Seguin introduced the word "tannin" in 1796 indicating materials suitable for converting animal hides into leather. Nowadays the words tannin or tannic acid cover a wide variety of products usually classified 3 families: proanthocyanidins (or catechins)
ellagi-tannins and gallo-tannins.
Proanthocyanidins are also called condensed tannins, while the so-called gallo-tannins and ellagi-tannins also known as hydrolysable tannins.
In nature condensed tannins are the most abundant and can be found - usually at low concentrations - in a large number of plant genera. Although condensed tannins represent more than 95 % of total world production they are usually applied as crude low quality extracts in applications such as leather production and the production of adhesives for plywood. Due to their dark colour, lower molecular weight and high level of impurities, they are not suitable for higher quality application (ie food and pharma).
Hydrolysable tannins (ie gallotannins) are far less abundant and only a limited number of plants contain sufficient amounts of these product to be of commercial value.
Where high degree of activity, high purity and a low influence on colour are important, hydrolysable tannins are the products of choice.
Depending upon the application choosing the right tannic acid with an appropriate molecular weight distribution has a major influence on final performance.
Furthermore the unique tannic acid chemistry provides a number of unusual properties combined in one molecule:
- Strong metal complexing
- Complex formation with proteins, alkaloids and certain polysaccharides
- Strong affinity towards polyamides
- Strong anti-oxidizing properties