13 
New Bile ....37° 5 neg. 
Old Bile 37° 5 neg. 
22 0 0 spr. 
3 2 0.. 
7 0 0 0 
3 0 0 spr. 
9 1 spr. 0 0 
spr. 2 0 0 
37° 5 neg. 
5 neg. 5 neg. 
5 neg. 5 neg. 
2 7 28 29 30 31 32 EXAMINATION OF VANILLA ICE CREAM. 
LOT 2, COMMERCIAL. 
Determination of Effect of Different Media, Different Dilutions and Different 
Temperatures of Incubation on Numbers of Bacteria Found. 
SAMPLE Al. 
Bacteria per c.c. 
Medium Temp. 1 .TO,OOO 1 TOO,OOO 1 T,000,000 
Dilution Dilution Dilution 
New Meat agar.... . .37° 1,360 233 13 
2,148 253 spr. 
20° 2,232 217 35 
„ 2,052 231 spr. 
Old Meat agar ..37° 1,170 spr. 23 
37° 1,170 spr. 23 
1,800 190 19 
1,560 219 28 
New Extract agar 37° 1,125 102 15 
20° 1,500 231 32 
1,416 132 33 
Old Extract agar 37° 1,788 90 18 
20° 1,058 191 27 
1,060 34 17 
20° 1,050 190 33 
900 108 19 
1,725 198 27 
New Casein agar 37° 890 91 16 
1,530 70 14 
Old Casein agar 37° 1,530 130 16 
1,524 126 spr. 
„ Acid Acid Acid 
New Dextrose 37° 1,210 1,200 982 48 0 0 
Lactose agar 960 957 90 85 0 0 
Old Dextrose 37° 890 887 120 115 1 0 
Lactose agar 460 457 106 96 spr. 0 
New Litmus 37° 685 680 spr. .. 1 0 
Lactose agar 760 757 92 88 spr. 
Old Litmus 37° 930 925 89 83 0 0 
Lactose agar spr. 107 95 3 3 
New Bile 37° 0 0 0 
37° 0 0 0 
Old Bile 37° 0 0 0 
0 0 0 
0 0 0 
0 0 0 
0 0 0 
SAMPLE A 2. 
Bacteria per c.c. 
New Meat agar 37° 2,004 285 43 
Medium Temp. 1 T 0,000 1:100,000 1:1,000,000 
Dilution Dilution Dilution 
1,764 258 29 
Old Meat agar 37° 1,890 265 30 
20° spr. 249 38 
2,115 285 28 
20° 2,088 223 30 
2,240 261 31 
1,266 196 31 
New Extract agar 37° 1,212 
1,308 151 17 
1.323 172 25 
Old Extract agar 37° L 590 212 29 
20° 1,550 214 28 
1,174 .. 30 
20° 1,608 235 44 
1,968 225 34 
New Casein agar 37° 1,164 181 47 
988 170 92 
Old Casein agar 37° 1,468 172 10 
New Litmus 37° 740 612 82 69 14 7 
912 211 13 
Acid Acid Acid 
Dextrose agar 530 418 59 53 spr. 
Old Litmus) 37° 1,140 1,123 111 93 spr.' 
Dextrose agar spr. .. 76 64 spr. .» 
New Dittmus 37° 1,000 988 107 102 24 24 
JLil L Llll Ub •••••« ■. u I I,UUU t/Oo J I IUZ 
Lactose agar 684 674 112 109 
Old Litmus 37° 780 773 106 86 24 20 
102 24 24 
oiu Jjiimus sr / pu i m zu 
Lactose agar 800 780 121 118 7 2 
New Bile 37° 0 0 0 
Old Bile 37° 0 0 0 
0 00 
0 0 0 
0 0 0 
0 00 
33 SAMPLE A3 
Bacteria per c.c. 
Medium Temp. 1:10,000 1:100,000 1:1,000,000 
Dilution Dilution Dilution 
New Meat agar 37° 880 180 15 
20° 1,827 247 45 
940 spr. 19 
1,974 248 38 
Old Meat agar 37° 1,020 192 8 
1,020 190 6 
2,289 247 spr. 
New Extract agar 37° 820 63 8 
20° 2,418 242 42 
20° 1,386 166 6 
1,197 166 29 
Old Extract agar 37° 588 196 10 
960 72 10 
37° 588 196 10 
20° 990 168 19 
553 150 9 
1,056 208 26 
New Casein agar 37° 780 260 21 
870 300 14 
Old Casein agar.. 37° 900 120 12 
840 110 13 
Acid Acid Acid 
New Dextrose 37° spr. 839 155 115 6 2 
Old Dextrose 37° 1380 1336 128 114 spr. 
Litmus agar spr. . . 75 70 13 11 
Litmus agar 850 84 76 11 9 
Lactose agar 1210 1206 spr.* .. spr. 
Old Litmus 37° 900 890 115 104 18 18 
Litmus agar spr. . . 75 70 13 11 
New Litmus 37° 910 896 146 129 18 16 
Lactose agar 660 636 85 81 8 1 
New Bile i. . .37° 0 0 0 
Old Bile 37° 0 0 0 
0 0 0 
0 0 0 
= alkaline. 
0 0 0 
0 0 0 
Dilution Dilution Dilution 
SAMPLE B. 
Bacteria per c.c. 
New Meat agar. ... . .37° 975 114 11 
Medium Temp. 1 :10,000 1 :100,000 1 :1,000,000 
1,915 205 30 
Old Meat agar 37° spr. 134 18 
20° 1,890 205 22 
1,008 115 18 
,37° spr. 134 18 
1,400 128 spr. 
20° 1,575 233 30 
New Extract agar....37° 888 122 15 
828 133 24 
1,512 202 39 
1,228 204 19 
Old Extract agar 37° 690 116 13 
20° 1,659 155 26 
1,449 186 16 
New Casein agar 37° 1,080 146 43 
20° 693 174 23 
740 104 10 
1,040 133 15 
Old Casein agar 37° 1,170 92 16 
New Litmus 37° spr. . . 49 48 6 4 
Dextrose agar 360 355 36 33 spr. 
Old Litmus 37° 240 205 64 64 1 1 
1,635 125 36 
Acid Acid Acid 
Dextrose agar 610 600 66 66 4 3 
New Litmus 37° 700 690 63 58 11 10 
Lactose agar 760 755 76 70 9 1 
Old Litmus 37 ° spr. . . 5 5 5 3 
Lactose agar 490 485 62 57 10 9 
New Bile .37° 000 
0 0 0 
Old Bile 37° 0 0 0 
0 0 0 
0 0 0 
0 0 0 
34 SAMPLE C. 
Bacteria per c.c. 
Medium 
Temp. 1 :10,000 1 :100,000 1 :1,000,000 
Dilution 
Dilution Dilution 
New Meat agar 37° 500 75 
spr. spr. 11 
20° 870 136 19 
900 141 30 
Old Meat agar 37° spr. spr. spr. 
Old Meat agar 37 spr. spr. spr. 
spr. ' 125 19 
20° 1,150 150 23 
660 spr. 23 
New Extract agar....37° spr. 34 13 
500 22 33 
20° 1,032 156 20 
1,134 132 19 
Old Extract agar 37° 202 32 213 
480 22 7 
20° 1.092 87 17 
1,092 118 10 
New Casein agar 37° 220 54 28 
560 61 21 
Old Casein agar.. ... .37° 340 49 6 
400 34 8 
Acid Acid Acid 
New Litmus 37° 427 417 spr. .. 4 1 
New Litmus 37° 427 417 spr. . . 4 1 
Dextrose agar 160 5 40 21 1 1 
Old Litmus 37° spr. .. 34 28 alk. spr. 
Dextrose agar 340 330 68 23 2 1 
New Litmus 37° 378 338 76 54 2 
New Litmus 37° 378 338 76 54 2 1 
Lactose agar spr. . . 56 30 1 0 
Old Litmus 37° 452 240 271 6 15 11 
Lactose agar -. . 850 845 148 1 7 1 
Lactose agar -. . 850 845 148 1 7 1 
New Bile 37° 0 0 0 
New Bile 37° 0 0 0 
0 0 0 
0 0 0 
Old Bile 37° 0 0 0 
0 0 0 
0 0 0 
0 0 0 
SAMPLE D, 
Bacteria per c.c. 
Medium 
Temp. 1 :10,000 1 :100,000 1 :1,000,000 
Dilution 
Dilution Dilution 
New Meat agar 37° spr. 144 spr. 
670 126 29 
20° 1.530 182 41 
1,920 231 46 
Old Meat agar 37° spr. 142 spr 
Did Meat agar 37“ spr. 142 spr. 
824 133 spr. 
20° 1,356 215 29 
1,692 spr. 31 
New Extract agar....37° 780 73 12 
spr. 87 15 
20° 1,092 160 34 
1.548 146 38 
Old Extract agar 37° 209 spr. 47 17 
Old Extract agar 37° 209 spr. 47 17 
240 spr. 48 10 
20° 1,596 165 39 
„ . 1.392 215 47 
New Casein agar 37° not plated 
Old Casein agar 37° 1,392 103 26 
696 139 21 
„ Acid Acid Acid 
New Litmus 37° 1,300 1,293 34 14 4 0 
Dextrose agar 1,080 1,073 spr. . . 6 4 
Old Litmus 37° 1.180 1,170 35 34 spr. 
Old L,itmus 37" 1.180 1,170 35 34 spr. 
Dextrose agar 970 47 42 5 
Dextrose agar 970 47 42 5 1 
New Litmus 37° 520 511 12 10 33 11 
Lactose agar 1.270 1.265 23 22 8 1 
Old Litmus 37° 650 640 spr. spr. 
Lactose agar spr. 117 103 9 6 
Lactose agar spr. 117 103 9 6 
New Bile 37° 0 0 0 
0 0 0 
0 0 0 
Old Bile 37° 0 0 n 
0 0 0 
0 0 0 
0 0 0 
35 37 38 39 40 Report on Ice Cream 
Examinations 
P. G. HEINEMANN REPORT ON ICE CREAM EXAMINATIONS MADE 
OCTOBER AND NOVEMBER, 1913. 
P. Gr. Heinemanx, 
Methods. 
The ice cream was bought in gallon cans. The samples 
were taken as follows:—The paper covering the ice cream 
was removed and a small layer of ice cream removed from 
the surface with a sterilized spoon. Four samples were 
then taken with sterile spoons and the ice cream trans- 
ferred to sterile petri dishes and allowed to melt at room 
temperature. A sample was then taken by boring with 
a sterile glass tube one inch below the surface. The glass 
tubes used for this purpose were sterilized in test tubes, 
and after the sample had been taken were replacd in the 
tubes and the ice cream melted. The test tubes were stop- 
pered with cotton. By using glass tubes as before one 
sample was taken two inches from surface, one three 
inches from surface. After these samples wTere taken the 
whole column of ice cream was dumped on a piece of 
sterilized filter paper. Hot water was run on the outside 
of the can until the ice cream would slip out. After this 
one sample was taken about three-quarters towards the 
bottom and two near the bottom. All these were melted 
in the respective test tubes. Finally two lots of about 
one half pint each were placed in sterilized beakers and 
allowed to melt. All samples excepting the two samples 
in the beakers were liquefied completely before samples 
were placed in dilution flasks. The two lots in the beakers 
were allowed to stand long enough to melt the ice cream 
so that one cubic centimeter could be removed. 
42 The samples were designated as follows : 
Al—Sample from beaker. 
A2—Sample from beaker. 
B1—Teaspoonfnl from surface. 
B2—Teaspoonfnl from surface. 
B3—Teaspoonfnl from surface. 
B1—Teaspoonfnl from surface. 
Cl—Bored from two inches below surface. 
C2—Bored from three inches below surface. 
C3—Bored three-quarters way down. 
C4—Bored from surface, about one inch down. 
C5—Bored from bottom. 
C6—Bored from bottom. 
One cubic centimeter of each sample respectively was 
transferred to a flask containing 99 cc. sterile water. 
From this dilution one cubic centimeter was transferred 
to another flask containing 99 cc. sterile water. This 
makes a dilution of 1:10,000. From this dilution 10 cc. 
were transferred to a flask containing 90 cc. sterile water. 
All flasks were of course thoroughly shaken and all usual 
bacteriological manipulations carried on in proper shape. 
From the two dilutions 1 -.10,000 and 1 ;100,000 each one 
cc. was transferred to each of four petri dishes. To two 
of each set of four petri dishes one cc. of 1% litmus 
solution was added. This litmus was added with as 
much care as possible to avoid the mixing of the bac- 
terial dilution with the litmus solution, the latter having 
some restraining effect upon bacteria. Mixing was ef- 
fected after addition of the liquified agar. Two of each 
set of four petri dishes were used for plain agar, the 
other two for dextrose-litmus-agar. Plain agar is the 
43 method used by the Committee on Standard Milk Analy- 
sis of the American Public Health Association and by 
the Government experts. Dextrose-litmus-agar favors 
the multiplication of lactic streptococci, the dextrose be- 
ing an almost needed pabulum and the litmus facilitating 
the counting, since lactic streptococci form red colonies in 
litmus. After the agar had hardened the plates were 
incubated at 37 degrees C. for two days, and then the 
colonies counted. A separate count was made on all 
dextrose-litmus-agar plates to be able to get a relation 
of the acid forming bacteria to the others. This is espe- 
cially important, since ice cream manufacturers often 
allow the cream to stand, which permits the multiplica- 
tion of these acid organisms, which are entirely harm- 
less. Colon bacilli would also multiply to some extent 
this way. 
Tables 1 to 6 give the detailed counts. All plates of 
1:10,000 and of 1 ;100,000 were counted, the dextrose-lit- 
mus-agar plates were counted twice in order to get the 
acid colony count. The dilution of 1:100,000 was not 
satisfactory, being too high and consequently giving high 
counts. The dilution 1:10,000 was satisfactory through- 
out. In the tables all these counts are given for the sake 
of completeness, but only the six counts of each sample 
were considered being of value. These six counts then 
were:—Two duplicate agar plates, which were averaged 
in a separate column. Two duplicate dextrose-litmus- 
agar plates, which were averaged in a separate column. 
The acid colonies on the two dextrose-litmus-agar plates, 
which were averaged in a separate column and then the 
percentage of acid colonies to the total estimated. The 
first six tables are too voluminous to give a definite idea 
of the results. In table 7 the results are condensed and 
show the total numbers of the bacteria found in a clear 
fashion. 
44 TABLE 1 
EXAMINATION OF ICE CREAM, LOT 1, CATERER, OCTOBER 26. 
PRICE $3.00. 
Explanation A stands for plain agar, DLA for dextrose-litmus-agar. All figures should be multiplied by 1000. 
Kind of Sample N„. Dilution SS?. C?S AVe“*nenatd<i “S 
1 250 
10.000 A 2 170 210 
Each sample = % Pint 1 DLA | 34® f00 
melted in sterile 2 4AQ °9' 100 1<5 4u 
beaker. 100,000 A 2 600 500 
1 1,800 1 000 
DLA 1,600 1,700 ’500 750 44 
1 800 
10.000 A 2 650 725 
0 1 1,200 500 
DLA | • MOO 1.150 400 450 39 
100.000 A 2 1,200 1,050 
1 1,900 500 
DLA 2 2,300 2A00 800 650 31 
CN B 1 400 
10.000 A 2 420 410 
1 480 200 
1 DLA 2 spreader 480 200 42 
100.000 A 2 500 600 
1 900 400 
DLA ? 700 800 300 350 44 
1 700 
10.000 A 2 800 750 
Bach sample = one tea- 2 DLA \ i’tiiu 1 non 599 
spoonful taken from { 1’500 400 350 23 
same place at sur- 100,000 DLA 2 L500 1,650 700 650 39 
10.000 A 2 210 195 
o 1 450 50 
DLA 2 380 415 40 45 11 
100.000 A 2 700 750 
1 900 200 
DLa 2 spreader 900 200 200 22 
10.000 A 2 90' 105 
„ 1 320 150 
4 DLA 2 360 340 150 150 44 
1 400 
100.000 A 2 500 450 
1 700 300 
i4EA 2 800 750 300 >300 40 C 1 270 
10.000 A 2 330 300 
1 820 300 
2 inches below surface. 1 DLA 2 760 790 300 300 38 
1 700 
100.000 A 2 500 600 
1 900 400 
DLA 2 700 800 400 400 50 
1 650 
10.000 A 2 840 745 
n 1 1,600 200 
H 3 inches below surface. 2 DLA 2 1,300 1,450 300 250 17 
« 1 700 
100.000 A 2 800 750 
C8 I 800 200 
DLA 2 900 850 200 200 24 
y, 1 960 
W 10,000 A 2 780 870 
Cd 1 1,800 400 
W About % ways down. 3 DLA 2 1,500 1,650 300 350 22 
Y* 1 1,900 
S 100,000 A 2 2,500 2,200 
Q 1 3,200 1,200 
DLA 2 2,100 2,650 300 750 28 
<4 1 900 
9 10,000 A 2 700 800 
£ 1 1,800 1,000 
Just below surface. 4 DLA 2 1,900 1,850 1,400 1,200 62 
y, 1 spreaders 
W 100,000 A 2 spreaders 
W 1 spreaders 
**1 DLA 2 spreaders 
H 1 360 
02 10,000 A 2 380 370 
H 1 750 200 
9 From bottom. 5 DLA 2 790 770 200 200 26 
9 1 900 
5 100,000 A 2 500 700 
1 spreaders 
DLA 2 spreaders 
1 1,040 
10.000 A 2 900 870 
1 1,160 280 
From bottom. 6 DLA 2 1,700 1,430 1,100 690 49 
1 1,200 
100.000 A 2 1,900 1,550 
1 3,200 800 
DLA 2 1,200 2,200 1,200 1,000 45 
47 TABLE 2 
EXAMINATION OF LOT 2, COMMERCIAL ICE CREAM, OCTOBER 25, 1913. 
PRICE $1.25. 
Explanation-—A stands for plain agar, DLA for dextrose-litmus-agar. All figures should he multiplied hy 1000. 
— ~~~ Per cent. 
A Kind Plate Colony Average Acid col. Average acid acid col. 
Kind of Sample No. Dilution Med. No. count count count count count 
10.000 A 2 1,800 2,150 
1 7,500 all 
Each sample = % pint 1 DLA 2 6,500 7,000 all all 100 
melted in sterile . 1 
beaker. 100,000 A - 2,400 3,100 8000 
DLA 2 8,400 8,800 5,000 6,500 74 
1 1,800 
10.000 A 2 2,000 1,900 
1 6,900 all 
2 DLA 2 6,400 6,650 all all 100 
1 1,100 
100.000 A 2 1,400 1,250 
1 2,900 1,000 
DLA 2 3,400 3,150 1,200 1,100 35 
» 1 1,900 
10.000 A 2 2,400 2,150 
1 9,500 all 
Each sample r= one tea- 1 DLA 2 8,500 9,000 all all 100 
spoonful taken from 1 3,500 
same place at sur- 100,000 A 2 2,900 3,200 
face 1 8,700 5,000 
DLA 2 9,100 8.900 4,500 4,750 53 
1 2,000 
10.000 A 2 3,600 2,800 
1 3,750 ail 
9 DLA 2 2,500 3,100 1,500 75 
1 2,800 
100.000 A 2 2,900 2,850 
1 5,600 all 
DLA 2 4,300 4,950 3,800 80 
1 2,900 
10.000 A 2 2,500 2,700 
1 9,200 all 
3 DLA 2 8,500 8,850 all 100 
1 spreaders 
100.000 A 2 1,100 1,100 
1 spreaders 
DLA 2 1,750 1,750 800 50 
1 2,800 
10.000 A 2 2,500 2,650 
1 7,600 5,700 
4 DLA 2 8,500 8,050 all 75 
1 6,100 
100.000 A 2 8,600 7,350 
1 QTIT*on rl OTG 
DLA 2 19,000 19,000 8,500 50 
48 c 1 1,700 
10.000 A 2 1,900 1,800 
1 2,100 1,100 
2 inches below surface. 1 DLA 2 2,900 2,500 1,500 1,300 52 
1 3,800 
100.000 A 2 2,800 3,300 
1 9,300 all 
DLA 2 8,100 8,700 all 100 
1 1,200 
10.000 A 2 1,300 1,250 
no 1 6,100 all 
Eh 3 inches below surface. 2 DLA 2 7,800 6,950 all 100 
P3 1 2,200 
100,000 A 2 2,700 2,450 
C8 1 9,500 5,000 
Li DLA 2 7,600 8,050 5,800 5,400 68 
g 1 2,800 
a 10,000 A 2 2,800 2,700 
1 6,400 all 
H About % ways down. 3 DLA 2 9,800 8,100 all 100 
1 3,300 
g 100,000 A 2 4,500 3,900 
Q 1 11,000 all 
_ i DLA 2 8,300 9,650 all 100 
S 1 2,300 
2 10,000 A 2 3,400 2,850 
« 1 8,400 4,500 
” Just below surface. 4 DLA 2 9,500 8,950 all 75 
£ 1 3,500 
H 100,000 A 2 5,200 4,350 
W 1 9,500 all 
<3 DLA 2 9,800 9,650 all 100 
1 5,200 
m 10,000 A 2 3,900 4,550 
a 1 9,200 all 
a From bottom. 5 DLA 2 11,200 10,200 all 100 
g 1 8,000 
s 100,000 A 2 13,000 10,500 
< 1 14,000 12,000 
DLA 2 15,000 14,500 8,000 10,000 69 
1 2,600 
10.000 A 2 2,400 2,500 
1 6,900 all 
From bottom. 6 DLA 2 4,200 5,500 all 100 
100.000 A 2 3’600 2,900 
1 7,500 all 
DLA 2 8.900 8,200 all 100 
49 TABLE 3 
EXAMINATIONS OF LOT 3, COMMERCIAL ICE CREAM, OCTOBER 24, 1913. 
PRICE $1.70. 
Explanation—A stands for plain agar, DLA for dextrose-litmus-agar. All figures should be multiplied by 1000. 
. — - - Per cent. 
a Kind Plate Colony Average Acid col. Average acid acid col. 
Kind of Sample No. Dilution Med. No. C°240 count count count count 
10.000 A 2 300 270 
1 700 __ 100 
Each sample = y2 pint 1 DLA 2 650 67o 100 100 •> 
melted in sterile 1 gOU 
beaker 100,000 A 2 200 250 
uea*el- 1 400 none 
DLA 2 500 450 none none 0 
1 270 
10.000 A 2 300 285 
1 420 310 
2 DLA 2 480 450 360 335 7o 
1 100 
100.000 A 2 200 150 
1 200 200 
DLA 2 200 200 200 200 100 
— — - I 190 
10.000 A 2 160 175 
1 600 300 
Each sample ~ one tea- 1 DLA 2 500 550 250 2i5 50 
spoonful taken from „ 4 1 400 
same place at sur- 100,000 A - 200 300 
fa pp 1 4UU 
dce‘ DLA 2 400 400 200 200 50 
1 410 
10.000 A 2 370 390 
1 2,240 1,800 
2 DLA 2 3,250 2,700 2,650 2,220 82 
1 720 
100.000 A 2 580 650 
1 1,180 all 
DLA 2 2,300 1,740 all all 100 
1 290 
10.000 A 2 250 270 
1 460 200 
3 DLA 2 370 415 120 160 39 
1 600 
100.000 A 2 500 550 
1 1,100 550 
DLA 2 1,800 1,450 400 475 33 
1 800 
10.000 A 2 900 850 
1 3,900 2,200 
4 DLA 2 3,100 3,500 1,900 2,050 59 
1 200 
100.000 A 2 300 250 
1 400 300 
DLA 2 700 550 400 350 64 c 1 160 
10.000 A 2 120 140 
2 inches below surface. 1 DLA 2 510 580 450 475 96 
1 200 
100,000 A 2 100 150 
1 400 200 
DLA 2 800 350 100 150 43 
1 450 
• • 10,000 A 2 400 425 
S o , t, , 1 2,500 1,900 
H 3 inches below surface. 2 DLA 2 2,900 2,700 2,200 81 
1 1,100 
2 100,000 A 2 1,900 1,500 
* 1 1,200 800 
t DLA 2 1,600 1,400 600 700 50 
1 160 
§ 10.000 A 2 180 170 
hh 700 
| About % way down. 3 DLA 2 900 800 400 500 62 
1 300 
£ 100,000 A 2 400 350 
A 1 1,100 700 
g DLA 2 800 850 400 550 65 
O 1 800 
10.000 A 2 900 850 
fc , 1 2,200 800 
Just below surface. 4 DLA 2 1,800 2,000 1,200 1,000 50 
§ 100,000 A 2 2’000 2,000 
3 1 4,500 2,100 
Eh DLA 2 3,900 4,200 2,200 2,150 50 
10.000 A 2 500 600 
3 1 850 700 
£ From bottom. 5 DLA 2 650 750 620 660 88 
§ 1 600 
3 100,000 A 2 800 700 
1 900 300 
DLA 2 1,200 1,050 400 350 33 
10.000 A 2 360 370 
1 750 700 
From bottom. 6 DLA 2 800 775 750 795 03 
1 1,100 
100,000 A 2 800 850 
1 1,600 1,500 
DLA 2 1,400 1,500 1,200 1,350 90 
51 TABLE 4 
EXAMINATIONS OF LOT 4, COMMERCIAL VANILLA ICE CREAM, OCTOBER 23, 1913. 
PRICE $1.25. 
Explanation—A stands for plain agar, DLA for dextrose-litmus-agar. All figures should he multiplied hy 1000. 
I — " PeFcent. 
V Kind Plate Colony Average Acid col. Average acid acid col. 
No. Dilution Med. No. count count count count 
Kind of Sample 1 0,920 
10.000 A 2 7,800 8,850 
1 22,000 all ,00 
1 ULA 2 18,000 20,000 all all 
1 12,000 
Each sample = % pint 100,000 A 2 8,000 10,000 
melted in sterile 1 21,000 ,, 11 100 
Sir. sterlle DLA 2 18,000 19,500 all all luu 
Sample taken when , 1 5,840 (0n 
enough melted. 10,000 A 2 L1--0 0,480 . 
1 lb,000 "41 -ion 
2 DLA 2 23,000 19,500 all all luu 
1 6,000 
100.000 A 2 8,000 7,000 _ 
2 28:500 26.500 21.000 
„ i T oiioo 
10.000 A 2 12,000 11,500 
1 33,000 „ all 
Eatfh sample = one tea- 1 DLA 2 33,300 a 
spoonful taken from 1 aaa 
same place at sur- 100,000 A 2 41,000 11,000 
face 1 39,000 ail aa 
tace- 2 50,000 44,500 all all 100 
1 9,200 
10.000 A 2 13,000 11,000 100 
1 24,000 all all luu 
2 DLA 2 26,000 25,000 all 
1 14,000 
100.000 A 2 10,000 12,000 
1 40,000 all 
DLA 2 45,000 42,500 all all 100 
1 43,000 
10.000 A 2 46,400 44,700 100 
1 48,000 all all ±uu 
3 DLA 2 46,000 47,000 all 
1 45,000 
100.000 A 2 48.000 46,500 
1 58,000 all 
DLA 2 56,000 57,000 all all 100 
1 41,000 
10.000 A 2 42,000 41,500 
DLA 1 59,000 A all 
4 DLA 1 59,000 55,000 all all 100 
1 60,000 
100.000 A 2 50,000 55,000 
1 55,000 all 
DLA 2 65,000 60,000 all all 100 
52 Cl 1 6,800 
10.000 A 2 6,200 6,500 
1 29,000 all 
2 inches below surface. 1 DLA 2 22.000 25,500 all all 100 
100 000 A 2 lliSGO 
DLA 1 38,000 16,200 all 
2 36,000 37,000 all all 100 
1 7,500 7,000 
10.000 A 2 6,500 
1 31,000 all 
H 3 inches below surface. 2 DLA 2 29,000 30,000 all all 100 
100.000 A 2 14,000 15,500 
S 1 48,000 all 
DLA 2 43,000 45,500 all all 100 
U 1 8,500 
| 10,000 A 2 9,700 9,100 
i 1 20,400 all 
0 About % way down. 3 DLA 2 ll’ooo 23,800 all all 100 
1 100,000 a 2 o’ooo 10,000 
5 1 35,000 all 
H DLA 2 28,800 31,900 all all 100 
a 1 9,900 
0 10,000 A 2 8,600 9,200 
P3 1 40,400 all 
Just below surface. 4 DLA 2 37,500 all all 100 
1 100,000 A 2 17,’500 18,000 
5 1 58,700 all 
3 DLA 2 55,200 56,900 all all 100 
Eh 1 , 8,500 
10.000 A 2 8,800 8,600 
I 1 24,000 all 
g From bottom. 5 DLA 2 20,500 22,500 all all 100 
g 100,000 A 2 12:000 10,500 
1 29,800 all 
6 DLA 2 32,000 29,900 all all 100 
1 5,900 
10.000 A 2 7,300 6,600 
1 18.400 all 
From bottom. 6 DLA 2 17,500 17,900 all all 100 
100.000 A 2 6,500 7,000 
] 19,000 all 
DLA 2 16,000 17,500 all all 100 
53 TABLE 5 
EXAMINATION OF LOT 5, COMMERCIAL STRAWBERRY ICE CREAM, NOVEMBER 7, 1913. 
PRICE $1.25. 
Explanation—A stands for plain agar, DLA for dextrose-litmus-agar. All figures should be multiplied by 1,000. 
Per cent. 
A Kind Plate Colony Average Acid col. Average acid acid col. 
Kind of Sample No. Dilution Med. No. count count count count count 
1 950 
10.000 A 2 750 850 
1 980 900 
1 DLA 2 spreaders 980 900 900 80 
1 700 
100.000 A 2 800 750 
Bach sample = % pint 1 900 300 
melted in sterile DLA 2 1,100 1,000 900 600 60 
beaker. 1 650 
10.000 A 2 720 685 
1 850 650 
2 DLA 2 900 875 800 725 90 
1 500 
100.000 A 2 700 600 
1 1,000 800 
DLA 2 spreaders 1,000 800 80 
B 1 800 
10.000 A 2 650 725 
1 850 750 
1 DLA 2 950 900 500 625 68 
1 900 
100.000 A 2 800 850 
1 800 700 
DLA 2 900 800 700 700 88 
1 880 
10.000 A 2 750 815 
1 1,200 400 
2 DLA 2 900 1,050 700 550 54 
1 800 
100.000 A 2 1,100 950 
Each sample = one tea- 1 1,300 1,300 
spoonful from same DLA 2 spreaders 1,300 100 
place at surface. 1 1,300 
10.000 A 2 1,100 1.200 
1 1,100 1,000 
3 DLA 2 spreaders 1,100 1,000 91 
1 1,500 
100.000 A 2 1,100 1,300 
1 1,800 1,500 
DLA 2 spreaders 1,500 83 
1 950 
10.000 A 2 800 875 
’ 1 900 800 
4 DLA 2 950 925 700 750 75 
1 1,100 
100.000 A 2 1,300 1,200 
1 1,500 1,200 
DLA 2 1,800 1,650 1,500 1,350 82 
54 r 1 950 
10.000 A 2 1,100 1,025 
1 1,400 1,200 
2 inches below surface. 1 DLA 2 1,200 1.300 1,000 1,100 85 
100.000 A 2 900 1,100 
1 spreaders 
DLA 2 1,600 1,600 1,600 1,600 100 
1 900 
10.000 A 2 1,200 1,050 
g 1 920 900 
P3 3 inches below surface. 2 DLA 2 1*200 L020 1,000 050 95 
Si 100,000 A 2 l’800 1,500 
r 1 1,800 1.500 
H ' DLA 2 2,000 1,900 1,500 1,500 79 
K 1 820 
S 10,000 A 2 930 875 
| 1 1,100 1,100 
fa About % way down. 3 DLA 2 1,200 1,150 1,000 1,050 90 
fa 1 700 
n 100,000 A 2 900 800 
° 1 1,200 800 
§ DLA 2 i ,500 1,350 1,200 1.000 74 
O 1 1,200 
« 10,000 A 2 1,050 1,125 
fa 1 1,800 1,300 
<z Just below surface. 4 DLA 2 1,600 1,450 1,200 1,250 86 
r—’ 1 1 2{)(1 
§ 100,000 A 2 D300 1,250 
3 1 1,600 1,200 
2 DLA 2 1,400 1,500 1.100 1,150 77 
_ 1 600 
H 10,000 A 2 550 575 
3 1 800 700 
fa From bottom. 5 DLA 2 850 825 700 <00 85 
a lira 1 1,200 
<! 100,000 A 2 1,400 1,300 
50 1 spreaders 
DLA 2 1,500 1,500 1.500 1,500 100 
1 700 
10.000 A 2 850 775 
’ 1 1,600 1,500 
From bottom. 6 DLA 2 l';]oO 1,325 900 1,200 90 
100.000 A 2 1.400 1,350 J 
DLA 2 1,200 1,300 1,000 1,200 92 
55 TABLE 6 
EXAMINATION OF VANILLA ICE CREAM, LOT 6, COMMERCIAL, NOVEMBER 9,1913. 
PRICE $1.25. 
Explanation—A stands for plain agar, DLA for dextrose-litmus-agar. All figures should be multiplied by 1,000. 
Per cent. 
A Kind Plate Polony Average Acid col. Average acid acid col. 
Kind of Sample No. Dilution Med. No. count count count count count 
1 4G0 
10.000 A 2 480 470 
1 700 700 
1 DLA 2 060 680 060 080 100 
1 500 
, 100,000 A 2 1,100 800 
Each sample = % pint 1 700 400 
melted in sterile DLA 2 1,200 950 700 550 45 
beaker. 1 1,000 
10.000 A 2 2,400 1,700 
1 4,200 4,200 
2 DLA 2 3,600 3,900 3,000 3,600 95 
1 5,000 
100.000 A 2 7,000 6,000 
1 10,000 8,000 
DLA 2 spreaders 10,000 8,000 8,000 80 
B 1 780 
10.000 A 2 900 840 
1 920 920 
1 DLA 2 960 940 960 940 100 
1 600 
100.000 A 2 900 750 
1 1,000 800 
DLA 2 1,700 1,350 1,700 1,250 93 
1 540 
10.000 A 2 - 840 690 
1 1,400 1,400 
2 DLA 2 1,020 1,210 1,020 1,210 100 
1 400 
100.000 A 2 700 550 
1 1,100 1,100 
Each sample = one tea- DLA 2 1,900 1,500 1,900 1,500 100 
spoonful from same 1 700 
place at surface. 10,000 A 2 800 750 
1 900 800 
3 DLA 2 740 820 500 650 80 
1 500 
100.000 A 2 600 650 
1 800 500 
DLA 2 900 750 400 450 60 
1 480 
10.000 A 2 540 510 
1 1,200 1,200 
4 DLA 2 1,100 1.150 900 1,050 91 
1 500 
100.000 A 2 600 550 
1 700 400 
DLA 2 800 750 600 500 67 
56 c 1 350 
10.000 A 2 390 370 
1 420 350 
2 inches below surface. 1 DLA 2 spreaders 420 350 83 
1 300 
100.000 A 2 400 350 
1 700 500 
DLA 2 600 050 400 450 70 
1 350 
10.000 A 2 400 375 
to 1 520 520 
S 3 inches below surface. 2 DLA 2 500 540 560 540 100 
05 1 300 
100.000 A 2 200 150 
fa 1 400 300 
r. DLA 2 500 450 500 400 89 
5 1 200 
ij 10,000 A 2 380 290 
P5 1 410 410 
H About % way down. 3 DLA 2 370 390 370 390 100 
fa 1 700 
fa 100,000 A 2 COO 650 
q 1 800 800 
DLA 2 spreaders 800 800 800 100 
2 1 210 
Q 10,000 A 2 170 190 
W 1 350 350 
fa Just below surface. 4 DLA 2 280 315 280 315 100 
£ 1 200 
H 100,000 A 2 200 200 
W 1 500 200 
<3 DLA 2 800 650 600 400 60 
H 1 450 
to 10,000 A 2 380 415 
H 1 740 740 
J Prom bottom. 5 DLA 2 560 050 500 620 95 
Ej 1 600 
S 100,000 A 2 700 650 
< 1 1.200 800 
m DLA 2 800 1,000 500 650 65 
1 300 
10.000 A 2 400 350 
1 900 900 
From bottom. 6 DLA 2 800 850 800 850 100 
1 800 
100.000 A 2 600 700 
1 1,200 1,200 
DLA 2 800 1.000 800 1.000 100 
57 TABLE 7 
A CONDENSED TABLE OF RESULTS. 
Explanation—A stands for plain agar, DLA for dextrose-litmus-agar. All figures should he multiplied by 1,000. 
ICE CREAM SAMPLE : 
1 2 3 4 5 6 
Sample Medium Count % acid Count % acid Count % acid Count % acid Count % acid Count % acid 
A oin 2.150 270 8,850 850 4*0 
1 DLA 395 45 7.000 100 675 15 20,000 100 980 89 680 100 
a a 72t 1 900 285 6,480 685 l,i00 
‘2 DLA 1.150 39 6,650 100 450 75 19,500 100 375 90 3,900 95 
a ITn 2 150 ~ 175 11,500 725 840 
1 “i m 42 i'§88 100 ill 50 'if:S88 100 Sis 08 8$ 100 
B i DLA LOO » |1«00 75 2,700 82 26,000 100 1,050 51 1,210 100 
r ,1 a 415 11 8850 100 415 39 47.000 100 1.000 91 820 80 
3 DLt t()5 2 800 850 41,500 875 510 
4 DLA 340 44 siSoO 100 3,500 59 55.000 100 925 75 1,150 91 
1 onjo 1 800 140 6,500 1.025 370 
1 DLA 790 38 2.500 52 580 93 25.500 100 1.300 85 420 83 
a 745 1 250 425 7,000 1.050 3<5 
2 DLA 1,450 17 e‘,950 100 2,700 81 30,000 100 1.020 95 540 100 
a 870 2 700 170 9,100 875 
C 3 DLA 1,650 22 8,100 100 800 62 23,800 100 1,150 90 390 100 
\ 800 2 850 850 9,200 1,125 190 
4 DLA 1,850 62 sifiSO 75 2,000 50 37,500 100 1,450 86 315 100 
a a. 550 000 8,000 51 o 415 
5 DLA 770 26 100 750 88 22,500 100 825 85 650 95 
* 070 2 500 370 6,600 775 3o0 
6 DLA 1.430 49 100 775 93 17,900 100 1.325 90 850 100 
Sample A 1 and sample A 2 represent the amount liquefied ice cream from one-half pint in a sterile beaker. One cc was taken 
aS SCSampleasamplei^wer^taken with sterile teaspoons from the same place at the surface, after scraping a thin layer 
°ff’ Sample C All “C” samples were taken with sterile glass tubes by boring into the ice cream. 
1 was taken 2 inches below Surface. 
2 was taken 3 inches below surface. 
3 was taken about three-quarters down from surface. 
4 was the first boring from surface. 
5 and 6 were taken from the bottom. 
58 B AVERAGES: 
Sample Plain agar Dextrose-litmus-agar Per cent, acid colonies 
1 530,000 1,020,000 35 
2 2,510,000 7.140,000 92 
3 400,000 1,325,000 66 
4 14,250,000 29,810,000 100 
5 881,000 1,106,000 83 
6 579,000 989,000 95 
C AVERAGES ACCORDING TO PART OF GALLON SAMPLE WAS TAKEN. 
All figures to be multiplied by 1,000. 
ICE CREAM SAMPLE NUMBER : 
Sample Med. 1 2 3 4 5 6 Average Ratio 
Melted in beaker. A ' 468 2.025 277 ' 7,665 767 2,170 2,227 11 
DLA 773 6,825 563 19,750 927 2.290 5.188 26 
From surface. A 365 2,575 421 27,175 904 697 5,356 27 
DLA 684 7,250 1,791 40,750 994 1.030 8.750 44 
2 in. below surface. A 300 1,800 140 6,500 1,025 370 1.689 8 
DLA 790 2,500 580 25,500 1,300 420 5,682 28 
3 in. below surface. A 745 1,250 425 7,000 1,050 375 1.807 9 
DLA 1,450 6,950 2,700 30.000 1.020 540 7,110 35 
%th wavs down. A 870 2,700 170 ’ 9.100 875 ~ 290 2,334 12 
DLA 1,650 8,100 800 23,800 1,150 390 5,982 30 
Just below surface. A 800 2,850 850 9,200 1,125 190 2,502 12 
DLA 1,850 8,950 2,000 37,500 1,450 315 8,677 43 
From bottom. A 620 3,525 485 7,600 675 500 2,234 11 
tn DLA 1.100 7.750 762 21.100 1,100 675 5,277 26 
vc — —— TABLE 7A 
RELATION OF NUMBERS OF LACTIC ACID STREPTOCOCCI TO AMOUNT OF ACID PRODUCED 
UNDER DIFFERENT TEMPERATURE CONDITIONS. 
• Per cent, acid is expressed in lactic acid. All numbers should be multiplied by 1,000. 
Colony Count 
Per cent. Per cent. Lact. Remarks 
Kind of Milk Temp. Incub. period Plain agar Dext.-lit.-agar acid col. acid 
fresh 36 160 91 0.12 
1 day 238,000 359,000 100 0.59 Sour, curd and whey. 
2 272,000 432,000 100 0.63 Sour, curd and whey. 
Raw Milk 37° C 3 289,000 361,000 100 0.67 Sour, curd and whey. 
4 268,000 401,000 100 0.69 Sour, curd and whey. 
5 spreaders 1.24 Sour, curd and whey. 
6 138,000 160,000 100 1.52 Sour, curd and whey, 
fresh 36 160 94 0.12 
1 day 156,000 185,000 100 0.26 Turning. 
Raw Milk 21° C 2 252,000 270,000 100 0.54 Sour, curd and whey. 
3 480,000 820,000 100 0.68 Sour, curd and whey. 
4 350,000 <30,000 100 0.74 Sour, curd and whey. 
5 spreaders 0.76 Sour, curd and whey. 
6 117,000 195,000 49 0.78 Sour, curd and whey, 
fresh 36 160 94 0.12 
1 day 54 170 100 0.12 No change. 
2 55 256 100 0.12 No change. 
Raw Milk 7° C 3 150 190 100 0.12 No change. 
4 4,100 10.100 100 0.14 No change. 
5 6,500 7,400 100 0.15 No change. 
6 15,000 31,000 45 0.16 Bitter taste. 
7 22,000 29,000 47 0.20 Bitter taste. 
8 31.000 44,000 45 0.24 Very bitter. 
9 47,000 52,000 55 0.24 Very bitter, 
fresh 28 175 100 0.12 
1 day 485,000 1,285,000 100 0.71 Sour, homog. curd. 
2 595,000 1,300,000 100 0.73 Sour, homog. curd. 
3 44,000 65,000 22 1.02 Sour, thick. 
Raw Cream 37° C 4 54,000 68,000 21 1.18 Sour, very thick. 
5 ' spreaders 1.40 Sour, very thick. 
6 66,000 85,000 00 1.61 Sour, bitter, thick, 
fresh 28 175 1(H) 0 12 
1 day 55,000 156,000 100 0.26 Sweet, homogeneous. 
2 135,000 350.000 100 0.65 Sour, thick. 
3 210.000 390,000 85 0.67 Sour, thick. 
Raw Cream 21° C 4 270.000 380.000 SO 0.69 Sour, thick. 
5 250,000 410,000 75 0.67 Sour, thick. 
6 310.000 460,000 80 0.72 Sour, thick. 
60 fresh 28 175 100 0.12 
Idav 38 214 100 0.12 No change. 
2 290 1.050 100 0.12 No change. 
3 4100 7,300 71 0.13 No change. 
4 8,500 11,300 91 0.15 No change. 
Raw Cream 7° 0 5 20,500 29,000 100 0.16 No change. 
6 36,000 53,000 39 0.18 No change. 
7 29,000 31,000 100 0.26 No change. 
8 37,000 42,000 000 0.30 Turning. 
9 85,000 120,000 000 0454 Bitter. 
fresh 9 26 100 0.12 
1 day 199,200 220,000 100 0.51 Sour, curd. 
2 250,000 240.000 100 0.63 Sour, curd. 
3 213,000 317.000 100 0.66 Sour, curd. 
Sterile Milk 37° C 4 spreaders 0.69 Sour, curd. 
Sterne Milk 224,000 339,000 100 0.99 Sour, curd. 
6 219,900 433,100 100 1-28 Sour, curd. 
fresh 9 26 100 0.12 
1 day 162,000 202.000 100 0.39 Sour, light curd. 
2 288.000 353.000 100 0.52 Sour, curd. 
3 310,000 680,000 100 0.66 Sour, curd. 
Sterile Milk 21* C 4 380,000 M0.000 100 0.72 card. 
6 415,000 760,000 100 C176 Sour, curd. 
fresh 9 26 100 0.12 
1 day 1,700 2,500 100 0.16 No change. 
2 16,000 21.000 3 00 0.17 No change. 
3 19 000 32,000 100 0.18 No change. 
4 36,000 100 0.19 No change. 
Sterile Milk 7° C 5 32,000 59,000 100 0.20 No change. 
Steuie Milk 3g 000 43,000 100 0.20 No change. 
7 72,000 117,000 100 0.23 No change. 
8 78,000 160.000 100 027 No change. 
relation of numbers of lactic acid streptococci to amount of acid produced under different 
TEMPERATURE CONDITIONS. 
The numbers in the table include all bacteria in the samples of raw milk and raw cream, excepting under the column “acid 
colonies ” In sterlized milk the numbers are streptococci only. All flasks were inoculated with a pure culture of lactic streptococci. 
Counts were made immediately after inoculation and after that at intervals of 24 hours. One set of flasks was kept at 7 C., 
an0tTltrSaetions wLe ‘ ma^1 dlilyUwith^uloth0 N.NaOH to determine the degree of acid developed. The results are expressed in 
per cent. LACTIC ACID, 
61 Table 7a shows a relation of acid colonies to total 
numbers. In a general way it can be stated that the 
higher the total count, the higher the proportion of acid 
formers. The highest count in sample 4 of 29,810,000 
bacteria per cc. all the colonies appeared to be acid col- 
onies. No doubt there were some others, but the acid 
formation by the large number of acid forming bacteria 
was so great that other bacteria could not counteract the 
influence. No doubt, if a much larger number of samples 
could have been examined the figures would be smoother 
and clearer. This also applies to table 7. Here all sam- 
ples were averaged according’ to the part of the original 
of ice cream the sample was taken from. In the last 
column a ratio was computed, which brings all the figures 
into a simple relation. This ratio indicated that samples 
B1 to 4 contained the largest numbers of bacteria. These 
samples were from the surface. Next in number are the 
samples taken one inch from the surface (C 4). Next 
in line is the number taken three-quarters way down. 
Why this should be high I have no explanation to offer. 
Larger numbers of samples would, no doubt, clear up 
such points. There is also the fact that the most expen- 
sive ice cream had small numbers, although some of the 
cheaper ones were low. In fact sample 6, which cost 
$1.25, was the lowest. 
The counts on dextrose-litmus-agar were always much 
higher than on plain agar. 
Report On Tests of the Relation of Lactic Acid Produced by Strep 
tococcus Lacticus to Numbers of Bacteria and the Relation of 
Numbers of Bacteria to Taste and Appearance. 
Nine flasks (1 liter Erlenmeyer) were sterilized. Into 
three flasks were placed 400 cc. certified raw milk, into 
three 400 cc. certified raw cream, and into the last three 
400 cc. certified milk were placed and these last three 
sterilized in the autoclave for fifteen minutes at two at- 
mospheres pressure. All flasks were inoculated with dex- 
62 trose broth cultures of a strain of Streptococcus lacticus. 
This streptococcus was isolated for this work from ice 
cream. This fact must be borne in mind as it may have 
influenced the results to some extent. Immediately after 
inoculation plates were prepared in plain agar and in 
dextrose-litmus-agar in dilutions of 1:1000 to determine 
the number of streptococci inoculated. The incubation 
temperatures were 37° C., 21° C. and 7° C. One flask 
with raw milk, one with raw cream and one with sterilized 
milk placed at each of the three temperatures. Daily 
tests were made as follows: 
1. The taste and appearance. 
2. The acidity was determined by titrating 5 cc. of the 
inoculated milk or cream, diluted to 50 cc. with distilled 
water, against one-twentieth normal sodium hydrate so- 
lution. The degree of acidity was then calculated in per 
cent, lactic acid. 
3. Plates in duplicates were made in plain agar, and 
dextrose-litmus-agar the same as with the ice cream ex- 
cepting that dilutions had to be carried to 1:10.000.000. 
Six counts were made of these plates after forty-eight 
hours. 
It should be stated here that the colonies formed by 
this particular strain of Str. lacticus were exceptionally 
small, so that the agar plates showed a relatively low 
count and undoubtedly the counts on dextrose-litmus-agar 
were frequently not as high as they should be. Here also 
the counts averaged much higher in dextrose-litmus-agar 
than on plain agar. 
Table 7a (See pages 60-61), shows the results in detail. 
The figures represent the averages of the duplicate 
plates, the percentage of acid colonies and the percen- 
tage of acid expressed in lactic acid. 
At 37° acid formed so rapidly that in twenty-four hours 
the cream and milk in all cases was curdled. The curd 
in the sterile milk was smooth and homogeneous, in the 
63 raw milk and cream there was considerable whey. The 
raw milk at 21° was beginning to show signs of turning 
after twenty-four hours and contained 185 million bac- 
teria in DLA. The raw cream was still sweet after 
twenty-four hours, but had curdled after forty-eight 
hours. It was sweet in spite of the 156 million bacteria 
after twenty-four hours. The sterile milk was curdled 
after forty-eight hours. After twenty-four hours it was 
turning with indications of curd formation (small flakes), 
and contained 202 million of bacteria. At 7% the sour- 
ing process and curdling were slow. In the raw milk 
there was no decided acid taste after nine days, and the 
bacteria numbered 52 million. A bitter taste had de- 
veloped. In the raw cream after eight days it seemed 
to be turning, although the taste was rather bitter than 
sour. After nine days the taste was decidedly bitter 
and the bacteria numbered 120 millions. In the steri- 
lized milk the taste was not decidedly sour, and there 
were no indications of curdling after eight days in spite 
of 160 millions acid forming bacteria. 
To make the results of this more striking I have plotted 
the results in curves in tables 9, a, h and c, and in 10, a, 
and c. Here also I feel that the curves would be smoother 
and better if a large series of tests were made and with 
different strains of lactic streptococci. 
Table 9a—(See page 66.) Raw milk at 37°. The 
numbers of bacteria are highest after two days, after 
which there is a falling off. The acidity, however, con- 
tinues to rise. Several explanations are possible for 
this. Acid is produced by an enzym, and therefore, will 
continue even after the bacteria have been removed or 
decrease. Thirty-seven degrees is a temperature at 
which such enzyms act more powerfully and more rap- 
idly than at lower temperatures. There is the other 
explanation which accounts for acid formation in the 
apparent absence of bacteria. Streptococcus lacticus 
64 multiplies only to a certain point. The so-called high 
acid forming bacilli then produce more lactic acid, but 
these bacteria cannot he demonstrated on ordinary 
media. It is also possible that this particular strain of 
Str. lacticus dies sooner than some other strains. In 
raw milk at 21° the curves are similar to those at 37°, 
the numbers are higher, but the acidity is lower. High 
acid formers multiply but slowly at this temperature, 
so that the acid naturally would be less and enzyms also 
act slower. At 7° the curves are low and practically 
parallel. (See page 67.) 
Table 9h—The sudden rise in numbers of bacteria in 
cream at 37° is enormous. The curves at 21° are even, 
and at 7° low. At 21° the numbers and the amount of 
acid are nearly parallel. (Seepage 67.) 
Table 9c—At 7° the respective curves remain par- 
allel. There is no great divergence at either 21° or at 
37°. As we are dealing here with pure cultures of the 
streptococcus, no complicating factors arise through the 
presence of other bacteria. 
Table 10a. (See page 69.)—This table shows the 
relative curves of the three KINDS of flasks at the 
same temperature. Cream has the greatest number of 
bacteria, milk next and sterile milk the smallest. The acid 
formation is highest in milk, next in cream and small- 
est in sterile milk. 
Table 10&. (See page 70.)—The acid curves in all 
three kinds are very consistent. In raw milk there is 
a decided drop in numbers, in the cream the numbers 
are relatively small, but are in good accord with the 
acid formation in the sterile milk. 
Table 10c. (See page 71.)—The curves are low and 
smooth. 
65 TABLE 9A 
66 TABLE 9b 
67 TABLE 9c 
68 TABLE IOA 
69 TABLE 108 
70 TABLE lOC 
71 Reports Concerning the Sig- 
nificance of Bacterial Counts 
and Bacillus Coli Tests 
H. D. PEASE, M. D. REPORTS OF BACTERIOLOGICAL INVESTIGATIONS 
CONCERNING THE SIGNIFICANCE OF BACTE- 
RIAL COUNTS AND BACILLUS COLI TESTS 
OF INDIVIDUAL LOTS OF MARKET ICE 
CREAM, REFERRED TO AND PRE- 
SENTED IN PART AT THE HEARING. 
H. I). Pease, M. D. 
Report in the matter of the examination of samples of 
vanilla and chocolate ice cream purchased from a Com- 
mercial Ice Cream Company, New York City, October 
22,1913, and of one sample of Commercial strawberry ice 
cream, purchased January 31, 1914. 
Technique. 
Source of Sample. A one gallon can of Vanilla Ice 
Cream made by a Commercial Ice Cream Company and 
marked October 22nd, was delivered by them to the Lederle 
Laboratories. 
Method of Taking Samples. Sterile teaspoons were 
used in digging out the samples and transferring them 
to sterile 2-oz. and 4-oz. glass stoppered bottles. • 
Twenty-five to 30 gram samples were taken except in 
the case of Experiment No. 4. The sample bottles were 
chilled in ice and salt previous to the taking of the sam- 
ples. Immediately after taking each sample the bottle 
was covered with ice and salt so that the ice cream re- 
mained frozen until the individual sample was removed 
from the ice and salt for examination. 
Method of Melting Sample Before Examination. A 
water bath held at 30° C. was used for this purpose. 
As soon as the sample was melted it was shaken and 
allowed to rest for one minute before sampling unless 
otherwise stated. 
Media. 9 liters of Standard Beef Extract Agar were 
made at one time. Previous to sterilization in the auto- 
clave for* 15 minutes at 20 lbs. pressure the agar was 
73 divided among 36 8-oz. flasks. All plates in this series of 
experiments were poured from this lot of agar. 
Dilution Bottles and Water. The bottles used were 
4-oz. Philadelphia ovals filled by automatic burettes to 
contain 99 c.c. of water after sterilization, in the auto- 
clave, 25 minutes at 20 lbs. pressure, and 1-oz. Phila- 
delphia ovals filled in the same manner to contain 9 c.c. 
of water after the same process of sterilization. The 
dilution water used contained in all cases 0.5% commer- 
cial sodium chloride. 
Pipettes. The 1 c.c. pipettes were in all cases straight 
sided pipettes of even bore and a uniform blunt point. 
The capacity pipettes were graduated by one mark to 
contain 1 c.c. of water. The volumetric pipettes were 
graduated by one mark to deliver 1 c.c. of water. 
In reading the amount of liquid in the pipette, care was 
taken that the end of the pipette rested on the side of the 
bottle above the sample or dilution in order not to carry 
over an extra drop of the sample or dilution. 
Petri Dishes. 10 x 1 y2 c.m. sterilized by dry heat at 
180° C. for 1y2 hours were used for all bacterial counts. 
Method of Making Dilutions and Plating. In each case 
unless otherwise stated the sample of ice cream was 
measured by a 1 c.c. capacity pipette and the pipette 
washed out in the dilution water. 
The method of dilution was as follows: 
1 c.c. of sample to 99 c.c. dilution bottle = 1:100 
1 c.c. of 1:100 to 9 c.c. dilution bottle = 1:1000 
1 c.c. of 1:100 to 99 c.c. dilution bottle = 1 .-10000 
1 c.c. of 1:10000 to 9 c.c. dilution bottle = 1:100000 
1 c.c. of 1:10000 to 99 c.c. dilution bottle = 1 rIOOOOOO 
Transfers for higher dilutions were made before 1 c.c. 
was transferred to the petri dish. 
Litmus Lactose Agar Plates. 1 c.c. of a 10% solution 
of lactose and y2 c.c. of a 1% solution of azolitmin were 
74 added to eacli plate before inoculation with 1 c.c. of the 
diluted sample. 
Test for Bacteria of the B. coli Type. Durham fer- 
mentation tubes were used. The outside tube was 6" x 
the inside tube 3" x %". The lactose-peptone-bile 
was made by adding 1% lactose and 1% peptone to fresh 
ox-bile which had been previously boiled and filtered. 
Twelve hundred fermentation tubes were prepared at 
one time from one lot of bile. Inoculated tubes were in- 
cubated 72 hours at 37° C. At the end of each 24-hour 
period the percentage of gas was recorded. From the 
two highest dilutions showing gas at the end of 48 hours, 
litmus-lactose-agar plates were made by transferring one 
3 mm. loopful to a 9 c.c. dilution bottle and one 3 mm. 
loopful from this dilution to a plate containing lactose 
and azolitmin as described above. 
After 24 hours at 37° C. isolations of characteristic col- 
onies were made on lactose agar slants. After 24 hours 
at 37° C. the growth on the slants were used for the inoc- 
ulation of tubes containing Durham’s peptone solution 
and nitrate solution. A stab culture was made in the 
lactose agar slant and in a tube of infusion gelatine. The 
inoculated peptone solution, nitrate solution and lactose 
agar stab were incubated 4 days at 37° C. 
The peptone solution was tested for the presence of 
indol by the addition of y2 c.c. of a paradimethylamido- 
benzaldehyde solution. 
The nitrate solution was tested for the presence of 
nitrites by the addition of y2 c.c. of a sulphanilic acid 
solution and y2 c.c. of a naphthylamene acetate solution. 
The presence of gas in the lactose agar stab was also 
noted as a control on the isolation. 
The gelatine stabs were incubated 10 days at 20° C. and 
the presence of liquefaction noted. 
Bacterial Counts. All plates were counted as far as 
possible. In reporting the bacterial counts averages were 
75 made in cases where the bacterial counts exceed 20 and 
less than 500 colonies to the plate. The number reported 
was not in accordance with the standard method of re- 
porting bacterial milk counts. 
Outline of Experiments. 
Experiment No. 1. Test of same location (see results 
reported under A, B, C, D, E and F). 
Six samples were taken from as near the same location 
as possible at a point about 3 inches below the top and at 
the middle of the can. 
Experiment No. 2. Test of separate location. 
Six samples reported under Gr, H, I, J, K, L, were 
taken as follows: 
Gr—top-side. 
I—center-side. 
K—bottom-side. 
H—top-middle. 
J—center-middle. 
L—bottom-middle 
Experiment No. 3. Test of triplicate dilutions made 
from same sample. 
The samples taken under Experiment No. 1 were di- 
luted in triplicate and are reported under At A 2 A3— 
Fx F2 F3. 
Experiment No. 4. Test of the evenness of melting. 
Six samples of about 70 c.c. were taken in 4-oz. chemical 
salt mouth bottles from the side of the can from top to 
bottom. Each sample was allowed to melt at room tem- 
perature (74° F.) for two minutes and the melted portion 
sampled with a 1 c.c. capacity pipette. These results are 
reported under M, N, 0, P, Q, R. 
Experiment No. 5. Test of method of measuring sam- 
ple for dilution. 
Six samples were taken from the same locality at a 
point immediately surrounding the place where the six 
samples were taken for Experiment No. 1. 
76 VANILLA ICE CREAM.—EXPERIMENT NO, 1 AND NO. 3 COMBINED. 
Six samples (A, B, C, D, E, F) taken from the same location ; about three inches from the top and middle of the can. 
Multiply results (except B. coli) by 1,000. 
Colony Count 37°—2 days ~~ — 
Sample Total Utmus-Uctos^rgAcU JS SK'mf'S t?c. Lac. 
D-utma 2j 72 US HR Indoi K.tcate G(.a..ne 
X.S B - S8 S J | | | ♦ = = , , 
10.000 Tr. Tr. 2 — 
» r- 
10.000 — 20 20 + — = I _ 
B2 10,000 2,450 F350 iTlSO 170 st~4 h arid ~~'TTht 2 
1,0®0000 l.ooo 1-300 400 76:4 3:o§0 1.000 Tr. IS |g 
10.000 — 20 25 + _ _ + 
B3 10,000 spreader 1,100 990 90 oq grTo o 700 rfF T-‘ -4 — — 
100.000 1,400 600 500 100 “ 865 9800 1 nun ™r‘ 15 15 
1.000. 4.000 2)800 1-000 Tr- 15 15 + _ _ + _ 
10,000 — 15 15 + + _ 
Cl 10,000 2,360 E110 740 340 %i cfTfi .7 -7, a -I00-’000 — — : 
i.3KS ffl 1'200 800 400 6e:e ®,1.00? S: i_S 18 : A = t - 
—f—?o- 
1.000. 1,000 b0-b 4’000 l-°°° Tr- 15 20 + _ _ + = 
10,000 — 15 20 — 
C3 10,000 2,430 810 720 80~ T7) cc q 9 tah 1 r\n —m 
100.000 2,100 800 500 300 63 3 2 200 1 non mr* 
1.000. 5,000 63'3 -200 00 Tr. 10 10 + _ _ + _ 
100,000 — _■ + — “ + - 
78 D1 10 000 3 240 1 080 1.020 50 10 94.4 3,000 100 Tr. 20 20 _ _ 
100.000 1,700 1,800 1,400 400 87.5 2,600 1,000 Tr. 25 30 + — + 
1.000. 2.000 100000 — RR + + ~’ + _ 
Do 10000 1480 610 510 90 10 83.6“ 100 Tr. 20 20 + — — + — 
IQO’,000 3’,200 800 600 200 66.6 3,300 1-000 Tr' 20 I? + + + + 
1.000. 100:000 r jo lo 
D3 10700 1J00 770 7690 60 20 89.6 2,600 100 Tr. 50 50 _ _ _ 
100.000 1,800 1,300 1,300 100.0 2,900 1-000 J in in t 
1.000. 10,000 JU J.U + — _ 
100.000 — — — _ 
FI Toooo •• OSO 540 460 70 10 “ 85.1 3,000 100 Tr. 20 20 + — 3 + 3 
100!000 liS00 1,100 800 300 72.8 2,900 1,000 Tr' 20 30 + — - t 
1.000. 2.000 108:800 - - Tr. 
F9 1 n nod 1 osa 700 720 70 91.1 2,600 100 Tr. 20 20 
looiooo l’,600 1,000 700 300 70.0 3,000 1,000 Tr. 40 50 + + — _ 
1.000. 3.000 10,000 lr. w + - - + _ 
100.000 — — — .... 
E3 ToltOO 1,070 750 620 130 82.6 2,800 100 Tr. 30 30 _ _ Z 
100.000 1.600 800 600 200 75.0 3.400 1,000 Tr. -0 + _ _ ± = 
1.000. 1,000 loo.ooo — “ 7 
FI 10 000 0070 750 700 50 93.3 2,700 lOlT”" “frT 20 30 
1 nRR’oRo J’90° 500 400 100 800 3’000 10.000 — 20 20 + - - + - 
1.000. 100,000 — Tr. 15 + + 77- + — 
F9 fo 000 l 380 510 410 90 10 80.4 2,700 100 Tr. 30 30 
100!000 2.200 500 400 100 80.0 2,900 i A’ooo Tr 50 60 + — — + 
1.000. 4.000 100,000 —’ — — 7 
10 000 T300 680 590 80 10 86.7 2~200 TOO Tr. ‘ 20 25 
100.000 900 400 200 200 50.0 3,000 1.000 Tr. 20 25 _ j 
1.000. 2.000 10-000 Tr- 50 75 17 — + — 
100.000 — — — 
79 Each of the six samples was examined in the follow- 
ing way: 
1. One gram of frozen cream weighed and 99 c.c. of 
water added. 
2. One c.c. of liquid not containing air bubbles re- 
moved with 1 c.c. capacity pipette. 
3. One c.c. of liquid not containing air bubbles re- 
moved with 1 c.c. volumetric pipette. 
4. One c.c. of liquid containing air bubbles removed 
with 1 c.c. capacity pipette. 
5. One c.c. of liquid containing air bubbles removed 
with 1 c.c. volumetric pipette. 
These results are reported under Si S2 S3 S4 Ss— 
X 2 X 3 X 4 X 5. 
80 VANILLA ICE CREAM.—EXPERIMENT NO. 2. 
Multiply results (except B. coli) by 1,000. 
a 
o,2 
So Colony Count 37°—2 days 
•g § Colony Gas Production Lit. 
Litmus-lactose-agar % Acid Count Lac. Pep. Bile Lac. Lac. 
Sample Total Colony 20°-5 da. Agar Agar 
Q°No. Dilution B.E.Agar_L.L.Agar Acid Inert Altai. Count B.E.Agar Dilution 24 48 72 Plate Stab. Indol Nitrate Gelatine 
10.000 1,700 650 580 70 “ 89.2 2,600 100 Tr. 10 10 
g-S 100,000 1,300 1,100 800 300 72.7 2,800 1,000 Tr. 10 10 + — — + = 
Ha 1,000,000 2,000 10,000 — Tr. 2 + — — + — 
100,000 — — — 
10.000 1,690 700 640 40 20 91.4 2,700 100 Tr. 20 20 
nS 100,000 1,100 400 300 100 75. 3,400 1,000 — 10 10 
22 10,000 — 40 50 + — = t = 
S 1,000,000 2,000 + 
100,000 — Tr. 25 + No growth 
£ a>I 10,000 1,910 Alkaline spreader 2,400 100 Tr. 30 40 + — + + — 
100.000 1,900 600 500 100 83.3 2,500 1,000 Tr. 20 20 + — — + — 
1,000.000 10,000 — — — 
u 100,000 — — — 
10.000 2,000 800 680 120 ~ 85. 2,500 100 Tr. 30 50 
gS 100,000 1,100 1,200 1,000 200 83.3 2,400 1,000 Tr. 40 50 + + + + = 
1.000. 4,000 10,000 — 20 25 + — — + — 
os - 100,000 — — — 
a K 10,000 1,530 880 770 100 10 . 85.5 2,600 100 Tr. 30 40 
100.000 700 600 500 100 83.3 2,300 1,000 Tr. 15 15 + + ? + — 
1.000. 6,000 10,000 — 10 10 + — — + — 
2 100,000 — — — 
a ajL 10,000 3,280 2,240 1,890 340 10 84.3 2,600 ~ 100 Tr. 20 20~ 
oS 100,000 2,600 1,800 1,400 400 77.7 2,300 1,000 Tr. 30 30 — 
£■3 1,000,000 14 con- 10,000 — — — 
®g tarn.? 100,000 — 10 15 + + — + — 
82 VANILLA ICE CREAM.—EXPERIMENT NO. 4. 
Six samples of about 70cc taken from the side of the can from top to bottom. 
Multiply results (except B. coli) by 1,000. 
Colony Count 37°—2 days „ , .. T.. 
Colony Gas Production Lit. 
Litmus-lactose-agar % Acid Count Lac. Pep. Bile Lac. Lac. 
Samnle Potal Colony 20°-5 da. Agar Agar 
No. Dilution B.E.Agar L.L.Agar Acid Inert Alkal. Count B.E.Agar Dilution 24 48 72 Plate Stab. Tndol Nitrate Gelatine 
M 10,00) 2,620 2,370 L920 440 10 81.0 2,320 100 Tr. 15 15 + J-_ = t 
100.000 2,400 2,200 2.000 200 90.9 1,900 1,000 Tr. 10 10 — 
1.000. 4,000 100000 — — — 
N 107000 L890 17560 L290 260 10 8277 1,700 100 Tr. 20 20 
100.000 1.400 2,000 1,600 400 80. 1,000 1,000 Tr. 5 10 + — + — 
1.000. 3.000 100 000 — 20 30 + — — + - 
O 10,000 4,070 1,200 est. alkaline spreader 100 Tr. 20 15 _ . 
100.000 3,100 1,800 1,400 400 77.7 2,900 1,000 lr- i- + t — t 
1.000. 3,000 10.000 — 10 lo — 
P i77000 27160 1,470 1,360 100 10 9273 5 30 30 . _ 
100.000 900 1,400 1,300 100 92.8 2,400 1,000 5 30 40 + t _ t 
1.000. 1,000 100000 — + t = 1 
Q io 000 27)20 27610 1,720 270 20 8515 100 Tr. 20 25 
100.000 3.100 500 500 100. 1,200 1,000 Tr. 20 20 + + — + — 
i nnn noo 2 000 10,000 — 20 25 —• — — + 
1.000. 2,uuu 100.000 — 10 30 + — — + = 
P UTOOO 2 050 1 940 1,560 380 80.4 27000 100 Tr. 30 30 
' 100!000 l’,500 13,200 12,000 1,200 90.9 1,100 1.000 Tr. 30 30 + 
1.000. 2.000 100000 — 40 50 + — — + — 
83 CHART NO. 1. 
Plot of the 20° C. and 37° C. beef extract agar bacterial counts of 
Vanilla Ice Cream samples, made from the 1-10,000 dilutions ; and of the 
means of these counts. 
SAMPLES 
84 VANILLA ICE CREAM.—EXPERIMENT NO. 5. 
Six samples (S, T, U, V, W, X) taken from the same locality at a point adjacent to the place where the six samples for Exp. No. 1 were taken, 
3 inches from top near the middle of the can. 
Multiply results (except B. coll) by 1,000. 
Colony Count 37°—2 days 
Colony Gas Production Lit. 
Litmus-lactose-agar % Acid Count Lac. Pep. Bile Lac. Lac. 
Sample Total Colony 20°-5 da. Agar Agar 
No. Dilution B.E.Agar L.L.Agar Acid Inert Alkal. Count B.E.Agar Dilution 24 48 72 Plate Stab. Indol Nitrate Gelatine 
51 10,000 2,770 1,610? 880? 730yalk.spd7 5476 2,300 100 Tr. 10 10 
100.000 2,100 2,300 1,800 400 100 78.1 2,900 1,000 Tr. 10 10 + = = t = 
1.000. 2,000 10,000 — 10 10 + + 4- + — 
100,000 — — — 
52 10,000 3,460 2.640 2,220 400 20 84.0 2,600 100 Tr. 10 10 
100.000 2,100 1.300 900 400 69.2 3,500 1,000 — 5 5 
1.000. 8,000 10,000 — 2 2 + — — + — 
100.000 — Tr. 25 + + = t = 
53 10,000 2,130 spdr. 1,460 760 700 52+) 3,100 100 Tr. 20 20 + — — + 
100.000 2,700 1,800 1,200 500 100 66.6 2,700 1,000 — 10 10 + — — + = 
1.000. 3,000 10,000 — — — 
100,000 — — — 
54 10,000 2.920 2,250 1,700 540 10 75.5 3,000 100 2 40 50 
100.000 2,600 1,400 1,000 400 71.4 2,400 1,000 — 10 10 + — — + — 
1.000. 10,000 — Tr. 2 — 
\ 100,000 — — — _ 
55 10,000 2,280 2,000 cst. alkaline spreader 2,100 100 10 30 40 
100.000 2,200 2,400 1.600 800 66.6 2,400 1,000 Tr. 20 20 + — — + — 
1.000. 4.000 10.000 — Tr. 2 — 
100,000 
T1 10,000 3,000 2,600 2,000 530 70 76.9 2,500 100 10 30 40 
100.000 2,700 1,600 1,200 400 75.0 2,700 1.000 Tr. 40 50 + + — + — 
1.000. 6.000 10,000 — Tr. 2 + — — + — 
100.000 — — — 
T2 10,000 2,570 2,770 1.950 780 40 70.3 2,200 100 2 30 ~ 40 
100.000 3,300 1,600 1,200 400 75.0 3.500 1,000 Tr. 20 30 
1.000. 5,000 10,000 — 20 30 
100,000 — 10 10 + — — + — 
T3 10,000 2,480 2,180 1.560 600 20 87.9 2,100 100 Tr. 10 20 
100.000 3.300 2,500 1,900 500 100 76.0 4,000 1.000 Tr, 10 20 + — — + — 
1.000. 10.000 10,000 — 10 15 — 
___ 100,000 — — — 
T4 10,000 3,460 3,200 est. 2,800 est. 400 est.alk.spdr. 87.5? 2,200 100 5 20 30 + + + + — 
over y2 plate 
100.000 3.600 2,800 2,200 600 78.5 3,100 1.000 Tr. 10 15 + — — + + 
1.000. 6,000 10,000 — — Tr. 
100,000 — — — 
T5 10,000 3,590 1,200 est. 1,200 est. alk spdr. 100.? 2,600 100 30 50 60 
100.000 3,500 2,400 1,800 600 75.0 3,000 1,000 Tr. 30 60 + + + + — 
1.000. 10,000 10,000 — 40 60 + — — + — 
100,000 — — — 
86 U1 10,000 2,910 2,170 1,620 530 20 74.6 2,400 100 2 30 30 
100.000 2,300 2,900 2,400 500 82.7 3,500 1,000 2 80 90 + + — + — 
1.000. 5,000 10,000 — 30 30 + — — + — 
100,000 — — — 
U2 10,000 2,780 alk. spreader - 2,750 100 5 30 30 
100.000 2,700 1,500 800 700 53.3 3,500 1,000 Tr. 10 10 
1.000. 1,000 10,000 Tr. 25 30 + — — + — 
100,000 — Tr. 10 — 
U3 10,000 2,430 2,000 est. 2,000 est. alk. spdr! 100. T 1,600 100 Tr. ' 30 50 
100.000 3,400 1,600 1,000 600 47.0 2,400 1,000 Tr. 20 30 
1.000. 6,000 10,000 — 20 30 + — — + — 
100.000 Tr. Tr. — 
U4 10.000 3,580 2,800 est. 2,200 est. 600 est.alk.spd. 71.4? 2,800 100 Tr. 10 15 
100.000 2,800 2,400 2,200 200 91.6 3,800 1,000 Tr. 10 15 + + — + — 
1.000. 2,000 10,000 — Tr. 2 + — — + — 
loo.ooo _ _ 
U5 10,000 2,620 2,470 1.910 550 10 77.3 2,100 100 10 30 40 
100.000 2,100 2,400 1,800 600 75.0 2,500 1,000 Tr. 10 15 4- — — + _ 
1.000. 1,000 10,000 — 5 10 + = = + — 
100,000 — — — 
VI 10,000 2,380 1,640 1,060 580 2,000 100 2 40 50~ 
100.000 2,800 1,500 900 600 60.0 2,400 1,000 Tr. 30 40 + = t t = 
1.000. 2,000 10,000 Tr. 40 50 + — — + — 
100,000 — — — 
V2 10,000 3,440 1,990 1,390 560 40 69.7 3,600 100 Tr. 20 20 
100.000 4,800 2,600 1,600 1,000 61.5 5,000 1,000 Tr. 10 10 
1.000. 8,000 10,000 — 30 30 — 
100.000 — 5 15 
V3 1 0.000 3,05 0 3,030 1,560 460 1 0 51.4 3,500 100 Tr. 50 ‘ 60 
100.000 3,500 1,300 1,000 300 76.9 3,000 1,000 Tr. 20 20 + — — + — 
1.000. 2,000 10,000 — 10 10 + — — + — 
100.000 — — — 
V4 10,000 2,880 1.770 1,270 480 20 71.7 2,400 “TOO Tr! 30 30 ~ 
100.000 2,400 1,600 1,200 400 75.0 3,000 1.000 Tr. 40 50 
1.000. 1,000 10,000 Tr. 20 20 — 
100,000 — 10 20 — 
V5 10,000 2,380 1,790 1,130 660 63.1 2,200 100 2 30 30 ~~ 
100.000 2,000 1,000 600 400 60.0 2,000 1,000 — 10 10 + — — + — 
1.000. 2,000 10,000 — 10 15 + — — + — 
100,000 — — — 
87 VANILLA ICE CREAM.—EXPERIMENT NO. 5.—(Continued) 
Colony Count 37°—2 days ' ~ —— 
T.. , . Colony Gas Production Lit. 
Sample . . Total Litmus-lactose-agar % Acid g Count Lac. Pep. Bile Lac Lac. 
nnn B r L,,L'ogar Acid Inert —lkaL Count B-E.Agar Dilution 24 48 72 pfate Stab. Indol Nitrate Gelatine 
100 000 2’670 o° 1,170 68.4 2.100 100 Tr7 20 20 7 
1 000 000 1 000 100 100 400 1-CK)0 Tr- 40 50 + — — + _ 
1.000. I.uoo 10,000 — 30 30 
— — 100,000 — — — 
4{M>6° 3,180 2,430 1,720 650 60 7027 2 750 100 * oL “Sn — 
1000 OOO 2'800 1'500 1'000 500 «*« WOO 1,000 Tr. 
1.000. 10,000 — — 
W3 10,000 2,660 1,950 1.420 520 10 72 8 3 000 Ven tv on —— 
.,5S l.a 1-9°° 1-4°° 600 ® jl.000 50 M + + - + - 
W4 10.000 2,690 2,360 1.720 620 20 3 200 ~~inn TV I?! = 
1 000 000 I’OOO 3,500 n° litmus in plate 2,’SOO 1,000 Tr! 15 20 + = = % 
1.000. 2,000 10,000 Tr. 40 40 + — — + _ 
8§ W5 10,000 3,730 3,180 2,190 950 40 3 200 T78 
i ooo’ooo I'oon 8,500 2,700 700 100 77,1 4'000 1.000 Tr. 10 15 
1.000. 7.000 10,000 — 30 30 + — — + _ 
— — . 100,000 — 5 10 — 
XI 10,000 2,910 2,300 1,550 740 10 67 3 2 60?) Too 6 7n a7\ 
1 000000 3000 1,700 1,200 400 100 70'5 2’000 1.000 Tr‘ 20 20 + = - * _ 
1.000. 3.000 10,000 Tr. 60 60 
— 100.000 — — — 
X2 B 2>740 2,320 1,760 510 10 75.8 2 600 100 5 20 20 
1000-000 la 4-3°° 3-800 600 38:3 ® 1.M0 Tr. f§ fo + - _ + _ 
1.000. 2,000 10.000 Tr. 15 20 + — — I _ 
— — . 100,000 — — _ 
X3 10.000 2,820 2,730 2,090 590 500 76l> 2600 Tnn tv nn nn — 
I 000M0 130°000° 2-9°° 2000 900 S2° 1.000 Trr: IS ■+ _ _ + _ 
1.000. 1.000 10,000 Tr. 70 80 + + — I _ 
— —— 100,000 — — 
X4 10,000 2,230 3,050 2,040 1,000 10 66.8 2 400 inn TV in 4n —— — 
1 000000 2000 3,100 2,00° 1,100 64,5 3,000 1’000 Tr' 20 20 + — — _ _ 
1.000. 2,000 10,000 — 10 15 I = — ♦ — 
— 100,000 — — Tr. 
X5 3,000 2,690 2,070 600 ~20 76.8 mo Tr 20 on —— 
looo'ooo i’000 1,600 1,200 400 75 0 2.800 1,000 -• 20 IS + + _ + _ 
1.000. 3.000 10,000 — 10 15 + — _ I 
— 100,000 — _ — + — SAMPLES 
Plot of the 20° C. and 37° C. beef extract agar bacterial counts of Vanilla 
lee Cream samples, made from the 1-100,000 dilutions; and of the means of 
these counts. 
CHART NO. 2. 
89 SAMPLES 
Plot of the 37° C. litmus lactose agar total and acid forming bacterial counts 
of Vanilla Ice Cream samples, made from the 1-10.000 dilutions ; and of the 
means of these counts. 
CHART NO. 3. 
90 SAMPLES 
CHART NO. 4. 
Plot of the 20° C. beef extract agar bacterial counts of Vanilla Ice Cream 
samples, made from the 1-10,000 and 1-100,000 dilutions of same samples ; and 
of the means of these counts. 
91 CHART NO. 5. 
SAMPLES 
Plot of the 37 C. beef extract agar bacterial counts of Vanilla Ice Cream 
samples made from 1-10,000 and 1-100.000 dilutions of the same samples; 
and of the means of these counts. 
92 SAMPLES 
Plot of the 20° C. beef extract agar counts of Vanilla Ice Cream samples 
made from the 1-10,000 dilutions. 
Samples A to F—Tests made in triplicate by the same method. 
Samples S to X, inclusive—Tests made by different methods of sampling. 
CHART NO. 6. 
93 Key to Plot of Samples. 
Heavy solid line—Plot of Sample examined by Method 
No. 1. 
Light solid line—Plot of Sample examined by Method 
No. 2. 
Dotted line—Plot of Sample examined by Method No. 3. 
Dash line—Plot of Sample examined by Method No. 4. 
Dash and dot line—Plot of Sample examined by Method 
No. 5. 
Method No. 1. One gram of frozen cream weighed out 
and 99 c.c. water added. 
Method No. 2. One c.c. melted ice cream not contain- 
ing air bubbles removed with 1 c.c. capacity pipette. 
Method No. 3. One c.c. melted ice cream not contain- 
ing air bubbles removed with 1 c.c. volumetric pipette. 
Method No. 4. One c.c. melted ice cream containing 
air bubbles removed with 1 c.c. capacity pipette. 
Method No. 5. One c.c. melted ice cream containing 
air bubbles, removed with 1 c.c. volumetric pipette. 
Samples A, B, C, D, E, F, S, T, U, V, W, X all removed 
from same immediate location. 
Comments on Results of Tests as Shown by Charts 1 to 6 (Inclusive). 
Vanilla Ice Cream. 
CHART XO. 1. 
1. The results of the tests on samples Ato F (inclu- 
sive), obtained from one portion of the can, as given for 
the 1 to 10,000 dilution at either of the two temperatures, 
show marked numerical differences, notwithstanding that 
these results are the averages of triplicate tests on each 
sample. The results of any individual test are not har- 
monious with the results of any of the others, as is shown 
for the 20° C. tests under Ato F (inclusive) in Chart 
No. 6. 
2. The results on these six samples at 37 °C. showed 
94 much greater variations than did those obtained from the 
20° C. tests. 
3. The variations in the results on these six samples 
from the one location, at 20° C., as already noted, were 
greater than those in the results of the tests of the follow- 
ing six samples, Gr to L (inclusive), obtained from various 
portions of the can contents, when tested at the same tem- 
perature ; but the reverse is true of the results of the tests 
at 37° C. 
4. In the tests of samples M to R (inclusive), made 
for the purpose of determining evenness of melting, there 
occurred the most extreme differences to be noted in any 
of the comparisons of results on this chart. While a gen- 
eral parallelism between the 20° C. and 37° C. counts was 
to be noted, the results of the tests made at the latter tem- 
perature were almost invariably higher than the former. 
This reverses the results of the tests on samples A to L, 
all of which were melted in the same manner. 
5. A greater degree of uniformity is to be noted in the 
results obtained in the case of samples S to X (inclusive), 
which samples were tested by five different methods of 
examination. This uniformity, however, is due, in large 
part, to the fact that these results are averages of those 
obtained by the application of the five different methods 
of examination. The full details of these differences are 
shown under samples S to X in Table 6. 
There is noted a parallelism between the 20° C. and the 
37 °C. counts on these samples, S to X; but the counts at 
the latter temperature were higher, which is a reversal of 
the results obtained from the tests of samples A to F, 
which samples were taken from the same portion of the 
can. 
chakt no. 2. 
6. The results of the counts of the Ito 100,000 dilution 
plates on all the samples showed generally greater vari- 
ations than those obtained from the 1 to 10,000 dilution 
95 plates shown in Chart 1. This is clearly brought out by 
noting the greater difference between the means of the 
counts at 20° C. and those at 37° C. in Chart 2, as compared 
with the means in Chart 1. 
7. There is a general resemblance between the outlines 
of the plottings of Chart 2 when compared with those on 
Chart 1, but upon studying the results in each chart for 
any one of several particular samples great variations 
are to be found. This is well illustrated by a study of 
sample P. 
8. Upon attempting to compare the details of Chart 2, 
as has been done in comments 2, 3, 4, and 5 for Chart 1, we 
find that the same statements would be inappropriate for 
this chart. In some instances the comments would be 
accurately descriptive of the results, but in other instances 
the reverse is true. 
chart xo. 3. 
9. A comparison of the results of the counts on sep- 
arate samples, when tested upon litmus lactose agar, 
using the plates of the 1 to 10,000 dilution, with the counts 
of acid colonies on the same plates shows a marked par- 
allelism between the two. 
10. The plottings in this chart show a general par- 
allelism with the 37° C. plottings in Charts 1 and 2, except 
for the samples Kto X. Among these samples we find 
some of the plottings similar to those in the previous 
charts, but others are quite unlike them. 
chart xo. 4. 
11. In this chart, comparing the results of counts of 
dilution plates 1 to 10,000 with those at 1 to 100,000, incu- 
bated at the one temperature (20° C.), we find an apparent 
parallelism between the plottings; but upon close exam- 
ination we find sometimes the 1 to 10,000 plates giving 
96 the higher results, and at other times the 1 to 100,000 
plates showing the higher counts. 
12. The average results of the triplicate samples, as 
shown for A to F (inclusive), together with the results of 
tests of samples from scattered locations in the can, -G 
to L (inclusive), show a greater degree of uniformity 
than do the results of the evenness of melting samples 
Mto E. The results in the latter group of samples greatly 
differ from those in the former in two general locations 
and are also quite at variance with the results of the aver- 
ages of the samples S to X. 
13. The averages of the results of the application of 
the five different methods to samples S to X (inclusive), 
showing variations of 1,000,000 in a maximum bacterial 
count of but little over 3,000,000, show clearly the unre- 
liability even of averages of five samples when the meth- 
ods are somewhat at variance. These variations are, 
however, but little greater than the variations to be found 
in the averages of three tests in which the same method 
was employed, as is shown by the plottings of the results 
of samples AtoF in this table. It cannot be said, there- 
fore, that the differences in methods were the causes of the 
variations in the results obtained in samples Sto X. Ap- 
parently slight variations in method do not lead to dif- 
ferences in bacterial counts of such magnitude as are 
liable to be caused by the natural variations in the bac- 
terial content of the ice cream itself. 
chart no. 5. 
14. In this chart we have the most extreme variations 
noted in any comparison of results from the examina- 
tion of the samples of the vanilla product. This greater 
variation is an expression of the result that has been ob- 
tained in all of the examinations of ice cream, namely, 
that in comparing the 37° counts with similar counts at 
97 20°, which are plotted in chart 4 in this case, the 37° 
counts are always more variable than the 20°. In com- 
paring chart 5 to chart 4, the wide difference in the means 
between the 10,000 and the 100,000 dilution results in 
chart 5 as compared to chart 4 show clearly this point. 
Among the evenness of melting samples we find the very 
widest extremes, although there is a certain parallelism 
between the two dilutions in each sample. On the aver- 
ages of the triplicate samples from A to F about two- 
thirds show reasonable uniformity between the two dilu- 
tions; the other third shows a wide variation, especially 
for averages. The averages of the results on samples 
S to X, in which five different methods were employed, 
show smaller differences than are to be found among 
the evenness of melting results; none the less, they are 
quite wide considering that they are averages of five tests. 
chart no, 6. 
15. Continuing comments 13 and 14 concerning the 
lack of uniformity in the variations on samples S to X, 
we find in chart 6 the details of the results obtained at 
one dilution, 1 to 10,000, at one temperature, 20 °C. We 
note that the results of the different methods of testing 
show little parallelism. While it would be conceivable 
that these different methods would not give uniform re- 
sults on any one sample, we might expect that the differ- 
ence in method would show the same for each sample, but 
when we compare the results on sample T with those of 
samples U or Y, we find wide differences. The results 
with one method are above the fair mean in one sample, 
and are below on another. In fact, there appears to be 
no uniformity whatever. This lack of uniformity, there- 
fore, has less to do with the difference in technique than 
in the composition of the indivdual portion examined by 
any one method. The variations in the averages in the 
98 individual results by the five methods in samples S to X 
are greater than the variations in the individual results 
of the triplicate analyses of samples Ato F. In the latter 
group, the results are more uniform than have been noted 
in any of the previous charts, and bring us back to the 
first comment on chart 1. 
99 CHOCOLATE ICE CREAM.—EXPERIMENT NO. 1 AND NO. 3 COMBINED. 
Six samples (A, B, C, D, E, F) taken from the same location about 3 inches from the top and at the middle of the can. 
Multiply results (except B. coli) by 1,000. 
Colony Count 37°—2 days ~ " “ ‘— 
T:. ., Colony Gas Production Lit. 
Sample Total Litmus-lactose-agar % Acid Lac. Pep. Bile Lac. Lac. 
L~L Agar Acid Alkal. Count B.E.Agar Dilution 24 48 .72 Plfte Stlk Indol Nitrate Gelatine 
A -1. 1 0 . 0 0 0 Q O A A A A m P ' “ ’ “ ' 
100.000 27,000 31,400 7,400 24,000 22.2 11,800 1 000 — _ __ + + + + ~ 
1-000,000 30,000 ; ifeoOO - - — 
A2 10,000 7 500 100 HZ pr -— 
100.000 19,200 19,000 5,200 13,800 27.3 6,800 1 000 — _ 
1-000-000 24,000 9-000 lOMOO - — — 
A3 10,000 6,300 100 u 
100.000 14,600 22,900 6,600 16,300 28 8 7 600 1 000 - Tr 
— 1,000,000 20,000 ; 1L000 10,000 - — — 
B1 10,000 0 ofin -|pf\ La ; ~ 
tooo’ooo 27’°°° 6-2°° 20'800 340 7’900 1-000 - Tr Tr. % - ~ £ = 
1.000. 23,000 _____ 7,000 10,000 — 
B2 10,000 3,000 spr 1?)0 ' SS 70 T T T r 
100.000 27,600 23,700 5,200 18,500 21 9 9 900 1 000 _ II _ + + + + ~ 
1.000. 40,000 1.2:000 10.000 — — _ 
B3 10,000 8 190 100 ZZ ~" 
100.000 19,200 31,600 5.600 26,000 17 6 8900 1 000 — — _ 
1.000. 24,000 • 8;000 mooo - _ 
Cl 10,000 8,820 100 Tr 5 -t- Z Z Z 
100.000 22,900 25,000 6,200 18,800 9 300 i 000 — xr. + + + + _ 
■ 1,000.000 18.000 5;000 KXOOO — — — 
C2 10,000 5,040 100 ZZ ZZ HI ‘ 
100.000 22,400 33,800 10,000 22,900 400 30.0 8,500 1,000 — — — 
1.000. 18,000 spreader 10,000 — — — 
100 C3 10000 : 8,820 100 — 5 Tr. + + + + — 
26,000 30,200 7,800 22,400 25.8 8,100 1-000 — — 10 
1,000!000 5,000 10,000 — — — 
dT~ 10 000 7,560 100 — 30 50 + + + + 
1 mould 
100.000 22,600 34,000 7,200 26,800 24.7 8,000 1.000 
1,000,000 22,000 10,000 10,000 — — 
m 10 000 6,930 100 — — Tr. 
100*000 23,200 29,500 7,900 21,600 26.7 8,200 1,000 — — Tr, 
1.000. 22,000 9,000 10,000 — — — 
D3 10 000 8,190 100 — • Tr. 
100.000 18,000 27,400. 6,000 21,400 21.9 8,800 1-000 — — — 
1.000. 13,000 ■ 5,000 10,000 — — — 
K1 —10 000 _~ 7,560 100 ~~ — Tr. 
lOoiOGO 23,200 30,200 7,000 23,200 23.1 10,100 1-000 — — Tr. 
1.000. 31,000 7,000 10,000 — — 
¥9 To 000 11,340 100 — Tr. 5 + + + + 
23,600 27,900 7,000 20,900 28.3 7,800 1,000 — Tr. 10 + ~ — 
1.000. 24,000 6,000 10,000 — — — 
E3 10 000 6,930 100 — Tr. 10 + + — — — 
looiooo 19,200 20,900 4,700 16,200 33.5 5,100 1-000 __ _ 5 
1.000. 31.000 13,000 10,000_ — == — 
¥T 10 000 6,930 100 — — Tr. 
100.000 23,200 24,800 6,200 18,600 25.0 6,800 1,000 
1.000. 26,000 15,000 JT000 — — — 
¥9 in 000 " 10,710 100 — Tr. 5 
looiooo 28,000 26,800 8,400 18,400 31.3 10,300 1.000 — Tr. 10 
1.000. 30,000 ■ 17,000 10,000 — — — 
F3 10 000 6,930 100 -— 10 
100.000 27,600 26,800 ' 7,000 19,800 26.1 7,300 1-000 — _ — 
1.000. 34,000 8,000 10,000 — ZZ IT 
101 Chocolate Ice Cream Experiments. 
Technique of Examinations Same 
as Outlined for Experiments on 
Vanilla Ice Cream CHOCOLATE ICE CREAM.—EXPERIMENT NO. 2. 
Multiply results (except B. coli) by 1,000. 
If Colony Count 37° 2 days Gas Production Lit, 
g § Lactose-Litmus-Agar % Acid Count Lac. Pep. Bile Lac. 
I oNomPlDilution B.E.Agar LJDAgar Acid Inert Alkal. Count Dilution 24 48_ 72 Plate Stab. Indol Nitrate Gelatine 
non TooOO 8,190 100 — Tr. 5 + — + + — 
S| 100,000 31,400 33,100 8,900 24.200 26.8 10.100 1,000 — — — 
I.OOOIOOO 32,000 6,000 10,000 — 
,2 a- 10 000 6,930 100 — 10 10 + + + + — 
loooiooo 24,900 28,100 5,900 22,200 21.0 7,900 to’non 
1,000,000 26,000 12,000 10,000 — 
g> 7 TooOO 10,710 100 Tr. 10 10 + + — + — 
100,000 38,700 35,800 11,700 23.900 200 32.7 9,200 1,000 — — Tr- 
1.000. 33,000 12,000 10’000 — 
irTnon 9,450 100 — — — 
#§ 100,000 32,700 27,900 7,000 20,600 300 25.0 6,700 1,000 — — ~ ± j = + = 
S3 1,000,000 18,000 10,000 1°’000 “ 1U 10 1 1 I 
iTTono 10,080 100 5 60 70 + + + + 
2|K 100.000 27.200 34,700 7,900 26,800 22.7 10,200 1,000 - = Tr- 
1.000. 32,000 .tl,000 10,000 — 
no, n cnn 6,300 100 Tr. 
-22 100,000 29,800 29,900 7,800 22,000 100 26.0 9,000 L900 — — “ 
*2 1,000,000 28,000 11,000 10,000 — 
£ S — — “ 
103 CHOCOLATE ICE CREAM.—EXPERIMENT NO. 5. 
Six samples (S, T, U, V, W, X) taken from the same locality at a point adjacent to the place where the six samples for Exp. No. 1 were taken, 
3 inches from top near middle of can. 
Multiply results (except B. coli) by 1,000. 
Colony Count 37°—2 days 
„ , Colony Gas Production Lit. 
Sample Total % Acid Count Lac. Pep. Bile Lac. Lac. 
Lactose-Litmus-Agar Colony 20°-5 da. Dilution 24 48 72 Agar Agar 
No. Dilution B.E.Agar L.L.Agar Acid Inert Alkal. Count B.E.Agar Plate Stab. Indol Nitrate Gelatine 
51 10,000 6,300 100 + Tr. 10 + + — + — 
100.000 24,000 28,700 6,100 22,600 21,2 7,800 1.000 — — — 
1,000,000 28.000 3,000 10,000 — — — 
52 10,000 13,230 100 — Tr. 5 + — — + — 
100.000 33,600 37,800 9,500 26,300 25.1 9,900 1.000 — — — 
1.000. 54.000 6,000 10,000 — — — 
53 10,000 8,820 100 — 10 10 ~ + + + + — 
100.000 28,200 31.500 7,900 23,600 25.0 8,200 1,000 — Tr. 5 + — — + — 
1.000. 36.000 8,000 10.000 — — — __ 
54 10,000 10.080 100 — — 10 
100.000 37,600 31,300 8,800 22,400 100 28.1 9,100 1,000 — — Tr. 
1,000,000 18.000 14,000 10,000 — — Tr. _ ■ 
55 10,000 13,800 100 — 60 60 + + — + — 
100.000 29,900 22,700 5,200 17.500 22.9 7,700 1,000 — 10 10 + — — + — 
1.000. 29,000 15,000 10.000 — — — 
T1 10,000 7,500 100 — 10 20 — 
100.000 21,000 19,300 5,200 14,100 26.4 6,500 1,000 — — Tr. 
1.000. 17.000 6,000 10,000 ' — — — 
T2 10,000 10,710 100 -- — 5 
100.000 33,500 31,900 10,000 21,900 31.3 8,700 1.000 — — Tr. 
1.000. 38,000 13,000 10,000 — — Tr. 
T3 10,000 8,190 100 — — Tr. 
100.000 17,800 30,300 6,200 24.100 20.4 8,700 1,000 — — — 
1.000. 30,000 7,000 10,000 — — — 
T4 10,000 6,930 100 — — Tr. 
100.000 24,700 22,300 7,500 14,800 21.3 8,200 1,000 — — — 
1.000. 36,000 10,000 10.000 — — — 
T5 10,000 5,670 100 — — Tr. 
100.000 24,900 32,100 11,300 20,800 35.2 6,800 1,000 — — — 
1.000. 25,000 8,000 10.000 — — — 
til 10,000 10,080 100 — Tr. 
100.000 25,200 28,200 3,600 24,600 12.0 8,000 1,000 — — Tr. 
1.000. 24.000 9,000 10.000 — — — 
U2 10,000 9,450 100 — 50 50 + + + + — 
100.000 32,000 45,000 11,700 33,300 200 26.0 9,200 1,000 — — — 
1.000. 37,000 5,000 10,000 — — Tr. 
U3 10,000 7,500 100 Tr. Tr. Tr. + — = + = 
+ + — + 
100.000 22,300 23,200 7.000 16,200 30.1 7,800 1,000 — — Tr. 
1.000. 26,000 ' 7,000 10,000 — — — 
104 U4 10 000 9,450 100 — 70 70 + + + — 
100.000 24,500 28,700 8,400 20,300 29.2 spread. 1,000 — — — 
1.000. 30.000 1_ 10,000 — — — 
U5 10 000 10,710 100 — 10 10 + + + + — 
100.000 20,100 12,700 unc. 6,700 1,000 — — — 
1.000. 26,000 5,000 10,000 — — — 
Vi io.000 ~ ■ - 7,560 100 — — Tr. 
100.000 30,600 32,200 6,600 25,600 20.5 7,800 1,000 — — — 
1.000. 46,000 10,000 10000 — — — 
V2 10,000 10,080 100 — — Tr. 
100.000 34,000 43,300 10,300 33,000 23.7 10,200 1,000 — — -~ 
1.000. 33.000 ’ 11,000 10,000 — — Tr. 
V3 10 000 7,560 100 Tr. 30 50 + — + — 
100!000 33,400 33,200 10,000 23,200 300 30.1 10,000 1,000 — — — 
1.000. 32.000 11,000 10,000 — — — — 
V4 10 000 8,190 100 — Tr. 10 + — + + — 
lOO’.OOO 30,000 28,800 6.800 22,000 23.6 8,800 1,000 — — — 
1.000. 38.000 ? 10,000 10,000 — — — 
V5 10 000 9,450 100 — 10 15 + + + — 
100!000 23,000 28,000 6,600 21,400 23.5 8,400 1.000 — — Tr. 
1.000. 33,000 2 14,000 10,000 — — 
W1 10.000 10,080 100 — — — 
100.000 26.200 30,700 7,800 22,900 25.4 7,800 1,000 
1.000. 30.000 6,000 10.000 — — — * 
10 000 10,080 100 — — Tr. 
100.000 29,400 31.200 6,600 24,600 20.1 8,200 1,000 — Tr. 10 — 
1,000,000 22.000 10,000 10,000 — — — 
W3 10 000 11,340 100 -- 60 60 
35,100 28,800 6,800 22,000 23.7 8,000 1,000 — — — 
1.000. 31.000 7,000 10,000 — — — ; 
W4 10.000 6,930 100 — — Tr. 
100.000 27.400 33,300 10,300 23,000 30.9 8,100 1.000 — — — 
1.000. 32,000 11,000 10,000 — — - ~ . 
W5 10.000 6,300 100 — — — 
100.000 20.500 26,500 6,400 20,100 24.9 5,100 1,000 — — — 
1.000. 39,000 6,000 10,000 -3 — — 
XI 10 000 9,540 100 — Tr. 5 + — + 
100.000 29.600 56.600 25,900 30,700 45.7 8,200 1,000 broken 
1.000. 28.000 9,000 10.000 -r- —; — 
X2 uTool) - — 8,820 100 — — Tr. + — — + — 
100.000 35.000 65.100 25,300 39,400 400 38.8 9,200 , 1,000 — — Tr 
1.000. 33,000 150,000 10.000 — 10 10 
X3 10 000 5,670 100 — — — 
100.000 31.200 67,800 31,200 36,400 200 30.6 9,300 , 1.000 — — 5 
1.000. 28.000 7,000 10.000 — ~“ 
X4 10.000 9,450 100 — 5 
100.000 28,200 alkaline spreader 7,500 ,1-600 — 
1.000. 27,000 8,000 10,000 — 
X5 iOllOO — ' 10,710 100 — 50 60 + + + + — 
100.000 26,200 26.100 7.000 19,100 26.8 8,400 1.000 — — — 
1,000,000 23.000 11,000 10.000 — — — 
105 CHOCOLATE ICE CREAM.—EXPERIMENT NO. 4. 
Six samples of about 70cc taken from the side of the can from top to bottom. 
Multiply results (except B. coli) by 1,000. 
Colony Count 37°—2 days 
Colony Gas Production Lit. 
Litmus-lactose-agar % Acid Count Lac. Pep. Bile Lac. Lac. 
Sample Total Colony 20°-5 da. Agar Agar 
No. Dilution B.E.Agar L.L.Agar Acid Inert Alkal. Count B.B.Agar Dilution 24 48 72 Plate Stab. Indol Nitrate Gelatine 
M 10,000 ~ 7,560 100 — Tr. Tr. + — — + = 
100.000 2,700 25,600 6.000 19,600 23.4 7,600 1,000 — — Tr. 
1.000. 3.200 10,000 10,000 — — — 
p N " 10,000 “ 6,930 100 — 5 10 + — + + — 
on 100,000 2,600 27,200 6,200 21,000 22.8 8,200 1,000 — 10 10 + — — + — 
1.000. 2,900 4,000 10,000 — — Tr. 
O 10,000 “ 9,450 100 — 10 20 + — — + — 
100.000 2.180 6,400 line. 8,100 1,000 — — — 
1.000. 2,600 7,000 10,000 — — — 
P 10,000 8,820 100 — 10 10 + + + + — 
100.000 2,720 27,600 6,400 21,200 23.1 7,200 1,000 — — — 
1.000. JkOOO __ 8,000 10,000 — Tr. 5 + — — — — 
Q 10,000 6,300 100 — 10 10 + — — + _ 
100.000 2,160 27,000 7,000 20,000 25.9 8,600 1,000 — — Tr. 
1.000. 2.100 7,000 10,000 — — Tr. 
R 10.000 7,560 100 — — Tr. 
100.000 2,300 28,400 6,600 21,800 23.2 8,400 1,000 — — — 
1.000. 2. QOQ 6,000 10,000 — — — CHART No. 1. 
SAMPLES 
Plot of the 20 °C. beef extract agar bacterial counts of Chocolate Ice 
Cream samples, made from the 1-10,000 dilutions ; and of the mean of 
these counts. 
107 CHART NO. 2. 
SAMPLES 
Plot of the 20° C. and 37° C. beef extract agar bacterial counts of Choco- 
late Ice Cream samples, made from the 1-100,000 dilutions; and of the means 
of these counts. 
108 SAMPLES 
Plot of the 37° C. litmus lactose agar total ami acid forming bacterial 
counts of Chocolate Ice Cream samples, made from the 1-100,000 dilutions ; 
and of the means of these counts. 
CHART NO. 3. 
109 Plot of the 20° C. beef extract agar bacterial counts of Chocolate Ice 
Cream samples, made from the 1-10,000 and 1-100,000 dilutions of same 
samples ; and of the means of these counts. 
CHART NO. 4. 
SAMPLES 
110 Plot of the 37° C. beef extract agar bacterial counts of Chocolate Ice 
Cream samples, made from i-100,000 and 1-1,000,000 dilutions of the same 
samples; and of the means of these counts. 
CHART NO. 5. 
SAMPLES Chocolate Ice Cream. 
Comments on Results of Tests as Shown by Charts 1 to 5 (Inclusive). 
CHART NO. 1. 
1. In comparing the results of the averages of tripli- 
cate tests on these samples from one location in the can, 
shown in chart 1, samples A to F, we find differences of 
somewhat less than 6,000,000 bacteria per c.c. to 8,500,000. 
For triplicate results, these differences are too great to be 
explained by anything but an actual difference in the bac- 
terial content of the particular amount of ice cream exam- 
ined in each test. We find still greater differences when 
we note the results obtained on individual samples from 
different portions of the can as shown on the chart on 
samples Gf to L (inclusive). Very much the same vari- 
ations are found among the samples tested for evenness 
of melting, M to R (inclusive), and we find but little less 
variation in some of the averages of the five different 
methods applied to samples S to X. 
chart xo. 2. 
2. In this chart we find a picture not previously seen 
of very wide variation between the means of the 20° and 
37° counts. There is a considerable degree of uniformity, 
however, among the counts for each temperature—a 
greater degree of uniformity in that respect than we have 
previously seen. This is especially true of the 20° plot- 
tings. 
chart no, 3. 
3. In this chart there is to be noted a wide variation 
between the total litmus lactose agar counts and the acid 
forming bacterial counts on the same samples. As in the 
case of the vanilla ice cream, there is a considerable par- 
allelism between the total counts and the acids counts, as 
would be expected. This parallelism is even extended to 
the inert bacteria. In this lot of ice cream the inert bac- 
112 teria played a superior role over the acid-forming 
organisms. 
4. A remarkable picture is presented by the variations 
in the results of different methods of testing samples S 
to X. Notwithstanding the fact that these samples all 
came from the same general location, we find an extreme 
divergence in the averages of the results. This divergence 
was not noted in the results of the tests at any tempera- 
ture or any dilution when beef extract agar was used, but 
appears to be incidental to the use of the litmus lactose 
agar. It applies in the Ito 100,000 dilution to both types 
of organisms present, the inert as well as the acid. This 
is a good example of the unreliability of litmus lactose 
agar counts in attempts to determine the sanitary condi- 
tion of ice cream. 
CHART HO. 4. 
5. The extreme variations found in the averages of 
the triplicate tests on samples A to F in this chart are 
noteworthy. The results on all the other samples in the 
chart show the usual mixed variability with no sort of 
uniformity whatever; sometimes the 100,000 plates are 
higher, and very frequently lower than the 10,000 plates. 
There is again a series of wide variations in the averages 
of the S to X sample results. 
chart xo. 5. 
6. Again we note the great variability in the averaging 
of the triplicate samples from the one location in samples 
from Ato F. The Ito 1,000,000 plates in this chart were 
on the average higher than the 1 to 100,000 plates, but 
none the less frequently show lower results than the lat- 
ter. The extremes of variations in results in this chart, 
which are the 37° temperature plottings, are greater than 
the results in the previous chart, which are the 20° tests. 
Again we find a wide difference in the averages of the 
113 five different methods of testing samples S to X, although 
there is a certain parallelism between the two dilutions— 
the 1 to 1,000,000 usually giving the higher results, al- 
though in the last sample, X, it fell below. 
STRAWBERRY ICE CREAM EXPERIMENTS. 
Technique. 
Source of Sample. A three-gallon can of Commercial 
Strawberry Ice Cream was purchased at a retail store 
and delivered by them to the Lederle Laboratories. 
Method of Taking Samples. Sterile teaspoons were 
used for sampling. The samples were transferred from 
can to 2-oz. and 4-oz. glass-stoppered bottles. 
Three of the samples collected from the same immediate 
location, 4" from the surface of the can, in center, were 
one spoonful only. Three larger samples collected from 
top, middle and bottom, center of can, were 4 oz. each. 
These samples, immediately after removing from can, 
were packed in ice, and placed in refrigerator until tested. 
Method of Melting Sample Before Examination. The 
smaller samples were melted after taking from ice, by 
placing in water bath, and shaking thoroughly. 
The large 4-oz. samples were allowed to stand at room 
temperature for ten minutes, and melted portion at bot- 
tom of bottle tested, without shaking. 
Media. Two batches of all media used were made and 
duplicate tests conducted, using both sets of media for 
each sample. One lot of media was made on January 21, 
1914, the second lot made on January 28,1914. The media 
was stored in refrigerator for ten and three days re- 
spectively, before starting experiments. 
The following Media were used in examination: 
Standard Beef Extract Agar 
Standard Inf, Agar. 
Lactose Bile (Durham Fermentation tubes). 
Standard Oasein Agar. 
114 Standard B. E. Agar plus litmus and lactose solutions. 
Standard B. E. Agar plus litmus and dextrose solutions. 
(All Beef Extract Agar used for making litmus lactose 
and litmus dextrose plates, was from same lots as that 
used for making Beef Extract agar plates.) 
Dilution Bottles and Diluting Water. The dilution bot- 
tles used were 1-oz. and 4-oz. Philadelphia ovals, filled by 
automatic burettes and to contain 99 c.c. dilution water 
and 9 c.c. dilution water, respectively after autoclave 
sterilization. The dilution water contained 0,5% com- 
mercial sodium chloride. 
Pipettes. The pipettes used were straight sided, single 
mark and blunt pointed. Capacity pipettes graduated to 
contain 1 c.c. water, were used for making primary dilu- 
tion of sample, and volumetric pipettes graduated to de- 
liver 1 c.c. water, for all other dilutions and inoculations. 
Petri dishes. Petri dishes 10 x 1.5 cm. sterilized by dry 
heat at 180° C, for two hours were used for all inoculations 
(plating). 
Method for Making Dilutions and Plating. In all cases, 
the sample of ice cream was measured by a 1 c.c, single 
mark capacity pipette, and the pipettes washed out with 
the dilution water. 
The Method of Dilution was as follows; 
1 c.c. of sample to 99 c.c. dilution bottle 1 .TOO 
1 c.c. of 1 TOO to 9 c.c. dilution bottle = ITOOO 
1 c.c. of 1 TOO to 99 c.c. dilution bottle = ITOOOO 
1 c.c. of ITOOOO to 9 c.c, dilution bottle = ITOOOOO 
1 c.c. of ITOOOO to 99 c.c. dilution bottle = ITOOOOOO 
Transfers for higher dilutions were made before 1 c.c. 
was transferred to petri dish. 
Litmus Lactose and Litmus Dextrose Agar Plates. 
1 c.c. of a 10% solution of lactose or dextrose, and y2 c.c. 
of 1% solution of azolitmin were added to each plate be- 
fore inoculation with 1 c.c. of diluted sample. 
115 Test for Bacteria of B. Coli Type. Durham fermenta- 
tion tubes were used. The outside tube was 6" x the 
inside tube 3" x The lactose-peptone bile media was 
made by adding 1% lactose and 1% peptone to fresh ox- 
bile, which had previously been boiled and filtered. 
Two lots of bile media were prepared in accordance 
with the demands of the experiment and held in the re- 
frigerator until used. 
The inoculated tubes were incubated for 72 hours at 
37° C., the percentage of gas formed at the end of each 24 
hours of incubation being recorded. 
From the tubes, litmus lactose agar plates were made 
at the end of 24, 48 or 72 hours, as gas formation was 
found. 
These plates were made by transferring from tubes, 
one 3 mm. loopful of bile to a 9 c.c. dilution bottle, and 
one 3 mm. loopful of this dilution to a plate containing 
lactose and azolitmin solutions. 
After incubation at 37° C. for 24 hours, characteristic 
colon colonies were isolated from plates to lactose agar 
slants. These slants were then grown at 37° C. for 24 
hours and transfers made from the growths to tubes of 
Durham’s peptone solution, and to nitrate solution. 
A stab culture was made in the lactose agar slant, and 
in a tube of infusion gelatin. 
The peptone solution was tested for the presence of 
indol by the addition of % c.c. of paradimethylamidoben- 
yaldehyde solution. 
The nitrate solution was tested for the presence of ni- 
trites by the addition of % c.c. of a sulphanilic acid solu- 
tion and % c.c. of a naphylamene acetate solution. 
The presence of gas in lactose agar stab was noted as 
a control on the isolation. 
The gelatin stabs were incubated 10 days at 20° C., and 
the presence of liquefaction noted. 
Bacterial Counts. All plates were counted, wherever 
possible. 
116 In reporting actual count per c.c., averages were made 
in cases where the bacterial count exceeded 20 and was 
less than 500 colonies to the plate. The number reported 
was not in accordance with the standard method of re- 
porting bacterial counts. 
To Determine Variations and Bacteriological Data Due 
to Media Differences. 
Outline of Experiments. 
Experiments were run in duplicate, using the same 
sample for both tests, but using two lots of media; the 
first lost being made on January 21st, 1914, and stored in 
the refrigerator until used January 31st, 1914 (10 days), 
the second lot being made on January 28th, 1914, and 
stored in refrigerator until used for test January olst, 
1914 (3 days). 
Experiment No. 1. Test of same location. 
Three teaspoonful samples: A, B, and C, were collected 
from the same immediate location, 4" below surface of 
cream, and at center of can. These samples were melted 
in water bath, well shaken, and tested in duplicate for 
count and coli, using 10-day-old media for one test, and 
3-day-old media for other tests. 
Experiment No. 2. Test of different locations. 
Three samples: (4 oz.) D, E, and F, were collected from 
top, middle, and bottom of center of can. These samples 
before testing were allowed to melt 10 minutes at room 
temperature (70° P.) and the melted portion sampled 
without shaking, with a 1 c.c. capacity pipette. 
117 STRAWBERRY ICE CREAM. 
g a, Multiply results (except B. coll) by 1,000. 
. BACTERIAL COUNT PER C.C. THREE DAYS AT 37° C. ON 
|2 Sample Beef Extract Agar ' 10 days 6 Lltmus A^fLVR 77". Lactose Litmus Agar 
~ Q dayS 3days Acid Alkal. Acid Inert Alkal. Acid ffeJT Altai Acid °lS Altai 
100.000 400 loo 300 100 6° foo 400 14° ton inn 60 tnr 500 60 350 560 
§5^11,000,000 1,000 l.OQQ “00 100 500 500 100 600 
IlL.I1’ 100,000 600 400 100 300 9° 300 100 too 190 450 40 Tit) 260 
S 52 1,000,000 2.00 0 400 1000 100 1000 9 Ann 100 300 100 500 200 
(US'»paaT —1 1’000 1.000 2,000 3.000 10,000 1,000 
-ia&fiC UlS 88 5:888 Ji I5S ™ 88 }|»S Js ® 50 S8 US 20 SSS US 
— — uuu Luuu 1,000 1,000 
|1D 100,000 500 800 200 600 " |(jo 200 4° |§§ fjjjj fjff 430 30 170 500 
spreader 1.888 i,g§8 1.J88 4°° 2$§ JJgg 
2|I: 100,000 900 700 300 300 " 1 QOO 400 6° 400 48° ?40 500 60 180 440 
&} 1,000,000 5.000 1,000 2'.000 1,000 1,000 100 f8o 300 500 
£§ 100,’000 700 400 700 600 300 600 400 100 300 fnn 80 260 380 
og 1,000,000 1,000 3,000 1,000 1.000 190 2 000 4°° 10° 300 100 300 100 
~ *— — [_ 1,000 
120 a THREE DAY BILE TEN DAY BILE 
Sft Lit. Lit. 
.S'! Gas Production Lac. Lac. Gas Production Lac. Lac. 
£02 Sample Lac. Pep. Bile Agar Agar Lac. Lit. Bile Agar Agar 
giwNo. Dilution 24 48 72 Plate Stab. Nitr. Pep. Gela. B.Coli 24 48 72 Plate Stab. Nitrate Peptone Gelatine B.Coli 
Q ® — 
a; A 100 Tr. 40 50 + + + + — 4- Tr. 60 60 + + + + — 4- 
1,000 — 60 60 + + + + — 4- — 15 25 + + + + — 4- 
10,000 — 10 10 -i- — — 10 15 +? ( = ) 
100,000 _ _ 10 + ( = ) — Tr. Tr. — J = 
fl - I = 
’S-Sg' 1,000,000 — Tr. 10 + ( = ) — — — 
ed'Jj+j — 
B 100 Tr. 55 60 + + + + — -i- 10 70 70 + + + si + — 4- 
S-’S 1,000 — 50 60 + + + + — 4- — 15 15 + — 
aSdfl 10,000 — 5 10 + — — 10 10 +■?( = )• 
ggog 100,000 No vials +? ( = ) — — 
1,000.000 — — — — — — 
• — — —— ■ - • " “ " — — ”” 
100 Tr. 50 60 + + + + — -I- Tr. 50 60 + + + 
<Us-’Sg 1,000 — 50 50 + + + + — 4- — 60 70 + + + + — 
flg.S'O 10.000 — 10 15 + ( = ) — 60 70 + + + + — + 
°£co's 100,000 — Tr. 10 + (=) — 10 10 + ( = ) 
1.000. — — — — — — 
D 100 Tr. 50 60 + + + + — 4- 10 50 50 + + + + __ 4- 
v 1,000 — 70 70 + + + + — 4- — 80 80 + + + + 
as 10,000 ■— 70 70 +(t)(t)(j) ( = )($) — 10 10 —■ i ( —) + ';ei>y + 
o-o ) + si 
100.000 — — 10 —? ( = ) — — 10 — ( = ) 
( = ) 
1.000. — — — — — — 
E 100 — 40 50 + (t) ( t ) ( t ) ( = ) ( t ) Tr. 50 60 + + + '. + ~ + 
o>a 1,000 — 80 90 + + + + — 4- — 50 SO + 
+33 10,000 — 10 20 + ?( t )( t )( = )( = )( t ) — 30 JO + + + + + 
a "3 100 000 — — — — — 10 + (=) 
rjg l.OOOiOGO — — Tr. — ($) (J) ( = ) ( = ) ($) — — 10 — 
si 
P 100 — 50 60 + + + + — 4- — 40 50 + + + ~ t 
d m 1,000 — 90 90 + + + + — 4- — 50 70 + + + + + 
is 10,000 — — 10 —? (i) (t) ( = ) (t) (=) — Tr- 10 +? i- 
£■§ — si si I — 
®S 100,000 — — — — — Tr. + • — 
m 1.000,000 — — — 
121 STRAWBERRY ICE CREAM. 
Multiply results (except B. coli) by 1,000. 
BACTERIAL COUNT PER C.C. 
5 days at 20° on 5 days at 30° on Casein Agar 
Beef Extract Agar Infusion Agar Total Counts Peptonizers 
Sample Dilution 10 da. 3 da. 10 da. 3 da. 10 da. 3 da. 10 da. 3 da. 
A 10,000 1,430 1,170 900 800 400 440 320 400 
100.000 1,000 1,600 1,100 500 400 500 300 
1.000. 4,000 5,000 1,000 1,000 1,000 1,000 
B 10,000 1.360 1,460 600 690 640 480 400 260 
100.000 1,200 700 500 1.100 500 1,000 300 500 
1.000. 1,000 1,000 2.000 2,000 
C 10,000 1,590 1,210 650 840 560 360 260 220 
100.000 2,000 2,600 1.000 1,000 400 300 300 10O 
1.000,000 1,000 1,000 2,000 
D 10,000 1,300 1,050 1,100 1,030 490 • 300 340 170 
100.000 1,400 1,500 700 400 500 300 500 
1,000,000 1,000 2,000 1.000 
E 10,000 ‘ 1,390 1,350 890 800 240 440 190 260 
100.000 1.200 1,100 800 500 400 300 400 200 
1.000. 5,000 1.000 1,000 1,000 1,000 
P 10,000 1,190 540 560 380 250 370 170 180 
100.000 1,100 500 700 600 200 100 100 
1.000. 1.000 1,000 2,000 1,000 
DESCRIPTION OF SAMPLES. 
Three samples A, B. C (one teaspoonful each) taken from the same loca- 
tion about 3 inches from the top, in the middle of the can. 
D. Top middle. E. Center middle. F. Bottom middle. 
Comments on Results of Tests. 
The object of these investigations was to determine, as 
far as one investigation wonld give results, the effect of 
different lots of culture media made in the same institu- 
tion, and by as near as possible the same methods, upon 
the variability of the bacterial counts. In the investiga- 
tions of the one lot of strawberry ice cream duplicate cul- 
ture media were used, one of which had been prepared 
three days prior to use, and the other ten days. The cul- 
ture media used included beef extract agar, litmus lactose 
agar, infusion agar, casein agar, and the usual lactose bile 
fermentation tube tests for Bacillus coli. 
1. There exists no uniform variation between the re- 
sults from the two lots of culture media. The differences 
that exist between the counts obtained on any one sample 
plated on the two media, incubated at any one dilution, 
122 at any one temperature, are no greater, and usually are 
less, than the differences between different samples taken 
from immediately contiguous locations in the can when 
tested on the same culture medium. Differences, there- 
fore, in the preparation of the culture media cannot be a 
factor which would, in whole or in part, explain the dif- 
ferences of results obtained in the examination of samples 
from one can of ice cream in any one particular labora- 
tory. 
2. It is not even necessary to chart the results of the 
examinations obtained on this particular lot of ice cream 
to show the general variability in counts, for the reason 
that the figures very clearly show very pronounced dif- 
ferences, even when comparisons are made between re- 
sults of examinations made under identical conditions, as 
far as possible. 
General Conclusions. 
1. The results of these investigations indicate conclu- 
sively the existence of a great variability in the bacterial 
counts of different portions of individual cans of ice 
cream. 
2. As a general rule, the bacterial counts obtained by 
the use of beef extract agar, incubated for five days at 
20° C., are subject to less variability than the bacterial 
counts obtained on the same medium incubated at 37 °C. 
for forty-eight hours. 
3. The wide differences noted in the results cannot be 
accounted for by variations in any of the following details 
of technique or methods of reading results: 
(a) Variations in different lots of beef extract agar, 
or other media, prepared in the same laboratory under 
routine conditions. 
(b) Slight variations in methods of measurement of 
the melted ice cream. 
(c) By any irregularity in the method of melting the 
123 sample, provided no destruction of bacteria is caused by 
any method pursued. 
(d) By utilizing the results obtained on plates made 
from dilutions of the melted ice cream yielding either too 
high or too low counts generally considered satisfactory 
for general reading. 
4. Variations in the bacterial contents of different por- 
tions of the can follow no uniform or regular system. One 
is as likely to find two contiguous samples having the 
extreme of difference, with widely separated portions 
showing great uniformity, as the reverse. 
5. The making of duplicate plates from any dilution 
and averaging the results is a waste of effort, for the 
differences between contiguous samples are far greater 
than those due to any possible errors in technique. 
6. Even the averaging of as many as twenty-four 
samples from a single can fails to give results which are 
accurately comparable within narrow limits, although the 
results are reasonably comparable on a broad basis. 
7. From the above conclusions applied broadly to vari- 
ous lots of ice cream, and especially when one considers 
the detailed relationships between counts at different 
temperatures, and the different classes of bacteria as to 
acid and non-acid production and digestion or non-diges- 
tion of casein, the conclusion is warranted that each lot of 
ice cream is a law unto itself. 
8. Bacterial counts on ice cream have an important, 
but very limited, usefulness. They give information only 
of a general character. It is entirely inappropriate to use 
them for passing judgment upon a product in any definite 
manner. The smaller the number of samples taken from 
a product, the less is the interpreter warranted in utilizing 
the results as a basis of judgment as to the sanitary 
character of the product. 
9. The conclusions arrived at concerning the value of 
bacterial counts and their sanitary significance have, to 
124 a large extent, equal applicability to the results of the 
determination of the numbers of B. cob, as ascertained by 
the lactose bile fermentation tube method. The standard 
methods for determining the numbers of B. coli in a given 
sample tend to develop in the casual observer, or even the 
technical worker, an unwarranted opinion of the ac- 
curacy of the results obtained. The methods do not call 
for the determination of numbers of B. coli between 
100 and 1,000, or 1,000 and 10,000, or 10,000 and 100,- 
000, etc. Competent bacteriologists have for years under- 
stood that any attempt to determine numbers of B, coli 
with greater accuracy than this method provides would 
tend to lead to erroneous conclusions. Therefore, reports 
of numbers of B. coli in samples on any other basis than 
the numerical system just described tend to lead to fic- 
titious values and should be discountenanced. The results 
of the examinations of the three lots of ice cream for the 
numbers of colon bacilli show that even the lactose bile 
fermentation tube method results are exceedingly vari- 
able, and warrant the conclusion that the distribution of 
these organisms in any one sample of ice cream is far 
from uniform when they are present in any considerable 
number. 
In the vanilla ice cream, one-half as many samples 
showed B. coli in I—l,ooo1—1,000 c.c. inoculations as there were 
in I—lo,ooo1—10,000 c.c, inoculations. Approximately one-twelfth 
of all showed the presence of B. coli in I—loo,ooo c.c. 
inoculations. Thus, a single examination of this ice cream 
might have given results indicating the presence of either 
1,000 or 100,000 B. coli per c.c. Dependence, therefore, 
upon one test of a sample from a can of ice cream as to 
the B. coli content would be absolutely valueless. The 
chocolate ice cream examined contained practically no 
colon bacilli in I—loo c.c. inoculations. The strawberry 
ice cream varied in its B. coli content from 100 B. coli per 
c.c. to 100,000, although 50% of the tests showed 1,000 
125 B. coli and 33% showed 10,000. These facts show conclu- 
sively a totally unscientific basis for attempting to pass 
judgment upon the sanitary quality of ice cream by attrib- 
uting sanitary significance to numbers of colon bacilli 
found in samples of this product, unless one attempted 
to draw the unwarranted conclusion that an ice cream 
containing more than a very small number, say 100 colon 
bacilli per c.c., was not prepared in a sanitary manner. 
H. D. Pease, 
Director, Dept, of Bacteriology, 
Lederlb Laboratories. 
To National Association of Ice Cream Manufacturers. 
126 Bacteriological Investigations 
Regarding Rates of Growth in 
Pasteurized Milk 
H. D. PEASE, M. D. REPORTS OF BACTERIOLOGICAL INVESTIGATIONS 
REGARDING RATES OF GROWTH OF BACTE- 
RIA IN PASTEURIZED MILK, PASTEUR- 
IZED CREAM, CERTIFIED MILK AND 
CERTIFIED CREAM REFERRED TO 
AND PRESENTED IN PART 
AT THE HEARING. 
H. D. Pease, M. D. 
Report in the matter of the Examination of Samples of 
Pasteurized Milk, Pasteurized Cream, Certified Milk and 
Certified Cream, purchased on the Open Market from 
Sheffield Farms Slawson-Decker Company, October 28, 
1913. 
Samples : Six one-quart samples of Certified Milk, six 
quart samples of Grade “B” Pasteurized Milk were pur- 
chased on the open market and received at Lederle Lab- 
oratories October 28, 1913. 
Method oe Obtaining Samples: Without shaking the 
bottles, 150 c.c. of cream were removed from each of five 
bottles of certified milk and each of five bottles of pas- 
teurized milk, by means of sterile pipettes. This cream 
was placed in sterile flasks and packed in ice. 
These samples are called certified cream and pasteur- 
ized cream respectively. 
Method oe Examinations: The certified cream and 
pasteurized cream respectively were placed in 2-oz. sterile 
bottles, making twelve samples of certified cream and 
twelve samples of pasteurized cream. 
The remaining quarts of certified and pasteurized milk 
were well shaken, and twelve 2-oz. sterile bottles were 
filled from each. 
These 48 samples were divided into three lots of 16 
128 samples, each lot containing 4 samples of certified cream, 
certified milk, pasteurized cream, pasteurized milk, one 
lot being placed at 12° C, one lot at 20° C and one lot at 
37 °C. 
All samples were examined daily, the first examination 
being of the fresh sample, and the examinations being con- 
tinued until souring took place. 
These examinations were made, for bacterial count, on 
Beef Extract Agar at 37° C. for 2 days, and for the pres- 
ence of Colon type organisms in Lactose Peptone Bile at 
37° C. for 3 days. 
Organoleptic tests were conducted on all samples daily 
until souring occurred, and finally on the sixth day of 
holding on all samples. 
129 CERTIFIED CREAM. 
Bacteria per c.c. on B.E.Agar, 2 days at 37 °C and organoleptic tests. Held at 12°C. 
SAMPLE NUMBERS : 
Period of 
Incubation 1 2 3 4 
Fresh 24,000 sweet 31,000 sweet 33,000 sweet 33,000 sweet 
1 day 4,800,000 sweet 26,000 sweet 67.000 sweet 27.000 sweet 
2 days 23,000 sweet 5,000,000 sweet 32.000,000 sweet 13,000.000 sweet 
3 “ 15,500 sweet 22,000,000 sweet 6,500.000 sweet 10,000,000 sweet 
4 “ unc TT turning 490,000,000 turning 65,000.000 turning 95.000,000 turning 
5 “ no growth M clabbered 400,000,000 curd whey 28.000,000 turning 300,000,000 turning 
6 “ curd whey 
Held at 20°C. 
SAMPLE NUMBERS: 
Period of 
Incubation 5 6 7 8 
Fresh 19.000 sweet 1,800 sweet 24.000 sweet 21,000 sweet 
1 day 910,000 sweet 710.000 sweet 50.000 sweet 50,000 sweet 
2 days 180,000,000 turning 63,000,000 turning 90,000,000 turning 160,000,000 turning 
3 “ 305,000,000 turning 12,000,000 clabbered 405,000,000 turning 400,000,000 turning 
4 “ 
5 “ 
6 “ curd & whey curd & whey curd & whey curd & whey 
Held at 37 °C. 
SAMPLE NUMBERS : 
Period of 
Incubation _9 10 11 12 
Fresh 27,500 sweet 35.000 sweet 32,000 sweet 40.000 sweet 
1 dav 560,000,000 turning 140,000,000 turning 560,000.000 turning 440,000.000 turning 
2 days 34,500,000 curd whey 30.000,000 curd whey 22.000.000 curd whey 94.000,000 curd whey 
3 “ 
4 “ 
5 “ 
6 “ 
130 CERTIFIED MILK. 
Bacteria per c.c. on B.E.Agar, 2 days at 37°C and organoleptic tests. Held at 12°C. 
SAMPLE NUMBERS : 
Period of 15 16 
Incubation 13 . lYnnri sweet 3,200 sweet 
fdfy "’OOO IZllt 900 IZllt SO’.OOO sweet 2.200 sweet 
2 days spreader TT sweet 15-000.000 sweet 100 000 sweet sweet 
3 “ 24.500,000 sweet _44.000.000 sweet 180 000000 turning 480,000.000 turning 
4 “ 510,000.000 turning 390,000,000 turaing 9 000 000 clabbered 900.000.000 clabbered 
5 “ 1.200,000,000 clabbered 3.000,000.000 clabbered y.uuu.uuu l curd whey 
6 » clabbered curd whey curdwney 
, Held at 20°C. 
SAMPLE NUMBERS : 
Period of 18 19 20 
Incubation 17 sweet T6.000 sweet 3.100 sweet 
S® «.§88 SIS 3.000 Sg 29«000 greet 04,000l000 SS&k 
|d“IS 175,000:000 Safe MOO.OOO IS 440.000.000 turning 810,000.000 turning 
I » curd whey clabbered clabbered clabbered 
° and gas — 
Held at 37 °C. 
SAMPLE NUMBERS: 
Period of 99 23 24 
Incubation 21 ——— r 9r nnn sweet 2.400 sweet 
Fresh 1.000 sweet , 1-300 p>05 000 000 sweet 440,000,000 sweet 
1 day 755,000,000 sweet Zoo non 000 clabbered '215.000,000 clabbered 160.000.000 clabbered 
2 days 520,000,000 clabbered 390,000,000 cianoerea 
3 “ 
I “ caseln casein curd whey curd whey 
precipitated precipitated ~ 
131 GRADE B PASTEURIZED CREAM. 
Bacteria per c.c. on B.B.Agar, 2 days at 37 °C and organoleptic tests. Held at 12°C. 
SAMPLE NUMBERS : 
Period of 
Incubation 25 26 27 28 
Fresh 62,000 sweet 74.000 sweet 130.000 sweet 54.000 sweet 
1 day 57,000 sweet 20.000 sweet 20.000 sweet 33.000 ' sweet (spr.) 
2 days 38,000,000 sweet 31,500,000 sweet 24,000.000 sweet 28,000.000 sweet 
3 “ 310,000,000 sweet 100,000.000 sweet 18,500,000 sweet 170,000.000 sweet 
4 “ 740,000,000 turning 520,000,000 turning 160,000.000 turning 260,000.000 turning 
5 “ 50,000,000 curd whey 15,000,000 curd whey 40,000,000 clabbered 180,000.000 clabbered 
6 “ curd whey curd & whey 
Held at 20°C. 
SAMPLE NUMBERS; 
Period of 
Incubation 29 30 31 32 
Fresh 94.000 sweet 84,000 sweet 90.000 sweet 42.000 sweet 
1 day 14,000,000 sweet 12.500,000 sweet 7,800,000 sweet . 15,000,000 sweet 
2 days 44,000,000 turning 1,100.000,000 turning 650.000.000 turning 1,120,000,000 turning 
3 “ 40,000,000,000 curd whey 690,000,000 clabbered 265.000,000 turning 230,000.000 turning 
4 “ . curd whey 
5 “ 
6 “ curd whey curd whey 
Held at 37°C. 
SAMPLE NUMBERS; 
Period of 
Incubation 33 34 35 - 36 
Fresh 82.000 sweet 82.000 sweet 120.000 sweet 52.000 sweet 
1 day 97,000,000 turning 125,000.000 turning 105.000,000 turning 77,000,000 turning 
2 days 74,000,000 curd whey 56,000,000 curd whey 77,000,000 curd whey 12.000,000 curd whey 
3 “ 
4 “ 
5 “ 
6 “ 
132 GRADE B PASTEURIZED MILK. 
Bacteria per c.c. on B.E.Agar, 2 days at 37 °C and organoleptic tests. Held at 12°C. 
SAMPLE NUMBERS: 
Period of 
Incubation 37 J58 39 40 
Fresh 11,800 sweet 9.800 sweet 60,000 sweet 14.000 sweet 
1 day 35,000 sweet 21.000 sweet 20.000 sweet 21,000 sweet 
spreader 
2 days 11,500,000 sweet 29,000,000 sweet 28,500,000 sweet 40,000.000 sweet 
3 “ 315,000,000 sweet 175,000,000 sweet 32,000,000 sweet 25,500,000 sweet 
4 “ 280.000,000 sweet 180,000,000 sweet 235,000,000 sweet 345.000.000 sweet 
5 “ 80,000,000 turning 14,000,000 turning 20,000,000 turning 70.000,000 turning 
6 “ curd whey clabbered clabbered clabbered 
and gas 
Held at 20°C. 
SAMPLE NUMBERS: 
Period of 
Incubation 41 _42 43_ 44 
Fresh 31,500 sweet 9,500 sweet 20.000 sweet No growth TT sweet 
1 day 7,900,000 sweet 10,000,000 sweet 10,800,000 sweet 11,500.000 sweet 
2 days unc H.T. turning 820,000,000 turning 940.000,000 turning 1,100,000,000 turning 
Spreader M 
3 “ 380,000,000 clabbered 380,000.000 clabbered 480,000,000 clabbered 450,000.000 clabbered 
4 “ 
5 “ 
6 “ curd & whey _ curd & whey curd & whey curd & whey 
Held at 37°C. 
SAMPLE NUMBERS : 
Period of 
Incubation 45 46 47 48 
Fresh 11,000 sweet 8,600 sweet 160.000 sweet 10.000 sweet 
1 day 220,000,000 turning 170.000.000 turning 170,000.000 turning 170,000,000 turning 
2 days 40,000,000 clabbered 54,000,000 clabbered 62.000,000 clabbered 40,000.000 clabbered 
3 “ 
4 “ 
5 “ 
6 “ casein casein casein 
precipitated precipitated precipitated 
133 CERTIFIED CREAM. 
Number of Bacteria of the B.Coli type per c.c. and organoleptic tests. Held at 12"C. 
SAMPLE NUMBERS: 
Period of 
Incubation 1 2 3 4 
Fresh 0 sweet 0 sweet —100 sweet —100 sweet 
1 day 100 sweet —10 sweet 1.000 sweet —100 sweet 
2 days 1,000 + sweet 1.000 + sweet 100.000 sweet 100.000 sweet 
3 “ 10.000 + sweet 100.000 + sweet 100.000 sweet 10.000 sweet 
4 “ 100.000+ turning 100.000+ turning 1,000.000 turning 100.000 turning 
10.000 clabbered 1.000.000 whey curd 100.000 turn, not cl. 1.000,000 turning 
6 “ whey curd turning turning 
Held at 20°C. 
SAMPLE NUMBERS: 
Period of 
Incubation 5 6 _ 7 8 
Fresh 0 sweet 0 sweet —100 sweet —100 sweet 
1 day 10,000 sweet 10.000 + sweet 10.000 sweet 10.000 sweet 
2 days 1,000,000+ turning 1,000,000+ turning 1.000,000 turning 1,000.000 turning 
3 “ 1.000.000+ turning 1,000,000+ clabbered 1.000,000+ turning 1.000.000 turning 
4 “ 
5 “ 
6 “ curd whey curd whey curd whey curd whey 
Held at 87 °C. 
SAMPLE NUMBERS: 
Period of 
Incubation 9 ‘ 10 11 12 
Fresh 0 sweet 0 sweet —100 sweet —100 sweet 
1 day 10.000 turning 10.000 turning 100,000 turning 100.000 turning i 
2 days —10.000 curd whey —10,000 curd whey —1,000,000 curd whey —10,000 curd whey 
3 “ 
4 “ 
5 “ 
6 “ 
134 CERTIFIED MILK. 
Number of Bacteria of the B.Coli type per c.c. and organoleptic tests. Held at 12°C. 
SAMPLE NUMBERS; 
Period of i« 
Incubation 13 "* — .— ; 
o 0 sweet —100 sweet —100 sweet 
iz* iToii aa 17oi°o aa =i:oo§ aa 
q1 i 000 sweet 10.000 sweet 100.000 sweet 199'999 sweet 
I “ uJSjB Sfe .,S S& i«888 S& iwJffi 
6 “ . clabbered curd & whey curd & whey _ cur(1 * ftP-g£_ 
Held at 20 °C. 
SAMPLE NUMBERS: 
Period of lg 19 20 
ir0 1000 -TOOO sweet 
IV iffli cfabbered t 1.008:888 + tuAtg *88:888 tSS 
4 “ 
| « curd & whev clabbered + clabbered clabbered 
- gas 
Held at 37 °C. 
SAMPLE NUMBERS : 
Period of 9 2s 24 
. 21 * 0 —100 “sweet ~~~ —100 sweet 
T£i !.00°oSt i&ed io°000+ clabbered Sired LOOOIOOO da&red 
3 “ 
4 “ 
| “ casein casein curd & whey curd* whey 
precipitated precipitated —______ — — • 
135 GRADE B PASTEURIZED CREAM. 
Number of Bacteria of the B.Coli type per e.c. and organoleptic tests. Held at 12°C. 
Period of SAMPLE NUMBERS ; 
Incubation 25 
Fresh 100 + sweet io7U ■- 27 oo 
2 days 10,000+ swelt 100,000+ —1.000 "wlet —100 s^T 
I “ 1.000,000 + turning 1 '?00 000+ 100,000 sweet 100 000 
~ -1-00°:000 -!.«§§ HMS S*. 
curd&whey curd&whev 
Held at 20°C. 
Period of ’ SAMPLE NUMBERS: 
Incubation 29 
Fresh 10 sweet 1Ar> 30 31 „o 
10.000.WO+ Sj 1000 000+ F'f 100.000 swS jooooSS 
I ;; 10.000,000 c„«Abej i:K« 8Sfe i:888-888 Si & 
5 “ curd&whey ’ turning 1,000.000 turning 
~ ~ ~ curd&whey curd&whev 
Held at 37 °C. 
Period of SAMPLE NUMBERS : 
Incubation 33 
Fresh 100 sweeF 35 
\*t 10-S88:ffi ~ 
5 •• 
6 “ 
136 GRADE B PASTEURIZED MILK. 
Number of Bacteria of the B.Coll type per c.c. and organoleptic tests. Held at 12°C. 
P„rlrw, SAMPLE NUMBERS : 
88 88 40 
|E ,,|+ 10£If lii 53 - 
I :;«+ §khCT s+ s a « s. 
curd & Whey clabbered clabbered clabbered 
—— and gas 
Held at 20° C. 
Period of SAMPLE NUMBERS : 
Incubation 41 42 43 
it ilk .iSi' ik ill IIL i;ii SL 
5 “ 
——— ———curd & whey curd & whey curd & whey curd & whey 
Held at 37°C. 
Pprlo(1 of SAMPLE NUMBERS : 
Incubation 45 „„ „ 4S 
|Ss 1,000:000 dabbed 10.000.000 Srtfe -iioOOOOO Sfed JffigS SVwhey 
4 “ 
5 “ 
® casein casein casein casein 
—— precipitated precipitated precipitated precipitated 
H. D. PEASE, 
Director, Dept, of Bacteriology. 
LBDBRLB LABORATORIES. 
E. D. BELL. 
Secretary. 
137 S. L. PARSONS & CO.. Inc., Printers, 45 Rose St., New York.