How to Blast Freeze Herring

Blast frozen herring can be safely thawed in the refrigerator overnight.

Herring can be blast frozen solid in its whole form or fillets in less than two hours. Fish that are left with their entrails intact must be kept at cold temperatures to avoid bacterial contamination of the flesh. Blast chilling speeds the freezing process to limit the amount of time the fish is in the temperature danger zone. Cold air is circulated inside the blast chiller to draw away the internal heat and freeze the fish to its core.

Instructions

1. Rinse the whole herring fish or herring fillets in cold water. Lift and separate the fins, mouth and gills under the running water to fully rinse the fish.

2. Pack the herring into the perforated blast freezing tray loosely. Slide the tray into the blast freezer. Turn all the fish so that the thickest portion, usually the head, is pointed toward the cold air outlet fans.

3. Close and secure the blast chiller doors. Set the controls on the freezing unit to -31 degrees Fahrenheit or -35 degrees Celsius. Turn on the internal fan to medium speed, approximately 10 feet per second or 3 meters per second.

4. Remove the herring after 90 minutes in the cold circulating air. Dip each frozen herring or fillet into cold water and lower them into a zip-top freezer bag. The water quickly forms an ice crystal layer on the outside of the herring that protects the flavor and consistency of the fish flesh.

5. Force all the air out of the zip-top freezer bag. Seal the bag and place it into a standard freezer that maintains temperatures below 0 degrees Fahrenheit or -18 degrees Celsius. Use the frozen fish within six months to avoid deterioration.

Tips & Warnings

• Write an expiration date six months in the future on the outside of bags of blast frozen herring.

• Thaw the herring slowly in a refrigerator where temperatures stay below 38 degrees Fahrenheit or 3 degrees Celsius. Place a shallow container below the herring to catch any moisture it releases.

References

• Food and Agriculture Organization of the United Nations: The Herring
• Food and Agriculture Organization of the United Nations: Installing an Air Blast Freezer