Effect of molecular weight reduction by⁶⁰Co irradiation and polymer concentration in chitosan coating surface properties in relation to the surface properties of red tilapia (oreochromis spp.)

This research assessed the effect of ⁶⁰Co irradiation and polymer concentration on the wettability of coating-forming solutions (CFS) of chitosan as function of the surface properties of red tilapia (Oreochromis spp.), showing the utility of wettability in the optimization of the CFS formulation. The wettability of red tilapia skin, a low energy surface, was estimated by the Zisman’s method. The red tilapia skin presented a surface tension of 84.26 mN/m, with polar and dispersive components of 81.92 and 2.34 mN/m, respectively. The value of critical surface tension was 84.09 mN/m. The rise of irradiation doses increased the wettability coefficient. The optimum value of the spreading coefficient (-2.6 mN/m) was achieved with CFS at 1.5% (w/v) of chitosan irradiated at 50 kGy and 0.1% of Tween 80 (v/v). Important information about the application of CFS on fish have been obtained, which possibly might contribute in the improvement of their durability.