Commercial-Scale Forced-Air Cooling of Packaged Strawberries
Strawberries are an extremely valuable crop, but they are also very sensitive to decay if not cooled and maintained at proper temperatures. Strawberries are typically packaged in the field and quickly transported to a cooling facility, where they are precooled by forcing cold air through the vents of the packaging. Over the last several years, there has been a shift in the packaging used for strawberries. Many of the open-top pint baskets have been replaced by clamshell designs with hinged lids and less vent area. In addition, there has been an increased retail demand for a larger tray that fits five trays to a pallet layer rather than six trays per layer. In this work, strawberries packaged in clamshell containers and a variety of tray designs were precooled in commercial cooling systems. To determine the speed of cooling for each treatment, both the 7/8th cooling time and the cooling coefficient were calculated. It was found that the control package combination (with a design that fits six trays per pallet layer) cooled significantly faster than the other treatments, which fit five trays per pallet layer. It is thought that the cross-orientation of trays that occurs in the five trays per layer configuration may slow cooling if the vents are not designed properly. No major differences were found for cooling using corrugated trays versus returnable plastic containers. It was found that the clamshell container and tray should be designed together and chosen properly to allow maximum air-to-product contact during cooling. Variations in air temperature during commercial cooling tests may cause errors in determining 7/8th cooling times.