Tea extracts and their applications

Tea can be consumed directly either by brewing loose leaves or tea bags or in a ready-to-drink form. In addition, extracts of tea (primarily green tea) may be prepared in a variety of physical forms in order to cover most application requirements. 

Strong infusions are made by soaking tea leaves in alcohol/water mixtures (the catechin content is about 2% w/v). 

Soft extracts are made by concentrating the strong infusion to a water content of 20-25% (the catechin content is about 20% w/w). 

Dry extracts or powders are made by spray drying the strong infusions after they have been concentrated to 40-50% solids (the catechin content is above 25% w/w). The residual water content is less than 5% w/w and the extract is usually processed as a powder containing inert processing aids to render it suitable for a variety of uses (tablets, capsules, dry mixes, etc.). 

Purified extracts contain higher contents of tea catechins obtained by further purification processes, for example solvent extraction or column chromatography techniques (Takeo, 2001). New techniques, such as membrane extraction and separation, may be beneficial in producing such extracts (Nwuha, 2000, Wang et al, 1995). 

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