Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2013
Publication Date: 1/1/2014
Citation: Brown, E.M., Latona, R.J., Taylor, M.M., Gehring, A.G. 2014. Powdered hide model for vegetable tanning. Journal of American Leather Chemists Association. 109:8-13.
Interpretive Summary: Several different multistep processes that have evolved more as art form than as science can accomplish the conversion of animal hides into leather, the most valuable byproduct of the U.S. meat industry. In previous research, ARS scientists developed a protocol for using powdered hide to elucidate tanning mechanisms. Vegetable tanning, using extracts from tree bark, is the oldest and least well understood of current tanning processes. In this study, we use powdered hide to explore possible mechanisms for vegetable tanning. Calorimetery and microscopy of powdered hide treated with crude quebracho, a common vegetable tannin, and purified quebracho, suggest that the vegetable tannage requires both the tannin, quebracho, and other components of the crude quebracho that fill and stabilize the hide structure.
Technical Abstract: Powdered hide samples for this initial study of vegetable tanning were prepared from hides that were dehaired by a typical sulfide or oxidative process, and carried through the delime/bate step of a tanning process. In this study, we report on interactions of the vegetable tannin, quebracho with these powdered hide samples. Prior to tanning, the powdered hide from oxidative dehairing was on average slightly more susceptible to attack by collagenase than was the powdered hide from sulfide dehairing. After tanning with as little as 20% quebracho, powdered hide from both processes was well protected against collagenase degradation. Apparent shrinkage temperatures ranged between 79 deg C and 87 deg C, increasing with increased quebracho offer. In contrast to chrome tanning, shrinkage temperatures for quebracho treated oxidatively powdered hides were generally 2 deg C lower than for sulfide dehaired samples. Comparison of micrographs of powdered hide treated wih crude and purified quebracho suggest that the tanning effect of quebracho is partly a function of quebracho/collagen interactions, and also a function of the filling effect of other components of the crude quebracho.