Mulberry (Morus alba L.) is nutritious and pharmacologically valuable but highly perishable. To extend its shelf life, mulberries are often processed into beverages, vinegars, wines, and dried products. Among these, mulberry wine offers exceptional added value through microbial fermentation. Fruit wine fermentation typically involves two critical stages-alcoholic fermentation and malolactic fermentation (MLF)-which jointly determine product quality. However, initiating and controlling MLF remains technically challenging. To address this, co-fermentation of yeast and lactic acid bacteria has been proposed, though studies have mainly focused on flavor and aroma, with limited insight into its effects on color and anthocyanin stability. Here, a simulated anthocyanin system using purified mulberry pigments was established, and untargeted metabolomics were applied to elucidate how co-fermentation influences color retention. During single Saccharomyces cerevisiae fermentation, degradation rates of cyanidin-3-O-glucoside (C3G) and cyanidin-3-O-rutinoside (C3R) reached 98.72% and 48.59%, respectively. In contrast, co-fermentation with Lactobacillus plantarum significantly improved retention of C3G (5.08% vs. 1.30%) and C3R (57.15% vs. 51.41%) (p < 0.01). Colorimetric analysis revealed that co-fermentation significantly preserved wine color, characterized by higher a* (redness/greenness), C* (chroma), color density, and absorbance at pH 1.0, alongside lower ΔE (total color difference) values. Pearson correlation indicated that a* changes were primarily governed by anthocyanin concentration. Metabolomic profiling further revealed that yeasts degraded C3G and C3R more rapidly than lactic acid bacteria. The enhanced color stability under co-fermentation was likely linked to anthocyanin-mediated regulation of amino acid metabolism, particularly the upregulation of DL-norvaline, L-isoleucine, and L-phenylalanine, which played pivotal roles in maintaining anthocyanin stability.
Yin et al. (Sun,) studied this question.