Potential application for genipin-modified gelatin in leather processing

Authors: Taylor, Maryann; Bumanlag, Lorelie; Marmer, William; Brown, Eleanor - Ellie

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2008
Publication Date: 3/1/2009
Citation: Taylor, M.M., Bumanlag, L.P., Marmer, W.N., Brown, E.M. 2009. Potential application for genipin-modified gelatin in leather processing. Journal of American Leather Chemists Association. 104(3):79-91.

Interpretive Summary: There has been considerable interest recently in the utilization of products from renewable resources for the production of goods that were customarily made from petroleum feedstuffs such as fillers used in leather production. Fillers are used to treat hides in order to give the leather more body. In this present study, we evaluated the potential of genipin-modified gelatin as a filler. Genipin is extracted from gardenia fruits and is a compound that forms a bond in which one protein can be linked (crosslinked) with another. Because it has very low toxicity, it is replacing the more commonly used but potentially toxic chemical crosslinking products presently available. We prepared genipin/gelatin products and determined that these products could indeed fill the leather and were not removed during washing. We scaled-up the processes and finished the hides by retanning, coloring, and adding fatliquor to make them pliable. Mechanical properties of the leather, such as how strong it was, and subjective evaluation with respect, for example, to softness and appearance, were determined. We found that the mechanical properties were not adversely affected when comparing the treated leather to untreated control samples, and, with respect to the subjective properties, the filled samples were improved over the untreated control samples. Genipin-modified gelatin thus has the potential to provide not only another environmentally safe alternative to the more conventional post tanning processes but also utilizes a renewable protein.

Technical Abstract: Genipin is an iridoid compound extracted from gardenia fruits. Because of its low cytotoxicity, genipin can be used to replace both glutaraldehyde and formaldehyde as a crosslinking reagent. In recent years, research into the utilization of genipin for the modification of gelatin, particularly in the area of biomedical products, has increased. In prior research we had shown the potential of chemical (glutaraldehyde) and enzyme (transglutaminase) modified gelatin as fillers for leather. In this present study, we investigated whether genipin-modified gelatin products would be applicable. We initially determined optimal reaction conditions of genipin with gelatin for the purpose of creating products with suitable molecular weight distributions, viscosities and melting temperatures that would be appropriate for them to be used as fillers in leather processing. We applied the products to blue stock and, using epifluorescent microscopy, verified that these products were uniformly distributed through the blue stock and were not removed during washing. We scaled up these treatments and applied them to different areas of the hides; subsequently the pieces were retanned, colored and fatliquored (RCF), mechanical properties were determined and subjective evaluation was carried out. It was found that the mechanical properties were not significantly different from those of the control pieces and, with respect to subjective evaluation (handle, fullness, break and color) the treated products fared better than the controls. We also investigated the hydrothermal stability of the blue stock and RCF samples and found that there was an improvement in the shrink temperature in the genipin/gelatin-treated samples. SEM showed that the fibers appeared to be coated with the product, a phenomenon that we had observed in studies using transglutaminase-modified proteins. Thus, genipin-modified gelatin has the potential to provide another environmentally safe alternative to the more conventional post tanning processes.