Chapter 4 - Non-Saccharomyces Yeasts in the Winemaking Process

Abstract

This chapter describes the role of non-Saccharomyces yeasts in the winemaking process and its contribution to the final product, both in terms of their influence on wine aroma and their role in the vinification process itself. Non-Saccharomyces yeasts can influence both the primary and secondary aroma. The varietal aroma is mainly determined by the quantity and chemical nature of the volatile secondary metabolites present in the grape. Of these, the terpenes have the greatest influence on flavor and aroma, particularly in wines derived from Moscatel grapes but also in other less aromatic varieties. Yeasts are also responsible for the secondary or fermentation aroma of the wine. This aroma arises during alcoholic fermentation and is determined by compounds produced as part of wine yeast metabolism. Numerous studies have characterized the non-Saccharomyces yeast strains found on different varieties of grape. In an effort to exploit the putative causal relationship between the presence of these strains and the type of wine produced, fermentations have been attempted with starter cultures that include both S. cerevisiae and yeasts belonging to the genera Kloeckera, Cryptococcus, Hanseniaspora, Candida, Pichia, and Hansenula. The wines produced with these mixed starter cultures differ significantly in both chemical composition and sensory characteristics.