Effect of UV Irradiation on Properties and Characteristics of Fish Gelatin-Based Film Containing Linoleic Acid and Ferrous Chloride

This study investigated the combined effects of linoleic acid (LA) incorporation and UV irradiation in the presence and absence of ferrous chloride (FeCl2) on the properties and characteristics of fish skin gelatin films. UV irradiation was implemented at different intensities (10,000–40,000 lux) and with different exposure times (1 and 5 min) by two different methods: irradiating the film-forming solution before casting (S-UV) versus irradiating the pre-cast film (F-UV). The UV treatment significantly increased the elastic modulus (EM) while decreasing the tensile strength (TS), elongation at break (EAB), and water-vapor permeability (WVP) of the films (p < 0.05), irrespective of the irradiation method used. This effect became more pronounced with higher UV intensity and longer exposure times. When both LA and FeCl2 were present, UV irradiation promoted the formation of non-disulfide covalent bonds, leading to increased cross-linking. This cross-linking improved the film’s strength and decreased its WVP, although it did cause the films to become yellowish. Fourier-transform infrared spectroscopy (FTIR) confirmed interactions between the gelatin and LA, indicated by a decrease in the intensity of Amide-A, Amide-I, and Amide-II bands. A key finding suggested that UV irradiation, combined with LA/FeCl2 incorporation, could significantly enhance the properties of fish skin gelatin films, especially their water-vapor barrier. The study’s novelty lies in demonstrating that applying the UV treatment to either the film solution or the final film yields similar results, providing flexibility in the manufacturing process.