Synthesis of volatile phenols by Saccharomyces cerevisiae in wines

TLDR

Vinylphenols (4‑vinylphenol and 4‑vinylguaiacol) are natural wine constituents that influence aroma, but only white wines reach concentrations above 725 µg L⁻¹ that can cause a negative phenolic or pharmaceutical character. The study aims to use a yeast strain with weak SCD activity to prevent phenolic taint in white wines from grapes rich in decarboxylable hydroxycinnamic acids. The selected strain expresses a constitutive, fermentation‑only SCD activity that decarboxylates (E)-p‑coumaric and (E)-ferulic acids into vinylphenols, with intensity varying by strain. The SCD enzyme is rapidly inhibited by catechic tannins, explaining the low vinylphenol levels in red and rosé wines despite higher precursor content.

Abstract

Abstract Vinylphenols (4‐vinylphenol and 4‐vinylguaiacol) are natural constituents of wine and can play a role in wine aroma. However, only white wines contain important quantities of these volatile substances which, beyond a certain concentration (limit threshold = 725 μg litre −1 of 4‐vinylguaiacol+4‐vinylphenol (1:1)), can be responsible for a depreciating ‘phenolic’ or ‘pharmaceutic’ characteristic, Saccharomyces cerevisiae possesses a type‐(E) enzymic activity, substituted cinnamate carboxy‐lyase (SCD), which is capable of transforming, by non‐oxidative decarboxylation, the phenolic acids in the must, (E) p ‐coumaric and (E) ferulic acids, into corresponding vinylphenols. This endocellular activity is constitutive, it is only expressed during alcoholic fermentation and with a variable intensity depending on the yeast strain. Furthermore, the enzyme is rapidly inhibited by catechic tannins, which explains why, in comparison with white wines, red and rosé wines contain low levels of vinylphenols despite having more precursors. A yeast strain with a weak SCD activity has been selected and its use in vinification should eliminate the appearance of the phenolic taint in white wines coming from grapes rich in decarboxylable hydroxycinnamic acids.