低温挤压对粳糙米营养特性及理化性质的影响

为了保留糙米的营养成分,改善糙米的粗糙口感,降低挤压糙米的消化速度,本文将粳糙米粉碎后在较低温度下挤压重组成米粒产品。将粳糙米在65 ℃低温挤压后,分析其营养成分、热特性、糊化特性、水合性质以及晶体结构等理化性质的变化。结果表明:低温挤压处理后粳糙米的脂肪含量从3.30%下降到1.07%,总淀粉、粗蛋白含量变化不显著,总膳食纤维含量从4.27%减少至3.60%,有助于改善糙米的粗糙口感。总酚含量和γ-氨基丁酸含量分别从33.99 mg/100 g、94.79 mg/kg增至36.59 mg/100 g、105.44 mg/kg。挤压后粳糙米粉的峰值黏度、回生值、糊化焓变分别由920.00 cP、869.50 cP、7.00 J/g降至406.00 cP、714.50 cP、2.28 J/g,糊化度为68.43%,挤压后糙米淀粉保持较低的糊化度。晶体结构在挤压后也发生了变化,挤压后粳糙米在2θ角为13 °、20 °存在衍射峰,晶体结构从A型转变成V型,相对结晶度从37.52%降至27.33%。此外,挤压粳糙米的吸水性指数和水溶性指数均升高。

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.