Germination-Induced Biofortification: Improving Nutritional Efficacy, Physicochemical Properties, and In Vitro Digestibility of Black Rice Flour.

Germination is an effective strategy for enhancing functional and processing characteristics of whole grains. This research aimed to explore the changes of nutritional components, physicochemical properties, in vitro digestibility, and microstructural characteristics of black rice flour (BRF) during 0-48 h germination. The results showed that germination significantly induced α-amylase activation of BRF, from 1.02 U/g to 4.46 U/g, leading to a 3.2-fold increase in reducing sugar content through starch hydrolysis. The content of apparent amylose was down-regulated during germination. The contents of free amino acids and minerals were markedly augmented in BRF. Specially, the GABA content was remarkedly enhanced, from 40.73 mg/kg to 258.35 mg/kg. Compared with BRF, the ratio of rapidly digestible starch (RDS) and resistant starch (RS) of germinated black rice flour (GBRF) increased by 12.04% and 0.43%, respectively, while the ratio of slowly digestible starch (SDS) decreased by 12.47% at 48 h. Scanning electron microscopy (SEM) analysis observed a more porous and loose surface structure in GBRF. X-ray diffraction (XRD) analysis illustrated that the relative crystallinity of GBRF was reduced with the prolonging of germination time. The dissociation of starch granules in GBRF ultimately led to a decrease in characteristic viscosity parameters, including peak, trough, final, and setback viscosity. In conclusion, germination improved the nutritional value and digestive characteristics of BRF, and altered its structure and physicochemical properties, which provides a reference for the development of whole grain-based products.