Effect of storage conditions on phytochemical characteristics and activities of black tea cultivated from geographically different landscapes

• Tea is the common non-alcoholic beverage used worldwide in the form of black, green and oolong tea. • Cultivation of tea plants over geographically different lands affects its antioxidant potential. • Tea packed in air-tight packing less vulnerable to accept environmental factors than non-packed. • OPLS-DA multivariate statistics analysis expresses the potential correlations among different parameters. • Non-packed black tea quality hampers on absorbing moisture, oxygen or light for a long time. The long-term shelf life and quality of fermented black tea depend largely on packaging. Air-tight packaging is considered more favorable for retaining tea quality than non-air-tight packaging. This study aimed to evaluate the quality parameters of commercially available non-air-tight-packed black tea samples. Two air-tight, multi-national branded black teas (MNB-BT1 and 2) samples were evaluated for comparison. The extraction was performed in water and methanol at room or boiling temperatures. The MNB-BT2 sample showed the highest total phenolic content (TPC) (1093.90 ± 4.06 µg/g), followed by the aqueous extract of Indian black tea (1008.69 ± 6.80 µg/g). Regarding total flavonoid contents (TFC), MNB-BT2 showed 314.23 ± 1.14 µg/g TFC, followed by MNB-BT1, which showed 236.73 ± 1.81 µg/g TFC. Among the tested samples, Kenya black tea extract in methanol showed a TFC of 26.22 ± 0.56 µg/g. The highest DPPH· radical scavenging activity, 64.95%, was observed with the MNB-BT2 extract, while the Kenya black tea aqueous extract showed 62.03%. Further antioxidant investigation revealed that the MNB-BT2 extract showed the highest reducing power and linoleic acid inhibition activity. Antibacterial activity was better demonstrated with black tea packed in air-tight packaging than with non-air-tight packaging. Multivariate statistics based on OPLS-DA identified potential correlations among the cultivation region, extraction conditions, and biological activities. This study concluded that non-airtight packing of black tea hampers its quality.