A virtual cold chain method to evaluate cooling heterogeneity, package designs and cold chain scenarios for fresh fruit

An important share of the food losses, energy consumption and carbon footprint in the fresh fruit supply chain originates from postharvest unit operations such as precooling, refrigerated transport and cold storage. Improving ventilated packaging is an efficient way to reduce product quality loss by better and more uniform cooling throughout the cold chain. Despite intensive research on packaging design for fresh fruits, most researchers mainly focused on evaluating the package design for a single unit operation (e.g., precooling). The integrated performance of packaging solutions throughout the entire fresh produce supply chain is still not fully understood. This study proposes a virtual cold chain (VCC) method to evaluate the performance of ventilated packaging by tracking the temperature history and predicting quality loss of each individual fruit on a pallet throughout the entire cold chain. The VCC method combines computational fluid dynamics (CFD) with kinetic quality modelling. In contrast to previous numerical studies, which looked at relatively small ensembles of fruit, this study evaluates an entire pallet of 3900-5210 citrus fruits packed in 65-80 cartons. Thereby, we aim to gain more insight into the thermal heterogeneity and the associated differences in quality evolution in a pallet. For the three typical unit operations in the citrus cold chain (precooling, transport and storage), significant differences in the fruit cooling time are found along the airflow direction, where the blockage of local vent holes is found to increase the cooling heterogeneity. Clear differences between different carton designs and cooling protocols were found. The difference in quality evolution between individual fruit is found to be limited if proper precooling is applied in the cold chain. In a cold chain with precooling in cold stores instead of forced-air precooler, about 20% more quality loss is found. The ambient (warm) loading protocol is found to be promising to remove field heat and maintain sufficient quality during refrigerated transport. The VCC method is shown to have a large potential for integrated assessment of package design.