Effect of Heat Moisture Treatment on Physicochemical and Structural Properties of Yam Flour

In order to study the effect of heat moisture treatment on the physicochemical and structural properties of yam flour, the samples with moisture content of 15%, 25% and 35% were subjected to 9 h heat moisture treatment under 90 and 110 ℃ conditions, respectively. The swell ability, gelatinization characteristics, thermodynamic properties, crystallization degree and infrared spectrum of the yam flour after treatment were measured. The results showed that heat moisture treatment increased the solubility of yam flour. When the processing conditions were 90 °C and 25% moisture content, the solubility increased to 9.88%, and the swelling power decreased from 3.90 g/g to 3.12 g/g. The gelatinization temperature of the heat moisture treatment yam flour increased significantly (P<0.05), but its peak viscosity, trough viscosity, breakdown and setback were all significantly (P<0.05) lower than those of the native yam flour, and the gelatinization enthalpy value showed an upward trend. The heat moisture treatment increased the crystallinity of yam flour from 23.5% to 27.22%, while the crystal form was still C-type. Infrared spectra showed that the short-range ordered structure of yam starch was slightly changed by heat moisture treatment. Heat moisture treatment is an effective method to improve the physicochemical properties of yam powder.