FOOD SCIENCE AND TECHNOLOGY NOTES

CANNING SEAFOOD

By Carolyn A. Raab

Extension Food and Nutrition Specialist

Oregon State University

(In consultation with Extension food specialists at
Washington State University and the University of Idaho)

Coastal waters and streams in the Pacific Northwest provide a variety of seafoods, including salmon and many other fish, clams, oysters, shrimp, and crab. These delicacies can be enjoyed throughout the year if they are preserved when supplies are abundant. Canning is the method of preservation commonly used. Seafoods are high in quality and safe to eat when canned correctly.

CANNING FISH AND SHELLFISH

The quality of fresh seafood deteriorates rapidly. To prevent spoilage, fish and shellfish must be kept cool, on ice or in a refrigerator. Can seafood as soon as possible after catching or purchasing.

Preparation

• Prepare fish as directed.
• Soak or cook shellfish in water containing salt, acid, or both, as directed. Either lemon juice or white vinegar can be used to prevent discoloration of light-colored shellfish. Citric acid, which is sometimes recommended, can be purchased at pharmacies.

Packing

• Pack fish and shellfish into pint or half-pint jars as directed. Safe processing times have not been determined for quart jars.
• Wipe the jar rims clean before sealing with the lid. (Fat or food particles will prevent sealing.)

Processing

• Process seafoods in a pressure canner as directed. The high temperatures reached under pressure are necessary to destroy Clostridium botulinum, bacteria that cause botulism food poisoning.
• Use a pressure canner that is in good condition. Replace the gasket if necessary. Dial pressure gauges should be checked for accuracy at least once a year. (Your county Extension office can tell you where to have your gauge tested.)
• Re-read and follow directions for the canner. If you no longer have an instruction manual, write the manufacturer.
• Exhaust steam from the canner before closing the petcock or putting on the weighted gauge. Canner directions will specify the venting time required (usually 10 minutes).
• Process foods at the correct pressure. At sea level, process foods at 10 pounds pressure. Increase the pressure 1/2 pound for each 1,000 feet altitude above sea level. (At 2,000 feet process at 11 pounds pressure, at 4,000 feet process at 12 pounds pressure.). If a canner has a weighted gauge, process at 10 pounds at altitudes below 2,000 feet, 15 pounds above 2,000 feet.

To make sure that the pressure stays constant during processing, check the gauge periodically. Weighted gauges should jiggle the number of times per minute specified in canner directions.

• Process foods for the correct length of time. When the required pressure is reached, write down the time and continue processing for the specified period. Remove canner from the heat at the end of the processing time.

Processing times listed in this publication are based on 10 pounds pressure. The same times should be used at higher pressures. When using a pressure saucepan, add 20 minutes to the processing time to compensate for faster heating and cooling off periods.

Recommended Processing Times at
10 pounds Pressure

Seafood	One-half Pint jar	Pint jar>
	Minutes	Minutes
Raw fish	100	100
Smoked fish	100	100
Whole clams	60	70
Minced clams	60	70
Crab	70	80
Oysters	75	75
Shrimps	45	45

Salmon, trout, steelhead, and other fish (except tuna)

1. When fish are caught, remove viscera at once. Chill the cleaned fish until ready to can.
2. Before canning, remove head, tail, fins, and scales. Wash fish carefully, removing all blood.
3. Split fish lengthwise. Cut into lengths suitable for jars.
4. Soak pieces in salt brine (3/4 to 1 cup salt per gallon of water) for 1 hour. (In place of the soaking, 1 teaspoon of salt can be added per pint before sealing.)
5. Drain and pack fish tightly into jars, leaving 1 inch of headspace.
6. Adjust lids and process half-pints and pints for 100 minutes at 10 pounds pressure.

Smoked fish

1. Cut smoked fish into lengths suitable for jars.
2. Pack into jars, leaving 1 inch head space.
3. Adjust lids and process half-pints and pints for 100 minutes at 10 pounds pressure.

Tuna, precooked*

1. Remove viscera and wash fish well in cold water. Allow blood to drain from stomach cavity.
2. Place tuna (cut in half crosswise if necessary) belly-down on a rack or metal tray placed in the bottom of a large baking pan.
3. Precook fish by baking at 225 to 250°F (110 to 120°C) for 2 1/2 to 4 hours (depending on size) or at 350°F (180°C) for about 1 hour. (The fish may also be cooked in a steamer for 2 to 4 hours.) When using a thermometer, cook to 165 to 175°F (70 to 80°C).
4. Refrigerate fish overnight to firm the meat.
5. Peel off the skin with a knife, lightly scraping surface to remove blood vessels and any other discolored flesh.
6. Separate the fish into quarters by cutting meat away from bones. Pull off and cut out all bones and fin bases. Scrape and cut out all dark flesh.
7. Cut quarters crosswise with a sharp knife into lengths suitable for jars.
8. Pack pieces into jars, pressing down gently to make a solid pack. Leave 1-inch headspace. (Covering the rim edge with foil will prevent a buildup of fat.)
9. Add 1/2 teaspoon salt and 1 to 3 tablespoons oil (cottonseed, soy or other vegetable oil) per half-pint; 1 teaspoon salt and 2 to 6 tablespoons oil per pint. If you prefer, water may be used instead of oil.
10. Adjust lids and process half-pints and pints for 100 minutes at 10 pounds pressure.

*Tuna can be packed raw by omitting steps 2, 3, and 4. However, precooking removes most of the body oils, which tend to be strong-flavored.

Clams, whole

1. Keep live clams cool until ready to can. Wash shells and steam to open. Remove meat, saving juice.
2. Wash meat in a weak salt brine (1 to 3 tablespoons salt per gallon of water).
3. Blanch meat for 1 to 2 minutes in boiling acidic solution of 2 tablespoons vinegar or lemon juice per gallon of water. (1/2 teaspoon of citric acid dissolved in 1 gallon of water may also be used.)
4. Drain meat and pack into jars, leaving 1 inch head space. Pour hot juice over clams. Add boiling water, if needed, leaving 1 inch head space.
5. Adjust lids and process half-pints for 60 minutes, pints of 70 minutes at 10 pounds pressure.

Clams, minced

1. Follow steps 1 through 3 for whole clams.
2. Drain blanched meat and grind, using a meat grinder.
3. Pack 4 ounces (about 3/4 cup into half-pint jars and 7 ounces (about 11/2 cups) into pint jars, leaving 1 inch head space. Cover with hot clam juice. Add boiling water, if necessary, leaving 1 inch head space.
4. Adjust lids, and process half-pints for 60 minutes, pints for 70 minutes at 10 pounds pressure.

Crab

1. Keep live crabs cool until ready to use. Remove back by forcing the edge of the shell against a solid object and breaking crab in two by folding it like a book. Shake out viscera and thoroughly clean the crab under running water.
2. Cook cleaned crab in boiling acidic brine (2 tablespoons to 1 cup salt, as desired, and 1/4 cup white vinegar or lemon juice per gallon of water) for 20 minutes.
3. Cool crab in cold water and then drain. Remove meat from body and claws.
4. Rinse crab in cool acidic brine (2 tablespoons to 1 cup salt and 1 to 2 cups white vinegar or lemon juice per gallon of water). Squeeze the meat to remove excess moisture.
5. Pack into half-pint or pint jars, leaving 1 inch of headspace. Add 1 tablespoon of white vinegar lemon juice per half pint, 2 tablespoons per pint. (1/2 teaspoon of citric acid per half-pint may also be used.) Cover with boiling water, leaving 1-inch headspace.
6. Adjust lids and process half-pints of 70 minutes, pints for 80 minutes at 10 pounds pressure.

Oysters

1. Keep live oysters cool until ready to can. Wash shells and steam to open. Remove meat.
2. Wash meat in weak salt brine (1/2 cup salt per gallon of water).
3. Drain meat and pack into jars, leaving 1 inch head space. Cover with a weak salt brine (about 1 tablespoon of salt per quart of water).
4. Adjust lids and process pints and half-pints for 75 minutes at 10 pounds pressure.

Shrimp

1. Remove heads as son as shrimp are caught. Chill until ready to can
2. Wash and drain shrimp.
3. Cook shrimp 8 to 10 minutes in boiling acidic brine (1/4 to 1 cup salt and 1 cup vinegar per gallon of water). Rinse in cold water and drain.
4. Peel shrimp.
5. Pack into jars, leaving 1-inch head space. Cover with boiling salt brine (1 to 3 tablespoons salt per gallon of water).
6. Adjust lids and process half-pints and pints for 45 minutes at 10 pounds pressure.

USING HOME-CANNED SEAFOOD

Test seals on jars the day after canning. If jars have not sealed, use a new lid and reprocess in the canner for the entire length of time. Also, the product could be refrigerated for use within the next few days, or frozen.

Examine home-canned seafood for spoilage before serving it. Bulging jar lids, spurting liquid, an "off" odor or mold indicate that the food is not safe to eat. Discard spoiled food out of the reach of pets. Do not even taste questionable food.

It is possible for underprocessed home-canned seafood to contain the botulinum toxin without showing signs of spoilage. For an extra margin of safety, home-canned seafood should be heated after opening the jar. Boiling the seafood for 10 to 20 minutes on the stove will destroy the toxin. To prevent undesirable texture changes, heating in the oven is a more satisfactory method for home-canned fish.

The following oven method for heating home-canned fish is suggested.

• Open the jar of fish and examine for spoilage. If spoilage is evident, discard the fish (without tasting) out of the reach of pets. Wash the lid before discarding or reusing it one the jar.
• Insert a meat thermometer upright into the center of the jar. The tip should be at the appropriate center of the fish.
• Cover the jar loosely with foil and place in an oven preheated to 350F (180C).
• Remove the jar from the oven when the thermometer registers 185F (85C). About 30 to 35 minutes will be needed.
• Let the jar stand at room temperature for about 30 minutes. This will allow the temperature to become uniform throughout.
• Serve the fish hot or refrigerate for later use.

Approximate Metric Equivalents for Metric Conversion
Pressure 1 Pound per square inch	6.9 kilopascals
Length 1 inch 1 foot	2.5 centimeters 0.3 meters
Mass 1 ounce	28.4 grams
Volume 1 teaspoon 1 tablespoon 1 cup 1 quart 1 gallon	5 millimliters 15 mililiters 250 milliliters 1 liter 4 liters

OTHER PUBLICATIONS

Other seafood-related Food Science and Technology Notes may be obtained (free) from the Department of Food Science and Technology, VPI&SU, or from local Extension Offices:

Smoking Fish at Home ­ A Step by Step Guide, VPI-SG-300-2, by Cherrie L. Kassem.

Salting Fish, VPI-SG-300-3, by Sharon R. Turner.

Squid: An Underutilized Species, VPI-SG-300-4, by Sharon Turner and Chieko E. Hebard.

Tuna, VPI-SG-300-5, by Jim Daniels and Chieko E. Hebard.

Government Guidelines on Nutrition ­ A Review of the Dietary Goals, VPI-FST-900-3, by Cherrie L. Kassem.

History of Colonial Foods in Virginia, VPI-FST-900-4, by William R. Hess, Jr.

Foods and Facts: A Consumer's Guide to the Code of Federal Regulations, VPI-FST-1800-1, by John W. Long.