预处理-低温挤压对留胚米粉理化性质的影响

以留胚米为原料，焙炒预糊化粉碎后，在挤压机螺杆转速100 r/min，水分含量30%，挤压温度50～90℃的条件下对留胚米粉进行挤压。研究在预糊化-低温挤压过程中不同的挤压温度对留胚米粉理化性质的影响。结果表明：随着挤压温度的升高，留胚米粉的糊化度逐步提高；淀粉、脂肪、蛋白质、γ-氨基丁酸(GABA)含量均有所下降，而当温度超过70℃后，可溶性膳食纤维含量显著(P<0.05)升高；留胚米粉的吸水性指数显著下降(P<0.05)，水溶性指数、膨胀势有所上升；总色差?E增大；粒径显著增大(P<0.05)；差示扫描量热仪分析发现留胚米粉的起始温度(T₀)、峰值温度(T_P)和终止温度(T_C)逐渐升高，吸热焓由1.14 J/g下降至0.82 J/g，糊化程度逐步增加；傅里叶红外光谱分析表明，在所有挤压温度下留胚米粉的淀粉结构中并未产生新的基团或化学键。上述结果显示，预糊化-低温挤压对留胚米粉的理化特征具有显著影响，适宜的挤压温度减少了营养成分的损失。

Effect of Pretreatment and Low-temperature Extrusion on the Physicochemical Properties of Embryonic Rice Flour

The embryonic rice flour was roasted, pre-gelatinized, and extruded at a screw speed of 100 r/min, a moisture content of 30%, and an extrusion temperature of 50~90 ℃. The effects of different extrusion temperatures on the physicochemical properties of embryonic rice flour were investigated in the pre-gelatinization-low temperature extrusion process. The results showed that with the increase of extrusion temperature, the pasting degree of embryonic rice flour gradually increased. The contents of starch, fat, protein, and GABA decreased, while the contents of soluble dietary fiber increased significantly after the temperature exceeded 70 ℃. The water absorption index of embryonic rice flour decreased significantly (P<0.05), the water solubility index and swelling potential increased. The total color difference increased first and then decreased. The particle size increased significantly (P<0.05). The analysis of differential scanning calorimetry showed that the enthalpy of heat absorption decreased from 1.14 to 0.82 J/g, and the degree of pasting increased gradually at the starting temperature (T₀), peak temperature (T_P), and termination temperature (T_C) of embryonic rice flour. Fourier infrared spectroscopy showed that no new groups or chemical bonds were formed in the starch structure of rice flour at all extrusion temperatures. The above results showed that pre-gelatinization-low temperature extrusion had a significant effect on the physicochemical characteristics of embryonic rice flour, and the appropriate extrusion temperature reduced the loss of nutrients.