The process of pigment dispersion can be classified into three phases: wetting, mechanical crush and dispersion. Actually, wetting agents and dispersants work in three phases in making paints in general, namely paint manufacturing (grinding), storage and painting/paint film formation. Shown below is how wetting agents and dispersants work in each process; (Figure-3)
Additionally, the base also converts caffeine molecules the may be present as salts to the
free base, increasing its solubility in methylene chloride.
Proteins and pigments
Proteins and pigments are very soluble in water and therefore do not present problems to
the separation of caffeine by extraction. The content of pigments varies between different
kind of teas and the level of oxidation that the leaves were exposed to.
Saponins
Saponins are compounds that have amphiphilic structure, i.e. molecules having a polar
water-soluble group attached to a water-insoluble hydrocarbon moiety. This amphiphilic
nature gives saponins detergent-like properties, which increases the solubility of organic
molecules in water. Saponins may therefore induce the formation of emulsions during
extraction, complicating the separation. Emulsions can be broken by addition of salt to
the aqueous layer (therefore increasing the polarity of the aqueous phase and reducing the
solubility of organic molecules in it) or by centrifugation.