Sea Herring Processing
The larger fish may be used for export, as there is a foreign market for this species where it is used for human food. The smaller herring, which are canned sardines, must be held in the purse seine (sometimes for longer than 24hrs) until the stomach is free from feed. This is done to prevent enzyme reaction, which would reduce the quality of the fish. Fish from nets are loaded on the boat with a large vacuum pump and are salted. More salt is added at the processing plant after the fish beheaded and eviscerated. The small herring are then reheated, placed in small rectangular cans, and subjected to steam for 18-20 min. The liquid in the cans is drained and replaced with vegetable oil. Tomato sauce, or mustard sauce; and the cans are sealed, heat processed, and cooled. The product is shelf-stable.
The larger herring are also canned whole but in larger oval cans, usually in tomato sauce. Some large herring are cut transversely into bite size pieces and packed in small cans in tomato sauces. This product is also shelf-stable.
Some herring are pickled (salt, vinegar, sugar, and spices) and packed in glass jars. Sour cream, onions, or other flavoring ingredients may be added before sealing the jars. Other pickled products include rollmops (pickled herring strips wrapped around a piece of pickle or onion) and kippered herring (salted and lightly smoked). These products must be refrigerated. Some herring are highly salted and heavily smoked, and this product is shelf stable. Large quantities of scales from the skins of herrings are recovered and used for the manufacture of pearl essence.
Sea Herring Processing
