Orthodox and CTC (crush, tear and curl) are the two principal types of black teas. Processing technique of orthodox and CTC teas differ considerably. In orthodox process shoots are withered, rolled, oxidized and dried whereas in CTC process shoots are withered, rotor vane/CTC, oxidized and dried. In orthodox process of manufacture maceration or disruption of the leaf cell is carried in a Rolling table. During rolling the juice from the leaf is come out and the leaf is also twisted and broken into smaller particles

The process objectives during orthodox rolling are therefore

• to rupture the cell walls and expose their contents
• to bring the contents of leaf cells in contact of air to start the process of oxidation
• to twist the leaf and give it the desired shape or appearance
• to break the larger twisted into smaller particles

In CTC process after withering and rolling shoots are cut into small particle size where cell rupture is more than orthodox teasto produce higher amount of TF and TR type of soluble pigment in black teas. In orthodox teas as much as a quarter of oxidisable polyohenols remain unchanged but in CTC teas most of the available polyphenols are converted into TF and TR. Orthodox teas are characterized by high flavour and light liquor but CTC teas are strong in liquor but less flavoury. The degradation of chlorophyll into pheophytin and pheophorbide are higher in orthodox than CTC teas.

Effect of storage on quality of tea

Teas stored at around 5°C for 24 weeks showed better keeping quality than teas stored at 19 to 36°C. Prolonged storage enhanced moisture content causing degradation of fatty acids. The change in colour of liquor from the bright orange brown to dull brown during storage was mainly due to the increase in level of high molecular thearubigins (TR) content and reduction of theaflavins (TF) content. The change in TR composition was brought about by gradual rise in peroxidase activity during storage with consequent decrease in the content of soluble solids. A significant change in volatile flavoury constituent (VFC) was recorded during storage up to six months adversely affecting the quality.

Darjeeling tea