Carotenoid composition, distribution and degradation to flavour volatiles during black tea manufacture and the effect of carotenoid supplementation on tea quality and aroma

Carotenoid content of tea leaves ranges from 36 to 73 mg/100 g dry weight, and is dominated mainly by β-carotene, lutein and zeaxanthin. Among the cultivars, China contained the maximum and Assam clone the least. Carotenoid fractions were found to degrade to different extents at different stages of tea processing. The carotenoid content was as low as 25 mg/100 g in the made tea. Only a small quantity was leached into the brew, the remaining being retained in the infused leaf/tea residue. The high stability of carotenoid in tea is mainly due to the presence of antioxidants, such as polyphenols and catechins. Carotenoid degradation was found to be greater in the CTC (Crush, Tear, Curl) process than the orthodox process, greater in withered than unwithered, and in the order β-carotene > zeaxanthin > lutin. Vitamin A value was greater in orthodox tea than CTC tea and it varied with clones. The carotenoid degradation was found to yield large quantities of desirable aroma volatiles in made tea, giving a high grown flavour status. An increase in endogenous carotene content enhanced all the quality parameters of tea, the VFC (volatile flavour compounds) index, almost being doubled. The tasters' evaluation also revealed the same trend. It was found that a 1:1 NK application at the rate of 300 kg/ha/year enhanced the carotenoid content of green leaves in the second week after application, with subsequent decline.