4 BULLETIN 47, HAWAII EXPERIMENT STATION. 
jelly resulted. The resultant " jelly series" was then studied to 
determine the relative merits of each of the different proportions of 
sugar to juice. Each member of the series was brought up to as 
standard a consistency as possible. 
CHEMICAL ANALYSIS OF JUICES AND JELLIES. 
The methods of analysis recommended by the Association of Official 
Agricultural Chemists 7 were employed in making analyses of the 
juices and jellies. Sucrose was determined by polarization before 
and after inversion with hydrochloric acid, reducing sugar, by the 
volumetric Fehling-solution method of Munson and Walker, and crude 
pectin, by the alcohol precipitate method. The acidity was then 
determined by titrating with fifth-normal sodium hydroxid, with 
phenolphthalein as indicator. Phenolphthalein sufficed for work 
of a practical nature, even with the highly colored juices studied, 
since the natural color of the juice faded somewhat, usually changing 
to pale green, before the end point with the indicator was reached 
and the color change of the latter was therefore readily discernible. 
THE GUAVA FOR JELLY MAKING. 
The common guava, which is used for jelly making, is a conspicuous 
part of the native vegetation of Hawaii. It grows over wide ranges 
of altitude and rainfall and on both the windward and the leeward 
sides of all the islands. The ripe fruit can be obtained the year 
round, but the main crop is produced from June to October. 
Although many of the large guava-producing areas are leased by 
commercial jelly companies, large numbers of guava shrubs are to be 
found growing along highways and on public lands where the fruit 
can be had for the picking. It is seldom found for sale on any of the 
markets, and the average housewife picks her guavas from whatever 
source she can obtain them. Probably the only well-established 
rule governing the selection of guavas in Hawaii is that fruit from 
the windward side of the island is inferior for jelly making to that on 
the leeward side. 
COMPOSITION OF GUAVA JUICE. 
To determine the composition of the juice of an average guava for 
jelly-making purposes, 5 pounds of medium ripe guavas was cooked 
in 2.5 pounds of water for one hour and then allowed to drain over- 
night. When it was analyzed, the juice was found to have the fol- 
lowing composition: 
Table 2.- 
-Composition of guava juice.a 
Constituent. 
Propor- 
tion. 
Constituent. 
Propor- 
tion. 
Sucrose 
Per cent. 
1.04 
4.18 
Per cent. 
0.96 
Reducing sugars 
Acidity (as H2SO4) 
1.16 
a Volume of drained juice, 1,200 cubic centimeters; Brix reading, 7.8. 
The production of jelly from the juice of the guava is usually con- 
sidered an easy task. Experienced jelly makers, however, frequently 
have difficulty in getting a firm consistency, and jelly factories in 
producing a uniform quality of jelly from guavas that have been 
1 Methods of Analysis of the Association of Official Agricultural Chemists. Revised to Nov. 1, 191S 
Washington, D. C, 1920, p. 153. 
