Evidence of a distinct lipid fraction in historical parchments: a potential role in degradation?

Parchment, a biologically based material obtained from the processed hides of animals such as cattle and sheep, has been used for millennia as a writing medium. Although numerous studies have concentrated on the structure and degradation of collagen within parchment, little attention has been paid to noncollagenous components, such as lipids. In this study, we present the results of biochemical and structural analyses of historical and newly manufactured parchment to examine the potential role that lipid plays in parchment stability. The lipid fraction extracted from the parchments displayed different fatty acid compositions between historical and reference materials. Gas chromatography, small-angle X-ray scattering, and solid-state NMR were used to identify and investigate the lipid fraction from parchment samples and to study its contribution to collagen structure and degradation. We hypothesize that the origin of this lipid fraction is either intrinsic, attributable to incomplete fat removal in the manufacturing process, or extrinsic, attributable to microbiological attack on the proteinaceous component of parchments. Furthermore, we consider that the possible formation of protein-lipid complexes in parchment over the course of oxidative degradation may be mediated by reactive oxygen species formed by lipid peroxidation.