Physico-chemical analysis of pekmez products made from grape varieties grown in the conditions of Uzbekistan

Abstract

This article presents the results of a study on the physical and chemical properties of pekmez products made from technical grape varieties grown in soil and climate conditions of the Parkent district of the Tashkent region. In the study, physico-chemical properties including water-soluble dry matter content (°Bx), pH level, titratable acidity, density, ash content, 5 phenolic compounds and active antioxidant content of pekmez obtained from technical grape varieties “Saperavi” (black-colored), “Hindogi” (black-colored), “Soyaki” (white-colored), “Bayan Shirey” (white-colored), “Muskat Rozovy” (pink-colored), “Morastel” (black-colored) were determined. According to the results of the analysis, the amount of water-soluble dry matter in the pekmez samples obtained from different grape varieties was in the range of 69.33-74.40%, the pH level was between 4.34-5.70, and the titratable acidity was 0.65-0.75 (gr-100gr/l) was determined that the total ash content was in the range of 1.40-3.30 (g/cm3). The amount of phenolic compounds preserved after thermal processing, including caffeic acid, gallic acid, ferulic acid, p-coumarinic acid, ellagic acid and active antioxidant, have also been analyzed. Among the studied acids, caffeic acid was the most abundant (9.10-11.40 mg/kg−1). Gallic acid (1.0-1.66), ferulic acid (0.70-2.10), p-coumarinic acid (0.68-2.67) and ellagic acid (0.20-0.40) tended to decrease during heat treatment. The highest antioxidant activity (66-68 µmol TE g/1) was recorded in black grape varieties, this indicator of pekmez made from white varieties was slightly lower (54-59 µmol TE g/1), the antioxidant activity of pink grape varieties had an intermediate expression (57.55 µmol TE g/1).