Study On Preparation Of High Quality Walnut Protein

Qingxiang walnut is one of the main walnut varieties in China,which is rich in protein and amino acids.However,in addition to direct consumption,the fragrant walnuts on the market are mostly used to extract walnut oil.The remaining walnut cake contains a large amount of protein,which is not fully utilized,causing a great waste of resources.The extraction rate of walnut protein is low and the quality of the obtained protein is unstable,which is a key issue affecting the development and utilization of walnut protein.Only by clarifying the structure and composition of walnut protein,optimizing the preparation process of walnut protein,and improving the solubility of walnut protein in aqueous solution,can the resources of walnut protein be fully utilized and its economic value improved.Therefore,this article aims at the development and utilization of walnut protein,and prepares walnut protein with low denaturation,high yield and high purity.The response surface method is used to optimize the preparation process,study and compare its functional properties,and provide a theory for the production of high-quality walnut protein.Guidance basis.The main research contents and conclusions are as follows:First,the use of multi-factor dual-index orthogonal test design to optimize the preparation process of low-denaturation walnut protein powder,walnut cake and walnut kernel as the research objects,by optimizing the material-to-liquid ratio,ultrasonic time,ultrasonic power and extraction of the ultrasonic degreasing process Four indicators such as frequency and oil content and protein dispersion index are used as the detection targets to obtain the best raw materials and process conditions for preparing walnut protein powder.The results show that the best raw material for preparing low-denaturation walnut protein powder is fragrant walnut kernels.The best preparation conditions for low-denaturation walnut protein powder using ultrasonic degreasing process: ultrasonic power is 400.0 W,material-to-liquid ratio is 1:25,and ultrasonic time is 150.0 min,2 extraction times,the walnut protein powder obtained under these conditions has the best quality,with an oil content of 0.62% and a protein dispersion index of 14.88%.Then,the walnut protein is prepared by enzymatic hydrolysis combined with alkali-dissolved acid precipitation method,and the low-denaturation walnut protein powder is used as the raw material to optimize the pH of the alkali-dissolving process;by optimizing alkaline protease,cellulase and ?-amylase,according to the enzyme Hydrolysis time,enzymatic hydrolysis pH,amount of enzyme added,enzymatic hydrolysis temperature and other indicators,with protein extraction rate as an indicator,combined with single factor test and Box-Behnken response surface method to optimize the preparation conditions;at the same time,the acid precipitation was carried out through the ultrafiltration process.Recovery of walnut protein from the liquid,single factor test was used to analyze the influence of the material liquid concentration and material liquid temperature on the rejection rate and membrane flux,so as to improve the recovery rate of walnut protein.At the same time,compare the rejection of different membranes under the conditions of different stock solution concentration and stock solution temperature.The impact of the rate.The results show that the optimal pH of the alkaline extraction process in the alkaline extraction and acid precipitation method is 10.0;cellulase is the most suitable hydrolase,and the optimal process conditions for the extraction of walnut protein isolate are enzymatic hydrolysis time 90.0 min and enzymatic hydrolysis pH 3.6,The amount of enzyme added is 0.20%,and the enzymatic hydrolysis temperature is 37.0 ?.Under the optimal process conditions of walnut protein isolate,the extraction rate of walnut protein isolate can reach 84.11%.Cellulose Acetate membrane has the highest average rejection rate of 80.01% under the condition of 0.363 mg/m L and 30.0 ?.Finally,the walnut protein isolate is purified with glucoamylase to obtain the best quality walnut protein isolate.On the basis of single factor experiment,orthogonal experiment was used to compare the differences of enzymatic hydrolysis temperature,enzymatic pH,enzymatic hydrolysis time,glucoamylase dosage,material-liquid ratio and other indicators.The walnut protein purity was taken as the goal and the walnut protein purification process was optimized.And compare the functional characteristics of walnut protein isolate products and low-denaturation walnut protein powder under different conditions,such as water retention,oil absorption and emulsification.The experimental results show that the optimal conditions for the walnut protein purification process are enzymatic hydrolysis temperature 55.0 ?,enzymatic hydrolysis pH 5.0,enzymatic hydrolysis time 40.0min,glucoamylase dosage 80.0 U/g,material-liquid ratio 1:8,and finally the purified enzyme The purity of walnut protein is 94.37%.The prepared walnut protein isolate product has better water retention(3.72 g/g),oil absorption(1.57 g/g)and emulsification(57.6%)than low-denaturation walnut protein powder,which proves that the prepared walnut protein isolate product has good functional characteristics.In summary,this article has carried out a systematic study on the extraction of walnut protein.By optimizing the extraction process of low-denaturation walnut protein powder,and optimizing the yield and purity of walnut protein,high-quality walnut protein with low denaturation,high yield and high purity is obtained.It provides a guiding basis for the development of walnut deep processing industry focusing on the development of walnut protein.