Effect of Alcohol-Malolactic Three-Strain Co-Fermentation Mediated by Lactobacillus brevis LB-21 on the Color of Dry Red Wine

This study aimed to investigate the effect of alcoholic-malolactic co-fermentation mediated by Lactobacillus brevis (LB-21) on the color quality of dry red wine, to provide the data support for optimizing this technology.

Using Marselan grapes from Turpan, Xinjiang, as raw material, alcoholic-malolactic co-fermentation treatments were designed with mixed inoculation of Saccharomyces cerevisiae SC-19, Pichia fermentans Z9Y-3, and lactic acid bacteria (Lactobacillus brevis LB-21 or Oenococcus oeni SD-2a). Concurrently, traditional sequential alcohol-malolactic fermentation group and single alcohol fermentation group served as the controls. After fermentation, the wines underwent conventional stabilization and were stored until June of the following year. Spectrophotometric methods were used to determine CIElab color parameters (L^*, a^*, b^*, C^*_ab, h_ab, etc.) and multiple pigment indicators, including 520 pigment (520P), chromaticity of free anthocyanins (FA), total pigment (TP), polymeric pigment (PP), percentage of polymeric pigments (PP%), total phenols, and tartrate esters. Principal Component Analysis (PCA) was employed to identify key compounds responsible for color differences among the wine samples, and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) was used to investigate compounds distinguishing the color characteristics of co-fermented samples.

Color differences among the wine samples primarily centered on CIElab parameter hue angle (h_ab) and pigment indicators such as 520P and TP. Compared with single alcohol fermentation, alcohol-malolactic fermentation increased red hue (a^*) and color saturation (C^*_ab) by 3.69%-13.74% and 7.24%-19.77%, respectively, and TP increased by 27.52%-47.41%, and PP by 4.39%-34.12%, respectively, significantly enhancing color stability (P<0.05). However, total anthocyanins and free anthocyanin levels decreased by 20.60%-25.69% and 14.03%-38.59%, respectively. PCA results indicated that under the alcoholic-malolactic co-fermentation treatment, the Lactobacillus brevis LB-21 group significantly outperformed the Oenococcus oeni SD-2a group in key indicators, including a^*, C^*_ab, TP, PP, and PP% (P<0.05). OPLS-DA analysis confirmed that L^*, a^*, C^*_ab, h_ab, ΔE_ab, and PP% were key color difference indicators in LB-21-mediated co-fermented wine samples, indicating this strain's significant advantage in maintaining dry red wine color.

Alcohol-malolactic three-strain co-fermentation, particularly the treatment mediated by Lactobacillus brevis LB-21, significantly enhanced a^*, TP, and PP in dry red wine, improved color stability, and outperformed traditional fermentation models in key color parameters. The optimized strain LB-21 and its application technology demonstrated substantial practical value for enhancing dry red wine fermentation processes.