1a.Objectives (from AD-416):
Evaluate methods of detection for Zygosaccharomyces; Determine the impact of selected strains of Zygosaccharomyces on wine composition and quality.
1b.Approach (from AD-416):
Strains will be grown on non-selective media for routine maintenance and preparation of starter cultures for wine inoculation. Modification and optimization of alternative selective media will focus on (a) substitution of carbon sources and (b) lowering the water activity of the medium. Selected strains of Zygosaccharomyces will be inoculated small scale. During incubation, general analyses to be performed include culturability (plate count), volatile acidity (Cash still), and, if applicable, rate of fermentation (soluble solids). For those strains were no obvious sensory differences exist between wines without or with inoculation of Zygosaccharomyces, vinification experiments of a larger scale will be conducted with additional chemical and sensory analyses.
This research supports objective 1B of the parent project. With increases in the importance of the wine industry, sluggish or slow alcoholic fermentations represent industry losses that easily exceed hundreds of thousands of dollars. It is therefore important to gain a better understanding of alternative methods to easily remove residual sugars found in partially fermented grape musts from the Pacific Northwest region. An alternative solution to this problem could be use of selected strains of Zygosaccharomyces, a yeast known to be fructophilic yet tolerant to high concentrations of ethanol. Non-spoilage strains of Zygosaccharomyces are being evaluated that could potentially utilize residual sugars from wines where alcoholic fermentation prematurely ceased. Data suggest that these species may exist in a “viable-but-not-culturable” state but additional evidence is required.