X-ray diffraction and FT-IR study of caprine and ovine hide

Summary The processing of animal hides to create parchment involves several steps. Our previous study characterized the effects of salting and liming on the structure of collagen, the predominant component of hides and parchment. The current study investigates the effects on collagen structure of the use of solvents propan-2-one and 2-ethoxy ethanol, treatments used historically to produce parchments of a high quality. It was found by small angle X-ray scattering (SAXS) that the axial dspacing of collagen was reduced in samples treated with these solvents as compared to control samples, indicating that the treatments have induced further dehydration and rearrangement of the molecules. However, wide angle X-ray diffraction (WAXD) indicated that, in the lateral direction, the distance between neighbouring molecules was not alted. WAXD also displayed clear peaks brought about by the presence of calcite in the samples, residual from the liming process. The presence of calcium carbonate was confirmed by Fourier Transform Ma-red spectroscopy (FT-IR). FT-IR was shown to differentiate between caprine and ovine samples, and the flesh and grain layers of the hide. The main difference, as inferred by principal components analysis (PCA) arises hom the calcite peaks, indicating that the different layers from the different skins take up calcium carbonate in a different way during the liming process. The solvent treatments did not appear to affect the FT-IR spectra in any way.