Stages of black tea manufacturing
▪ Roasting kills enzymes in the leaves causing oxidation.
▪ For this, the leaves are brutally heated to a temp. of above 100°C, in large pans (the Chinese method) or by steam cooking (the Japanese way), for 30 sec to a few mins.
▪ The leaves thus become soft and easily bendable for the rolling process.
▪ The harvest is spread evenly over trellis-work trays placed above ducts carrying air blown by fans at a constant temp. from 20°C - 24°C.
▪ This phase lasts for 18 - 20 hours, during which few biochemical reactions occur, releasing a floral scent.
▪ The rolling of black tea leaves is not to twist the leaf but to break down its cell structure, in order to facilitate the enzymes reaction of the oxidation.
▪ Lightly rolled leaves produce mild tea
▪ More twisted tea leaves have a more pronounced flavour.
▪ Rolling can be carried out either by hand or by machine.
▪ This step determines the profile of the future tea.
▪ After leaving the roller, the leaves are laid in layers a few cms thick where heat and humidity levels are controlled.
▪ The room must be well ventilated.
▪ Oxidation occurs at the heart of the leaf for a period of 1-3 hours, wherein no human intervention is required.
▪ To stop oxidation the tea has to be brought to a high temperature quickly
▪ Roasting usually takes place in large, cylindrical drying machines that heat the leaves at 90°C for 15 - 20 mins.
▪ Tea is immediately sorted into 2grades:
- broken leaves
- whole leaves
▪ Broken leaves are obtained either naturally when, whole leaves are broken during handling, or artificially by being cut with a machine.
▪ Whole leaves are classified according to the fineness of the harvest.