Colorimetric Sensing Films of Visible-Light Curable Furfuryl Gelatin for Visual Monitoring of Chicken Freshness

In this study, colorimetric films were developed based on the photooxidation of furfuryl gelatin (f-gelatin) mediated by singlet oxygen generated from grape anthocyanins under visible light irradiation. The successful conjugation of gelatin with furfuryl groups was confirmed using ninhydrin assay, 1 H-NMR, ATR-FTIR, and TGA analyses. The photosensitizing capacity of grape anthocyanins was illustrated using singlet oxygen-induced rubrene oxidation under visible light. The effect of the furfuryl group and the concentration of grape anthocyanins (1% and 2% w/v) on the mechanical, barrier, structural, thermal stability, and morphological properties of films were investigated. Mechanical, barrier, and thermal properties of f-gelatin films were improved while a rougher cross-sectional morphology was observed after the incorporation of grape anthocyanins. Ammonia vapor sensitivity of f-gelatin films increased with anthocyanins concentration. The freshness of skinless chicken breast samples was monitored with F1A2 films, which had the best ammonia sensitivity and physicochemical properties among the tested films. The change of color and thereby, variations in Δ E and a * values of F1A2 films agreed well with TVB-N release and microbial growth in chicken samples during 9 days of storage at 4 °C. Overall, the successful use of anthocyanins both as a visible light photosensitizer and a colorimetric freshness indicator was demonstrated.