De-oiled neem cake as potential bio-additive for low-salt raw skin preservation: a process for salinity reduction in tanneries

Animal skin, a proteinaceous material containing about 60–65 % moisture, is an ideal substrate for the growth of microorganisms, if not preserved properly. Conventionally, large quantities of sodium chloride are used for skin preservation. De-salting and soaking carried out during processing of the skin generates serious environmental constraints. In view of this, low-salt skin preservation with de-oiled neem cake is attempted. To ensure the antimicrobial properties of de-oiled neem cake, aqueous and solvent extracts of the cake were studied against bacteria and fungi which were isolated from raw skin. The antimicrobial assay was performed using the well diffusion method for aqueous, methanol and hexane extract of de-oiled neem cake, which showed maximum zone of clearance for aqueous and methanolic extract against the isolated bacteria and fungi, respectively, present in raw skin. The percentage of inhibition study reveals that the methanolic extract showed 100 % inhibition against many organisms and the water extract against some organisms. The raw skin was cured using de-oiled neem cake with reduced amount of salt and left for a period of 21 days. The skins were checked periodically for microbial growth as per the conventional methods. Finally, the low-salt preserved skins were processed into chrome-tanned leathers and their strength properties were compared with leathers which were preserved by the conventional method. The results suggest that de-oiled neem cake along with minimal salt has adequate curing efficiency on raw skin and if this system is implemented, pollution caused due to sodium chloride would be significantly minimized.