CITRUS PECTIN 
13 
jellying power. Barker (3) states that pectin must be present in 
quantities of 0.5 per cent or more to give a good cider apple jelly. 
Tarr (48) found a direct relation between jelly formation and active 
acidity of hydrogen-ion concentration, which can not be correlated 
with total acidity. The minimum hydrogen-ion concentration at 
which jelly formation occurred was pH 3.46. 
By the standard test used throughout this work for determining 
the jellying quality of the citric acid pectins obtained (p. 5), it was 
found that 0.20 per cent pectin in the finished product gave a good 
jelly in one instance and 0.25 per cent in several other instances. In 
order to determine the variations in citric acid and sugar that could 
be used with the better grades of pectin, a large number of tests were 
made by this standard- jelly test. 
Six pectins of high-jellying quality were obtained from three lots 
of lemon peel as follows: No. 1, from peel No. 1, by extracting for 
45 minutes at 98° C. in 0.1 per cent acid solution; No. 2, from peel 
No. 1, by extracting for 15 minutes at 98° C. in 0.1 per cent acid 
solution; No. 3, from peel No. 1, by extracting for 4 hours at 70° C. 
in 0.1 per cent acid solution; No. 4, from peel No. 2, by extracting 
for 30 minutes at 98° C. in 0.1 per cent acid solution; No. 5, from peel 
No. 3 ; by extracting for 45 minutes at 98° C. in 0.1 per cent acid 
solution; No. 6, from peel No. 3, bv extracting two samples twice 
for 45 minutes, one in 0.1 per cent acid solution and the other in 0.5 
per cent acid solution, and then combining the two. The pectins 
were precipitated from solution twice with alcohol, washed, dried, 
and ground. 
The effect of using varying quantities of citric acid with 0.26 per 
cent of pectin 1, 2, 3, and 4 was tested. The results are shown in 
Table 15. All of the percentages are based on the finished jelly. 
A good jelly was obtained with as little as 0.045 per cent of acid. 
The 0.5 per cent acid jelly was considered the best tasting and enough 
of the sucrose (about 65 per cent) was inverted to prevent crystalli- 
zation. 
Table 15. 
■Effect of variation of acid on consistency of jelly (pectin and sucrose 
nearly constant) 
Sample No. 
Citric 
acid 
Consistency of 
jelly 
Sample No. 
Citric 
acid 
■noy of 
jelly 
Pectin 1: 
1 
Per cent 
0.000 
.020 
.040 
.045 
.052 
.080 
.100 
.200 
.300 
.400 
.500 
.600 
.750 
.900 
1.300 
1.800 
2.500 
Sirup. 
Do. 
Barely jellied. 
Good jelly. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Pectin 2: 
1 
Per cent 
0.027 
.035 
.039 
.046 
.048 
.049 
.020 
.046 
.073 
.020 
.043 
.046 
.056 
.065 
.073 
Sirup. 
2. 
2 
3 
4 
5 
6 
Pectin 3: 
1 
2 
3 
Pectin 4: 
1 
2 
3 
Do. 
3 
Do. 
4 
Do. 
Good jelly. 
6 
Do. 
7 
8 
Sirup. 
9 
Fair jelly. 
10 _ 
Good jelly. 
11 
12 
Sirup. 
13 
14 . 
Do. 
15. 
4 
5... 
6 
Fair jelly. 
16 
Good jelly. 
17 
Do. 
