Decoding antioxidant mechanisms in specific inactivated yeast

Abstract

Inactivated yeasts, like many other enological biotechnologies, are routinely characterized by producers to assess their functional performance. Glutathione content, in particular, is commonly used to classify products as “Inactivated yeast with guaranteed glutathione level, implying enhanced protection against oxidation. But, as already shown, its concentration alone cannot fully predict the antioxidant capacity of a yeast biomass1. Antioxidant activity is in fact multifactorial, involving a combination of redox active molecules, nucleophiles, and other reactive compounds. In this study, we combined advances in biotechnology and analytical chemistry to investigate how yeast strain selection and production processes influence the antioxidant potential and mechanisms of inactivated yeasts. One Saccharomyces (ISY) and one non-Saccharomyces (INSY) inactivated yeast both from selected strains and both produce to improve their antioxidant properties, were evaluated for their capability to consume oxygen, to trap reactive species (DPPH scavenging capacity, radical species trapping by electron paramagnetic resonance (EPR), as well as their ability to release nucleophilic compounds and thus having a quinone-trapping activity estimated by UHPLC-MS. Despite a fivefold difference in glutathione content, the two products showed similar DPPH indices, indicating that additional compounds contribute significantly to radical scavenging. Both studied inactivated yeasts consumed oxygen efficiently, with slightly higher rates observed for ISY. The most striking difference emerged from nucleophilic fingerprinting. ISY displayed a broad and diverse nucleophilic profile, while INSY exhibited a much narrower chemical signature. This limited diversity was directly reflected in a weaker quinone trapping capacity, highlighting a distinct mode of antioxidant action. Overall, ISY appears to rely mainly on nucleophile mediated quinone trapping, whereas INSY seems to act predominantly through redox active compounds. By integrating complementary assays, this work provides a clearer understanding of how different yeast biotechnologies express antioxidant potential and offers a robust framework for their rational selection. Beyond fundamental insight, this multidimensional approach opens new perspectives for the wine sector, where oxidative challenges are increasing and demand more precise, mechanism‑oriented tools to guide the development of next‑generation enological solutions.