UNITED STATES DEPARTMENT OF AGRICULTURE 
I BULLETIN No. 335 
Contribution from the Bureau of Chemistry, 
CARL L. ALSBERG, Chief 
Washington, D. C. 
April 11, 1916 
DEVELOPMENT OF SUGAR AND ACID IN GRAPES 
DURING RIPENING. 
By William B. Alwood, Enological Chemist, with the collaboration of B. J. Hart- 
mann, J. R. Eoff, M. J. Ingle, and S. F. Sherwood. 
CONTENTS. 
Introduction 1 
Changes in the chemical composition of grapes 
during the ripening period 2 
Sources and preparation of samples 4 
Methods of analysis 7 
Analytical results on the juice samples 9 
Composition of the whole fruit 22 
Analytical results on the whole fruit samples. 24 
Comparison of results on juice and whole fruit 
samples 27 
INTRODUCTION. 
In Bulletin 140, Bureau of Chemistry, a preliminary report is made 
on the changes in sugar and acid content of several varieties of grapes 
as determined in 1909 and 1910 during a period of several weeks 
previous to ripening and at full maturity. The results of a further 
and more extended examination of several of these varieties of grapes 
made during the seasons of 1911 and 1912 are presented in this bulle- 
tin. The examinations were made at Sandusky, Ohio, and at Char- 
lottesville, Va. 
The period of observation and analysis of the fruit samples was con- 
siderably extended beyond that previously reported and more com- 
plete analyses were made so as to secure additional data covering 
several important questions, such as the presence of other acids than 
tartaric and the changes in the ratio of combined and free tartaric 
acid. The study of the increase of sugar content and the changes in 
total acid content remain, however, as heretofore, the prime object 
of the investigation. 
Study of the fundamental changes which occur during the ripening 
of grapes is of importance in the determination of the normal compo- 
12253°— BuU. 335—16 1 
