Pulsed light decontamination of vegetables and fruits before packaging in modified atmosphere

Pulsed light (PL) is an emerging technology which has considerable potential as an alternative to thermal and chemical methods for rapid inactivation of microorganisms on food surfaces. The technique involves the use of intense short duration light pulses of a wide broad spectrum light including wavelengths from ultraviolet (UV) to close infrared region (100-1100 nm). In this work the effect of PL pre-treatment of strawberry before their packaging in modified atmospheric (MAP) on the shelf-life of the fruits was investigated. Samples of strawberries were exposed for 8 s to pulsed light treatments at an energy dose of 10 J/cm2/side before being packed in MAP (20% O2, 5% CO2, 75% N2) and then stored under refrigerated conditions (4°C) for up to 28 days. The parameters measured during the preservation period were: pH, °Brix, color, texture, ascorbic acid content, and microbial spoilage. During the shelf-life, PL-treated strawberries appeared to better preserve their fresh smelt and appearance than the untreated samples. Moreover, while the microbial population of untreated fruits progressively increased during storage, it was significantly decreased (2 Log-cycles) by the exposure to PL treatment and the product kept its microbiological stability during the whole storage period of 28 days. The initial ascorbic acid content was not affected by the light treatment. Moreover, it was better preserved for PL treated samples for the entire storage time, as compared with the untreated fruits. Similarly, the quality characteristics of the fresh strawberries were not adversely affected by PL processing and a high retention of the quality attributes was observed during the storage time. In conclusion, our results suggest that the surface decontamination treatment with PL before packaging in MAP has the potential to extend the shelf life of strawberries while preserving the properties of the fresh product.