Investigation of some physicochemical and bioactive properties of tea, during black tea manufacturing

In this study, it is aimed to investigate some physicochemical and bioactive properties of tea samples taken from various black tea manufacturing steps. For this purpose, the amount of dry matter, color parameters (L *, a *, b *), pH values of the samples taken from tea leaves (Camellia sinensis), withering, curling, oxidation, drying and grading stages, the total phenolic content of tea and water extracts were detected. Antioxidant activity (DPPH and CUPRAC methods) and total monomeric anthocyanin content were evaluated. The fatty acid composition of the tea samples was also determined. In this study, it was determined that the production stages had a significant effect on the studied properties (p <0.01). While the pH value was 5.97 ± 0.01 in the highest tea leaves, it decreased to 5.27 ± 0.01 during the oxidation stage. The highest increase in the amount of dry matter of tea was detected in the drying phase, while a part of the water loss was realized during the withering phase. The L * value was determined in the highest tea leaves and after the withering step and the lowest after the grading step (18.5 ± 0.85). In tea samples, a * and b * parameters were detected after the highest oxidation stage (5.56 ± 0.99 and 20.69 ± 2.13). When the solvent effect was examined, the mean of antioxidant activity was higher with ethanol and the mean of total phenolic content was higher with pure water as solvent. The interaction of different solvents and production steps had a significant effect on total phenolic content and antioxidant activity (p <0.01). The highest antioxidant activity was detected in tea leaves and getting decreased during the stages in both methods. The total amount of phenolic substances was compatible with the antioxidant activity. In addition, when the fatty acid composition of the tea samples were examined, it was found that the dominant profile was composed of saturated fatty acids, (palmitic acid, myristic acid and capric acid) and saturated fatty acids (oleic acid, heptadecenoic acid and eicosenoic acid). During the stages, palmitic acid was the dominant fatty acid in tea samples.