Analysis of Sacchoromyces During Normal and Problem Fermentations

The aims of the first three years of this proposal were to acquire, develop and optimize technologies for the analysis of problem fermentations. The goal of this work is to develop better fermentation management strategies to reduce and hopefully eliminate the incidence of slow and incomplete fermentations. In this first phase of the research we have successfully adapted functional genomic analysis to Saccharomyces grown under enological conditions. We have identified several key differences in the physiology of yeast grown under nutrient sufficient versus nitrogen-limited conditions. We have begun identifying molecular markers associated with healthy or robust fermentations and those associated with nutritional or environmental stress. The project is well poised to complete this analysis in the next year and to identify key yeast strain and physiological input factors needed for full optimization of the predictive potential of neural networks. We have developed bacterial-specific primers for direct analysis of bacterial strains in wine. In addition, we have developed and tested several yeast specific primers and employed them on samples obtained from commercial wine fermentations. This approach has resulted in direct identification of viable but non-culturable yeast populations, a potential factor in stuck fermentations. The project is well poised to complete this analysis in the next year and to identify key yeast strain and physiological input factors needed for prediction of fermentation kinetics. In addition to the molecular and physiological work, we are currently completing detailed analysis of samples from over 200 commercial Chardonnay fermentations from the 2001 harvest. Analysis of the juice and wine from these fermentations, which ranged from normal to sluggish and stuck, will allow us to identify juice characteristics and processing choices that are critical in determining fermentation kinetics. We have also developed bacterial-specific primers for direct analysis of bacterial strains in wine. In addition, we have developed and tested several yeast specific primers and employed them on samples obtained from commercial wine fermentations. This approach has resulted in direct identification of viable but non-culturable yeast populations, a potential factor in stuck fermentations. With all yeast physiological and microbial ecology factors, juice characteristics, and processing parameters identified that are critical in determining wine fermentation kinetics, we will be able to predict problem fermentations and their resolution early in the fermentation process.

PDF: Analysis of Sacchoromyces During Normal and Problem Fermentations