Study On Hydrolysis Process Of Whey Protein And Functional Properties Of Hydrolysates

Whey protein is a high-quality protein of high nutritional value, but some people are allergic to ?-LG or ?-LA, which largely limits the application of whey protein in food.Enzymatic hydrolysis is widely used to reduce protein allergies due to its mild reaction conditions and less damage to amino acids. Enzymatic hydrolysis of whey protein can not only significantly improve its application characteristics but also produce bioactive peptides with special physiological functions. In this paper, the most suitable protease for hydrolyzing whey protein was chosen out,and the hydrolysis process of the enzyme and allergenicity, application properties and antioxidant activity of hydrolysates were studied.Considering the color, state, bitterness, degree of hydro lysis,the reduction rate of ?-LG allergenicity of five protease hydrolysate and the economy in the production, the neutral protease was selected as the hydrolysis protease.The effects of hydrolysis time, temperature, pH and E/S on the degree of hydrolysis were investigated by single factor experiments:the effect of hydrolysis time and E/S on the degree of hydrolysis was similar and the degree of hydrolysis increased with the prolongation of hydrolysis time and the increase of E/S, and then became stable to a certain degree.In the selected temperature and pH range, with the increase of temperature and pH,the degree of hydrolysis first increased and then decreased. The effects of pH, T, E/S on the?-LG antigenicity and the degree of hydrolysis were studied by the central composite rotation design experiment, and it was found that they were not completely positive correlation. The optimal conditions for the hydrolysis of whey protein by neutral protease were: hydrolysis time 3 hours, temperature 45 ?, pH 7, E/S 2500u/g, taking into account the reduction rate of P-LG allergenicity and the degree of hydrolysis.The application characteristics of whey protein improved significantly after hydrolyzed by protease, the effects of the degree of hydrolysis and pH on the application characteristics were as follows:the solubility of whey protein significantly increased comparing with unhydrolyzed protein and the solubility increased with the increase of degree of hydrolysis. The solubility of whey protein also increased at isoelectric point which expanded its application in the acidic system. The emulsibility and foaming capacity of hydrolysates increased first and then decreased with the increase of the degree of hydrolysis, however the emulsion stability and foaming stability of hydrolysates decreased with the increase of degree of hydrolysis. Compared with the unhydrolyzed protein,hydrolysates had better water-holding capacity and it increased with the increase of the degree of hydrolysis. Different from water-holding capacity, hydrolysates were poor in oil-holding capacity compared with the unhydrolyzed protein, and it decreased with the increase of the degree of hydrolysis.The antioxidant activities of whey protein were characterized by DPPH radical-scavenging activity, reducing ability and metal chelating ability. The effects of the degree of hydrolysis on the above three indexes were as follows:the DPPH radical-scavenging activity and reducing ability of whey protein hydrolysates were higher than that of unhydrolyzed protein, and they increased with the degree of hydrolysis. The Cu2+ chelating ability of hydrolysates were significantly higher than that of unhydrolyzed protein, and it increased with the degree of hydrolysis, while Fe2+ chelating ability of hydrolysates increased with the degree of hydrolysis, but it was not significant. The antioxidant ability of hydrolysates were significantly higher than that of the unhydrolyzed protein in terms of DPPH radical-scavenging activity, reducing ability and metal chelating ability.