Study On Rice Milk Process And Nutritional Characteristics By Extrusion And Enzymatic Integrated System

Using three different processes: extursion, phytase and cellulose digestion, a combination ofextrusion process and enzymatic treatment was studied in this paper while brown rice was as rawmaterial to get the optimal process and nutritive peculiarity of these three kinds of brown ricemilk. The paper mainly focused on the extrusion process parameter of brown rice flour, theprocess of phytase enzyme treatment, the preparation process and nutritive peculiarity of brownrice milk.Firstly, phytic acid degradation rate and water-soluble carbohydrates of brown rice flourwas as the indicator parameters, the effects of material particle size, water content, barreltemperature and the screw speed on the anti-nutritional factor of brown rice was studied. Basedon the single factor experiment, these four factors were selected appropriate range to do centralcomposite design. The response surface analysis was used to optimize processing parameters withthe phytic acid degradation rate and water-soluble carbohydrates as the main target. The resultshowed that the optimal extruding parameters were: material particle size was60mesh size,water content was17%, barrel temperature was135℃and the screw speed was130rpm. Thephytic acid degradation rate was about31.9%, the water-soluble carbohydrate was26.79%, andthe degree of gelatinization reached91.7%at the optimal parameters.Based on the optimal process parameters, the enzyme dosage, temperature, reaction timeand substrate concentration were selected as experimental factors with the changes of phytic acidphosphorus content rate as evaluation index, to do phytase single factor and response surfaceexperiment for brown rice flour and puffed rice powder. The result showed that the optimumprocess parameters of brown rice flour were: temperature was53℃, hydrolysis time was104min, the ratio of liquor to material was10.6, and the optimal process of puffed rice powder were:enzymolysis temperature was55℃, reaction time was108min, the ratio of liquor to materialwas12.9. The changes of phytic acid phosphorus content rate of brown rice flour and puffedrice powder were57.3%and50.5%at the optimum hydrolysis conditions.Bacause of the high starch content in brown rice, affecting product taste and stability, two-step enzyme treatment of amylase and glucoamaylase was used for the brown rice folur and puffed brown rice flour, the hydrolysis procedure was as follows:14mL high-temperature α-amylase hydrolyzed30min at90℃, substrate concentration10, pH6.0for brown rice flour;10mL low-temperature α-amylase hydrolyzed50min at45℃, substrate concentration12,pH6.0for puffed rice powder. Then60U.mL-1saccharifying enzyme hydrolyzed120min at60℃, pH4.5for both brown rice flour and puffed rice powder to reduce starch content. Byadjusting the formula, the optimum formula of process1and process2were: enzymolysis liquidratio was30%, creamer was1.4%, sugar was6%and the optimum formula of process3was:enzymolysis liquid ratio was30%, creamer was1.0%, sugar was6%. The product could sustainideal taste and flavor after homogenization and sterilization.Finally, taking the stability coefficient R as evaluation index of thickener and emulsifier’sstability, the result showed that the optimal additive amount of thickener and emulsifier were:0.048%xanthan gum,0.072%sodium alginate tech grade,0.1%lecithin,0.1%sucrose ester inproduction1;0.06%xanthan gum,0.04%sodium alginate tech grade,0.05%lecithin,0.1%sucrose ester in production2&3. By using the joint method of extrusion and enzymolysistreatment, rice milk had delicate taste, the best flavor and higher nutritive value.