Amine-responsive PVA-based fluorescent indicator films incorporating β-Glucan/FITC for visual detection of chilled meat freshness

Amine-responsive fluorescent indicator films for meat freshness were constructed by incorporating β-glucan grafted with fluorescein isothiocyanate (FITC) in polyvinyl alcohol (PVA). The structural, thermal, and responsive properties of grafted copolymers (βGlu-FITC) were investigated. The results of 1 H NMR spectra showed that βGlu-FITC exhibited proton signals between 6.5 and 6.7 ppm, suggesting the successful grafting of FITC onto β-glucan. The fluorescence quantum yield of βGlu-FITC was 18.72%, which was higher than that of β-glucan of 12.94% at the optimum excitation wavelength of ultraviolet light of 365 nm. With the incorporation of PVA as a film-forming matrix, βGlu-FITC/PVA films showed high yellow-green fluorescent responsiveness under volatile ammonia and pH solution. When the film was used for meat freshness, the 0.06βGlu-FITC/PVA film provided a noticeable fluorescent indication of pork freshness that corresponded to increases in total volatile basic nitrogen, total colony counts, and drip loss, suggesting its potential for meat packaging and as a freshness indicator.