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

Area of Science:

• Oenology and Viticulture
• Food Chemistry
• Biochemistry

Background:

• Global climate change is altering grape phenolic maturity, affecting wine sensory properties like astringency.
• Increasing wine pH to values near 4 is a consequence of warmer climate conditions.
• Mannoproteins (MPs) from enological yeast are utilized to mitigate these climate-induced changes and improve wine quality.

Purpose of the Study:

• To investigate the effect of different pH values (3 and 4) on the interaction between Saccharomyces cerevisiae mannoproteins (MPs) and wine flavanols.
• To assess the role of MPs in modulating wine astringency under changing climate conditions.

Main Methods:

• Isolation and purification of a MP-rich extract from Saccharomyces cerevisiae cell walls using Zymolyase digestion.
• Characterization of the MP extract.
• Analysis of MP-flavanol interactions at pH 3 and pH 4.

Main Results:

• MP-flavanol binding capability is pH-dependent.
• Larger MP fractions precipitate galloylated dimers at both pH 3 and 4.
• Medium molecular weight MPs (approx. 60 kDa) enhance the solubilization of non-galloylated flavanols at pH 4, potentially modulating astringency.

Conclusions:

• MP-flavanol interactions are influenced by pH, with implications for wine astringency.
• In a climate change scenario with rising wine pH, medium-sized MPs can be strategically used to counterbalance astringency.
• Wineries can optimize MP addition to mitigate undesirable taste profiles in wines affected by climate change.