Yeast-induced changes in the concentration and structure of oligomeric proanthocyanidins during simulated wine fermentation

Abstract

Background and Aims: Proanthocyanidins (PAs), the predominant phenolic substances in wine, are responsible for the astringency of wine. The present work aims to understand the effect of yeast on the concentration and composition of the subunits of PAs during fermentation. Methods and Results: The concentration and cleavage products (subunits) of PAs were measured during fermentation. Early in fermentation (within about 4 days), the concentration of PAs decreased significantly by around 78% for strain BH8 and 67% for strain AWRI R2; in addition, the mean degree of polymerisation and composition of PAs underwent considerable change. At the later phase of fermentation, no significant change was recorded in the concentration and mean degree of polymerisation of PAs, whereas the composition of PAs evolved progressively. Conclusions: Yeast can exert a significant influence on the concentration and structure of PAs during wine fermentation in a strain- and time-dependent manner. Significance of the Study: The results will enable a better understanding of the effect of yeast on the evolution of PAs in winemaking, as well as increase knowledge of the interaction between yeasts and phenolic substances to improve wine composition.