The Penetration Process of the Simple Phenolics and the Polyphenols

• 1、National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University

Abstract：The penetration process of the tannin extracts were investigatedwhile prodelphenidin (Bayberry tannin), procyanidin (Larch tannin) andprodelphenidin-procyanidin complexes (Acacia Mangium tannin) were used as tanning agents. Compositions of the tanning liquids were tested with a butanol-acid method, a Prussian blue method, a conductivity tester as well as a HPLC. The results shows that, from 0h to 16h, the total phenolics, simple phenolics and the polyphenols were all reduced. From 16h to 64h, both the total phenolics and simple phenolics weredecreased to the lowest value then gradually increased, whilethe content of the polyphenols was keep decreasing. From 64h to 112h, both the simple phenolics and the total phenolics were increased to the maximum value, however the polyphenols were found to keep decreasing then tends to equilibrium.Based on these results, the penetration of the tannin extracts can be concluded as: in the beginning of the tanning process, both the simple phenolics and the polyphenols starts to penetrateinto the hide; then simple phenolics complete the penetration and bonded to the collagen reversibly, meanwhile polyphenols penetrate gradually and replace these simple phenolics from collagen; At the end of the tanning process, most of the simple phenolics are replaced by the polyphenols. The results will provide valuable information to understand the vegetable tanning process.

Keywords： vegetable tanning penetration tannin extracts simple phenolics polyphenol