Integral performance evaluation of the fresh-produce cold chain: A case study for ambient loading of citrus in refrigerated containers

• Standard ambient loading could cool the cargo within about 3 d.
• Two new container airflow strategies were evaluated.
• Fruit cooling rate, quality, shelf life, pests and energy consumption were targeted.
• The way of stowing and convectively cooling a container has a large impact.

More integrated evaluation of cold chain performance is key for developing a more resource-efficient, energy-smart food supply chain. The present study applies this rationale to evaluate the ambient loading protocol for overseas export of citrus fruit in refrigerated containers. Ambient loading implies that fruit, packed into ventilated boxes, are directly precooled in the container. This technique provides several economic and logistical advantages but is particularly challenging for phytosanitary cold disinfestation treatments. For such an integral approach, multiple relevant product and process parameters were monitored throughout the cold chain, such as fruit cooling rate, quality parameters, shelf life, pest disinfestation efficacy, and their spatial uniformity throughout the cargo load. Also energy consumption of the refrigeration unit was measured. The performance of the standard ambient loading practice was compared to two novel airflow strategies: the channelling configuration, which reduced airflow bypass between pallets, and the horizontal configuration, which forced air horizontally through the pallets. Standard ambient loading was able to cool the produce within about 3 d to the seven-eighths cooling time. The channelling configuration exhibited similar cooling behaviour but the fruit lost less moisture, lasted longer in shelf life conditions and had a better quality. The horizontal configuration performed worse on all aspects. The cooling performance of the container clearly depended on the way in which it was stowed and convectively cooled. This more holistic evaluation of the cooling strategy unveiled several trade-offs and allowed a multi-parameter evaluation of technological improvements to cold chain practices.