The leucoanthocyanins In White Grapes: their Distribution, amount, and Fate during Fermentation

Abstract

A study was made of the evolution of leucoanthocyanins during the maturation of grapes, and of their distribution in the different parts of the cluster. Leucoanthocyanin values based on a purified leucoanthocyanin standard were obtained by counter-current fractionation from seeds of white grapes. The leucoanthocyanin values are referred to as percentages of total poyphenol content. The fate of leucoanthocyanins was studied during fermentation, including their loss and solubility characteristics from each part of the cluster.

Some varieties of grapes were rich in Ieucoanthocyanins, and others were poor.

The leucoanthocyanin content corresponded to the tannin content and stability of the wine produced. If was highest in immature grapes and those which had herbaceous stems and seeds.

The seeds and stems contain the most leucoanthocyanins, yet the green parts (skins and pulp) were the tissues which released them most readily. Grape crushing, which ruptures the stems and grinds the seeds, results in the release of considerable leucoanthocyanin into the wines. However, the same phenomenon may result from the large quantities of fibrous parenchymal material in the pulp—the quantity depending on the variety, degree of maturity of the grapes, and the crushing technique. Settling, centrifugation, and filtration of musts may be useful in diminishing the content of the, easily oxidizable polyphenols in the wine.