Oxidative dehairing: To relime or not to relime?

Authors: Dudley, Robert; Marmer, William

Submitted to: American Leather Chemists Association Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/2006
Publication Date: 6/20/2007
Citation: Dudley, R.L., Marmer, W.N. 2007. Oxidative dehairing: To relime or not to relime? [abstract]. American Leather Chemists Association Meeting. p. 35.

Interpretive Summary:

Technical Abstract: Reliming serves several purposes and traditionally immediately follows the removal of hair (liming/dehairing; 2% sodium sulfide, 2% lime, and 1% sodium carbonate are used at ERRC). Reliming lowers the pH of the hide and opens up the collagen fibers, allowing the uptake of both calcium and water. The opening up of the collagen fibers also aids in the removal of non-collagenous proteins and any residual sulfide. The oxidative protocols that we have developed for the tannery usually use 4% sodium hydroxide. This concentration of base is sufficient to open the collagen fiber and there is an uptake of water by the hide during the dehairing process. Is this opening up of the fiber during dehairing sufficient for the removal of the non-collagenous proteins? We have extracted proteins from raw cattle hide using 2% lime, 4% NaOH, or 4% NaOH/4% sodium percarbonate. The lime extraction of cattle hide yielded approximately an order of magnitude less protein than the NaOH or NaOH/oxidative chemical extraction. Only one protein was common to both the lime and NaOH extracts. The addition of the oxidative chemical to the base extraction did not change thr composition of the proteins extracted from the hide. These studies led to the identification of the isolated proteins and their effect on the functionality of the treated hide. The reliming may not be necessary following oxidative dehairing.