Polyphenolic compounds and antioxidant activity of CTC black tea of North-East India.

Sixty black tea samples from different agro climatic zones of northeast India were assessed for biochemical constituents that determine quality and also influence organoleptic perception. The antioxidant activities such as α,α-diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging, lipid peroxidation inhibition, nitrite scavenging and super oxide scavenging, of the collected samples were analysed. Out of the four antioxidant activities, the super oxide scavenging activity was lowest and nitrite scavenging activity was highest. Theaflavin was significantly and positively correlated with nitrite scavenging and lipid peroxidation inhibition activities. Thearubigins showed a significant positive correlation only with nitrite scavenging activity. Correlations between relative antioxidant capacity index (RACI) and TF, TR and tasters' quality were positive and significant. Tea tasters' parameters were significantly and positively correlated with each other. Principal component analysis showed that Upper Assam, North Bank and South Bank produced better quality tea than other regions with respect to TF, TR, RACI and tasters' quality.