PHYSICAL AND BIOCHEMICAL CHANGES IN BROCCOLI THAT MAY ASSIST IN DECISION-MAKING RELATED TO INTERNATIONAL MARINE TRANSPORT IN AIR OR CA/MA

In conducting a supply chain project for the US Army, we learned that broccoli is one of the most commonly rejected items during marine transport of mixed loads of fresh fruits and vegetables in the Pacific region. Preliminary MAP experiments with freshly harvested broccoli indicated that temperature control alone is sufficient to maintain broccoli quality during shipping for up to 3 weeks. Those results suggested that the broccoli in the shipments being simulated is not always freshly harvested at the time of container loading. Therefore, in this research we investigated potential indicators of broccoli freshness (i.e., physiological age) using delayed establishment of CA conditions. Fresh broccoli was obtained locally and held overnight in air at 0.5°C prior to the start of each experiment. Broccoli was placed into air or CA (1 kPa O₂ plus 10 kPa CO₂) at 0.5°C immediately or after 5 or 10 days in air at 0.5 or 5°C. Color changes on the florets and the cut surface of the stalks, weight loss, chlorophyll fluorescence, and overall subjective visual quality were evaluated after 10 and 20 days of storage at 0.5°C and after 20 days of storage plus 2 days shelf life at 20°C. Additional samples were stored for later analyses of vitamin C, chlorophyll a, chlorophyll b, total chlorophyll, total sugars, total amino acids, total phenolics and total protein. Although there were changes during storage and differences between treatments, none of the indices could be used as a ‘freshness indicator’ due to variability between different lots of broccoli that precluded determination of the physiological age. Optimum temperature conditions during transport can prevent rapid deterioration of freshly harvested broccoli for 3 weeks without further benefit from the use of CA/MA, but without specific knowledge of the product’s prior temperature history, such shipments remain risky.