Biochemistry

In industry, enzymes of microbial origin are used: proteolytic, lipolytic, amylolytic, oligosugar hydrolases that break down pectin, cellulose and hemicellulose. Characterization of oxidoreductases Glucose oxidase is an aerobic dehydrogenase. It catalyzes the removal of H 2 from the substrate and its transfer to O 2 of air with the formation of hydrogen peroxide. The substrate is glucose, which is converted into gluconic acid, and the resulting hydrogen peroxide is broken down by catalase into water and atomic oxygen. Glucose oxidase is synthesized by mold fungi. The enzyme molecule as a coenzyme contains two FAD molecules (flavinodenindinucleotide) . This enzyme is widely used in the food industry (table. 6.2), as well as in clinical chemistry for analysis. Glucose oxidase removes oxygen and glucose. It is used to remove oxygen from those nutrients whose color and aroma deteriorate as a result of oxidative processes (beer, fruit juices, and foods containing fats). This enzyme is also used in cases where the products are dried, during which glucose interacts with proteins to form dark-colored products (Maillard reaction). This takes place upon receipt of egg and milk powder. In the food industry, glucose oxidase as an endogenous enzyme of molds is used in the fermentation of gluconic acid to produce calcium D-gluconate. Xanthioxidase catalyzes the oxidation of substrates of various chemical nature, for example, xanthine andformaldehydes. This reaction has low specificity. The oxygen acceptor is oxygen. The electron donor is formaldehyde. Methylene blue is used as an indicator. This reaction is used in the dairy industry to test raw and pasteurized milk. As a result of sufficient pasteurization, xanthine oxidase denaturation occurs and methylene blue does not decolorize. Diphenol oxidase is involved in the oxidation of tyrosine, phenol, cresol. The final products are dark-colored compounds - melanins. The enzyme is found in mushrooms, potatoes, fruits. The functional group of phenol oxidase is Cu. Inhibitors of this enzyme are important, since the enzymatic browning of fruits, juices and other plant materials during their processing is a big problem. The process of darkening of fruits, juices, and products of their processing under the influence of diphenol oxidase can be slowed down by vitamin C, sulfur dioxide, sodium sulfite, and the addition of sodium chloride. Preliminary heat treatment of vegetables and fruits, in particular, blanching, reduces the activity of this enzyme. In some cases, the action of diphenol oxidase leads to the appearance of the desired color, flavor of food products, for example, in the fermentation of tea. 96