SOP: Tea and Coffee — Introduction, Composition and Quality Parameters
GIFSQ — Global Institute for Food Safety & Quality
1. Introduction of tea
Tea and coffee are widely used beverages, preferred by most of the people around the world. Nepal has a long history of tea cultivation, with the first commercial production and processing in Ilam. Demand for tea and coffee greatly depends on the type, cost, taste, availability and cultural behavior of the community. Similarly, coffee is a high value product which is among NTIS products and needs to be taken into account. Nowadays, health benefits of tea have been considered. Now it has become an adulteration problem, which may have either acute or chronic effect on public health. Quality of tea and coffee, as well as adulteration, can be judged by means of laboratory testing and using valid methods.
Tea consists of the prepared leaves of various species of genus Camellia (Thea). The most common are Camellia sinensis, Camellia viridis and Camellia assamica.
Categorization of tea — depending upon the different ways of processing, tea can be categorized as:
- Green Tea
- Black Tea — (i) CTC Tea, (ii) Orthodox Tea
- Oolong Tea
- Other special tea — (i) White Tea, (ii) Yellow Tea, (iii) Silver needle tea, (iv) Golden Tea
Functions of tea:
- As mood refresher
- Possess antioxidant properties
- Physiological and medicinal properties
Chemical composition of tea — the chemical composition of tea varies according to the varietal differences, environmental effects, methods of processing and mode of preparation of tea. The chief constituents of tea are:
- Moisture
- Tannin
- Nitrogenous matter including caffeine
- Oil
- Wax
- Inorganic matter
- Alkaloids
The constituents important in relation to overall tea flavor are:
- Caffeine (1,3,7-trimethyl xanthine)
- Tannin (polyhydroxy benzoic acid)
- Theophylline (1,3-dimethyl xanthine)
In a good tea, the ratio of caffeine : tannin should be 1:3. The color and strength are associated with theaflavin and thearubigin, while the briskness with flavin and caffeine.
The quality control parameters in case of tea are:
- Total Ash
- Water Extract
- Acid Insoluble Ash
- Water Soluble Ash
- Alkalinity of Ash
- Crude fibre
- Caffeine
2. Introduction to coffee
Green or unroasted coffee means the seed of Coffea arabica, Coffea liberica, Coffea excelsa or Coffea robusta. The external layer of seeds of coffee is removed by processes including washing, drying and fermentation. On roasting, coffee attains brown color and develops its characteristic aroma, and the pulverized coffee is obtained from husk-free roasted beans. Instant coffee is solid coffee extract. Coffee products are hygroscopic in nature.
Chemical composition in coffee — the process of manufacture, plant source and environmental conditions determine the quality of coffee. The chief constituents of coffee are:
- Moisture or water content
- Protein
- Caffeine and other alkaloids
- Oils
- Trigonelline
- Minerals
- Various forms of carbohydrates and cellulose
- Non-volatile acids (chlorogenic acids)
The quality control parameters in case of green and roasted coffee are:
- Total Ash
- Water Extract
- Acid Insoluble Ash
- Water Soluble Ash
- Alkalinity of Ash
- Crude fibre
- Caffeine
Instant coffee may be examined for:
- Solubility
- Moisture
- Ash
- Alkalinity of soluble ash
- Sugars
- Caffeine