Wine pH could affect the interaction between yeast mannoproteins and flavanolic compounds

Global climate change is noticeably influencing the phenolic maturity of grapes. As a consequence, certain sensory properties of wine, such as astringency, are being altered. Additionally, the warmer conditions are gradually increasing the pH of wine to values close to 4. The addition of mannoproteins (MPs) derived from enological yeast is one of the various strategies that are being implemented in winemaking to mitigate these changes and to enhance wine quality. In this study, a MP-rich extract from the cell wall of Saccharomyces cerevisiae was isolated through Zymolyase digestion, purified and characterized to assess the effect of different pH values (pH 3 and pH 4) on the interactions between the extracted MP and a mixture of wine flavanols.

The results obtained indicated that the capability of the different MP fractions to bind flavanols was pH dependent. At both pH values, the largest MP fractions were involved in the precipitation of galloylated dimers. However, in a climate change scenario, where wine pH is progressively increasing to values near 4, the addition of MPs with a medium molecular weight (ca 60 kDa) could play an important role in modulating astringency by enhancing the solubilization of non-galloylated flavanols.

The findings from this study provide valuable insights for optimizing the use of MPs to modulate wine astringency. If wine pH continues rising, wineries might consider adding medium-sized MPs derived from the cell wall of S. cerevisiae to counterbalance astringency and to reduce undesirable taste profiles. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.