Abstract

With the characteristics of high efficiency, specificity and mild reaction conditions, enzymes are able to catalyse many biochemical reactions. Hence, they are widely used in the soaking, unhairing, degreasing and bating processes in the leather industry. At present, there are a lot of studies on the interaction laws between protease and collagen under conventional water bath heating; however, under microwave irradiation with both thermal and non-thermal effects, corresponding research has not yet been reported. In this work, enzymatic unhairing (EU), bating (EB) and wet-blue leather treating (ET) processes were investigated under microwave irradiation heating compared with water bath heating. Hydroxyproline concentration and chrome content were analysed by ultraviolet-visible absorption spectroscopy. The grain of the sample was observed with a microscope. Thermal performance and physical and mechanical properties of the collagen composites was characterised by the shrinkage temperature, softness, tensile and tear strength, respectively. The results showed that microwave could increase EU and EB rates, EU was completed 2 hours earlier and the end of EB was 1 hour in advance. After microwave irradiation, the grain of the skin or leather had better flatness and softness. It also promoted enzymatic proteolysis, in which the hydroxyproline concentration in EB and ET was decreased by 0.26 mg/L and 0.12mg/L, respectively. In addition, microwave use lowered the removal of chromium in ET, and the chrome content was reduced by 11.96mg/L. Quite a long exposure to microwave irradiation would inactivate enzymes, slightly weakening the tensile and tear strength of the leather. The results indicated that microwave treatment could promote the leather manufacturing process and improve the performance of collagen composites, which may lay a foundation for the application of microwaves in the leather industry.