Direct Gas Chromatographic Determination of Levo- and Meso-2,3-Butanediols in Wines and Factors Affecting their Formation

Abstract

The levo and meso stereoisomers of 2,3-butanediol formed by yeast fermentation of grape juice, were seperated and identified by gas chromatography and infrared spectrophotometry. Samples of each isomer in wine were collected from the exit port of the chromatographic column and were compared with authentic samples by infrared spectrophotometry. The levo and meso forms exhibited similer spectral absorbence properties except that the levo has an extra peak at a wave number of 960 cm^-1. For gas chromatographic analysis, 3-µl wine samples were injected directly onto a column at 125°C packed with Ucon 75-H-90,000 coated Chromosorb WAW. Two other liquid substrates were also found applicable for separating the glycol isomers. The concentrations of the two isomers were determined by comparing their respective peak areas with those given by standard solutions containing 30% meso and 70% levo forms in water. The 2,3-butanediol contents of a number of experimentally and commercially produced wines were determined. Concentrations ranged from 340 to nearly 2000 ppm. The influence of various production factors on the levels formed was studied in an attempt to account for the wide range of concentrations found. In general, the formation of 2,3,-butanediol increased significantly with increasing fermentation temperatures, and also as the initial sugar content of the must increased.