Changes to the Collagen Structure using Vibrational Spectroscopy and Chemometrics: A Comparison between Chemical and Sulfide-Free Leather Process

Chemical and physical changes take place when hides and skins are processed to leather that affect the quality and strength of the material. Understanding the structure at each leather-making stage is the basis of this study but also intend to improve the process through a biochemical approach, employing a proteolytic enzyme for processing leather more cleanly with reduced environmental impact. Raman and ATR-FTIR spectroscopy in conjunction with chemometrics was used to investigate each leather-making stage from fresh green cattle hide to dry crust leather. The changes in proteins, lipids, nucleic acids and other biomolecules with leather processing was measured and reported using three novel Raman ratiometric markers, 920/1476, 1345/1259 and 1605/1476 cm-1, to discriminate the structural changes in collagen of hide using standard chemical and enzymatic method. Amide I band was deconvoluted to investigate thecollagen secondary structures using curve fitting by Gaussians function. The results of Principal Component Analysis are well-corroborated with the ratiometric markers of structural changes.