PROJECT REPORT 
* COMMITTEE ON FOOD RESEARCH 
QUARTERMASTER FOOD AND CONTAINER INSTITUTE 
FOR THE ARMED FORCES > 
CH ICAGO ILLINOIS 4 
RESEARCH AND DEVELOPMENT BRANCH 
MILITARY PLANNING DIVISION 
OFFICE OF THE 
QUARTERMASTER GENERAL 
coo p TC>fi owelavrare 
utewaim, Delaware 
DIVISION 
/.gricultural Experiment Station 
DEP ARTM ENT 
Chemistry 
O FFI Cl A L _l N VESTI GATOR 
G. L. Baker 
COLLABORATED RJS- 
«.*. GaJJ^iurray 
REPORT NO. 
5 
FILE NO. 
3E10 
CON TRACT NO. 
r0R 0 IE Dec ember 31, 1945. 
1N SIJ AL'onAflftbh 
TITLE: 
PROGRESS REPORT 
PHASE REPORT 
ANNUAL REPORT 
TERMINATION REPORT 
Pectinic „cids and Obher Hydrocolloids and Their Gelation 
S U MMA RY 
*4 study cf pectinic acids as related to the texture and quality 
of dehydrated fruits and vegetables has shevm that grade as cal- 
culated from viscosity of pectins present in the dehydrated pro- 
ducts may be an index to their quality* n straight-lino relation- 
ship was found in the case of apples and poaches, but not with 
apricots. Dehydrated carrots, apparently, can be graded in this 
same manner. The viscosities of solutions of pectins obtained from 
samples of dehydrated white potatoes, sweet potatoes, beets, raisins, 
currants, prunes, and pears were boo low for correlation with eating 
quality- 1 phase report is attached. 
CQMD FORM 
5 April 46 
I2“I2I ( tfevi Bed) 
1 Pectinic Acids as Related to Texture and Quality of Dehydrated 
Products^ 
The acceptance of dehydrated fruits and vegetables depends 
upon the general appearance, flavor,-and eating quality of the 
rehydratod,. cooked food. An index of quality which depends upon 
some constituent of the dehydrated food products would be desirable,. 
An index of this nature Could be used by the* processor in improving 
his methods and it could serve as a guide to the wholesale purchaser. 
Deterioration or the aging of a product could also be fallowed. The 
poctinic acids as one constituent present in fruits or fruit products 
may offer such an index of quality.-* Poctinic acids have therefore 
boon extracted from several dehydrated products in order to investi- 
gate their possible relationship to qua lity. The results are re- 
corded herein.. 
Method of Extracting Pectins * 
The pectins wore extracted from dehydrated fruits and vege- 
tables by the method which produced an extraction liquor of the 
rhighest viscosity. It has boon found that polyphosphates have a 
sequestering action for calcium which is advantageous when used in 
the extraction of pectin (l, 2). Since polyphosphates are valuable 
in the extraction of pectins above pH 3, sodium hexamotaphosphate 
was used at its optimum .concentration in the present experiments 
following a brief survey of the best conditions of acidity and 
boiling time for the extraction of pectin from each of several de- 
hydrated products, An example will serve to illustrate the survey 
procedure as applied to dehydrated apricots, this is as follows:* 
Tv/onty gram samples of dehydrated apricot (blanched, de- 
hydrated apricots,,1945 crop, hold in cold storage) wore soaked 
in 180 ml.-of v/ator for one hour and then broken down to a fine 
particle size in a Haring Blonder through five minutes of blending 
action.. The finely-divided sample was extracted by boiling for 
five minutes with various amounts of sodium h-exametaphosphate 
(0 to 5 per cent domestic Calgon) with or without the addition of 
1. Problem resulted fron an inquiry by Dr.. Gertrude Gottschall, 
Special Assistant in the Office of the Quartermaster General. 
BB10 
Report No* 5 acid (0 to 5 ml. Il/l HCL). In the case of this apricot sample 
the optimum conditions for extraction, as determined from a 
series of six trials, was the presence of 2.5 per cent polyphos- 
phate based on the weight of the dehydrated fruit without added 
acid; the pH was 4,.12. Under these conditions, an extraction 
liquor was obtained which had a relative viscosity (Ostwald) 
of 6.4-2 at 26°C. 
Following the establishment of the optimum conditions of 
acidity and polyphosphate concentration as determined by optimum 
viscosity, additional samples were extracted under similar con- 
centrations of extraction ingredients, but the time of extraction 
was varied from five to 15 minutes, M hen this was done in the 
case of this apricot sample, it was found that boiling 10 minutes 
pro deuced the highest viscosity in an extract. 
Since the actua 1 grade of the pectin present in the dehy- 
drated fruit or vegetable product vras of primary interest, it 
vras necessary to extract and prepare several grains of pectin 
from each dehydrated product. This was cone by extracting 100 
g. of the dehydrated fruit. In the case of the same apricot 
example discussed in the above paragraphs, 100 g. of the de- 
hydrated apricot mas so a. hod for one hour with 900 ml. of water 
at 26°C. containing 2.5 g. dom -Stic Calyon and then it was 
blended in the '.Taring Blonder the some as the earlier, smaller- 
sized preparations. Thu blended product was boiled for 10 
minutes, then the extract was strained and pressed through 
coarse muslin. The strained liquor was clarified by passing 
through a filter pad consisting of coarse filter paper and GO 
g. of Johns Hanville Standard Super-Cel placed on a 10-inch 
Buchner funnel. A like amount of filter-aid was mixed with the 
strained liquor. Suction was applied to aid the clarifying 
filtration. The pectin in the clarified liquor was precipita- 
ted in twice its volume of 90 per cent isopropyl alcohol. 
•Following precipitation the pectin was recovered by filtering 
using, closely woven muslin; it was pressed as dry as possible 
and then washed, in turn, with 100 ml. of the alcohol and 100 
ml. of ethyl other. The pectin was dried at 6d°C..for 20 hours. 
The yield, mothoxyl content, viscosity, and appearance of tho 
pectin wore recorded, Tho grades of the pectins were calculated 
from the viscosities of 0,5 per cent solutions by the formula— 
Grade = 200 (log y - 0.2), whore y = the viscosity of a 0.5 per 
cent solution of pectin* 
BB10 
Report No. 5 Results 
The pectins extracted from the dehydrated white potatoes, 
sweet potatoes, beets, raisins, currants, prunes, and pears wore 
all found to have low viscosity values; all except prunes had 
loss than a relative viscosity of "2" for 0,5 per cent solutions 
at 26°C. One sample of seeded prunes had a relative viscosity 
of 3.65, but the other two samples had a \risccsity of less than 
W3M• These samples wore considered worthless for purposes of 
correlation until further dehydrated products are evaluated. 
Pectins extracted from samples of freshly dehydrated and 
from three-year old dehydrated carrots had relative viscosities 
in one per cent solution at pH 6.3 of 5,63 and 1.66, respectively. 
This would indicate grades of 55 and 2 when compared with the 
grades of pectins of commerce whore 100-grado pectin is pectin 
which will support 100 pounds of sugar per pound of pectin as a 
65 per cent soluble solids gel of standard strength at its 
optimum pH of gelation. Upon giving the freshly-dehydrated 
carrots a rating of 100 as far as quality and texture wore con- 
cerned. the thrac-vonr old samnio would rate about four. Those 
ratings represent a good index of the texture and quality of the 
dehydrated carrot samples at the time of examination. 
The pectins obtained from the apples, apricot, and poach 
products were of higher grade and more suitable for correlation 
with the quality and texture of the prepared, dehydrated pro- 
ducts. The results of their examination are given in the table. 
Correlations between the qua lity of fruit, which represents the 
averages of judgement by fire individuals, and the grade of the 
pectin as calculated from viscosity are illustrated by the curves 
in the figure. A rating of "lOO" for quality is considered as 
very good, while M0,t is considered to represent a worthless pro- 
duct. 
The results show that there are good correlations between 
poetic quality and product quality for those particular fruits; 
apples, apricots, and poaches. Some level of acceptability has 
to bo taken for the quality of fruit. In practice this might be 
"60”, Below this level of acceptability the dehydrated products 
are worthless from the edibility standpoint. It can bo assumed 
that the viscosity of pectin extracted from fruits will bo a good 
index of edibility, This is because the viscosity of pectin 
solutions of constant concentration, in this case 0*5 per cent, 
is an index of degree of polymerization of the pectin. The 
BB10 
Report No, 5 
4 Table Showing 
Quality of Dehydrated Fruit as Fele.ted to Grade of Pectin Present in Fruit 
Tissue 
Kind of 
Fruit 
Shelf 
History 
Amt. Pectin 
Extracted, 
f} 
Viscosity 
0.5 % 
3oln. 26°C. 
Calculated 
Grade 
of Pectin 
CH~0 
of* 
p 
Quality of 
Fruit / 100 
- Very Good 
Apple 
IS44 
Cold Storage 
1.74 
9.3 
154 
6.3 
90 
Apple 
1942 
Cold Storage 
1.65 
6.3 
126 
6.3 
65 
Apple 
7 
»42 or '43 
1.16 
5.5 
103 
4.6 
50 
Apple 
Pacific 
Theatre 
1.93 
3.9 
72 
6.5 
20 
Apricot 
1945 
Dehyd. Fruit 
•Assn'. 
2.31 
O A /? 
Ut it • O 
243 
6.7 
100 
Apricot 
l9a5 
Drum-Dried 
3.75 
10.9 
190 
5.9 
80 
Apricot 
1944 
Blanched,CoId 
Storage 
c. a 2 
7.2 
132 
6.3 
75 
Apricot 
l'$45 
Blanchea,CoId 
Storage 
. ro 
• 
CD 
o 
L 
4.7 
94 
6.4 
65 
Apricot 
" 1944 
Cold Storage 
4.44 
4.2 
84 
C.l 
45 
Apricot 
1944 
Vacuum Dried 
3.17 
3.9 
78 
5.9 
30 
Apricot 
Pacific 
Theatre 
4.37 
3.5 
6S 
4.7 
15 
Peach 
1944 
Blanched,Cold 
Storage 
3.71 
4.8 
96 
4.7 
90 
Peach 
1944 
Cold Storage 
4.06 
3.5 
63 
4.3 
60 
Peach 
1944 
Cold Storage 
4.36 
2.3 
32 
4.6 
30 
Peach 
7 
Pacific 
Theatre 
4.03 
2.3 
32 
5.4 
10 
3BI0 
Report No * 5 Quality of Fruit as Judged by Grade of Pectins Present in 
Its Tissues 
Grade of Pectin - Calculated 
Quality of Fruit - % 
BB10 Report No. 5 degree of polymorization of pectin appears to be a good index 
of tho treatment and conditions of storage which the pectin has 
undergone whether it is still present in vegetative tissues or 
extracted from such tissues and held in liquid or powdered form. 
It is unnecessary to convert the viscosity values to grade except 
in order to convey a better conception of quality of the pectin 
to the reader who is interested in, production and who is un- 
familiar with viscosity as a tern. 
Straight lines are found when the values for apples and 
peaches are plotted. Tho figure shows that the values for the 
apricots do not produce a smooth curve; however, when grade is 
multiplied by mothoxyl content of each particular pectin then a 
smoother curve is obtained. Pectin loses its methyl ester con- 
tent at a rato depending upon storage conditions of moisture, 
temperature, and acidity. It. is possible, therefore, to have 
two indices of deterioration—grade and mothoxyl content. How- 
ever, grading, or viscosity, appears to be a better index when all 
the results presented at this time are considered. 
1* Baker, G. L., and ’ .roodmans ee, C. M., Polyphosphates in the 
Extraction of Pectin, Frv.it Prod. J. 23, No. 6, 164 (1944). 
2, Mac lay, ll. D., and Nielson, J. P*., Method of Extracting 
Peetinous Materials, U. S. Patent 2,375,376, May 8, 1945. 
References 
7 
BB10 
Report No. 5