Improvement of Phenolic Bioaccessibility and Gut Microbiota Modulation Potential of Black Rice by Extrusion Combined with Solid-State Fermentation

Black rice has gained increasing attention due to its abundant phenolic compounds and gut microbiota modulation potential, but its health benefits are highly dependent on processing methods. In the present study, the effects of extrusion, traditional cooking, and their combinations with solid-state fermentation (SSF) on phenolic bioaccessibility and the gut microbiota modulation potential of black rice were compared. Results indicated that extrusion combined with SSF (E-SSF) was the most prominent in improving the bioaccessibility of phenolics, flavonoids, and antioxidant activities of black rice during in vitro gastrointestinal digestion. In addition, black rice after SSF induced significantly lower gas production and higher pH during in vitro fecal fermentation. Particularly, black rice after E-SSF showed great advantages in the yield of propionic acid, butyric acid, and total short-chain fatty acids. Consequently, black rice after SSF increased alpha diversity and Bacteroidetes abundance but decreased Firmicute abundance of gut microbiota, while black rice after E-SSF induced the highest alpha diversity and Bacteroide abundance. These results suggested that SSF was beneficial to improve the gut microbiota modulation potential of black rice, and E-SSF was the most preferred. In conclusion, E-SSF was the most suitable to improve the phenolic bioaccessibility and gut microbiota modulation potential of black rice.