Abstract: The objective of this study was to investigate the effects of coumarin at various concentrations (0, 0.03, 0.06, 0.09, 0.12, and 0.15 g/100 mL) on physical properties and microstructure of edible films from tilapia scale gelatin. The results showed that the addition of coumarin did not affect the thickness and water content of the gelatin film, but significantly decreased the water vapor permeability (WVP). When coumarin was added at 0.09 g/100 mL, the WVP was lowest. The tensile strength (TS) and elongation at break (EAB) increased first, reaching the maximum at a coumarin concentration of 0.09 g/100 mL, and then decreased with the increase of coumarin addition. Differential scanning calorimetry (DSC) analysis showed that coumarin had good compatibility with the gelatin film, and could remarkably improve its glass transition temperature (Tg). The results of scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) showed that the cross-linking effect of coumarin and gelatin increased with increasing concentration of coumarin in the range of 0–0.09 g/100 mL, making the film surface smoother and more compact. With further increasing coumarin, the performance and structure of the gelatin composite film were deteriorated. Addition of coumarin effectively reduced the UV and visible light transmittance of the gelatin film. These results showed that coumarin at 0.09 g/100 mL holds promise for the development of packaging materials with better moisture resistance, higher mechanical properties and smoother surface.

Key words: coumarin, gelatin film, structure, properties, application