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.