Metabolomic and Physicochemical Evolution of Mango (Mangifera indica L.) Juice during Kombucha Fermentation: NMR-Based Insights into Sugar Degradation, Organic Acid Accumulation, and Color Change

Abstract

This study investigated the metabolic evolution of mango (Mangifera indica L.) juice-based kombucha during fermentation in order to identify the most favorable stage for bioactive compound enrichment and compositional stability. Fermentation was conducted for 0, 3, 5, and 7 days using a symbiotic culture of bacteria and yeasts (SCOBY). Samples were analyzed through physicochemical assays and ¹H NMR-based metabolomics. Significant acidification was observed, with pH decreasing from 3.83 to 3.29 and titratable acidity increasing from 0.21% to 0.59% (p < 0.05). Sucrose depletion was accompanied by progressive accumulation of organic acids, particularly acetic and malic acids. Alanine and γ-aminobutyric acid (GABA) increased during fermentation. Color parameters exhibited significant differences (p < 0.05), with increased lightness (L*) by day 5. Principal component analysis (PCA) showed that PC1 and PC2 explained 39.37% and 22.46% of total variance, respectively, clearly separating unfermented and fermented samples and indicating progressive metabolic convergence after day 5. From day 5 onward, increased levels of malic acid, alanine, and GABA were observed, accompanied by a moderated acetic acid concentration. Collectively, these findings suggest that 5 days of fermentation may represent an optimal balance between bioactive compound production and sensory-relevant acidification.