| Millet is a kind of small grains containing rich nutrients and a variety of health ingredients. Millet is a good kind of health food, and after long term consumption can improve physical health. In order to meet the diverse and convenient dietary needs of modern people while increasing the additional value of agricultural products, processing technology of nutritional rice flour was explored in this paper with millet as raw material. The research was carried out using the technology of enzyme hydrolysis spray drying and extrusion expansion to conduct laboratory simulation studies, to provide theoretical support for the industrialization, large-scale production of millet.In this experiment, millet flour was produced by technology of enzyme hydrolysis spray drying. The effect of enzymatic hydrolysis on spray drying was analyzed by single factor test and response surface test, using the glucose value(DE value) and viscosity as the index. The optimal conditions by response surface analysis were as follows: substrate concentration 30.5%, enzyme dosage 0.74%, reaction time 36 min. It was proved that the DE value of the feed liquid was 30.36% in this hydrolysis conditions, with a difference of 0.96% compared with the predictive value of 31.32%.The viscosity was proved to be 102 c P, with a difference of 2.86% compared with the predictive value of 105 c P. The two indicators above were within the error range of the confidence interval, so the model is available. In addition, the millet flour we ob tained had good sensory evaluation, fine solubility, smooth and sweet taste.Extrusion technology was used to produce millet flour in this test. To study the optimal extrusion process conditions of millet flour, the single factor test and orthogonal exper iment were used and the glucose value(DE value) and viscosity were taken as the index. The optimal conditions by response surface analysis were as follows: material moisture 14.3%, screw speed 432 rpm, temperature 141 ℃. Under optimum conditions, the gelatinization of millet was 95.08%, with a difference of 1.29% compared with the predictive value of 96.37%. The error was within the confidence interval, so the model could be used. The main ingredients in millet include d starch, protein, fat, etc. Under the vigorous puffing action of the extruder, the starch was gelatinized and partially degraded to small molecules sugar, which lead to the rise of gelatinization,the decline of starch content, and the significant increasing of reducing sugar content; With the total content decreasing slightly, the protein was denatured irreversibly; The starch-lipid complexes were produced because of the reaction between free fatty acid and gelatinized starch, thus the fat content which could be measured reduced. The millet powder prepared by extrusion method had good dissolution characteristics, moreover, it had the color of natural millet, and the sweet and delicious taste after brewing.The properties of millet flour processed by different methods were also different. Compared with the extruded millet flour, the millet flour produced by technology of enzyme hydrolysis spray drying had higher water solubility index and water absorption index, smaller agglomeration rate and punching viscosity. The extruded millet flour was not as good as the millet flour produced by technology of enzyme hydrolysis spray drying in the aspect of resolvent index,but its nature could meet the requirements, and had better organoleptic properties after reconstit ution of extrusion. In addition, the extruded millet flour had more natural millet color, enough aroma, more full taste, only lack of a little sweetness than spray drying millet powder. In comprehensive evaluation, extrusion millet flour had better solubility quality and higher sensory evaluation, and its lack of sweetness could be made up by means of adding sugar and other methods, so the extrusion millet flour had better market prospects. |
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