Co-extrusion of proanthocyanins from Chinese bayberry leaves modifies the physicochemical properties as well as the in vitro digestion of restructured rice

Abstract

• Proanthocyanidins from Chinese bayberry leaves were coextruded with rice flour. • Extrusion process significantly reduces the degree of starch crystallinity. • Proanthocyanidins affect the gelatinization of rice starch. • Co-extruding proanthocyanidins with rice could reduce its digestion significantly. Proanthocyanins from Chinese bayberry leaves (CBLPs) were co-extruded with rice flour at different concentrations. The physicochemical properties of the restructured rice were analysed with XRD, RVA, and DSC, while the digestibility was analysed with an in vitro digestion model. Results indicated that the extrusion process significantly reduced the degree of starch crystallinity and the addition of CBLPs enhanced this effect. The restructured rice with CBLPs showed higher peak viscosity and lower pasting temperature than those of the samples without CBLPs. With the increasing of CBLPs concentration, the equilibrium hydrolysis of rice starch decreased from 86.61% to 70.89% with a kinetics constant ( k ) ranged from 7.51 × 10 −2 to 4.71 × 10 −2 (min −1 ), indicating a good retardation of CBLPs on starch hydrolysis. Our results indicate that co-extruding CBLPs with rice flour could reduce its starch digestion significantly and be an option for producing staple rice food with lower digestion.