Plasma-treated PLA incorporated with purple tomato anthocyanins-based coating to fabricate bilayer indicator films for monitoring the freshness of minced pork.

In this study, plasma-treated polylactic acid (PLA) was employed as the substrate, and a mixture of purple tomato anthocyanins (PTA) and polyvinyl alcohol (PVA) was utilized as a functional coating to fabricate a novel, environmentally friendly, multifunctional bilayer smart indicator film. The results indicate that, with increasing PTA concentration, the elongation at break varies from 94.98% to 159.16%; water vapor permeability decreases from 9.3 × 10-11 to 7.97 × 10-11 g·m/(m2·s·Pa); oxygen permeability declines from 1.18 to 0.65 cm3/(m2·d·0.1 MPa); total migration increases from 0.62 to 2.31 mg/dm2; the water contact angle rises from 57.57° to 69.76°; and the pH-sensitive ΔE increases from 4.46 to 16.70. During pork mince packaging, the color of films (PTA content ≥10 g/dL) shifted from light purple to light green as the meat deteriorated, highlighting its smart indicator function. The developed film enhances PLA's barrier properties, integrates smart indicator characteristics and expands PLA's application prospects in food packaging.