Recent progress in cleaner preservation of hides and skins

Abstract

The hides and skins are flayed from animals and further processed into leathers. As the main constituent of hides and skins is protein, these materials are highly susceptible to bacterial action. Therefore, adequate preservation of hides and skins is crucial in slaughterhouses and tanneries. Preservation using sodium chloride (SC) remains the most popular curing technique worldwide due to its ease, cost-effectiveness and the quality of the finished leather produced. The use of SC (approximately 40–50% on raw hides/skins weight) enhances the pollution load of tannery effluent, however, which becomes highly contaminated with increased total dissolved solids (TDS) and chlorides. To overcome this hurdle, researchers are constantly searching for alternative preservation techniques which are either totally void of SC or use only a small amount of SC. Based on the literature published mainly in the past decade, this review systematically and comprehensively summarizes current status and development trend about the cleaner preservation methods used in curing and soaking processes in leather industry. The discussed sodium chloride less curing methods contain SC + EDTA, SC + silica gel, SC + sodium meta-bisulphite and SC + boric acid, while the illustrated alternatives used in sodium chloride free curing methods include inorganic preservatives (potassium chloride, sodium sulfate, silicate and ozone), organic preservatives (natural and synthetic preservatives) and other chemical antiseptics. Emphasis is put on natural preservatives (paste plant formulations, essential oils, chlorophyll and bacteriocins), polyethylene glycol, ozone and physical preservative methods containing electric current, chilling and vacuum. Furthermore, several proposals are addressed for the development of eco-friendly and efficient preservation methods for hides and skins.