Physical and Chemical Properties and Characterization of Resistant Starch Prepared by Different Chemical Methods

The resistant starch was prepared from sweet potato starch by three chemical methods. Physical and chemical indexes such as enzymatic hydrolysis,water retention,transparency,solubility,swelling and freezing-thawing property were studied. The results showed that starch released 0.79 g reducing sugar after enzymatic hydrolysis for 4 h,while esterified starch,etherified starch and cross-linked starch released 0.18,0.21 and 0.33 g reducing sugar,indicating that resistant starch had strong enzymatic hydrolysis resistance. The water holding capacity of the three kinds of resistant starch was higher than that of starch,and the water holding capacity of etherified starch was the highest. The transmittance,solubility and swelling of esterified starch increased by 103.05%,14.56% and 13.94%,etherified starch increased by 334.11%,356.97% and 124.73%,while the cross-linked starch decreased by 54.54%,67.75% and 31.51%. The freezing-thawing property of three kinds of resistant starch was better than that of starch,and etherified starch had the best freezing-thawing property. The surface of starch granules was smooth and regular and round. The internal and external structures of esterified starch and cross-linked starch were destroyed and lost their original morphology. Etherified starch still maintained the original morphology of starch. Infrared spectrum proved that esterified starch introduced acetyl group,etherified starch introduced carboxymethyl group,crosslinked starch introduced phosphate group.