Study on the preparation of antioxidant peptides from donkey whey protein by computer simulated enzymatic hydrolysis
Donkey milk, known as the “best substitute for human milk”, has low fat content, high content of unsaturated fatty acids, vitamins, and lactose, and has strong health benefits and the ability to treat immune related diseases in the human body. As a whey protein dairy product, donkey whey protein contains high levels of alpha lactalbumin, beta lactoglobulin, and lysozyme. Alpha lactalbumin can effectively inhibit harmful bacteria, which is beneficial for the growth and development of infants and young children; β – lactoglobulin can specifically bind to nutrients during digestion, playing a role in protecting nutrients; The high content of lysozyme endows donkey milk with strong antibacterial properties. In addition, donkey whey protein contains various trace components such as immunoglobulin, serum albumin, and epidermal growth factor, which have important effects on the body’s disease resistance mechanism. Therefore, the development and utilization of donkey milk has enormous social value and market prospects. However, currently there is a single product of donkey milk in China, and the utilization rate of donkey whey protein is greatly limited, resulting in the inability to maximize its economic benefits. The use of protease hydrolysis to prepare bioactive peptides from donkey whey protein is helpful for further research on the comprehensive value of donkey milk products.

Bioactive peptides refer to small peptide substances that are beneficial for the activity and health of living organisms, and can optimize the metabolic environment of the body. They have various bioactive functions such as antibacterial, antioxidant, immune regulation, and blood pressure lowering. Among them, antioxidant peptides can clear excess free radicals in the body by providing protons, metal ion chelates, and inhibiting lipid peroxidation. At the same time, the proportion of hydrophobic amino acids and aromatic amino acids in peptide chains is positively correlated with the antioxidant activity of peptides. The higher the proportion, the stronger the antioxidant activity, and the more beneficial it is for the body’s oxidative defense. At present, animal milk protein is a hot topic in the research of antioxidant peptides at home and abroad, but most of them are made from cow milk protein, and there are not many studies on the antioxidant peptides of donkey milk protein.
Studies abroad have confirmed that the total antioxidant capacity of donkey milk is higher than that of human milk, indicating that the peptides released from donkey milk after enzymatic hydrolysis have certain antioxidant capacity. Donkey milk is a high-quality raw material for extracting antioxidant peptides. However, there is relatively little research on donkey milk derived antioxidant peptides in China. Finding a feasible process technology route for preparing donkey whey protein antioxidant peptides is of great significance for the application of antioxidant peptides in medical, food, health and other fields, and can also play a role in the development and market economic benefits of donkey milk. Therefore, in this experiment, the most suitable protease was screened through computer simulation for enzymatic hydrolysis of donkey whey protein, providing a theoretical basis for the development of antioxidant peptide functional products.

Using the UniProt database to obtain the amino acid sequences of proteins with high content in the raw material protein, and using them as bioinformatics templates, the built-in software in the BIOPEP database was used to simulate enzymatic hydrolysis of donkey whey protein. The α – chymotrypsin that can produce antioxidant active peptide segments was screened. The Design Expert V8.0.6 response surface experiment was designed to determine the optimal process conditions for preparing antioxidant peptides from donkey whey protein: substrate concentration of 4%, enzymatic hydrolysis time of 4 hours, temperature of 39 ℃, pH of 8, and enzyme substrate ratio of 4%. The maximum DPPH radical scavenging rate of the enzymatically hydrolyzed peptide obtained under this condition is 46.23%.