Methanol in Wines and Musts: Source and Amounts

Abstract

An analysis of the methanol content of wines was conducted using gas chromatography. Methanol production was followed after complete maceration of the grapes, during fermentation, and in several wines treated with commercial pectolytic enzyme preparations. A survey of some varietal wines was also made.

Following maceration there was no detectable change in the methanol content of the grapes within about the first 30 minutes or any large change up to 36 hours for grapes stored at 32 or 70 F (room temperature). However, for grapes stored and macerated at 100 F methanol content increased significantly after 48 hours. There was no significant difference in maceration effects between a red and a white grape.

The methanol produced during fermentation soon reached a plateau in white varieties of which only the free-run juice was fermented. Red varieties, however, with skin contact produced methanol continuously throughout fermentation. A temperature difference between 60 and 70 F made little difference in the methanol content of the wines.

The use of commercial pectic enzyme preparations does increase the methanol content of wines, though more so for red varieties. Though the use of these preparations increased the methanol content proportionately more for white varieties, the final methanol content is less than that for similarly treated red varieties. The use of these preparations increased the methanol content of red wines during the early stages of fermentation.