Preparation of modified shiitake mushroom stem insoluble dietary fiber and black rice anthocyanin complex and its effects on the gel properties, rheological properties and microstructure of rice starch.

This study constructed a complex of steam-exploded shiitake mushroom stem insoluble dietary fiber (SEIDF) and black rice anthocyanins (BRA) and elucidated the interactions between SEIDF and BRA, the structural features of the SEIDF-BRA complex, and the effect of this complex on the rice starch gel structure and property. Results showed that SEIDF had higher surface porosity and roughness after steam explosion. BRA was adsorbed onto SEIDF in a multilayer manner, and the interaction between BRA and SEIDF involved non-covalent binding (including hydrogen bonds), resulting in the formation of a thermally stable complex. Structure characterization indicated that the hydrogen bonding of the SEIDF-BRA complex was greatly enhanced, and more functional groups (such as C-O) were exposed in the SEIDF-BRA complex. Moreover, the addition of the SEIDF-BRA complex not only increased the gelatinization temperature and viscosity of rice starch while inhibiting starch retrogradation, but also improved the rheological behavior, texture property and sensory quality of rice starch. Structurally, the SEIDF-BRA complex reduced the relative crystallinity and short-range order degree of rice starch and improved the porosity and cross-linking of the gel network. This study might contribute to the development of SEIDF-BRA complex as a potential functional food ingredient.