CHANGES IN THE 



CHEMICAL COMPOSITION OF GRAPES 

 DURING RIPENING 



BY 



F. T. BIOLETTI, W. V. CRUESS, AND H. DAVI 



The investigations reported in this paper were undertaken to 

 determine the changes in chemical composition of vinifera varieties 

 of grapes in California during the growing and ripening stages. A 

 survey of the literature indicated that, although the subject had been 

 quite fully investigated in Europe with vinifera varieties and in 

 America with the native varieties, very little had been published upon 

 the ripening of vinifera varieties under California Conditions. A 

 great many analyses of different varieties of grapes have been made 

 by chemists of the University of California Experiment Station, nota- 

 bly by G. E. Colby, and are reported in the publications of this station. 1 

 A paper by G. E. Colby 2 gives data upon the nitrogen content of a 

 number of varieties of ripe vinifera grapes. Most of the analyses, 

 however, do not show the changes in composition during ripening. 



Of the more recent European investigations 3 some deal with the 

 changes in general composition, others are confined to a discussion of a 

 single component, such as sugar, or coloring matter, or acid principles. 



The changes in composition of American varieties of grapes during 

 ripening have been studied quite thoroughly by W. B. Alwood 4 and 

 his associates. These investigations gave particular attention to the 



1 Hilgard, E. W., The composition and classification of grapes, musts, and 

 wines. Eept. of Viticultural Work, Univ. Calif. Exper. Sta. Rep., 1887-93, pp. 

 3-360. 



2 Colby, G. E., On the quantities of nitrogenous matters contained in Cali- 

 fornia musts and wines. Ibid., pp. 422-446. 



s Kelhofer, W., The grape in the various stages of maturity; trans, by E. 

 Zardetti. Gior. Vin. Ital., vol. 34 (1908), no. 30, pp. 475-477. 



Barberon, G., and Changeant, F., Investigations on the development and 



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