Effect of yeast-lactic acid bacteria differential inoculation sequence on the accumulation of key aroma compounds in chardonnay wine.

Mixed-culture fermentation involving Saccharomyces cerevisiae, non-Saccharomyces yeasts, and Oenococcus oeni has the potential to significantly enhance winemaking efficiency. The inoculation timing of microbial strains greatly influences the chemical composition and flavor profile of the finished wine. In this study, indigenous Metschnikowia pulcherrima NX-2 was inoculated into Chardonnay juice to initiate alcoholic fermentation, while Saccharomyces cerevisiae VW and indigenous Oenococcus oeni ZX-1 were introduced at staggered time intervals. The fermentation kinetics, chemical components, and sensory profiles of the resulting wines were systematically characterized. Results showed that simultaneous inoculation of NX-2, VW, and ZX-1 shortened the fermentation cycle to 6 days, yet significantly increased the titratable acid content of the samples. As the inoculation time of the mixed culture (VW and ZX-1) was delayed, ZX-1 gradually inhibited the activity of VW. In addition, the inoculation timing of these strains significantly affected the levels of esters, higher alcohols, fatty acids, and C6 compounds in the wine. Compared to simultaneous inoculation, the contents of key differential volatile markers, namely, ethyl caprylate, ethyl caprate, and ethyl hexanoate, in wines inoculated with NX-2 for 48 h before co-inoculation of ZX-1 and VW increased by 59.87%, 61.92%, and 47.26%, respectively. Thus, the tropical fruit, stone fruit, floral, and sweet aromas of this Chardonnay wine were intensified, enabling it to achieve the highest sensory score. The study offers new insights for winemakers to optimize fermentation protocols and improve wine flavor.