The effect of wine yeast on colour extraction and stabilisation in red wine (in collaboration with The Australian Wine Research Institute)

Abstract

Colour is an important initial cue to the consumer in terms of the perception of quality in red wines. Previous work has revealed that choice of wine yeast can have a strong influence on the colour of wine. This project, through the activities of a PhD student, sought to confirm this effect and begin to more fully define the basis for this phenomenon.

Summary

Colour is a critical sensory and hence quality attribute of red wine. Modulating wine colour is therefore as important as managing wine flavour, aroma, mouthfeel and taste. Being able to specifically manipulate wine colour is best achieved with an understanding of the mechanisms that impact on this attribute. Previous studies have revealed that colour development in red wines is a very dynamic process, involving the extraction of anthocyanins from grape skins and their transformation to more stable pigmented polymers. This process is influenced by several factors, both chemical and microbiological. We seek to gain a greater understanding of these factors and their interaction as a basis for colour development and stability in young and aged red wines. Currently, unrelated studies have implicated yeast metabolites, biomass and some hydrolytic enzymes as modulators of colour development. We seek to expand on this previous research and develop a detailed understanding of the relative importance of these mechanisms by which yeast affect red wine colour. Ultimately, this information will be used to produce strains with multiple colour-enhancing properties which result from enhancements to two of more of the following: 1) increased liberation of anthocyanins from grape skins by hydrolytic enzymes, 2) reduced degradation of anthocyanins, 3) increased formation of metabolites which favour pigmented polymer formation and 4) reduced loss of pigments through binding to yeast lees.