Volatile Sulfur Compounds: Incidence and factors affecting their formation in Californian Wines

The GC used for analysis of sulfur volatiles has been recalibrated to permit evaluation of the split effluent of the GC by sensory (sniff) evaluation and by flame photometry. In all surveys of headspace of spoiled wines, no new volatiles were detected other than those previously reported (Park et al, 1994). The natural wine yeast strain, Saccharomyces cerevisiae UCD934, was investigated to determine the number of genes responsible for H2S production during yeast fermentation. The strain is heterozygous for the MET5 gene which encodes for a component of sulfite reduaase. The parental strains were sporulated, tetrads dissected, and crossbreeding was conducted. Compared to the parents, the progeny strains showed dramatic variation in H2S production capacity. By the tetrad analysis of these yeast and further crosses made since the submission of the progress report in March, 1995, it was confirmed that five genes including MET 5 are involved in H2S production.