June 15, 1925 Environment and Chemical Composition of Grape Juices 1139 
In the first two years of the work, 
1919 and 1920, the determinations 
made in the field were confined to acid 
content, specific gravity, and sugar 
content by the Brix scale saccharim- 
eter. Beginning in 1921, determina¬ 
tions of total astringency and nontan¬ 
nin astringency were also made. All 
the determinations upon any given 
sample of juice were invariably com¬ 
pleted within 30 minutes after pressing 
was completed. The remainder of the 
juice was then placed, after again stir¬ 
ring to secure uniformity, in quart 
bottles, half-gallon glass jugs, or in 
fruit jars of the Lightning Seal type, 
sealed, numbered serially for identifi¬ 
cation, and pasteurized by submerging 
in cold water, bringing to 80° C. for 
5-15 minutes, and cooling slowly out 
of drafts. Analytical work upon the 
juices so prepared had to be postponed 
until the winter of 1921-22, the juices 
in the meantime having been stored in 
the original containers after shipment 
to Washington from Vineland. The 
desirability of securing additional data 
upon the freshly pressed juices for 
comparison with those subsequently to 
be obtained from the same juices after 
pasteurization became apparent as 
soon as the analytical work was well 
under way. In consequence, the prepa¬ 
ration of samples in 1922 and 1923, in 
addition to samples pasteurized as in 
the previous years, included the prepa¬ 
ration of duplicate samples which were 
preserved with bichloride of mercury, 
without heating, for sugar determina¬ 
tions. The bulk of the juice was pas¬ 
teurized as in previous years. 
The methods employed in the field 
determinations were essentially those 
of the Association of Official Agricul¬ 
tural Chemists (10), with the following 
modifications: 
Acidity. —Twenty-five c. c. of juice 
was pipetted into a 400 c. c. beaker and 
made up to 250 c. c. with water, placed 
in such a position before a shuttered 
window that a beam of sunlight illumi¬ 
nated it from the side opposite the op¬ 
erator, and titrated with N/10 sodium 
hydroxide against phenolphthalein as 
indicator. By careful attention to the 
series of color changes occurring in 
the solution it was possible to be cer¬ 
tain of the end point, even in the 
deeply colored juices, but the read¬ 
ings obtained upon such juices were 
checked by the use of phenolphthalein 
powder and a spot plate. While it 
is recognized that titration of a liquid 
such as grape juice against phenol¬ 
phthalein gives high results through the 
inclusion of some gallotannic acid, as 
Gore (2/ f ) has shown, no other method 
capable of being used under field con¬ 
ditions gives more accurate or satis¬ 
factory results. Since the method has 
been used in practically all published 
determinations upon grape juices, it 
serves the purpose of the present work 
by yielding results which permit direct 
comparison. 
Specific gravity. —A precision hy¬ 
drometer, reading to the third decimal 
place, was employed. 
Sugar content by Brix scale.— 
The value of data obtained by the use 
of an instrument intended for deter¬ 
minations upon relatively pure sucrose 
solutions when juices containing mainly 
or wholly reducing sugars and widely 
varying amount of nonsugar solids were 
to be tested seemed questionable at the 
outset, but as it was impossible to keep 
the analytical work abreast of the 
field work spindle readings were made. 
Alwood (6) has discussed the com¬ 
parative accuracy of Oeschle, Balling, 
Baume, specific gravity, and Brix 
spindles, reaching the conclusion that 
Brix determinations with a specially 
made type of spindle are sufficiently 
accurate for comparative purposes in 
work upon grape and apple juices if an 
average of the nonsugar solids of the 
different varieties is allowed in each 
case, notwithstanding the fact that 
such nonsugar solids range from 1.5 to 
4 per cent in different varieties. 
Thompson and Whittier (66) take 
issue with this conclusion, stating that— 
methods employing specific gravity determinations 
(as by the use of the Brix spindle) as a basis for cal¬ 
culating the total sugars or even the solids, are very 
questionable on unknown solutions. In order to use 
such a method on a fruit juice, it is first necessary 
to accomplish an accurate analysis upon each fruit 
juice and even upon each variety of the same fruit 
before a spindle can be used with any degree of ac¬ 
curacy for determining the total sugars. 
Brix precision hydrometers, cali¬ 
brated to 0.1 per cent of sugar at 
17.5° C., of the type recommended by 
Alwood, were used. As the tempera¬ 
tures at which the field readings had to 
be made were those of an open shed and 
varied from 6.5 to 32.7° during the 
work, it was not expected that the cor¬ 
rected readings would give more than 
approximations of the sugar content 
as determined by analysis. As soon as 
the analytical work was under way it 
became evident that the readings were 
without much value either for com¬ 
parison of varieties with one another 
or for comparing the juices of the same 
variety in different years. The non¬ 
sugar solids of the varieties studied 
range from 0.57 to 4.5 per cent, and the 
amount in a given variety fluctuates 
very considerably from year to year. 
The occasional presence of varying 
amounts of cane sugar in grape juice 
