Effect of different drying methods on the physicochemical and functional properties of Dioscorea opposita Thunb. starch

The effect of sulfur fumigation and freezedrying on the physicochemical and functional properties of Dioscorea opposita Thunb. starch was investigated. Freezedrying markedly decreased the AM content of starch from 16.68 to 8.59%. Both sulfur fumigation and freezedrying decreased the protein content but obviously increased the water absorption capacity and swelling power. Sulfur fumigation significantly increased the solubility of starch. Retrogradation tests showed that Chinese yam starch had a poor stability of retrogradation in water, salty, sugar, and acidic medium, but a good stability in alkaline medium. SEM analysis showed that different drying methods had minor effects on the morphological properties of D. opposita cv. Ma starch. Although the pattern of D. opposita cv. Ma starch was C-type and was not affected by drying methods, sulfur-fumigation, and freezedrying increased the crystalline degree of starches from 23.24 to 25.16% and 34.40%, respectively. A minor difference was found in the Fourier transform infrared spectra of native and treatment starches. After sulfur fumigation and freezedrying, the peak gelatinization temperatures increased from 71.03 to 76.03 degrees C and 83.07 degrees C, respectively, whereas the gelatinization enthalpy and gelatinization range decreased.