Regardless of tasters and methods of manufacture five biochemical factors, total oxygen uptake of unprocessed tea shoots and theaflavins (TF), thearubigins (TR), (-)-epigallocatechin gallate (EGCE) and theogallin (TG), of blackteaarethe main contributing factors of colour of North East India plains tea. Similarly, three constituents, TF, TR and (-)-epicatechin gallate (ECG) of black tea, are main the factors for brightness. Four factors, total oxygen uptake and ECG of unprocessed tea shoots and TF and moisture of black tea are the main contributing factors of strength of North East Indian plains tea.

An attempt has been made to determine, by using the miiltiple regression technique, the most importank biochemical constitirents affecting 'briskness ', 'quality' and 'cash valiration' and also