Comparison Of The Extraction And Properties Of Legumes Starch

Starch was extracted from mung bean, red bean and kidney beans, chemical properties, granule properties and texture properties of the starch paste were studied.Sour liquid processing was used to extract the starch, effects of water, soaking time and soaking temperature on extracting yield was studied. The results showed that for mung bean, extracting yield reached the maximum (47.2%) when water was 400mL, soaking at 40℃for 14h, for red bean, extracting yield reached the maximum (53.8%) when water was 400mL, soaking at 40℃for 16h, for kidney bean, extracting yield reached the maximum (32.4%) when water was 400mL, soaking at 40℃for 20h. The optimal purifying conditions for the starch was obtained through response surface, which was as follows, shaking time,45min, alcohol 74 mL, rotating speed 133r/min, at above conditions, the residual protein was 0.29672%.Amylose and amylopectin was determined by iodine colorimetry. The order of the amylose content was kidney bean>red bean> mung bean. The order of the degree of acidolysis by hydrogen chloride was starch of mung bean> starch of red bean> starch of kidney bean, the order of the degree of zymohydrolysis was starch of red bean> starch of mung bean> starch of kidney bean. Iodine complex property analyzing results of purified starch and its fractions bynormal butanol showed that the maximum absorption wavelength for mung bean starch, read bean starch and kidney bean starch was 602nm,615nm and 617nm, respectively. The blue values of amylose and amylopectin for mung bean starch, red bean starch and kidney starch was 1.08 and 0.16,1.08 and 0.16, and 0.72 and 0.2, respectively. X-ray diffraction results showed that, the crystalline structure mung bean starch was A type, red bean starch was C type, and kidney bean starch was A type.Granules of legume starch was almost round, ovoid or oval, the distribution of granules of mung beans and red bean starch was not even, while kidney starch was much even. The granule distribution of the starch of the mung bean, red bean and kidney bean starch was of normal distribution. Mung bean and red bean starch had obvious light transmittance, kidney bean starch had much more obvious, and light transmittance of potato starch was the most obvious.The results of solubility and swelling powe of the starch paste showed that within 50～90℃, solubility and swelling poweof all the three starch increased with the increase of temperature. Retrogradation speed was obtained by the comprehensive analysis of retrogradation, translucency and texture properties of the starch paste, the order was kidney bean>red bean>mung bean. Freeze-thaw stability results showed that when the concentration of the starch paste was 2%, the stability of all the three starch was poor, when the concentration was 4%and 6%, the stability order was kidney bean<red bean<mung bean, when the concentration was 8%, the stability of red bean and mung bean was better than that of kidney bean, at 10%, the stability order was kidney bean>mung bean>red bean. DSC results showed that the order of geletinization degree was kidney bean>red bean>mung bean. Effect of salt, alum, sugar and acid on the viscosity of the starch paste was also studied by RVA.