Abstract: This study aimed to evaluate the sensory quality of Merlot dry red wine produced by sequential inoculation of Lachancea thermotolerans and Schizosaccharomyces pombe instead of malolactic fermentation, in order to provide technical support for the application of non-Saccharomyces cerevisiae strains in quality improvement of dry red wine. In this work, Merlot grapes from Wuwei region of Gansu province were used for wine-making. Sequential inoculation of one of three strains of L. thermotolerans and one strain of S. pombe at intervals of 4 days and single inoculation of S. pombe were conducted as experimental treatments, and single inoculation of S. cerevisiae was taken as control. Yeast populations were monitored during the fermentation process, and the main physicochemical indexes, flavor components and sensory quality of wine were analyzed. The results showed that the treatment groups completed the alcoholic fermentation in 16 days. The viable cell population of S. pombe was stable until the alcoholic fermentation started. The population of L. thermotolerans reached the maximum on the 4th day, and it decreased significantly after the addition of S. pombe and disappeared completely from the 10th to 12th day. L-lactic acid concentrations in three sequential inoculation groups were not significantly different (2.46–2.86 g/L), but they were significantly higher than that in the control group (P < 0.05). Sequential inoculation reduced the volatile acidity by 0.11–0.16 g/L and increased the total acidity by 0.96–1.97 g/L. In addition, it increased the color aroma and decreased the hue. The production of esters, higher alcohols and acids in the sequential inoculation groups were decreased by 38.46%–49.34%, 13.36%–19.42%, and 46.84%–49.71%, respectively, compared with the control. However, the concentrations of terpenes, phenylethyl alcohol and damascene were increased and the aroma complexity was enhanced. Sensory analysis showed that the wines produced by sequential fermentation were more acidic than the control, while they had a better color appearance and stronger fruity and flowery aroma. These results indicated that sequential inoculation of L. thermotolerans and S. pombe is a potential alternative to malolactic fermentation and has a positive effect in improving the acidity and sensory quality of wine.

Key words: Merlot, Lachancea thermotolerans, Schizosaccharomyces pombe, sequential inoculation, sensory quality