Evaluation of logistic alternatives in container transport of apples and pears

The objective of this project is studying the capacity of integral containers with respect to loading temperature of apple and pear fruit. The study aims to develop a tool to track and evaluate the spatiotemporal temperature profile and quality loss in a shipment and examines the effect of loading fruit at a pre-optimum temperature. 

Computational fluid dynamic (CFD) models of the spatiotemporal temperature and airflow dynamics inside refrigerated containers were developed and validated. The model validation and evaluation was based on commercial scale experimental tests in collaboration with Tru-Cape Fruit Marketing and Two-A-Day Group Ltd. The study used Golden Delicious apple and Packham’s Triumph fruits as a case study. The validated CFD model was used to develop a virtual refrigerated container method (VRCM). The VRCM was used to track fruit core temperature and fruit quality dynamics during refrigerated transport. 

Fruit core temperature taken from a pallet near the door should be used as the gauge to measure the level of pre-optimality. It is observed experimentally and by use of simulated data that Golden Delicious apple fruit not packed in plastic bags and at pre-optimum fruit core-temperature of 13 °C can be pulled down to a near 0 °C by the reefer within: 3, 12 and 16 days in the region near the cooling unit, container middle region and door region, respectively. On the other hand, if fruit is packed in plastic bags, the cooling dynamics is significantly low that a 16-days of cooling in the reefer and reaching to 0 °C is only possible from a pre-optimum fruit core temperature of 7°C.

The loading of pome fruits into refrigerated containers at above-optimum temperature, depending on the time temperature interaction, should be considered as an extraordinarily serious operation which, if not properly planned, can lead to excessive quality loss. Ambient condition (temperature and insolation), packaging condition (with or without plastic bag), reefer service condition (cooling capacity, insulation) are crucial factors to consider. Sensitivity of a refrigerated container to temperature changes should be taken into consideration. The initial pulp temperature (precooling operation) and the ambient condition (temperature) during the loading, transportation, and handling at the port, are crucial factors to plan the above-optimum loading scenario.  

Not  the reefer cooling capacity but the time-temperature history before vessel departure that matters the most. A pulp temperature of 7 °C when in bags and 13 °C if loose, measured from a pallet near the door when the vessel departs is critical condition. Effect of position of the reefer on the sheep deck (exposure to sunlight) and the condition of the external environment should be further analysed based on a dedicated experimental setup.