The Total Phenolic Content of Grape Berries during the Maturation of Several Varieties

¹ Department of Viticulture and Enology, University of California, Davis.

A study was made during two seasons of the total extractable phenolic substances assayed by the Folin-Denis colorimetric procedure from representative entire berries of a total of 12 varieties of grapes (7 without anthocyanins, 5 with: 2 Vitis labrusca, 10 Vitis vinifera) from mid-July until they were commercially ripe. A general trend downward in total phenols per unit weight of berry was found. However, the total phenol content per berry actually increased rather rapidly over a considerable portion of the development and ripening period. A considerably greater biochemical activity of the total phenolic substances carrying over into later periods of ripening than expected was observed not only as indicated by this net synthesis or accumulation in the berry, but also by shorter-term increases and decreases of considerable magnitude. Additional criteria of practical use for harvesting grapes for improved quality, particularly regarding wine-tannin relationships as well as new understanding of the grape's physiology and biochemistry, are anticipated from further extension of these studies. Great differences were found among the varieties tested in total extractable phenols per single berry or per unit weight of berry and in browning tendency of the juice. There appeared to be generally greater browning in the riper harvests for white grapes and during onset of anthocyanin synthesis in red grapes.

This article has been cited by other articles:

				M. A. Amerine The Search for Good Wine Science, December 30, 1966; 154(3757): 1621 - 1628. [PDF]