Establishment of regularities of biochemical transformations in grape berries during refrigerated storage with preliminary thermal treatment

The paper is devoted to the study of biochemical transformations in grapes during refrigeration storage with preliminary heat treatment. The object of the study was nine table grape varieties. Of these, white – Ganja Table, Karaburnu, Chasselas White, Agadai; pink – Nimrang, Marandi Shamakhi, Taifi Pink; red – Kyzyl Izyum and Muscat Hamburg. For better preservation of table grapes and reduction of nutrient losses before placing them in the refrigeration chamber, they were preliminarily subjected to heat treatment for 5 minutes at a temperature of 65–70 °C in a drying cabinet. Then the grapes were stored in refrigeration chambers for 6–8 months, at a temperature of 0–1 °C and air humidity of 85–95 %. Biochemical studies of the grapes were conducted before placing them and every 30–40 days until the end of storage, as well as before and after heat treatment. After heat treatment, all grape varieties show a gradual restoration of the activity of the studied enzymes during the storage period, but this activity does not reach the initial level. Studies have shown that after heating the products, reactivation is possible if at least a weak enzyme activity is preserved, and it is more intense during the first day of storage. During long-term refrigeration of grapes in a refrigeration chamber, a decrease in the catalytic activity of enzyme systems leads to a decrease in the rate of catalytic processes, that is, biochemical transformations of carbohydrates, phenolic substances, vitamins, organic acids, pectin substances and other components, and thereby contributes to the preservation of the nutritional value of grapes. However, storing grapes with preliminary heat treatment contributes to a greater decrease in the catalytic activity of enzymes, and thereby inhibition of biochemical transformations of grape nutrients. This, ultimately, contributes to better preservation of grapes, their aroma, taste, appearance and their chemical components. Marandi Shamakhi, Nimrang, Ganja Table and Karaburnu are distinguished by a smaller change in the content of vital components.