Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2006
Publication Date: 5/1/2007
Citation: Ding, K., Taylor, M.M., Brown, E.M. 2007. Genipin -Aluminum or -Vegetable Tannin Combinations on Hide Powder. Journal of American Leather Chemists Association. 102(5):164-170. Interpretive Summary: Tanning of animal hides or skins produces leather, a high value co-product of the meat industry. Salts of the mineral chromium are the most commonly used tanning agents for the production of high quality leathers. Because of environmental considerations, and customer preference, the tanning industry is interested in developing chrome-free tannages. Although the art of tanning is highly developed, the mechanisms are poorly understood. The research reported here evaluates genipin, a small molecule isolated from the fruit of the gardenia plant, as a potential tanning agent in combination with aluminum and vegetable tannins. Combinations of vegetable tannins with genipin showed little advantage over either component alone. The thermal stabibity of hide powder was most improved when it was pretanned with aluminum salts and then retanned with genipin. The development of genipin as a tanning agent or component of a combination tannage could be a step toward providing the leather industry with biofriendly, safe formulations for production of high quality chrome-free leathers.
Technical Abstract: Genipin, a naturally occurring protein crosslinking agent, isolated from the fruit of Gardenia jasmindides Ellis, is beginning to replace glutaraldehyde as a fixative for biological tissues. Earlier research in this laboratory demonstrated that the apparent shrinkage temperature of hide powder could be increased from 60 C to 79 C by treating the powdered hide with 5% genipin at pH ~ 7 and 35 C for 24 h, a significant improvement, but not enough for most leather uses. Typical tannages proposed to reduce the use of chromium are combinations of vegetable tannins or aldehydes with each other or with minerals. In this study, the tanning effect on bovine hide powder of genipin in combination with aluminum or vegetable tannins has been investigated. In terms of thermal stability, vegetable tannins in combinations with genipin appear to offer little advantage over either component alone, suggesting little if any synergy. Likewise, aluminum tanning over a genipin pretannage appears to provide little advantage. However, when hide powder was first tanned with 8% aluminum and then retanned with genipin the thermal stability increased linearly with increasing concentrations of genipin (2% to 10%). The apparent shrinkage temperature was > 100 C for aluminum post-tanned with 8% - 10% genipin, suggesting the possibility that a practical combination tannage based on genipin could be designed.