Localization of volatile acidity reducing factors in grape
1992
Delfini, C. | Pessione, E. | Moruno, E.G. | Giunta, C.
Must clarification processes cause an increase in the acetate content of wine at the end of the alcoholic fermentation process, this phenomenon being particularly noticeable when fermentation is obtained by means of the so-called 'high acetate-producer' yeast strains. The influence of different must fractions (free run juice, pressed juice, skins and seeds) on acetate production in white grape was investigated, and the addition of skins and seeds to a synthetic nutritive medium (MNS) was seen to cause a considerable reduction in acetate production. Strain-related differences become evident when the grape bunch is subjected to heat shock (90 degrees C) before musting. In such conditions acetate content after fermentation is approximately the same as that of the control specimen (not heat treated) for the low acetate-producer strain (S191c) and higher for the high producer strain (S22b). This suggests the presence of some thermolabile factor that is responsible for inhibiting acetate production. In order to determine the chemical nature of this factor, a series of tests was performed on two substances contained in grape skins and seeds, i.e., polyphenolic compounds and unsaturated fatty acids. A reduction in acetate production was observed in the presence of both substances, their effect being greater when used in connection with high acetate-producer yeast strains.
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