Location of 2-Methoxy-3-isobutylpyrazine in Cabernet Sauvignon Grape Bunches and Its Extractability during Vinification

Abstract

The precise location of 2-methoxy-3-isobutylpyrazine in Cabernet Sauvignon grape bunches was identified before véraison, after véraison, and when grapes were picked. Regardless of ripeness, the compound was mainly located in stems, then in skins and seeds, while the flesh contained very little. During ripening, the proportion of 2-methoxy-3-isobutylpyrazine in stems and seeds decreased, while it increased in skins. During the winemaking process, this methoxypyrazine was easily extracted from Sauvignon blanc (at the beginning of pressing) and Cabernet Sauvignon grapes (after 24 hours in vat). The concentration in Sauvignon blanc must may be reduced by settling (decreasing by half). The 2-methoxy-3-isobutylpyrazine content of Cabernet Sauvignon wines varied relatively little during vatting, irrespective of the length of time or the number of times it was pumped over. Press wines, however, had higher concentrations of this compound than free-run wines. Although settling white must and careful addition of press wine to blends had a certain impact, the 2-methoxy-3-isobutylpyrazine content of the wine depended primarily on the composition of the grapes.