Extraction and Purification Process Optimization and Functional Properties Analysis of Walnut Meal Protein

To obtain high-quality walnut meal protein, the process conditions for extraction of walnut meal protein by alkaline solubilization and acid precipitation method and purification of walnut meal protein by glycolytic enzyme were optimized by single-factor experiments and response surface method, respectively, and the functional properties such as solubility, water absorption, and emulsification were analyzed. The optimal extraction process conditions were: pH12, temperature 55 ℃, time 90 min, and material-liquid ratio 1:40 g/mL. Under these conditions, the extraction rate of walnut meal protein could reach 81.89%±1.64%, and its settling point was pH4.5. The optimal purification process conditions were: pH4.5, material-to-liquid ratio 1:40 g/mL, enzymatic digestion time 129 min, enzymatic digestion temperature 53°C, and enzyme addition 0.4%. The purity of walnut meal protein purified under these conditions could reach 94.48%±1.83%. The results of functional properties of walnut protein showed that its solubility was 24.82%, water absorption 3.06 g/g, oil absorption 3.15 g/g, emulsification 16.10 m²/g, emulsification stability 38.87 min, foaming 30.53% and foaming stability 75.44% under the same pH conditions, and the purified walnut protein had better functional properties.