Investigating asymmetrical packaging as a technique to reduce heterogeneity during precooling of fresh produce.

The start of the cool chain for horticultural produce is often a forced-air cooling process, which is used to remove product field heat. This process involves flowing refrigerated air through packed fresh produce stacked upon pallets, for a relatively short time period (usually several hours). The nature of the process creates a unidirectional flow of air, that causes one side of the pallet to receive cool air and hence cool rapidly while the other side of the pallet receives warm air and cools much more slowly. Ultimately, the effectiveness of precooling depends on the slowest point of cooling within the entire packaging system, hence in order to improve pre-cooling processes, cooling rates of the fruit at the back of the pallet are assessed. With exception of reversing the airflow during the precooling, there seems to be little other options in avoiding the temperature heterogeneity during cooling. An alternative approach is to design the package in such a way that cool air is delivered to areas in which rapid cooling is otherwise difficult to achieve. Asymmetrical packaging designs provide the potential to direct airflow for the advantage of cooling. In this work, application of an asymmetrical packaging design (assessed in both orientations) is compared to symmetrical packaging applied to the precooling process for packaged table grapes. While the asymmetrical designs did not enhance overall cooling performance (speed of cooling the slowest cooling location) significant differences in the patterns of heterogeneity during cooling were observed, including locational shifts in the slowest point of cooling. While not successful in this occasion in reducing cooling times the results suggest that asymmetry may be a tool of interest in achieving more homogenous cooling of fresh produce in precooling systems.