Stress Responses in Wine Yeast

Saccharomyces cerevisiae is employed as pure starter cultures in industrial wine fermentations and usually within 2 days predominates in the must fermentations. Its physiology and genetics have been extensively studied and it serves as a model organism for all eukaryotes. In this chapter we will focus on the responses to different stresses the yeast encounters from its desiccation for distribution until the final stages of vinification. Stress signalling pathways explained in detail are those for response to high and low medium osmolarity (HOG and CWI), response to high temperatures, oxidative stress, and their interconnection with the general (environmental) stress response. These pathways are discussed regarding their relevance in vinification, followed by addressing more wine specific stress conditions, such as high ethanol concentration, nutrient limitations, acid stress, sulphite resistance, and cold stress. The chapter is concluded by a discussion of emerging issues.