Effects of Three-Strain Mixed Cultures on Fermentation and Aroma of Merlot Wine

In order to enhance the malolactic fermentation efficiency and aroma quality of Merlot wine, this study introduced non-Saccharomyces yeasts (Hanseniaspora uvarum Hu2, Hanseniaspora osmophila Hos39, and Pichia kluyveri Pk6) to construct a triple-strain starter culture consisting of Saccharomyces cerevisiae, non-Saccharomyces yeast, and lactic acid bacteria (LAB). The results showed that the co-fermentation strategy significantly accelerated the MLF process and shortened the fermentation cycle by 40%. The introduction of Hanseniaspora significantly increased the content of acetate esters, particularly ethyl acetate (31.8% to 40%). Heatmap analysis further indicated that the contribution of Hanseniaspora to wine aroma exhibited genus commonality. Wine fermented with P. kluyveri had the highest content of 2-phenylethyl acetate, which was 9 times that of the control group. Furthermore, sensory analysis revealed that non-Saccharomyces yeast co-fermentation reduced the green and vegetal notes of the wine. Specifically, H. osmophila Hos39 enhanced the pome fruit-like aroma, while P. kluyveri Pk6 significantly intensified the floral aroma. This study confirms that triple-strain co-fermentation effectively increases the rate of malolactic fermentation and improves wine aroma, which is of theoretical significance for the development of mixed-strain fermentation technologies.