Chilling Fish Fillets In 10 to 25 Pound Containers

Introduction

Experimental

Ten lbs. of fillets were packed into 2.75-4.5 inch (7-11.4 cm) deep plastic containers, 2.56 inch (6.5 cm) deep steel containers, poly bags (5.5 inches or 14 cm thick when filled), and into poly bags placed into 2.875 inch (7.3 cm) deep wax-coated cardboard containers.

Twenty lbs. of fillets were packed into 4.25 inch (10.8 cm) deep metal containers, and poly bags (7 inches or 17.8 cm thick when filled).

Twenty-five lbs. of fillets were packed into 5.25 inch (13.3 cm) deep plastic containers.

Two thermocouples were inserted into fillets in the center of each container and connected to a recorder. The containers were placed into bottom-iced 100 lb. wax-coated cardboard "wetlock" shipping boxes. The containers were surrounded by at least one inch of ice. The 100-lb. boxes were held at 40°F (4.4°C). Fillet temperatures were monitored every 10 minutes until the centers of the containers reached 35°F (1.7°C). Two containers of each size were included in the tests.

Chilling Times

Chilling times were directly related to container depth with two exceptions (Figure 2). Poly bags containing 10 lbs. of fillets appear to have cooled more rapidly than other containers of the same depth. These poly bags may have settled and flattened after the height of the bag was initially measured and ice was added.

Figure 1. Chilling curves for fresh fish fillets iced in plastic containers 2.75, 3.31, 4.5, and 5.5 inches deep.	Figure 2. Container cooling rates vs. container depth for poly bags and HDPE plastic, metal, and bag-in-box containers.

The other exception was the 10 lb. poly bag of fillets inside of a waxed cardboard carton. The fillets in this container cooled more slowly than in containers of similar depth. In this case, the outer cardboard container probably insulated the fillets from the surrounding ice, causing the fillets to cool more slowly.

Chilling Times and Shelf Life

Similarly, fillets chilled in a poly bag inside a wax-coated cardboard container lost over day of shelf life during chilling.

Fillets chilled in 2 inch deep rectangular plastic containers, however, lost only about 3 hours of shelf life during the chilling process.

Recommendations

Waxed cardboard have the disadvantage of insulating the fish fillets from the surrounding ice and causing the fillets to cool slowly. These containers could be acceptable if the fillets were prechilled to 35°F (1.7°C) before packaging.

Poly bags become almost round when filled and iced. Ten and 20 lb. poly bags of fish fillets are thicker than most plastic and metal containers. This additional thickness results in slow chilling of the fillets. Poly bags could be acceptable if the fillets were prechilled to 35°F (1.7°C) before bagging.

Plastic and metal containers are available in a range of lengths, widths, and depths. Because cooling rates are proportional to container depth, containers for fish fillets should be relatively shallow. A maximum depth of 3 inches is recommended for containers used for fresh fish fillets. These shallow containers allow the fish fillets to cool quickly.

Some plastic container dealers promote the use of a "bubble wrap" pad in the bottom of the containers to separate the fillets from any liquid in the container. These pads insulate the fish fillets and should be used only when the fillets are prechilled before packaging.