SOME EFFECTS OF SEASONAL CONDITIONS UPON THE 
CHEMICAL COMPOSITION OF AMERICAN GRAPE 
JUICES 1 
By Joseph S. Caldwell 
Physiologist, Office of Horticultural Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 
PURPOSE OF THE WORK 
The studies here reported were under¬ 
taken for the purpose of obtaining in¬ 
formation as to the effects of variation 
in climatic conditions over a series of 
years upon the chemical composition of 
some of the more important varieties 
of American grapes, when grown to- 
ether under known and controlled con- 
itions of cultivation, pruning, and fer¬ 
tilization upon a soil of known physical 
character and chemical composition. 
While a considerable number of 
chemical analyses, covering most of the 
older and more widely known commer¬ 
cial varieties of grapes, may be found 
in the literature, few of them are accom¬ 
panied by any data on the cultural 
treatment received by the vines or the 
climatic conditions under which the 
analytical material was grown. Before 
the results of chemical analyses can be 
employed to formulate the definition 
in chemical terms of desirable dessert 
quality or to guide the breeder in selec¬ 
tion of more desirable varieties, the 
extent to which annual variations in 
environmental conditions affect chem¬ 
ical composition must be definitely 
known. 
No systematic attempt, so far as is 
known to the writer, has ever been 
made to secure uniformity in all cul¬ 
tural treatments over a series of years 
for a large number of varieties growing 
side by side and to determine the nature 
and extent of the fluctuations in chemi¬ 
cal composition of the fruit resulting 
from the variations in environmental 
conditions encountered during the pro¬ 
duction of a number of crops. The 
writer knows of no data in the literature 
indicating the extent to which such 
seasonal conditions as drought, exces¬ 
sive rainfall, minimum sunshine during 
the growing period, or other departures 
from normal in environmental condi¬ 
tions affect the chemical composition of 
the crop. 
Investigations of methods for the 
more effective utilization of some of the 
varieties of grapes grown throughout 
the Central and Eastern States were 
undertaken by the Office of Horticul¬ 
tural Investigations of tlie Bureau of 
Plant Industry, United States Depart¬ 
ment of Agriculture, in 1918. These 
investigations were made on account 
of the fact that there is sometimes a 
considerable surplus of varieties grown 
for dessert use and the products from 
varieties formerly grown extensively 
for wine making have not yet found a 
profitable place in legitimate markets. 
One outlet for a considerable part of 
the grape surplus is in the manufacture 
of unfermented grape juice, where there 
is a demand in excess of the supply. 
To satisfactorily meet this demand,- 
the juices must not only be acceptable 
in beverage quality but must be 
standardized and uniform in character. 
Relatively few grapes produce juices 
having such a balance between sugar, 
acid, and astringent constituents as to 
be wholly satisfactory for making un¬ 
fermented beverages; no other grape 
has seriously rivaled the Concord, 
which possesses such a balance, as a 
source of juice. Successful additions 
to the - beverage-juice supply are 
scarcely to be looked for through the 
making of single-variety juices, but 
the blending of juices of two or more 
varieties offers wide possibilities for 
the making of products of any desired 
character. 
Before such work can proceed in any 
-other than purely haphazard, cut-and- 
try fashion, accurate information as to 
the chemical composition of the vari¬ 
ous new materials must be in hand. 
In order not to be misleading, such 
information must furnish an idea as to 
the extent and nature of the variations 
in chemical composition which are 
likely to occur in the juices of given 
varieties from year to year as a result 
of varying seasonal conditions. Such 
1 Received for publication June 30,1924; issued July, 1925. 
Journal of Agricultural Research, 
Washington, D.C. 
(1133) 
Vol. XXlCNo. 12 
June 15, 1925 
Key No. Q-433 
