Chitosan-Based Colorimetric Smart Label: A Real-Time Indicator for Monitoring Freshness of Animal and Plant-Based Foods

Abstract

Background: A chitosan-based smart label integrating ginger essential oil and anthocyanins was developed to provide an environmentally friendly, visually detectable means of monitoring food freshness. The label aims to detect quality changes in animal- and plant-based food products during storage through observable color variations.

Method: The smart label was prepared by casting a chitosan-based film containing butterfly pea anthocyanin extract and ginger essential oil, then oven-drying. The label performance was evaluated by monitoring changes in color change (ΔE) using an Android-based color detector application, pH was monitored using a pH meter, Total Volatile Basic Nitrogen (TVB-N) was measured using the Conway microdiffusion method; and Total Plate Count (TPC) was assessed using the pour plate method. Experimental data were collected in triplicate, and results are expressed as the mean ± Standard Deviation (SD).

Results: In animal-based foods, label color variations correlated with protein degradation and the release of volatile base compounds. In contrast, distinct color transitions occurred in milk, despite minor pH fluctuations. In plant-based foods, color responses reflected changes in pH, vitamin C degradation, microbial growth, and weight loss. The label exhibited the highest sensitivity to milk for animal-based foods and to grapes for plant-based foods, with ΔE values exceeding 5 and 11, respectively, indicating strong visual detectability. The decomposition of proteins in animal-based foods produced volatile base compounds with a TVB-N value of 1.12-11.76 mg/100 g. The base compounds increased the pH up to 8. In plant-based foods, pH and the number of microorganisms increased during storage, while vitamin C decreased. The pH value increased from 3 to 5, while the number of microorganisms increased from 0.008 to 0.086 Colony Forming Units (CFU)/ml. Vitamin C decreased from 204 to 43 ppm.

Conclusion: The developed chitosan-based smart label effectively monitored freshness deterioration in both animal- and plant-based foods through visible ΔE. The label features a real-time freshness indicator, thanks to its biocompatibility, antimicrobial activity, and stable color response.