Preventing Enzymatic Damage to Hides by Timely Inhibition of Trypsin Activity with Soybean Flour during Bating Process

Enzymatic bating is important for producing clean, soft, and high-yield leather. However, it is prone to cause damage to hide collagen fibers and result in loose grain or damaged grain surface due to the longer enzymatic hydrolysis time of the grain layer than the middle layer caused by the slow mass transfer and the rapid hydrolysis reaction of the bating agent in hide. Considering trypsin is the most common bating agent, soybean flour (SF) that contains environmental friendly Kunitz trypsin inhibitor (KTI) was used after delimed hides were treated with trypsin for a certain time to opportunely inhibit its activity in the grain and avoid bating defects. The fluorescence micrographs of hides bated with fluorescently labelled trypsin and KTI showed that KTI could cover only the surface layers when it was added after bating for a certain time, whereas trypsin could penetrate the hide completely. When sufficient SF was added to the bating float at 2 h, the damage to hide collagen caused by trypsin was effectively reduced. In particular, the grain surface remained intact after bating for 8 h. The decrease in the strength of leather caused by bating was also reduced. In addition, the usage of SF scarcely affected the fiber dispersion of the middle layer, thereby ensuring the softness of leather. In summary, opportunely inhibiting the activity of trypsin in the grain could prevent hide damage and improve the quality of leather.