SUSTAINABLE TECHNOLOGIES FOR PROCESSING OF HIDES, LEATHER, WOOL, AND ASSOCIATED BYPRODUCTS
Location: Eastern Regional Research Center
Title: Tanning Effects of Aluminum -Genipin or -Vegetable Tannin Combinations
Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 2008
Publication Date: November 1, 2008
Citation: Ding, K., Taylor, M.M., Brown, E.M. 2008. Tanning Effects of Aluminum -Genipin or -Vegetable Tannin Combinations. Journal of American Leather Chemists Association. 103(11):377-382.
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. An aluminum pretannage followed by genipin tanning produced leather with properties suitable for upholstery or garments. 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.
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 when hide powder was first tanned with 8% aluminum and retanned with (2% to 10%) genipin, the thermal stability increased linearly with increasing concentrations of genipin, suggesting the possibility that a practical combination tannage based on genipin could be designed. When pieces of bated hide were pretanned with 6% aluminum, then split and tanned with 6% genipin based on the split wet-white pelt weight, the hydrothermal stability was about 89 deg C as determined from the onset of the melting curve in a differential scanning calorimetry (DSC) experiment, or shrinkage T = 92 deg C by a traditional shrinkage temperature measurement. Values for the physical-mechanical properties were similar to those measured for aluminum-glutaraldehyde and mimosa-aluminum leathers prepared, as controls, under equivalent conditions. By subjective evaluation, the appearance of aluminum-genipin tanned leather was rated 4 on a scale of 1 to 5, and the leather was more stable to washing than were control leathers. These results suggest the potential for development of practical genipin-based tannages.