Effect of citrate transporter deficient strain of Lactiplantibacillus plantarum XJ25 on the flavor of wine malolactic fermentation

In order to investigate the effect of Lactiplantibacillus plantarum XJ25 citrate transporter deficient strain XJ25-ΔcitP on the flavor of wine malolactic fermentation (MLF). The deficient strain XJ25-ΔcitP was added into the malolactic fermentation process of wine, and the changes in the flavor characteristics of wine were comprehensively revealed by measuring the total acid, volatile acid, key organic acid contents, volatile flavor components and sensory evaluation, and combining with multivariate statistical methods. The results showed that deficient strain XJ25-ΔcitP could complete malolactic fermentation without relying on the citric acid metabolism pathway. Compared with the wine fermented by wild strain XJ25, the total acid content of the wine fermented by deficient strain XJ25-ΔcitP significantly increased by 5.14% (P<0.05), while the contents of volatile acid, acetic acid, lactic acid and succinic acid significantly decreased by 37.80%, 41.65%, 3.94% and 8.97%, respectively (P<0.05). The citric acid in the fermented sample by wild strain XJ25 was completely metabolized and not detected, while the fermented wine sample by deficient strain XJ25-ΔcitP retained 81.56% of the citric acid. A total of 118 volatile flavor components were detected in the 3 groups of wine samples. There were significant differences in volatile flavor components among different wine samples. According to the variable importance in projection (VIP) value>1 and P<0.05, a total of 53 differential volatile flavor components were screened out. Inoculation with the deficient strain XJ25-ΔcitP for malolactic fermentation not only reduced the raw green flavor of the original wine, but also enhanced the fruity, floral and roasted aromas. Moreover, it avoided the overly creamy and pungent taste of the wild strain XJ25 after fermentation. This research provided a new strain improvement strategy for targeted regulation of wine quality.