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Transient acetaldehyde production by SO2 producing S. cerevisiae promotes survival of Oenococcus oeni during co-fermentation

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Jun 27, 2023 version files 59.91 KB

Abstract

Stuck or sluggish malolactic fermentation (MLF) can be problematic in limiting wine conditions, particularly white and sparkling base musts / wines. In these cases, knowledge of yeast-bacteria strain compatibility and the amount of sulfur dioxide (SO2) a yeast strain produces are important considerations for successful MLF.

Here, the effects of yeast-derived SO2 production on O. oeni survival was investigated in laboratory- and pilot-scale co-fermentations in Chardonnay. Further to the S. cerevisiae strain affecting O. oeni survival and MLF, we show that SO2 production by yeast (to approximately 65 mg/L) can be uncoupled from O. oeni survival in early stages of co-fermentation. Bacterial survival with certain SO2-producing yeast strains was correlated with early, transient formation of a high concentration of acetaldehyde.  Upon co-inoculation, an extremely low concentration range (approximately 1–44 µg/L) of calculated molecular SO2 is indicated to regulate O. oeni survival. Possible strain-dependent sensitivity of O. oeni to bound SO2 may also occur, although the extent and nature of such inhibition by the SO2 adduct itself during co-fermentation remains unclear.

Choice of co-inoculation yeast strain also influenced wine diacetyl concentration, which was only detected in wines co-inoculated with high-SO2-producing S. cerevisiae strains. These wines also had comparatively high citation frequency for a buttery sensory attribute. Both the SO2 and acetaldehyde production capacity of yeasts are therefore seen as meaningful co-inoculation selection criteria. The range of yeast strains suitable for MLF induction by co-inoculation could be widened to include SO2-producing strains which transiently produce an early, high concentration of acetaldehyde. Reliance on total / bound SO2 concentration may also potentially provide an inaccurate measure of SO2 toxicity towards O. oeni, particularly for co-inoculation, and the impact of low, equilibrium concentrations of molecular SO2 should also be considered.