蒸汽酶解调质-挤压膨化工艺改善速食米粉冲调分散性和预消化性

为建立具有良好冲调分散性和消化特性的速食米粉加工技术，本研究以大米为原料，分析了蒸汽酶解调质-挤压膨化工艺对速食米粉冲调分散性、淀粉糊化度、体外消化特性、以及可溶性蛋白和还原糖含量等的影响。结果表明，与直接挤压膨化相比，蒸汽酶解调质-挤压膨化制得的速食米粉的水溶性指数提高了96.60%，吸水性指数、结块率及分散时间分别降低了72.68%、51.39%及38.27%，米糊的粘度也显著降低，且该速食米粉在低剪切速率下具有较低粘度，其粘度曲线趋于平直；其休止角及滑角均显著降低，说明蒸汽酶解调质-挤压膨化工艺显著改善了速食米粉的冲调分散性及其粉体流动性。此外，蒸汽酶解调质-挤压膨化制得的速食米粉的亮度和总色度显著低于直接挤压膨化，产生了肉眼可见的色差。蒸汽酶解调质-挤压膨化处理还显著增加了速食米粉的可溶性蛋白和还原糖含量，其快消化淀粉比例也较直接挤压膨化明显提高。总之，蒸汽酶解调质-挤压膨化较直接挤压膨化进一步改善了速食米粉的冲调特性及其预消化性。

Extrusion Pretreated by Steam Conditioning Accompanying Starch Enzymolysis Improved the Dispersibility and Predigestion of Instant Rice Flour

To establish preparation technique of instant rice flour with desirable dispersibility and digestive characteristics, the effects of pretreatment of steam conditioning accompanying starch enzymolysis on the dispersibility and predigestion of extrusion-cooked instant rice flour were analyzed in this work. The dispersibility, gelatinization properties and in vitro digestion properties of starch, the contents of soluble protein and reducing sugar were determined in the instant rice flour samples cooked by extrusion with or without pretreatment of steam conditioning accompanying starch enzymolysis. The results showed that compared with simple extrusion, the technology of extrusion pretreated by steam conditioning accompanying starch enzymolysis increased the water solubility index of the instant rice flour by 96.60 %, decreased the water absorption index, agglomerate rate, dispersion time by 72.68%, 51.39%, and 38.27%, respectively, while the viscosity of the rice paste was significantly decreased. The instant rice flour was prepared by the new technology had lower viscosity at low shear rate, and its viscosity curve tended to be straight. Besides, the pretreatment of steam conditioning accompanying starch enzymolysis decreased the angle of repose and slio angle of the rice flour, indicating that the dispersibility and fluidity of the instant rice flour were significantly improved by the technology of extrusion pretreated by steam conditioning accompanying starch enzymolysis. In addition, the brightness and total chroma of instant rice flour prepared by the new technology were significantly lower than those prepared by simple extrusion, resulting in visible chroma difference. The contents of reducing sugar and soluble protein in the instant rice flour were significantly increased after the pretreatment of steam conditioning accompanying starch enzymolysis. Besides, the proportion of rapidly digestible starch was also increased after the pretreatment of steaming conditioning accompanying starch enzymolysis. In conclusion, compared with simple extrusion, the technology of extrusion pretreated by steam conditioning accompanying starch enzymolysis could improve the dispersibility and the predigestion of instant rice flour.