Structural Characteristics of Cooked Black Rice Influenced by Different Stabilization Treatments and Their Effect Mechanism on the In Vitro Digestibility

Superheated steam (SS), far-infrared radiation (FIR), and microwave treatment (Mw) are emerging stabilization treatments to improve the shelf life of black rice. However, their effects on the digestibility of cooked black rice remain unclear. Therefore, the structural characteristics of cooked black rice influenced by the above treatments and their effects on in vitro digestibility were compared. Results indicated that cooked SS stabilized black rice (CBR-SS) had the highest crystallinity (9.17%), the lowest porosity, and the completest protein network. Besides, the lowest level of rapidly digestible starch (31.02%) and the highest level of resistant starch (32.75%) were observed in CBR-SS. Consequently, CBR-SS showed the lowest equilibrium hydrolysis rate, kinetic constant, and expected glycemic index during in vitro starch digestion among the cooked stabilized black rice samples. Furthermore, the level of total bioaccessible phenolic compounds and antioxidant activity was the highest in CBR-SS. Therefore, SS stabilization treatment is the most valued as it grants cooked black rice the slowest starch digestibility and the highest level of bioaccessible phenolic compounds.