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. (C) 2011 Elsevier Ltd. All rights reserved.