UNITED STATES DEPARTMENT OF AGRICULTURE 



ft BULLETIN No. 335 



Contribution from the Bureau of Chemistry, 

 S^^'^J-U CARL L. ALSBERG, Chief 



1 



Washington, D. C. T 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. 



Introdnction 1 



Changes in the chemical composition of grapes 

 during the ripening period 2 



Analytical results on the juice samples 9 



Composition of the whole fruit 22 



Analytical results on the whole fruit samples. 24 



Sources and preparation of samples 4 Comparison of results on juice and whole fruit 



Methods of analysis 7 | 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°— Bull. 335—16 1 



