Properties of pregelatinized rice flour made by hot air or gum puffing

Three varieties of rice, TCW 70, TN 67 and TCN 1, with an amylose content of 1.0, 20.3 and 32.0%, were used to produce pregelatinized rice flour by using hot air fluidized-bed puffing or gun-puffing methods. Serious molecular degradation was introduced by the gunpuffing process. However, there were no significant differences in the molecular weights of rice flour before or after the hot air fluidized-bed puffing process. Pasting properties of pregelatinized rice flours were dependent on the rice variety and the types of pretreatment, and were significantly affected by the puffing method. Hydrothermal pretreatment had different effects on the pasting and hydration properties of pregelatinized rice flour, depending on whether it was made from waxy or non-waxy rice. Various properties of pregelatinized rice flour could be attributed to the combined effects of gelatinization, retrogradation and degradation of starch molecules during processing.