CITRt T S PECTIN 
METHODS OF EXTRACTION 
During the course of the work, the quantity of pectin obtained by 
extracting at different temperatures with solutions containing 
various percentages of citric acid was determined several times. 
The sample was heated with three times its weight of solution for 
two hours and filtered, and the residue was repeatedly extracted 
until only a trace of pectin was obtained, five or six extractions being 
sufficient. The jellying quality of the pectins varied decidedly, 
depending upon the treatment. 
Table 3. — Effect of acidity and temperature on quantity of pectin extracted 
Sample 
No. 
Materia] 
Acidity of 
Weight of 
solution 
Temper- 
sample 
(citric 
acid) 
ature 
Grams 
Per cent 
°C. 
650 
0.02 
98 
200 
.02 
98 
200 
.02 
98 
400 
.02 
98 
f 200 
200 
.02 
98 
.02 
125 
| 200 
I 100 
.01 
110 
.02 
110 
100 i .06 
98 
/ 200 .21 
\ 200 1 .64 
98 
98 
f 200 I .01 
98 
\ 200 
.39 
98 
Pectin in 
material 
Peel from frozen lemons . 
Peel from frozen oranges. 
Grapefruit peel 
Lemon residue. „ 
Orange peel 
Orange residue . 
Lemon peel 
Grapefruit peel . 
Per 
cent 
1.53 
1.28 
1.48 
1.95 
2.71 
2.50 
2.63 
2.27 
2.73 
2.54 
3.64 
2.36 
4.08 
The percentages of pectin in the samples analyzed (Table 3) de- 
pend largely upon the maturity of the fruit. Higher results would 
probably have been obtained on samples 1 to 6, inclusive, if the 
acidity of the solution had been increased. 
A series of experiments on the extraction operation was made to 
determine the effect of temperature, time of heating, and acidity on 
the quantity and quality of the product. The following jelly test 
to determine the quality of pectin was adopted: 
Thirty-one gramsof sucrose was placed in a 150 cc. beaker with 
19 cc. of distilled water and 0.25 gram of citric acid. The solution 
was brought to boiling, which in this case took 2% minutes. The 
flame was then removed and a known weight of the dry pectin was 
dissolved in 6 cc. of water and added to the contents of the beaker. 
The solution was boiled gently for a minute. The beaker was then 
left overnight, after which the character of the jelly was noted. 
If, according to Goldthwaite's standard (28) , it was tender enough 
to cut easily and yet so firm that the angles produced retained their 
shape, and was not sirupy, gummy, sticky, or tough, it was con- 
sidered a good jelly. Otherwise the test was repeated, using a differ- 
ent quantity of pectin. 
As about 7 cc. of water evaporated during the test, the quantity 
of jelly obtained remained at a standard weight of about 50 grams. 
The rate of boiling and the quantity of water used should be regu- 
lated to give the standard weight. The weight of pectin used, 
divided by the weight of jelly obtained, gives the percentage of pectin 
required tor a good jelly. 
