Quality Parameters
The major quality parameters that are tested in made tea include Theaflavins (TF), Thearubigins (TR), High polymerized substances (HPS), Total liquor color (TLC) and Total soluble solids (Water extract). TF has a direct correlation with quality and price realization. TF contribute towards the briskness and brightness of tea liquor. During the course of fermentation, TF progressively increases till an optimum fermentation time, the period at which maximum quality is observed. In addition to having maximum value for TF, there has to be proper balancing of the liquor parameters for which the guide line stating the value of TR to be ten to twelve times as that of TF can be followed. TR are complex condensation products of oxidized catechins with TF. Together with HPS, TR increases the color, mouth feel and body of the tea liquor. Very high levels of TR indicate over fermentation. Similarly, very high levels of HPS and TLC also imply over fermentation. Low levels of TR indicate under fermentation and the liquor tastes harsh.
Properties of Caffeine
Parameters such as caffeine and catechin play an important role on the quality of tea and require minimum stipulation. Caffeine is relatively a stable molecule and is a direct stimulant of the Central Nervous System. Together with TF it imparts briskness to the tea liquor. Caffeine level increases during processing and high levels of caffeine indicate a good leaf standard (caffeine decreases with the maturity of the crop shoots). Water extract or TSS has a direct influence on the cuppage. Higher values of TSS indicate a better quality of the raw material.
Briskness and Color Indices
In addition to the above quality parameters briskness and color indices developed at UPASI TRI, correlate well with quality of made tea. Briskness index is given as percent ratio of TF to TF+CAF and the normal range for south Indian CTC tea is above 23. The color index is given as percent ratio of TF to TR+HPS and the normal range for south Indian CTC teas is from 5 to 11. Teas having maximum TF and a balanced TR/TF ratio (10 to 12) with optimum level of briskness and color indices will definitely have a better quality.
Quality Parameters of Black Tea Though the PFA (Preventive of Food Adulteration) Act requirements specify limits for tea and to great extent restricts adulteration, the various parameters listed under PFA requirements cannot be solely taken as quality standards for various teas. The problem of setting quality standards to made tea arises due to multitude of factors affecting the quality starting from the raw material to the variations in manufacturing conditions.
Standards as Per Pfa Act Tea means the tea derived solely and exclusively and produced by acceptable process notably formation and drying, from the leaves, buds and tender stems of the species of cultivated “Camellia”, known to be suitable for making tea for consumption as a beverage. Tea shall also comply with requirements specified in the following table in which all the requirements are expressed on the basis of the material oven dried at 103o C (+ or -2oC) by the method described in IS 3852.
Chemical Requirements for Tea
| Characteristic | Requirement | Method of Test Ref. No. |
|---|---|---|
| Water extract, percent by mass, Min | 32.0 | IS 13862 |
| Total ash, percent by mass | 4.0 – 8.0 | IS 13854 |
| Water soluble ash, water of total ash, percent by mass, Min | 4.0 | IS 13855 |
| Alkalinity of water soluble ash (as K2O), percent by mass | 1.0 – 2.2 | IS 13856 |
| Acid insoluble ash, percent by mass, Max | 1.0 | IS 13857 |
| Crude fibre, percent by mass, Max | 17.0 | IS 10226 (Pt 1) |
| Lead, mg / kg, Max 10.0 IS 12074 | 32.0 | IS 13862 |
| Copper , mg / kg, Max 150.0 IS 11123 | 32.0 | IS 13862 |
Pesticide Residue Limits for Tea (See also Pesticide Residues)
| 1 | Dicofol, mg / kg, Max | 5.0 | IS 14629 |
| 2 | Ethion, mg / kg, Max | 5.0 | IS 11773 |
| 3 | Quinolphos, mg / kg, Max | 0.01 | IS 14437 |