Optimization of Nano-SiO₂/Tea Polyphenol/Pullulan Edible Composite Films for Postharvest Preservation of Cherry...

Edible composite coatings represent an alternative approach to reducing postharvest losses and extending the shelf life of perishable fruits. This study developed a nano-biopolymer coating by integrating pullulan (PUL), nano-silica (Nano-SiO₂), and tea polyphenols (TP) to retard deterioration in cherry tomatoes (Solanum lycopersicum var. cerasiforme). Optimized through response surface methodology (0.06% Nano-SiO₂, 0.1% TP, 1.8% PUL, 0.77% glycerol), the resulting Nano-SiO₂/PUL/TP composite film showed improved barrier properties (water vapor permeability, WVP: 0.2063 g·mm·m^-2·h^-1·kPa^-1) and increased mechanical strength (tensile strength, TS: 2.62 MPa; elongation at break, EB: 67.67%), which may be attributed to a homogeneous microstructure stabilized via intermolecular hydrogen bonding. The composite coating exhibited significant (p < 0.05) antioxidant activity (59.04% DPPH·scavenging) compared to the PUL film (1.17%) and showed efficacy against S. aureus. When applied to cherry tomatoes stored at 4 °C for 15 days, the coating contributed to improved postharvest quality by reducing weight loss (-27.6%) and decay incidence (-32.3%), delaying firmness loss (2.40 vs. 0.54 N in uncoated group, CK), suppressing respiration rate (-38.8%), and enhancing the retention of total acidity (+9.7%), vitamin C (+49.6%), and total soluble solids (+48.6%) compared to the CK (p < 0.05). Principal component analysis supported sensory evaluation results, indicating the coating helped maintain sensory quality (scores > 6.0) and commercial value while extending shelf life from 9 to 15 days. These results suggest that the Nano-SiO₂/TP/PUL composite coating may serve as a preservative for extending the shelf-life of cherry tomatoes by effectively reducing decay and mitigating quality degradation.