Effects of Anthocyanin Loading on the Properties of Intelligent Films for Food Freshness Monitoring: A Molecular Dynamics Simulation Study

We compared the effects of anthocyanin loading on the tensile properties and color response of chitosan/sodium alginate (CS/SA) composite films and used molecular dynamics simulations to examine local contacts between a representative pigment and the polysaccharide matrix. Among the six formulations containing 0–5 mL of extract, the 2 mL group had the highest recorded tensile strength (9.57 MPa) and extension at break (3.77 mm), 45.66% and 95.34% above the 0 mL group, respectively. In models M0–M5, which represented relative pigment counts, M2 had the highest short range peaks in the CS–SA and anthocyanin–matrix radial distribution functions (1.547 and 3.875, respectively) and the highest target hydrogen bond count per pigment molecule (2.49 ± 0.31) over the analysis window. M4 had the highest component binding energy per pigment molecule (486.39 ± 5.69 kcal mol−1), giving a different ranking from the tensile measurements. In the chicken packaging test at 4 °C, the 2 mL group showed the largest color difference at every measured time point from 48 to 120 h, reaching 31.1 at 120 h. Among the formulations tested, the 2 mL group combined the highest recorded tensile values with the largest color differences in the middle and late stages of storage.