Studies on the tannins of Fruits and Vegetables

Part XI. Adsorption of tannins with chitin

Abstract

The absorbability of tannin with chitin which is known as an insoluble agent, was studied. The tannin removing ability of chitin was little affected by pH in the range of pH 3-7, however its ability was reduced with the temperature increase. It was also reduced with the presence of sucrose and ethanol, however it was increased with the presence of sodium chloride.
When chitin was coated on celite, its absorption efficiency was greatly improved. Since chitin poorly absorbed low molecular polyphenolics, such as catechin and chlorgenic acid, but well absorbed ordinary tannin, the majority of tannin existed in fruits extracts were removed with chitin treatment and only the low molecular polyphenolics were left in the extracts as a residue. It is, therefore, supposed that chitin will be utilized as an astringency removing agent of fruit or vegetable juices.
Chitosan, the deacetylated product from chitin, showed stronger activity than chitin, however it is not recommended to use chitosan for practical purpose, since it was dissolved in an acidic solution pH less than 4 and did not precipitate tannin.