Study On Preparation Of Rice Dregs Foaming Protein

The foam powder with high protein content was obtained from rice dregs after sugarremoval, enzymatic hydrolysis, decoloration and spray dying.It was milky and odorless. Italso had excellent foaming properties.Pretreatment of raw material——removal of sugar. Glucoamylase hydrolysis andwater washing was used to remove the undydrolyzed starch and the remains of dextrin thatwas produced in the process of rice liquefaction. The optimum conditions of glucoamylasehydrolysis were as follows: enzyme dosage was30U/g, enzymatic time was3h, pH was4.5, temperature was50℃and the ratio of stuff to liquid was1:5. The protein content ofrice dregs was in73%~74%after removal of sugar.The rice dregs was hydrolyzed by neutral protease to improve the foaming ability. In thesingle factor test, enzyme dosage, enzymatic time, and the ratio of stuff to liquid had lagerimpact on the foaming ability. Then the response surface methodology(RSM) was used tooptimize the conditions of enzymatic hydrolysis of neutral protease. The results showedthat the optimum conditions were as follows: enzyme dosage/substrate(E:S) was1.33%,enzymatic time was2.16h, the ratio of stuff to liquid was1:10. The highest foamingability in theory was277mL and the actual value was275mL. The relative molecularweigh distribution was detected primarily by gel Sephadex G-15. The relative molecularmass distribution of rice dregs hydrolysates under the optimum conditions was between1000-100.Decoloration by activated carbon. In the single factor test, activated carbon dosage,time, and temperature had lager impact on the decoloring rate and the nitrogen loss rate.Then the orthogonal experiment L9(33)was used to optimize the conditions of decolorarion.The results were as follows: activated carbon dosage was6%, temperature was50℃, timewas20min, pH was6.5.The solubility of the foam powder was perfect between pH2-12. The nitrogensolubility index was a little higher in the alkaline environment (over99%) than in theacidic environment. Emulsification ability was also good (over60%).The foaming abilityof the foam powder was influenced by protein concentration, pH and temperature.The relative molecular mass distribution of the foam protein was detected by the highperformance liquid gel chromatography. The proportion of relative molecular massbetween500-189was62.24%. The proportion of the relative molecular mass between1000-500was26.33%, so the proportion of oligopeptide was88.57%.This results and the results detected by gel Sephadex G-15are in agreement.The scanning electron microscopy (SEM) figure showed that the structure of ricedregs through enzymatic hydrolysis had changed, specific surface area increased greatly,solubility increased, and then the functional property changed, so the foaming ability wasalso improved.The infrared spectra showed the distinction between raw materials and foampowder. In raw material, It had vibration absorption peak of-OH in the1054cm-1place,while in the foam powder that there were no. This result explained hat the effect ofremoval of sugar was remarkable.