SUGAE AND ACID IN GRAPES DURING RIPENING. 17 



The Norton samples were unfortunately destroyed by the berry 

 moth before fully ripe, but the total sugar shown in this variety at 

 Sandusky is remarkable, considering that it is distinctly a Southern 

 grape. Possibly with extra effort it might be matured in the San- 

 dusky district so as to show a lower acid content than it usually 

 does. 



The Concord grape samples at Charlottesville showed but small 

 increase of sugar after they were fully colored. The season was 

 very hot and dry and the fruit ripened quickly, then deteriorated 

 rapidly, as shown by the analyses. This is the only variety sampled 

 at Charlottesville after full maturity. The fruit burst and was badly 

 attacked by birds and insects, hence the later samples were not 

 normal. 



Cynthiana was 30 days in reaching full maturity after the berries 

 were colored. The increase of sugar during this long period was not 

 really marked. The results show only about 40 per cent more sugar 

 in the last than in the first sample; but the loss in acid in 100 cc of 

 juice was 63 per cent. This gave a rich juice with a very moderate 

 acid content — only 0.75 gram in 100 cc. 



Delaware was sampled at Charlottesville for 21 days after the 

 berries were colored until full ripeness. The increase of sugar was 

 57 per cent and the drop in acid slight. The final sugar content is too 

 high for the acid strength, as is also noted for the Sandusky samples. 

 This fruit can not well be held at Charlottesville for study after full 

 maturity. It would, however, most likely show final sugar equal 

 to the Sandusky samples. (Note that the acid-sugar ratio for 

 Delaware at wine-ripeness is practically the same for both districts.) 



Norton was sampled for 34 days at Charlottesville, after it was 

 fully colored but before it was fully ripe, with an increase of only 5.35 

 grams of sugar in 100 cc of juice; but the decrease in acidity of 1.33 

 grams is the greatest noted for any variety from the period of full 

 coloring until ripe. The final acid of 0.80 gram in 100 cc shown by 

 this crop is remarkably favorable for this variety. 



It is a noteworthy point that free tartaric acid practically dis- 

 appeared from the grapes having dark-colored juice, both at San- 

 dusky and at Charlottesville, some time previous to maturity. The 

 very large amount of fixed acids other than tartaric (which are 

 treated in this discussion as malic acid), shown in the green Catawba, 

 Clinton, Cynthiana, and Norton, is interesting. None of the other 

 varieties nearly equal these four in this regard. The data show that 

 the loss of acid during the maturity of the fruit is very largely due 

 to the changing of the malic acid, but there is in every instance a 

 greater loss of total acid than of malic. This is in accordance with 

 what should normally occur through the combination of free tar- 

 taric with potassium and other bases forming cream of tartar and 



