Factors affecting mass transfer of protease in pelt during enzymatic bating process

Bating pelt with protease is an important process, which removes unwanted non-collagenous proteins from the pelt and moderately disperse hide collagen network. However, the grain surface, may be excessively hydrolyzed during bating due to the longer retention time of protease in the grain than in the middle layer caused by the low mass transfer rate of protease in pelt. Here, the effects of protease dosage, common auxiliaries and molecular weight of protease on protease transfer during bating were investigated so that we can find the key points to avoid excessive collagen damage, particularly in the grain. Observably, increasing protease dosage led to faster protease transfer and softer leather, but along with more considerable grain damage. Using penetrating agent JFC (fatty alcohol-polyoxyethylene ether) and ammonium sulfate enhanced protease transfer and simultaneously alleviated collagen damage due to the decrease in interfacial tension and electrostatic attraction between protease and pelt, respectively. Additionally, proteases with lower molecular weight transferred faster in pelt, which suggests that a potential strategy to solve the conflict between the mass transfer and the reaction of protease in pelt might be to produce/employ smaller bating proteases. Graphical abstract