Black teas, which the Chinese call red tea due to the coppery colour of the infusion, are teas whose leaves have undergone full oxidation.
Legend has it that in the 17th century, a cargo of green tea from China arrived in London after a particularly long voyage. During the journey the tea chests had gone mouldy and the tea they contained had turned from green to black. Not great tea connoisseurs, the English enjoyed it so much that they asked for a new delivery to the Chinese…
WITHERING
This first step is essential to get the final result. The purpose of roasting is to kill those enzymes in the leaves that cause oxidation. In order to do this, the leaves are brutally heated to a temperature of around 100°C, either in large pans (the Chinese method) or by steam cooking (the Japanese way), for anything from 30 seconds to 5 minutes. The leaves thus become soft and easily bendable for the rolling process.
For this operation, the harvest is spread evenly over trellis-work trays placed above ducts carrying air blown by fans in a room kept at a constant temperature of between 20°C and 24°C. This phase generally lasts for about 18 to 20 hours, during which a certain number of biochemical reactions occur, releasing a characteristic floral scent.
Rolling
The rolling of black tea differs from green teas: its objective is not to twist the leaf but to break down its cell structure, in order to facilitate the enzymes reaction of the oxidation. If the leaves are lightly rolled they will produce a mild tea; if they are more twisted the tea will have a more pronounced flavour. Rolling can be carried out either by hand or by machine.
Oxidation
This step determines the profile of the future tea. After leaving the roller, the tea leaves are laid out in layers a few centimetres thick in rooms where the heat and humidity levels are controlled. The room must be well ventilated, without for all that creating draughts. Oxidation occurs at the heart of the leaf for a period of between one and three hours, during which no human intervention is required.
Roasting
To stop oxidation the tea has to be brought to a high temperature as quickly as possible. Roasting usually takes place in large, cylindrical drying machines that heat the leaves to an average temperature of 90°C for 15 to 20 minutes.
Grading
The next thing that must be done is to sort the tea by grade. The tea is immediately sorted into two grades:
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.
