Modified collagen hydrolysate, potential for use as a filler for leather

Partially hydrolyzed collagen, previously extracted from chromium-containing leather waste, in which more than 50% of the fragments had molecular weights less than 21 kDa, was chemically modified with glutaraldehyde (0 to 18%). Glutaraldehyde, even at low concentration (6%), formed intermolecular crosslinks, as evidenced by a shift in the molecular weight distribution to higher weights. The 12% glutaraldehyde-hydrolysate protein (12% GHP) was used in a demonstration of leather filling. 12% GHP adhered better to chrome tanned calfskin from both back and flank areas than did 0% glutaraldehyde-hydrolysate (HP). To visualize the filling effect, 12% GHP and HP were labeled with a fluorescent dye, and treated leather samples evaluated by fluorescence microscopy. The results suggested a potential for this material as a filler for leather, but were difficult to interpret clearly. To better utilize the sensitivity of fluorescence techniques, additional experiments were performed using a low quality recovered gelatin (90 Bloom; more than 50% of the fragments had molecular weights less than 50 kDa). Gelatin was fluorescently labeled prior to crosslinking. Microscopy showed that in samples treated with 0% glutaraldehyde-gelatin, the fluorescence was localized on the inner surface of veins, whereas with 0.5% glutaraldehyde-gelatin the fluorescence filled the entire cross section of the vein. The results suggest that with appropriate treatment, the small fragment-proteinaceous material recovered from solid leather waste could be used in further leather production.