Forced-air Cooling Packaged Blueberries

Abstract

Harvested blueberries, packaged in plastic covered 0.47-L (1-pt) fiber cups, arranged 12 cups to a corrugated master and palletized (96 masters to a pallet) were cooled with forced-air pulled horizontally through the stack. Air flow rates varied from 0.0011 to 0.0022 m3/s/kg (1.06 to 2.12 cfm/lb) of fruit. The variations in cooling rates are discussed in terms of time required to reduce the temperature one-half the difference between the starting pulp temperature and the room air temperature. Average cooling half-times ranged from 48 to 65 min for forced-air cooled fruit. The variations were attributed to differences in the air flow rate. With forced-air cooling, the differences in cooling rates at various points inside the pallet were generally small. For comparison, similar pallets were room cooled at the same time and location. The average half cooling time near the center of the pallet of room-cooled fruit was projected to be over 12 h. Average half cooling times for fruit near the outside of the pallet was approximately 6 h, indicating significant internal temperature variations. The results of this study suggest that the application of forced-air cooling can significantly reduce cooling times of packaged and palletized blueberries and provide more uniform temperatures within the pallet.