Study On Preparation And Properties Of Walnut Meal Protein By Non Acidification

Xinjiang have geographical and resource advantages in walnut processing. The main products are processed into walnut oil, resulting in a large number of walnut meal after extract oil. Walnut protein, which contains 50%~60% protein, could not be fully utilized and cause the waste of resources.Walnut meal was used as raw material to extract protein, but the traditional alkali soluble acid precipitation method has the bad color, flavor and processing characteristics, which needs a large amount of acid precipitation to get protein, which cause environmental pollution and resource consumption; Therefore, experiment used walnut dregs as raw materials, did walnut protein alkaline extraction, determined and optimized walnut protein exaction without acidification technology. This study compared alkali soluble acid precipitation method and non acidification method of walnut protein physicochemical properties and functional properties. The main conclusions were as follows:(1) Optimized alkali soluble acid precipitation extraction walnut protein process parameters: temperature 56?, p H value 9.60, liquid material ratio 25:1, time 56 min, the protein extraction rate was 61.05%. The isoelectric point of protein extracted from walnut protein was pH value 4.00.(2) Response surface optimized experiments, it was found that the membrane separation and the optimum process parameters for operating pressure 0.15 MPa, velocity 19 m/s, temperature 42?, under these conditions, the obtained membrane flux was 9.12 L/(m2·h), protein retention rate was 98.41% and the content of protein was 84.57%. Determined the cation exchange resin for the processing of walnut protein supernatant conditions: time 62 min, shaker speed 120 r/min, water bath temperature of 46?, under these conditions, walnut protein recovery rate was 92.75%, protein content was 75.14%. Through compared and analyzed the protein content, protein yield, color(L*), ash, sensory indicators. Then determined the membrane separation method for walnut protein without acidification was preparation process.(3) The total amino acid content of alkali soluble acid and membrane protein of walnut were 848.40 mg/g and 818.10 mg/g. Amino acid coefficient ratios were 90.55 and 91.46. SDS-PAGE electrophoresis Results showed that the protein molecular weight distribution range was 17 kDa~63 kDa, the protein molecular weight was 8 subunits, and the molecular weight range was wider than that of 17 kDa~75 kDa. Scanning electron microscope showed that the alkali soluble acid walnut protein was lamellar structure, and the membrane protein was block structure.(4) Under different treatment conditions,the solubility, emulsifying and emulsifying stability, foaming ability of membrane walnut protein were better than that of acid walnut protein; The oil holding capacity, the water holding capacity, the foaming stability were lower than that of acid precipitation protein.