Retrogradation behavior and mechanistic exploration of fermented mung bean starch gels during cold storage

To elucidate the unique gelling mechanism of mung bean starch (MBS) coproduced during the production of mung bean sour liquid and broaden its potential applications, this study initially investigated the impact of natural fermentation on retrogradation behavior of MBS gels during 7 d of cold storage at 4 °C. MBS was extracted from mung bean liquid fermented naturally at 30 °C for 2 d and 4 d to prepare gels (FTG and FFG), which both showed higher whiteness but lower gel strength after 7 d storage than the native MBS gel (NMG). Lower reduction rates in T₂ values were observed for FTG (25.93%, 10.71%) and FFG (23.27%, 14.31%) relative to NMG (55.84%, 14.91%) after 4 and 7 d, respectively, indicating enhanced water holding stability. Compared to NMG, FTG showed no significant changes in hardness, gelatinization enthalpy, relative crystallinity, R_1047/1022 ratio (p > 0.05), and semicrystalline layer thickness before 4 d of storage. However, its hardness decreased from 1384.30 g to 1168.70 g (p < 0.05) on day 7. Conversely, FFG increased in all the above parameters before day 4, and its hardness decreased to 1216.60 g on day 7 (p < 0.05). Moreover, fermentation for 4 d promoted V-type but inhibited B-type crystallinity, confirming its potential to inhibit long-term retrogradation of MBS. This helps manufacturers understand MBS retrogradation properties and mechanism across fermentation stages, guiding tailored MBS gel product development.