A starch-based AS/PEI/MAC smart packaging film: Dual-mode freshness monitoring through color display and signal...

The development of sustainable and intelligent food packaging materials with integrated active and sensing functions is of increasing importance. In this study, a biodegradable multifunctional smart film was fabricated based on acrylate-modified starch (AS), polyethyleneimine (PEI), 4-mercaptobenzoic acid (4-MBA), and mulberry anthocyanins (MAC). Acrylate starch provided reactive backbones for synergistic crosslinking with PEI and 4-MBA, forming a dense network structure that significantly enhanced the mechanical strength and barrier properties of the film. The optimized composite film exhibited a tensile strength of 10.44 MPa and demonstrated significant antibacterial activity, with inhibition zones of 19.5 mm against Escherichia coli and 15 mm against Staphylococcus aureus. Meanwhile, MAC endowed the film with highly sensitive pH-responsive colorimetric behavior (ΔE > 50), enabling visual detection of spoilage-related alkaline volatiles. Furthermore, integration with a color sensor system allowed the color variation of the film to be converted into digital signals, achieving dual-mode (visual and digital) freshness monitoring. Application tests demonstrated that the film effectively delayed quality deterioration of strawberries and provided real-time indication of shrimp freshness during storage. This work offers a promising strategy for constructing biodegradable smart packaging materials that combine structural reinforcement, active preservation, and intelligent monitoring functions.