A pH-responsive fluorescent film with the smartphone-assistance for real-time and visual detection of food freshness

Abstract

Monitoring food freshness is considerably important for food safety. In this study, a smart pH-responsive fluorescence hydroxypropyl methyl cellulose-κ-carrageenan-fluorescein isothiocyanate-NH₂-CaAl₂O₄ (H-K-F-N) film was prepared. Taking synergetic advantage of the pH-dependent behavior of fluorescein isothiocyanate dye and the luminescence characteristics of calcium aluminate phosphor, the film exhibited a unique strong pH-responsive fluorescence with an exceptional linear relationship (correlation coefficient, R² = 0.9993) across a wide pH rang of 2.0-12.0. Moreover, the H-K-F-N film, as a smart sensor, could be used to estimate the total volatile basic nitrogen and total viable count through fluorescence intensity based on the partial least squares regression model and support vector machine regression, respectively. Leveraging the relationship between the fluorescent image's digital signals and food freshness indicators, a smartphone-assisted system was developed. These results demonstrated that H-K-F-N film is promising for applications in intelligent food packaging and food safety monitoring.

Keywords: Fluorescence film; Food freshness; Smart packaging; Smartphone-assistance; pH-responsive.