BIOMODIFICATION OF COLLAGEN-CONTAINING BY-PRODUCTS BY ENZYMATIC HYDROLYSIS

Low-value by-products can be processed using biotechnological methods, which seems to be the optimal solution for the problem of rational use of secondary raw materials. The authors introduce a method of biotransformation using whey and enzyme preparation of proteolytic action with subsequent massaging. The method neutralizes the specific smell, reduces the time of heat treatment, increases hydrophilicity, and reduces the mechanical strength of mutton rumen tissue. The experiment proved that the enzymatic effect on the connective tissue of the mutton rumen contributes to the destruction of disulfide and hydrogen bonds of the triple helix of the collagen macromolecule. It significantly reduces the mechanical strength and hydrothermal stability of collagen, which, in its turn, reduces the heat treatment time while increasing the functional and technological properties. The research revealed an increase in collagen digestibility. After 4 hours of fermentation, it was 4.5%, after 6 hours – 5.9%, and after 8 hours – 5.9%. Hence, the optimal period of fermentation was determined as 6 hours, since between 6 and 8 hours the main physical and chemical parameters improved insignificantly. The experiment in the cutting pressure of the raw lamb rumen tissue demonstrated softening of the structure as a result of the effect of the acidic medium on the collagen structure. An excess positive charge formed due to the suppression of dissociation of carboxyl groups of side chains. The loosening of the collagen structure occurred due to the expansion of fibrils in the polar areas, which can be attributed to the repulsion between similarly charged groups. As a result, the brine penetrated into the expanded area and caused swelling. The use of whey and fermentation contributed to an additional increase in moisture-binding and moisture-holding capacity. It loosened the structure of proteins and, thus, increased the degree of penetration and the immobilized moisture in the rumen. As a result, its mass increased by 10–20%, and the heat loss reduced. The composition of the brine contributed to the swelling, increased the diameter of the collagen fibers, and enlarged the surface of interaction in during massaging. Moisture was allowed to enter freely, which increased the water binding capacity by 22.2 ± 0.31%. The increase in the water binding capacity could be explained by the modification of collagen and its destructive changes. The changes occurred due to the additional interaction of whey molecules with the protein and the formation of new intermolecular bonds. Fermentation, combined with the massaging of the tripe, contributed to the development of lactic microflora and hydrolytic decomposition of protein components, thereby reducing the heat treatment process. Such changes are associated not only with the processes of protein hydrolysis under enzyme preparation, but also with the complex activity of lactic acid bacteria, as well as endo- and exoenzymes that hydrolyze proteins. The changes can also be attributed to the fact that low-molecular protein substances can assimilate and contribute to bacterial growth. In addition, lactic acid reduces the pH of the medium, thus activating the enzymatic properties. The proposed method of biotransformation of collagen-containing raw materials makes it possible to create environmentally friendly and low-waste technologies.