Changes in functional activities and volatile flavor compounds of fermented mung beans, cowpeas, and quinoa started with Bacillus amyloliquefaciens SY07.

In this work, the functional activities including α-glucosidase, α-amylase, angiotensin converting enzyme (ACE) inhibitory activity, and antioxidant activity of mixed grains (mung beans, cowpeas, and quinoa) fermented with Bacillus amyloliquefaciens SY07 were investigated. The volatile flavor of the mixed grains collected every 12 h during 72 h-fermentation were further detected as well. The inhibition on α-glucosidase and α-amylase reached up to 89.34 % and 50.03 % with the sample concentration of 5.17 and 9.38 mg/mL, respectively. Moreover, the ACE inhibitory activity reached to 93.66 % with the sample concentration of 0.59 mg/mL. The antioxidant capacity of the mixed grains, evaluated by ABTS and DPPH radical scavenging capacities and ferric ion reducing power, was also significantly improved (p < 0.05) during fermentation. The maximum of ABTS and DPPH radical scavenging capacities increased to 8.64 and 3.21 mg TE/g DW, respectively, and the maximum ferric ion reducing power reached to 5.73 mg TE/g DW. Twenty-one volatile flavor compounds with odor activity values (OAVs) ≥ 1 were detected, and six key volatile flavor substances were identified by OPLS-DA analysis, namely, isovaleric acid, acetoin, phenylacetic acid, (Z)-2-nonenol, 1-hexanol, and 1-octen-3-ol, with overall strong creamy, sweet, baked-potato, and cocoa flavors upon fermentation. These findings revealed a favorable pathway for B. amyloliquefaciens SY07 to be used to improve the functional and flavor properties of fermented grains, which would also be of great value for further elucidating the mechanism of the formation of the volatile flavor differences and developing novel quality cereal-based products.