Modification of Gelatinization Properties of Rice Flour by Heat-Treatment

Abstract

The effects of autoclave and oven treatments on gelatinization properties of rice flour and on crystallite structures of rice starch in rice flour were studied using dynamic oscillatory measurement, differential scanning calorimetry (DSC), X-ray diffractometry, and scanning electron microscopy (SEM). Autoclave-treated rice flour (ATR) and oven-treated rice flour (OTR) were prepared using an autoclave at 120 °C for 60 min and oven at 160 °C for 60 min. Dynamic oscillatory and DSC measurements demonstrated that autoclave treatment modified the gelatinization properties that delayed gelatinization temperature (T_G' and T_o) and decreased in peak storage modulus (G'_p). Autoclave treatment caused formation of amylose-lipid complexes and partial gelatinization of starch granules in ATR studied by DSC and X-ray diffractometry. Autoclave-treatment engendered formation of amylose-lipid complexes and partial gelatinization of starch granules in ATR studied by DSC and X-ray diffractometry. Alteration of gelatinization properties of ATR flour is attributed to changes in rigidity of starch granules during treatment. Similarly to ATR, oven treatment was effective for gelatinization properties. Nevertheless, it was insufficient for rearrangement of starch chains in OTR flour.