Effect of Different Vineyard Treatments on the Phenolic Contents in Tannat (Vitis vinifera L.) Grapes and their Respective Wines

Abstract

Phenolic composition of Tannat variety grapes grown in South of Uruguay and harvested during two consecutive years (1999 and 2000) was determined. The effect of the cluster thinningin settingand veraison, etephon applications, and pruningat 4 and 6 buds per rod on the phenolic composition of the grapes and their respective red wines was compared. During the harvest, which took place in the technological maturity, the phenolic maturity indices of grapes were estimated. Wines were analysed a month after the alcoholic fermentation, determiningits colour and phenolic content. The different treatments had a different incidence on the total phenolic content, the total and extractable anthocyanins of the grapes, depending also on the year of harvest. There was no correspondence between the technological and phenolic maturity indices, which varied depending on the treatments and the years of harvest. The anthocyanic contents of the grapes and wines did not correlate significantly due to the diverse incidence of the environmental conditions and the harvest practices, the conditions of the maceration and the evolution of the polyphenols duringthe vinification.