Modulation of adzuki ( <i>Vigna angularis</i> ) bean milk analog substrates and metabolites through singular and/or combined treatment of germination and lactic acid fermentation

Given the growing interest in dairy-free milk analog products, new and diversified alternatives are pivotal to push the market forward. Germination and fermentation are traditional processing technologies used in plant-based milk production. However, the combination of both has not been extensively investigated. The aim of this study was to investigate the potential combined beneficial effects of coupling germination and fermentation on selected substrates and metabolites in adzuki bean milk analog. It was found that germination increased essential amino acids to 1193.44 from 421.46 mg/L in control while raising simple sugar and "green" (green odor) volatile compounds. Fermentation with probiotic Limosilactobacillus fermentum enriched the adzuki bean milk analog with probiotics and organic acids, whereby it also reduced some free amino acids (especially arginine) and "green" volatiles. Germination coupled with fermentation was able to overcome the deficiencies of the respective single treatment by elevating essential amino acid content (with a 4.8-fold increase in lysine and a 3.8-fold increase in histidine) and removing "green" odor volatiles while biofortifying the bean milk with probiotics, organic acids, and vitamin (nicotinic acid). Overall, a combination of germination and fermentation merits further research for substrate and metabolite modulation to develop novel and nutritious plant-based milk analogs with desirable flavor.