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.
Highlights
One of the important ways of milk whey proteins processing is their proteolysis [1]
Much closer values of the absorption coefficient has the main protein of milk – β-lactoglobulin (E280/1 %=9.6)
The total casein preparation was isolated by the way of repeated precipitation in the isoelectric point
Summary
One of the important ways of milk whey proteins processing is their proteolysis [1]. It is used for producing low-allergenic food mixtures, food products for children, athletes, as well as for the production of bioactive peptides [2, 3, 4]. Many proteolytic preparations of animal, plant and microbiological origin are tested in the process of development of the technology for (2019), «EUREKA: Life Sciences» Number 5 such products [5] For this reason, there is often a need to compare their proteolytic effect on milk whey proteins. In the case of determining the concentration of milk whey proteins, as well as products of their proteolysis, these results differ a lot from the actual ones. This is due to the significant difference in values of absorption coefficients for total milk whey proteins (E280/1 %=12.3) and BSA (E280/1 %= 6.3) [7]. When the BSA calibration is used the results differ from the actual ones by almost 2 times
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