Preparation And Functional Study Of Walnut Protein And Peptide

Walnut,an important nut food in China,has a variety of nutritional effects.In addition to being eaten directly,walnut products on the market are mostly used to extract walnut oil.The remaining walnut meal contains a large amount of high-quality protein,which has not yet been fully utilized.The purpose of this project is to improve the added value of walnut protein products,explore the impact of raw material processing methods on the quality of waln ut protein,optimize the preparation process of walnut peptides,develop their functional characteristics,and provide theoretical basis for the utilization of walnut resources.The main research contents and conclusions are as follows:Firstly,the multi-factor dual-index orthogonal test design was used to optimize the condition seticization of the degreasing process of walnut cake,enzyme hydrolysis combined with alkali-soluble acid sink method to prepare walnut protein process and glycetic treatment of walnut protein purification process.The results showed that the best process conditions for degreasing were: 1:20 g/m L,ultrasonic power 500.0 W,ultrasonic time 140.0 min,the best preparation conditions were: liquid ratio 1:20 g/m L,enzyme solution time 2.0 h,the amount of enzyme 2.0%,temperature 50.0 ?,p H 8.0,and the best purification process conditions were: enzyme solution temperature 50.0 ?,p H 4.5,enzyme solution time 140.0 min,enzyme added 0.4%.The degreasing rate was 91.23%,the protein yield was 78.16%,and the protein purity was 94.16%.Then,the peptides were prepared by alkaline protease enzyme solution protein.The peptide preparation process was optimized by orthogonal experimental design,and the chemical properties of peptides obtained from different material treatment were compared.The results showed that the optimal preparation process conditions for peptides were: temperature 50.0 ?,p H 9.0,plus enzyme amount of 3.0%,enzyme solution time of 5.0 h.The hydrolysis was 22.63% and the peptide yield was 88.24%.the peptides were prepared by unskinned roasted-pressing,unskinned cold-pressing and deskinned cold-pressing,it was found that the quality of deskinned cold-pressed preparation peptides was the best,the moisture content was 0.79%,the crude protein content was 82.68%,the residual oil was 0.36%,the nitrogen dissolved index was 96.12%,molecular content of less than 1000 Da reached 91.61%.Finally,the functional characteristics of the peptides prepared by different material treatment methods(unskinned roasted-pressing,unskinned cold-pressing and peeling cold-pressing)were compared.The results showed that the walnut peptides prepared by deskinned cold-pressing had the best water holding,oil absorption,emulsification,emulsification stability,foaming and foam stability,and had the highest ACE inhibition activity,reaching 63.04 %.Peeling and cold pressing was the most suitable processing method for walnut materials.The walnut peptides prepared by it have good ACE inhibitory effect.In conclusion,through the process technology of walnut protein and walnut peptides optimized,and the chemical properties and functional characteristics of peptides evaluated,the suitable material treatment methods was proposed,providing guidance for high quality of walnut protein products.