Black Tea Manufacture

Black Tea

The freshly picked leaves are withered for 16 - 18 hours. The leaves are laid on wire mesh in troughs and warm air is blown through them until the leaf moisture content drops from 78 - 82% down to 63 - 73%.

The withered leaf can be processed as Orthodox large leaf tea, or as CTC (crush, tear, curl) tea with tiny leaf particles suitable for tea bags.

Orthodox tea is rolled slowly using traditional rolling tables that mimic the action of hand rolling. This unhurried disruption of the leaf cells causes a slow oxidation of the catechins, due to the realease of a natural leaf enzyme that causes the green catechins to change to orange red polyphenols. Slow oxidation favours aroma and flavour at the expense of intense colour.

CTC processing chops the withered leaf in seconds and initiates such rapid oxidation that the leaf heats up. The CTC process gives the intense colour that teabag brewing requires.

During oxidation, often incorrectly referred to as fermentation, the leaf colour changes from green to coppery red. It takes up to four hours during orthodox manufacture, but only 90 minutes for CTC.

When oxidation is complete, it is arrested by applying heat: this process is often called firing. The oxidised leaf is passed into a hot air dryer for twenty minutes whie the moisture content is reduced to 3% and the familiar black colour of the tea develops. Care has to be taken to maintain the dryer temperature within close limits so that unwanted aromas are not formed.

The dried tea is then sifted into its different grades, based on size and shape.