Preserving fish safely
Table of contents
Why and how does freshly caught fish spoil?
Freshly caught fish spoil easily and need to be properly preserved. The four most popular methods of fish preservation are freezing, canning, smoking, and pickling.
Top quality fresh fish are essential for fish preservation. Of all flesh foods, fish is the most susceptible to tissue decomposition, development of rancidity, and microbial spoilage. Keep freshly caught fish alive as long as possible. A metal link bag will permit fish to remain alive longer in the water than a stringer. Spoilage and slime-producing bacteria are present on every fish and multiply rapidly on a dead fish held in warm surface water.
Fish begin to deteriorate as soon as they leave the water. To delay spoilage, clean the fish as soon as possible. Thorough cleaning of the body cavity and chilling of the fish will prevent spoilage. Fish spoilage occurs rapidly at summer temperatures; spoilage is slowed down as freezing temperatures are approached.
This is the simplest, most convenient, and most highly recommended method of fish preservation. A good quality frozen product requires the following:
- Careful handling of the fish after catching.
- Wrapping material or method that is airtight and prevents freezer burn and the development of undesirable flavors.
- A freezer storage temperature of 0° F or lower.
To freeze fish
Remove the guts and thoroughly clean the fish soon after catching.
Prepare the fish as you would for table use. Cut large fish into steaks or fillets. Freeze small fish whole.
Wrap the fish in heavy-duty freezer bags. Separate layers of fish with two thicknesses of packaging material for easier thawing. Store at 0° F or lower. When ready to use, thaw in the refrigerator.
Cut large fish into steaks or fillets.
Small fish, such as sunfish and panfish, or small servings of fish can be frozen in ice. Place the fish in a shallow pan or water-tight container. Cover with ice water and place in the freezer until frozen (8-12 hours). Remove block from container, wrap, and store in freezer.
The storage life of good quality frozen fish held at 0° F or lower follows:
(Source: Minnesota Sea Grant, 2012)
- Northern pike, trout, whitefish, smelt, lake herring, carp – four to six months
- Chinook salmon, coho salmon, white bass – five to eight months
- Walleye, bass, crappie, sunfish, yellow perch, blue gill – eight to twelve months
Fish is a low acid food and can be processed safely only at temperatures reached in a pressure canner. Failure to heat process fish at 240° F or higher may allow spores of the dangerous heat-resistant bacteria, Clostridium botulinum, to survive, germinate, and grow. The poison produced by botulinum bacteria causes botulism, a deadly food poisoning. The addition of small amounts of vinegar, or packing fish in tomato juice or tomato paste, does not remove the requirement for heat processing fish in a pressure canner.
Use standard heat-tempered canning jars. All processing times in this publication are for 1-pint jars. Wide-mouth pint jars will be easier to fill than narrower ones.
General USDA method for canning fish without sauce (including blue, mackerel, salmon, steelhead, trout, and other fatty fish except tuna)
Clean and gut fish within 2 hours after catching. Keep cleaned fish on ice until ready to can.
Note: Glass-like crystals of magnesium ammonium phosphate sometimes form in canned salmon. There is no way for the home canner to prevent these crystals from forming, but they usually dissolve when heated and are safe to eat.
Remove head, tail, fins and scales. Wash and remove all blood. Split fish lengthwise, if desired. Cut cleaned fish into 3½ inch lengths. Fill pint jars, skin side next to glass, leaving 1 inch headspace. Do not add liquids. Adjust lids and process.*
processing Procedures for Minnesota Altitudes
- Dial-gauge Pressure Canner
Pints—100 minutes 11 PSI
- Weighted-gauge Pressure Canner
Pints—100 minutes 15 PSI
Heat fish to boiling temperatures for 10 minutes before tasting or serving. Canning fish in quart jars see http://www.uaf.edu/ces/pubs/catalog/detail/index.xml?id=318
Pickling is an easy method of preserving fish. Pickled fish must be stored in the refrigerator at no higher than 40° F (refrigerator temperature), and for best flavor must be used within four to six weeks. Only a few species of fish are preserved commercially by pickling, but almost any type of fish may be pickled at home. Refrigerate the fish during all stages of the pickling process.
Ingredients for Pickled Fish
- Fish – Use only fresh, high quality fish.
- Water – Avoid hard water, as it causes off color and flavors.
- Vinegar – Use distilled, white vinegar with an acetic acid content of at least 5 percent (50 grains means the same thing). This percentage of acetic acid is needed to stop bacterial growth.
- Salt – Use high grade, pure canning or pickling salt. It does not contain calcium or magnesium compounds which may cause off color and flavors in pickled fish.
General method for precooked pickled fish
Soak fish in a weak brine (1 cup salt to 1 gallon of water) for one hour.
Drain the fish; pack in heavy glass, crock, enamel, or plastic container in strong brine (2-½ cups salt to 1 gallon of water) for 12 hours in refrigerator.
Rinse the fish in cold water.
Combine the following ingredients in a large pan or kettle. This makes enough for 10 pounds of fish.
- ¼ oz bay leaves
- 2 T allspice
- 2 T mustard seed
- 1 T whole cloves
- 1 T pepper, ground
- 1-2 T hot, ground dried pepper
- ½ lb onions, sliced
- 2 qt distilled vinegar
- 5 c water (avoid hard water of high mineral content)
Bring to a boil, add fish, and simmer for 10 minutes until fish is easily pierced with a fork.
Remove fish from liquid, place on a single layer on a flat pan. Refrigerate and cool quickly to prevent spoilage.
Pack cold fish in clean glass jars, adding a few whole spices, a bay leaf, freshly sliced onions, and a slice of lemon.
Strain the vinegar solution, bring to a boil, and pour into jars until fish is covered.
Seal the jar immediately with two-part sealing lid, following the manufacturer's instructions. Pickled fish must be stored in the refrigerator as stated in general directions.
Caution: the broad fish tapeworm
The broad fish tapeworm infection can be contracted by humans from eating raw or undercooked species of fish found in the Great Lakes area.
Those who wish to prepare raw pickled fish should first freeze the fish at 0° F for 48 hours.
The larvae of the broad fish tapeworm pass through smaller fish until they lodge as hatched small worms in the flesh of large carnivorous species of fish, like northern pike, walleye pike, sand pike, burbot, and yellow perch. This worm, if eaten by humans in its infective stage, can attach to the small intestine and grow to lengths of 10 to 30 feet.
The infective worms are destroyed readily either by cooking or freezing. Two recent outbreaks of this tapeworm in Minnesota were related to eating uncooked pickled pike. Those who wish to prepare raw pickled fish should first freeze the fish at 0° F for 48 hours.
Smoking has long been used as a means of temporarily preserving fish. The steps in the smoking process are necessary not only for safe preservation, but also to produce good flavor and aroma. Carp, suckers, buffalo catfish, salmon, trout, and chubs may be successfully smoked. A safe, high quality product can be produced using the following brining and smoking procedures.
Certain steps in the brining and smoking process require careful attention.
- Use correct amount of salt in the brine.
- Use enough brine for a given amount of fish.
- The temperature during brining must be no higher than 40° F.
- Use similar size and kinds of fish in the brine.
- There should be uniform heat treatment of all fish in the smoking chamber.
- Use freshly caught, dressed fish, whole or filleted. Wash fish thoroughly.
Steps for safe smoked fish
Use freshly caught, dressed fish, whole or filleted. Wash fish thoroughly.
- Fish for smoking must be brined.
- 1 ½ cups salt to 1 gallon water—12 hours in refrigerator.
- 4 cups salt to 1 gallon cold water—15 minutes.
- Remove from brine, rinse.
- Place short stem of meat thermometer in thickest portion of flesh of largest fish.
- Put fish in smoker when air temperature is 100° F (you need a second thermometer to measure this).
- During smoking, air temperature should rise to 225° F.
- Fish flesh should reach 180° F and be kept there for 30 minutes.
- Fish smoked must be stored in refrigerator. Use within one month.
- Canning smoked fish procedure see http://nchfp.uga.edu/how/can_05/smoked_fish.html
Peer reviewed in 2012 by Suzanne Driessen, Extension Educator, University of Minnesota