Effect of Lower-temperature Extrusion on the Nutritious and Physicochemical Properties of Japonica Brown Rice

In order to preserve the nutrients of brown rice,improve the rough taste of brown rice,and reduce the digestion speed of extruded brown rice,the brown rice was crushed and then pressed to reconstitute the rice product at a lower temperature. The japonica brown rice was extruded at 65 ℃,and its nutritious properties,thermal properties,gelatinization properties,hydration properties and crystal structure were analyzed. The results showed that the fat content of japonica brown rice decreased from 3.30% to 1.07%,and the total starch and protein content did not change significantly after lower-temperature extrusion. The total dietary fiber content decreased from 4.27% to 3.60%,which could reduce the rough mouth feel of brown rice. The total phenolic content and γ-aminobutyric acid content increased from 33.99 mg/100 g,94.79 mg/kg to 36.59 mg/100 g,105.44 mg/kg,respectively. The peak viscosity,retrogradation value and gelatinization enthalpy of japonica brown rice flour after extrusion were reduced from 920.00 cP,869.50 cP,7.00 J/g to 406.00 cP,714.50 cP,2.28 J/g,respectively. And the degree of gelatinization was 68.43%,indicating that the extruded starch maintained a low degree of gelatinization. The crystal structure also changed after extrusion,diffraction peaks of 2θ angle of the extruded japonica brown rice appeared at 13 ° and 20 °,showing the crystal structure changed from A type to V type and the relative crystallinity decrease from 37.52% to 27.33%. In addition,both the water absorption index and the water solubility index of the extruded japonica brown rice were increased.