The use of a specific glutathione-rich inactivated yeast to protect organic Catarratto grape must and wine from oxidation in the pre-fermentative phase

This study aimed to investigate the effects of using a specific glutathione-rich inactivated yeast (GIY) during the pre-fermentative stages of winemaking. The antioxidant properties of GIY were evaluated both alone and in combination with a selected strain of Metschnikowia pulcherrima, at various grape pressing stages. The assessment included measuring soluble oxygen levels and color browning in the musts. Additionally, the impact of different oenological protocols on the final aromatic profile of the wines was assessed through volatile organic compounds (VOCs) and sensory analysis. The results showed that inoculating M. pulcherrima during the pre-pressing phase, followed by GIY addition during the post-pressing stage, effectively reduced O2 uptake (1.49 mg/L) and minimized browning (0.093 OD at 420 nm) during the pre-fermentative phase. Furthermore, the protocol involving GIY addition during pressing resulted in higher concentrations of specific compounds associated with fruity and floral aromas, such as ethyl octanoate (26.03 mg/L) and ethyl decanoate (26.87 mg/L). Sensory evaluations confirmed that all treatments had no off-odours or off-flavours, but the M. pulcherrima and GIY combination received the highest scores for smoothness and colour attributes. In conclusion, GIY treatments offer a promising alternative to enhance wine colour and mitigate oxidation effects, potentially reducing the reliance SO2 in wine production.