Influence of Clamshell Position and Size on Strawberry Fruit Cooling Rate Using Forced-air Cooling

Abstract

Strawberries are among the most perishable fruits, and forced-air cooling plus maintenance of low pulp temperature are critical to extend postharvest shelf-life. However, cooling may not be uniform due to variability in airflow characteristics, clamshell size, and location in the carton or pallet. ‘Strawberry Festival’ fruit were forced-air cooled in oversized, 2-lb or 4-lb clamshell containers and cooling rate was determined according to fruit position under simulated commercial conditions at 0.5 °C. Pulp temperature was measured in fruit located in the front (air inlet) and rear (air outlet) of individual cartons. The T7/8 cooling times (time required for the product to undergo a temperature drop equal to 7/8th of the difference between the initial product temperature and the temperature of the air entering the system) for 4-lb and 2-lb clamshells were 145.89 and 116.34 min, respectively. Fruit in 4-lb clamshells cooled 36% slower, most likely due to the orientation within the carton. Independent of size of the clamshell (4 lb or 2 lb), strawberries located in front of the flat cooled faster than strawberries located in the rear of the flat. Thus, the determination of cooling time must be based on the cooling time required for strawberries located in the rear of the carton.