Improvement of the Method of Comparative Study of Milk Whey Proteins Enzymatic Hydrolysis

Abstract

Milk whey proteins are valueble nutritional ingredients with a number of health-beneficial properties. Whey proteins are also a source of bioactive peptides that can be released in the process of proteins enzymatic hydrolysis. In this connection, there often is a need to compare their proteolytic action on milk whey proteins. It is important to take into account the specificities of the composition and properties of milk whey proteins. The aim of the research was to improve the method of comparative study of milk whey proteins enzymatic hydrolysis. Casein and whey were obtained from fresh cow skimmed milk. The whey was separated by centrifugation after casein precipitation at the isoelectric point. The following enzyme preparations were used in the research: neutral protease, papain, trypsin, chymotrypsin and pancreatin. To select β-LG, gel filtration of the milk whey on the chromatographic column with Sephadex G-150 (Pharmacia) was used. The homogeneity of the received β-LG preparation was analyzed by express electrophoresis in the polyacrylamide gel plates (PAG). The preparation of general casein was isolated by repeated precipitation at the isoelectric point. The fractional composition of the casein substrate was analyzed by electrophoresis in the anode system of homogeneous PAG in the presence of urea. Quantitative treatment of electrophoregrams of the β-LG preparation was performed using the imread reading function. Determination of proteolytic activity of enzyme preparations was carried out according to the method of V. F. Selemenev [6]. In the course of the research, it was determined, that for the research of proteolysis under conditions of identical total proteolytic activity, the concentration of neutral protease should be increased by 1.02 times, papain – by 4.2 times, trypsin – by 2.8 times, pancreatin – by 2.12 times as compared to chymotrypsin. As a result, it has been shown that the use of β-lactoglobulininstead of serum albumin in spectrophotometric determinations allows obtaining more accurate values of the concentrations of whey protein and proteolytic products. In determining the ratio of enzyme : substrate it is advisable to take into account the general proteolytic activity of various enzyme preparations in comparative studies of whey proteins proteolysis with various enzyme preparations. These will simplify the methodology and reduce the time for objective evaluation of enzymatic preparations for proteolysis of milk whey proteins. In some cases, considering the specificity of proteases it could increase the yield of biologically active peptides.