Study On Preparation And Functional Properties Of Cottonseed Protein Products

Cotton is an enormous resource in China，the protein content can up to40%-50%after cottonseed oil was extracted．Cottonseed protein is a kind ofdeveloping vegetable protein with high nutritional value and good quality．Defatted cottonseed meal as the raw material，the preparation of cottonseedprotein concentration and cottonseed protein isolate，the physical modification ofcottonseed protein concentration and the functional properties of cottonseed proteinisolate were studied．The program aims at improving the utilization value ofcottonseed protein resource and developing cottonseed protein products．The mainresults of the study are as follows：1．Defatted cottonseed meal as the raw material，the alcohol solution washingmethod was used to prepare cottonseed protein concentrates． Effects of solventconcentration，alcohol washing temperature，time，frequency and solvent／solidratio to protein content of product were investigated． Under the optimumconditions： ethanol concentration70%，alcohol washing temperature was50℃，alcohol washing3frequencies(20mins each frequency)，the ratio of solid to liquid1：7， the protein content of prepared cottonseed protein concentrate was68.25%(N*6.25，dry basis)，and the content of free gossypol felled to0.0345%．Andthe physical modification conditions of alcohol washed cottonseed proteinconcentrate，such as heating temperature，mashed homogenization time，proteinsolution pH，ultrasonic treatment time were studied to raise the soluble propertiesof the product．Under the optimum conditions：heating temperature of95℃，mashedhomogenization time was10min，solution pH9，ultrasonic treatment time was15min，the NSI value of modified cottonseed protein concentrate increased from12.30%to26.59%，higher than that of the raw cottonseed meal24.46%．Moreover，the microstructure of cottonseed protein concentrate was observed before and afterthe physical modification．2．Defatted cottonseed meal as the raw material, the method of alkalineextraction and acid precipitation was used to prepare cottonseed proteinisolate．Protein extraction ratio and protein content as the index, the effect oftemperature，time，pH value and the ratio of liquid to solid and other factors on theextraction of cottonseed protein were considered． Through orthogonal and confirmative test，the optimize extraction condition：extraction temperature of60℃，extraction time of1h，pH of10，liquid to solid ratio of12：1．Under the optimumconditions，the extraction ratio of cottonseed protein reached71.21%．Washed by95%ethanol，the extracted was acid precipitated under the pH of4.8and then thesolid residue was washed to neutral to freeze drying． The prepared isolatedcottonseed protein content was90.76%(N×6.25,dry basis)，and the final freegossypol content reduced from1.2%to0.0327%．Moreover，SDS-PAGE was usedto analyze the subunit molecular weight distribution of prepared cottonseed proteinisolate．3． The functional properties of cottonseed protein isolate products werestudied，results showed that when pH4~5，the cottonseed protein isolate has thelowest solubility，which is2.11%；when pH=7，the water holding capacity，foamingand foam stability，emulsification of cottonseed protein isolate were increased withthe increase of protein concentration，emulsion stability were less affected．The oilabsorption decreased with temperature increasing． By means of differentialscanning calorimetry，the denaturation temperature of cottonseed protein isolateis95.18℃，higher than of soybean protein isolate88.64℃；denaturation enthalpyis137.6J/g，lower than that of soybean protein isolate178.7J/g．Through physicaltester，the gel strength of cottonseed protein isolate stronger than that of soybeanprotein isolate under the same conditions．...