Physico-chemical properties of rice starch gels: Effect of different heat treatments

Physico-chemical properties of rice starch gels prepared by microwave, ultrasonic–microwave synergistic and conventional heat treatments were investigated in this study. The results showed that the gel firmness and the hydrolysis degree of non-waxy rice starch gels obtained from microwave heat (75.3 ± 3.8 g, 60.8 ± 1.7%) and ultrasonic–microwave synergistic treatment (88.2 ± 2.1 g, 65.1 ± 2.2%) were significantly lower than that from the conventional heat (115.7 ± 3.1 g, 78.5 ± 3.0%). It was observed that the less damage to starch granules was induced by microwave treatment for non-waxy rice starch gels. The retrogradation data of the tested samples were analyzed by the DSC. The results indicated that the retrogradation rate of non-waxy rice starch gels prepared by microwave and ultrasonic–microwave synergistic treatments was lower than that by the conventional heat. These findings suggest that the differences in physico-chemical properties of rice starch gels were mainly attributed to the damage extent of starch granules under the different treatments.

► Microwave and ultrasonic–microwave yield synergistic effects.
► The synergistic treatment improves gelatinization and retrogradation properties of rice starch gels.
► The study provides better insight to the mechanisms behind starch gelatinization and retrogradation.