JELLY MAKING WITH HAWAIIAN FRUITS. 6 
followed by the Association of Official Agricultural Chemists was 
used. 4 
Table 1 gives the 'pectin number" and percentage, as well as the 
Brix hydrometer reading of several guava juices and of one juice 
each of the poha. grape, and roselle. 
Table 1. — Comparison of "pectin number" and pectin per cent in fruit juices. 
Frui- juice. 
Pectin. 
b 
Brix 
reading. 
Character of precipitate. 
a 
a b 
Guava 
Number. Per cent. 
3i 0. 446 0. 137 
4} .578 . 136 
H • 794 . 151 
S\ .963 .148 
1\ 1. 141 . 157 
9| 1.661 .180 
•1\ . 431 . 172 
4" .888 .223 
Degrees. 
3.6 
5.2 
J: J 
9.6 
15. 4 
12. 6 
3.8 
Spongv with medium Long fibers. 
Do 
Do 
Do.i. 
Do 
Do 
Do 
Do 
Do. 
Do 
Do. 
Poha 
Dense with long, tough fibers. 
Grape... . 
Roselle 
5J . 977 . 186 
Spongy with short fibers. 
1 Average. 
b . 
Table 1 shows that the factor - is fairly constant for guava juice. 
a 
Any increase in this factor for juices having a higher pectin content 
is, of course, due to the increased pressure exerted by the greater 
bulk of precipitate and the resultant smaller proportion of alcohol 
remaining in the mass. Guava juices, however, seldom contain a 
pectin number greater than 7^ or less than 3, and the factors within 
this limit vary only little. 
The factors for the juices of different fruits vary considerably. 
This variation is directly traceable to the character of the precipitate 
because the swelling power of the precipitate, or its capacity to absorb 
alcohol, varies with the character of the pectin. 
The Brix reading of a juice, as an indication of the pectin content, 
is unreliable, unless only one fruit is used in the experiment. The 
percentage of pectin in a juice may be computed by multiplying its 
pectin number by the factor -• This method of computation was 
used throughout the investigation. 5 
PROPORTION OF SUGAR TO JUICE. 
The following method was used for systematically determining the 
best proportion of sugar to add to the fruit juice. 
A series of jellies was made with varying quantities of sugar to 1 
cupful 6 of juice, a start being made with three-quarters of a cupful 
of sugar to 1 cupful of juice. The quantity of sugar was increased a 
quarter of a cup at a time until a sirup or gummy mass instead of a 
* Methods of Analysis of the Association of Official Agricultural Chemists. Revised to Nov. 1, 191'.) 
Washington, D. C. 1920. p. 1-56. 
* For use of the "pectin number" method in investigational work, each worker should determine the 
factor - for himself so as to eliminate eventually the personal factor. For practical work, however. 
variations due to this cause are negligible. 
6 Wherever the term '•cupful" is used in connection with measurements of juice and sugar, 24o cubic 
centimeters of juice and 200 grams of granulated sugar are taken as the equivalent. The actual volume of 
a half-pint cup is 235.6 cubic centimeters. However, the value assumed is believed to be nearer the actual 
measurements, made by the average jelly maker, than the true value. 
