Bran from composite grain mixture as an object of deep processing. Part 1. Protein-proteinase complex

Deep processing of grain bran is an important, promising direction that allows the use of by-products (secondary products) of flour milling in order to obtain valuable food components for the creation of enriched food products, as well as specialized grain-based products. Polycomponent bran, obtained during the joint processing of cereals (wheat), legumes (lentils) and oilseeds (flax), in terms of its chemical composition and the state of the proteinproteinase complex, is a unique raw material that can be used for further processing. In particular, it is suitable for the use in producing hydrolysates and other structurally modified products using enzymatic biocatalytic methods. An assessment of the chemical composition and biochemical characteristics of new types of bran showed a high protein content, in which the proportion of the albumin-globulin fraction predominated (78.5-86%), while a significant part of the protein (7.6-10%) was strongly bonded to other biopolymers. The bran proteolytic enzymes acting in the neutral (pH 6.8) and acidic (pH 3.8) pH zones were isolated and studied. It was shown that lentil-flax bran was characterized by the highest proteolytic activity, while the activity of neutral proteinases exceeded the activity of acid proteinases in all three variants: 1.32, 1.37 and 1.56 times, respectively. It was established that protein inhibitors of trypsin and their own proteinases were present in all studied bran types. They inhibited the activity of acid proteinases to a greater extent than neutral ones (% inhibition): 37.5 versus 28.2 (option 1); 32.3 versus 24.5 (option 2); 48.6 versus 32.4 (option 3). The molecular weight, according to gel chromatography, was as follows: neutral proteinases 250,000 200,000 Da, acid proteinases 100,000 75,000 Da. Protein inhibitors isolated from multicomponent bran had a molecular weight of 25,000-20,000 Da. The data obtained will be used in experimental studies on targeted biocatalysis in order to obtain products of a given composition and properties.