Fruity aroma modifications in Merlot wines during simultaneous alcoholic and malolactic fermentations through mixed culture of S. cerevisiae, P. fermentans, and L. brevis

As a group of wine lactic acid bacteria, Lactobacillus has gained growing interest in malolactic fermentation due to possessing diverse aroma-related enzymes. In this study, a Lactobacillus brevis 26 with high β-glucosidase activity was isolated, and co-inoculated with yeasts (Saccharomyces cerevisiae and Pichia fermentans) to characterize fruity aroma modifications in Merlot wine. Compared with the traditional inoculation (sequential inoculation of L. brevis 26 after alcoholic fermentation by yeasts), co-inoculation of the three species induced simultaneous alcoholic and malolactic fermentations, leading to a pronounced reduction in total fermentation duration. P. fermentans increased L. brevis 26 cell viability when co-fermented with the predominant species S. cerevisiae. Meanwhile, the β-glucosidase activity of L. brevis 26 elevated terpene contents, and P. fermentans induced the production of higher alcohol acetates and fatty acid ethyl esters. Sensory analysis showed that co-inoculation-based wines had enhanced complexity of fruity aroma profiles associated with jammy and temperate fruity notes.