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University of California Publications in Agricultural Sciences [Vol.3 



was reached are probably within the experimental error. The large 

 difference between the total solids and sugar noted during the first 

 stages of ripening is no doubt due to the high acid content of the 

 unripe grapes. The fact that the difference remains fairly constant 

 after the grapes have become mature is to be expected, because the 

 cream of tartar, total acid, and protein remain fairly constant as 

 maturity is approached and during the periods of maturity and over- 

 ripeness. 



7OT 77& 



Fig. 11 — Variation in non-coagulable protein content for three varieties, 1916. 



Protein. — The total nitrogen content of the various samples was 

 multiplied by 6.25 to convert it into its protein equivalent. Owing 

 to the fact that the samples were sterilized by heat and filtered before 

 analysis, the figures represent only the protein not coagulated by heat. 



The curves show that there is a slow increase in protein content 

 during growth and ripening and the greatest increase occurs during 

 the period of most rapid increase of sugar and most rapid decrease 

 of acid. The increase amounted to about .2 per cent in the case of the 

 Muscat and .6 per cent in the case of the Cornichon. The increase 

 seems to be quite definite, although the protein curves are not so 

 regular as those of total solids, sugar, and total acid. 



