ARS | Publication request: The quest for a comprehensive tanning mechanism

Submitted to: International Union of Leather Technologists and Chemists Societies
Publication Type: Proceedings
Publication Acceptance Date: July 11, 2011
Publication Date: N/A

Technical Abstract: The conversion of animal hides into leather was one of mankind’s earliest ventures into biomaterial engineering. The methods for production of leather have evolved over many centuries as art and engineering with little understanding of the underlying science. Through empirical methods, several classes of tanning agents with a variety of properties were identified. The unique structure of fibrous collagens, a long triple helix that further associates into fibers, provides an insoluble scaffold that gives strength and form to the skin, tendons, bones, cornea and teeth. The function of tanning is to stabilize the structure of the collagen matrix of the hide, increase its hydrothermal stability and protect it from microbial degradation. Current commercial tannages include mineral (mainly Cr(III)), vegetable (polyphenolic tannin), and organic (aldehyde). The product of each of these tannages is leather, despite the different chemistries. From a 21st century perspective, none of these processes is ideal, and a comprehensive tanning mechanism would provide a basis for the design of more sustainable and eco-friendly tanning processes. ERRC leather researchers have developed both theoretical, the collagen microfibril molecular model, and experimental tools to investigate methods for stabilizing collagen structure. Experimental models range from bench scale models using soluble collagen to pilot scale tanning of hide pieces. This research includes studies of mineral and vegetable tannages, enzyme-catalyzed and aldehyde-based covalent crosslinks, electrostatic and hydrophobic interactions. Insight gained from these studies and those of other leather and biomaterials scientists will be evaluated as steps toward the still elusive, comprehensive mechanism for tanning.