Abstract:
Abstract: In order to improve the structure and qualities of general rice starch products, effects of retrograded resistant starches (RSⅢ) made from Castanea henryi (C. henryi), potato and mung bean on microstructure and physicochemical properties of rice starch gels were investigated by using modern analysis methods, including RVA-4 rapid viscosity analyzer, S-3400N scanning electron microscope, TA-XT Plus structure analyzer, D/max2500 automatic X-ray diffractometer and DSC200 differential scanning calorimeter. The results demonstrated that the structure and properties of rice starch gel had a significant change (P<0.01)after adding C. henryi, potato and mung bean RSⅢ, respectively. Especially the role of C. henryi RSⅢ was the most prominent. The C. henryi, potato and mung bean RSⅢ had no effect (P>0.05) on viscosity properties of rice starch pastes. Rice starch gel without RSⅢ had a lot of irregular, deep and shallow large holes, while the net structure of rice starch gel with RSⅢ became more uniform and dense. RSⅢ had little influence on gumminess and cohesiveness of rice starch gel (P>0.05). The C. henryi, potato and mung bean RSⅢ could accelerate the formation of rice starch gel. Compared with the rice starch gel without RSⅢ, their hardness increased by 2.38, 1.97 and 1.25 times (P<0.01), stickness increased by 2.56, 1.99 and 1.32 times (P<0.01), and spring increased by 1.07, 0.81 and 0.53 times (P<0.01), respectively. A-type crystal was dominant in rice starch, and V-type crystal was dominant in C. henryi RSⅢ, while B-type crystal was dominant in potato and mung bean RSⅢ. Whether or not adding RSⅢ, V-type crystal in rice starch gel powders was transformed as the main crystal shape, and their total relative crystallinities had not changed (P>0.05). In addition to a low temperature endothermic peak, rice starch pastes with RSⅢ showed a high temperature endothermic peak. Whether or not to add RSⅢ, the change of temperature parameters of low temperature endothermic peak was a little (P>0.05), but its endothermic enthalpy decreased significantly (P<0.01). As for the high temperature endothermic peak, all parameters of rice starch pastes with potato and mung bean RSⅢ had no difference (P>0.05), but they were significantly higher than those of rice starch paste with C. henryi RSⅢ (P<0.01). To sum up, adding RSⅢ with different sources can effectively improve the structure and quality of rice starch gel. The present results can provide an important reference for using the RS to improve the qualities and nutritional functions of the rice products.