Effects of cornstarch on the gel properties of black bean protein isolate

The effects of common starch (CS) and high amylopectin starch (HAS) from corn on the properties of heat induced black bean protein isolate (BBPI) gels prepared by heating at 95°C for 30 min were investigated by using dynamic oscillatory rheometer, texture analyzer, and scanning electron microscopy (SEM). Compared with BBPI alone, the presence of cornstarch (1-4%, wt/vol) could improve storage modulus (G') and textural properties of BBPI (10%, wt/vol) gels. The mixed system of BBPI and 4% (wt/vol) HAS exhibited the highest G' and formed the gel faster and more easily, which resulted in firmer and more elastic gel than BBPI-CS at all starch concentrations. It was possible that HAS had lower pasting temperature and higher viscosity than CS, which was beneficial to the formation of BBPI gel network and strengthened the stability of network structure. Moreover, it might also be related to the synergistic effect between protein and starch. The CS and HAS existed in the BBPI gel network could bind water, leading to the increase in the water-holding capacity (WHC) of mixed gels, especially 4% (wt/vol) HAS, which was related to homogeneous and compact microstructure with small pores.