[Biochemical processes at the stage of withering during black tea production].

We determined the molecular weight and some properties of multiple forms of phenol oxidase from tea leaves and four other perennial plants. It was shown that multiple high- and low-molecular forms of phenol oxidase differed in substrate specificity. Low-molecular forms of the enzyme mostly demonstrated hydroxylase activity, while high-molecular forms showed catechol oxidase activity. It was revealed that the withering stage of black tea production is accompanied by the formation of only high-molecular forms of phenol oxidase, which possess catechol oxidase activity crucial for the procurement of oxidative reactions and the quality of the product.

[Regulation of phenol oxidase activity with sulfur dioxide as the base for production of high-quality instant green tea].

The possibility to regulate phenoloxidase activity with sulfur dioxide was studied. It was found that this compound is a potent inhibitor of phenoloxidase of the reversible and mixed type. The inhibitory effect of sulfur dioxide on phenoloxidase provided grounds for a new biotechnological approach to the production of instant green tea. This approach allows increasing the yield of the extractive and the proportion of phenolics in the extractive, thereby improving the organoleptic quality of the product.

[Thermostabilities of plant phenol oxidase and peroxidase, determining the technology of their use in food industry].

Stabilities of phenol oxidase and peroxidase from tea plant (Camellia sinensis L.) clone Kolkhida leaves, apple (Malus domestica L.) cultivar Kekhura fruits, walnut (Juglans regia L.) green pericarp, and horseradish (Armoracia lapathifolia Gilib) roots were studied using different storage temperature modes and storage duration. It was demonstrated that both enzymes retained residual activities (approximately 10%) upon 20-min incubation at 80 degrees C. Phenol oxidases from tea, walnut, and, especially, apple, as well as tea peroxidase were stable during storage. A technology for treatment of plant oxidases was proposed, based on the use of a natural inhibitor phenol oxidase and peroxidase, isolated from tea leaves, which solving the problem of residual activities of these enzymes, arising during pasteurization and storage of beverages and juices. It was demonstrated that browning of apple juice during pasteurization and beer turbidity during storage could be efficiently prevented using the natural inhibitor of these enzymes.

[Comparative study of soluble and immobilized phenol oxidase from the fungus Mycelia sterilia IBR 35219/2]. / Sravnitel'noe izuchenie rastvorimoi i immobilizovannoi fenoloksidazy griba Mycelia sterilia IBR 35219/2.

Phenol oxidase (EC 1.14.18.1) from the microscopic fungus Mycelia sterilia IBR 35219/2 was immobilized using glutaraldehyde on macroporous silica carriers. The enzyme immobilized on amino-Silochrome SKh-2 or aminopropyl-Silochrome 350/80 exhibited maximum activity. Soluble and immobilized phenol oxidases were compared. Compared to the soluble enzyme, the activity of which was optimum at pH 5.5, immobilized phenol oxidase exhibited optimum activity under slightly more acidic conditions (pH 5.2). Immobilization considerably increased the enzyme stability. Both soluble and immobilized forms of phenol oxidase from M. sterilia IBR 35219/2 catalyze oxidative conversion of phenolic compounds of the green tea extract.

[Intracellular localization and characteristics of monophenol monooxygenase in the leaves of tea plants]. / Vnutrikletochnaia lokalizatsiia i kharakteristika monofenol-monooksigenazy list'ev chainogo rasteniia.

The intracellular localization and some properties of monophenol monooxygenase (MPMO) from fresh tea leaves have been studied. It has been demonstrated that MPMO activity is located in cytosole and chloroplasts. These two forms have different properties. Molecular weights of cytosole and chloroplasts MPMO are 41 and 28 kD respectively. The chloroplasts and cytosole forms of MPMO reveal maximum activity at pH 5.3 and 7.1 respectively.