Vinification And Phenolics

As seen in Figures 3,4, and 6, the phenolic content of wines changes from vintage years and by grape varieties. Further phenolic changes in grapes have been noted from site of production, probably depending on a number of factors such as weather and soil conditions and grape degree of maturity. Catechins and procyanidins are observed at the highest level during the early stages of grape maturity and then decrease somewhat rapidly. Anthocyanins, developing in grape skins, steadily increase during maturity.

There are three main technological practices during vinification that change the flavonoid content of wines (12).

Destemming of Grape Clusters

After grape harvest, American winemakers usually first destem the grapes. Destemming in some European cellars is a current enological practice. Destemming grape clusters produces wines with less catechins and procyanidins. Some evidence indicates only a small reduction in epicatechins as compared to about a 25% reduction in catechin and procyanidins in wines from destemmed grapes.

Length of Maceration

Macerating red grapes with skins and seeds, and in some cases with stems, usually does not exceed 10 days because the maximum level of anthocyanin extraction then seems to occur. However, it has been noted that even with pro-

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