Effects of PLA-Based Antimicrobial Composite Films and Low-Energy X-Ray Irradiation on the Quality and Shelf Life of Strawberries

Strawberry is a nutritive fruit with a short life and postharvest losses. In this study, the quality and shelf life of strawberries during storage at 4 °C were evaluated after applying hurdle treatment of packaging with active polylactic acid (PLA)/Gelatine (G)-based films loaded with essential oils (EOs) and/or AgNPs and combined with low-energy (L-E) X-ray at a dose of 0.5 kGy. The results showed that the addition of EOs, AgNPs, or their combination decreased the tensile strength (TS) of films from 16.70 to 6.65–10.01 MPa and increased elongation at break (Eb) from 215.4 to 218.2–398.2%. The oxygen transmission rate (OTR) of films increased from 219.7 to 274.8–298.6 cm3/m2·day, which promoted the development of gas selective films for equilibrium-modified atmosphere packaging (EMAP). A level of 20% decay (primary shelf life criterion) of strawberries was observed on day 8 for the commercial control (polyethylene terephtalate clamshell), on day 9 for the PLA/G-AgNPs films, and on day 10 for the PLA/G-EOs films and PLA/G-EOs + AgNPs films. The combined application of the active films with L-E X-ray irradiation (PLA/G/EOs + AgNPs + I) extended the time to reach 20% decay to day 13 compared to day 9 for irradiated commercial control. An EMAP was achieved after 6–9 days of storage, with a gas composition around 13–14% O2 and 8–9% CO2. The combined treatment of EOs, AgNPs containing films, and L-E X-ray irradiation prevented firmness and total soluble solid loss of strawberries. The redness of strawberries and their total phenolic/anthocyanin content increased after irradiation treatment and maintained significantly higher levels (p ≤ 0.05) than those of non-irradiated samples during storage. This study demonstrates the effectiveness of combining active PLA/G films and L-E X-ray irradiation in extending the shelf life and preserving the quality of fresh strawberries.