VALIDATION OF THE TWO-LEVEL MAP SYSTEM IN COMMERCIAL STRAWBERRY DISTRIBUTION AND SIMULATED RETAIL HANDLING

The two-level modified atmosphere packaging (MAP) system is intended to maximize postharvest quality retention by maintaining atmosphere modification throughout distribution and retailing. Experiments were conducted to validate this approach with commercial strawberry (Fragaria × ananassa) shipments in Tectrol^® pallet MAP from California (USA) to Florida (USA). The Tectrol^® system is designed to maintain a modified atmosphere of approximately 10 kPa O₂ plus 15 kPa CO₂ during 4 days shipping at about 2°C. Upon arrival at the retail distribution center the atmospheres were measured and the pallet covers removed, then the strawberries, in 1-lb (455-g) plastic clamshell containers, were either placed into Ste-Pac retail MAP bags and sealed or kept in air. The Ste-Pac MAP was designed to establish an atmosphere of 10 kPa O₂ plus 15 kPa CO₂ at 20°C. The strawberries were then transferred by automobile (approximately 80 km) to the University of Florida and kept at 20°C for 2 days to simulate retail display. Evaluations were performed after 4 days of shipping and after 1 and 2 days at retail display temperature. The two-level MAP was successful in maintaining a beneficial atmosphere around the fruit throughout distribution and retailing, with the MAP pallet cover maintaining an average of 11.3 kPa O₂ plus 11.3 kPa CO₂ and the retail MAP achieving 9.4 kPa O₂ plus 10.9 kPa CO₂ after 1 day and 7.7 kPa O₂ plus 14.0 kPa CO₂ after 2 days. Continuous gas modification resulted in higher overall quality in terms of visual and physical quality (subjective appearance rating, color and firmness). There was also a clear benefit of the two-level MAP in terms of reducing decay incidence during the simulated retail display, with decay incidence decreased by 88% after 1 day and 45% after 2 days compared to the retail display control without MAP.