Calcium ion binding ability of tilapia skin hydrolysate and its antioxidant activity

By digesting tilapia (Oreochromis mossambicus) skin with neutral protease, Protamex1.5L and alkaline protease, we studied the binding ability of different enzymatic products to calcium ions (Ca²⁺), compared the antioxidant capacity of enzymatic hydrolysates and their combinations, and analyzed the Fourier infrared spectrum of the conjugate. The results show that the enzymatic hydrolysate of Protamex1.5L hydrolyzed tilapia skin had the highest calcium ion binding rate of 87.79%. All the three tilapia skins hydrolysates had antibacterial properties, and the DPPH free radical scavenging rate, OH radical scavenging rate and reducing power of the products of Protamex1.5L enzymatically tilapia skin were 51.46%, 17.26% and 0.09, respectively. After the tilapia skin hydrolysate (TSH) was combined with calcium ions, the DPPH free radical scavenging rate and hydroxyl radical scavenging rate of calcium ion chelate (TSH-Ca) decreased, but the reducing power was enhanced. Fourier transform infrared spectroscopy reveals that calcium ion had combined with amino nitrogen atom and carbonyl oxygen atom in TSH.