Enfriamiento De Fresas En Envase Plástico

May 1997

Perishables

Handling

Newsletter

Issue

No.

90

Page 29

Forced Air Cooling of Strawberries in Clamshell Baskets
James Thompson and Jerry Knutson Department ofBiological and Agricultural Engineering, UC Davis

Background Strawberries are increasingly marketed in one poundcapacity, lidded containers (commonly called clamshell baskets). These containers have areputation of being slow to cool compared to other containers. Manufacturers have responded to this by developing containers with new air vent designs. The purpose of this test was to compare cooling timefor a range of commercial and prototype clamshell baskets. We did not compare other other basket performance characterisitcs such as basket strength and its effect on berry moisture loss, decaydevelopment and mechanical damage to the fruit. Procedure We packed all containers with Selva strawberries from the same field. The fruit were uniform sized and had a minimum shoulder diameter of about 1.25inches. All baskets were placed in the same style 16" x 20" tray. It had recessed sides along its short dimension and four vents near the bottom edge of the side wall for air flow. The trays had novents on the bottom for verticle air flow. Baskets from five manufacturers were tested. Two trays of each clamshell basket style were transported to UC Davis and cooled in a laboratory forced aircooler. Trays were placed two across in a layer and oriented so air flowed parallel to the 20" tray dimension and through both trays, to simulate the air flow path in a commercial cooler. Five layers oftest baskets, each of a different basket style, plus a non test layer on top were placed on the laboratory cooler. Pressure drop across the double stack of boxes was 0.35 - 0.38 inch of water column.Fruit temperature was monitored with thermocouples (± 0.2°C accuracy) placed in the center of berries near the shoulder. Monitored berries were in the center of the top berry layer in each of four...