CHEMICAL COMPOSITION OF GRAPES 425 



investigations referred to, there is a slight increase in both of these 

 constituents. 



In the investigations reported in the present paper, particular 

 attention was given to increase in total solids and sugar, decrease in 

 total acid, and changes in protein and cream of tartar in the must or 

 juice of the grapes. The ripening of the leaves was traced by noting 

 the changes in starch, sugar, acid, and protein content. 



Sampling. During 1914 and 1915 samples of fruit were taken 

 from the time the grapes had reached full size but were still hard and 

 green until they had become overripe. During 1916 the first samples 

 were taken shortly after the berries had set and before the seeds had 

 formed. The last samples were taken when the grapes had become 

 overripe. Samples of leaves were also taken in 1916 on the same 

 dates that samplings of the grapes were made. The samples were 

 taken at intervals of approximately one week. They were in all cases 

 taken from the experimental vineyard at Davis. 5 



Five-pound samples of grapes were used. The grapes were picked 

 from the first crop, except in 1914, when a comparison of the ripening 

 of first and second crops was made. An ordinary five-pound grape 

 basket was filled with leaves at each sampling. The samples of grapes 

 and leaves were shipped from the vineyard to the laboratory at 

 Berkeley, where the grapes were placed in an Enterprise fruit crusher 

 and pressed. The juice was sterilized in bottles at 212 F. The leaves 

 were ground in an Enterprise food chopper and sterilized at 212 F 

 in wide mouth, air tight bottles. The samples were then reserved for 

 chemical examination. 



In 1914 it was found that there was considerable irregularity in 

 the variation of samples from week to week. For example, instead 

 of an increase of total solids during the periods between samplings, a 

 slight decrease was found in a few samples. During the 1915 season 

 it was therefore considered of interest to note what effect certain 

 factors might have upon the composition of samples taken on the 

 same date. 



1. Effect of Age of Vine. The entire first crop from three large 

 old vines and from three small young vines, all of the Muscat variety, 

 was picked, crushed, and pressed. Analyses of the juices were made 

 with the following results : 



5 The authors wish to express their appreciation of the assistance of F. C. 

 Flossfeder, of the University Farm at Davis, who gathered most of the samples 

 reported upon in this paper. 



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