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Fermentation Atlas

Fish and seafood from Norway

Rakfiskrakfisk

Gutted trout or char are dry-salted, layered in tubs and kept under their own mild brine in the cold for months. Fish enzymes break down the flesh and lactic bacteria sour the brine a little, which gives the soft texture and strong smell. Rakfisk is eaten raw. Made in 4 steps over 3.3 months – 12 months. The longest step, ripen cold under brine, takes 3–12 months (Bjerke G.A 2019) and runs at up to 10 °C (Mattilsynet 2006). Salt is 4–6 % (Mattilsynet 2006). Latilactobacillus sakei and Leuconostoc do most of the fermenting.

Key numbers
Main step3–12 monthsReported[bjerke2019]Ripen cold under brine
Temperatureup to 10 °CSet[valdres-pgi]Ripen cold under brine
Salt4–6 %Set[valdres-pgi]Dry-salt, layer in tubs and top up with brine
AciditypH 6.4–7.2Measured[bjerke2019]Ripen cold under brine
Fully documentedFish and seafood3.3 months – 12 monthsMore fish and seafoodMore from Norway

Recipe

No fixed amounts recordedThe Valdres PGI rule fixes the brine strength (4–6 % salt) but not the fish-to-salt amounts; each producer follows a house recipe.
Rainbow trout or brown trout, gutted and washed · Arctic char is also used outside the Valdres PGI[valdres-pgi][bjerke2019]
Salt · Dry salt first, then brine topped up to 4–6 % salt[valdres-pgi]
Sugar and spices (optional) · Each producer's own tradition[valdres-pgi][bjerke2019]
Starter: spontaneous (a few producers add a lactic starter culture)

Total time across the recorded steps: 3.3 months – 12 months

Start
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What changes: The trout are gutted and cleaned of blood, then the wash water drains away

Step 1 of 4
Gut, bleed and wash the fish
Time
up to 2 h
Set
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactic acid bacteria
Latilactobacillus sakei
Leuconostoc codominant

Farmed fish are starved to an empty gut first. Entrails are sucked out and the wash water drained off. Output: gutted fish with blood, kidney and gills removed.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

What makes this one different

Rakfisk uses freshwater trout or char in a mild brine of about 4–6 % salt kept cold for months. Fish enzymes do much of the work, with a light lactic ferment on top, and the fish is eaten raw.

Related ferments

Variants

  • Rakfisk fra Valdres (PGI)Rainbow trout hatched and farmed in Valdres, or trout from Valdres waters; brine 4–6 %.
  • Char rakfiskMade from Arctic char, wild or farmed.

Safety

Rakfisk is eaten raw, so nothing kills pathogens after ripening. The Valdres rule caps ripening at 10 °C with 5–6 % salt in the water phase and 9 °C with 4–5 %, and the finished fish must be kept chilled. In a challenge study the acids formed were too weak to stop Listeria; 4 °C held it almost still, while 7 °C let it grow about 100-fold in two weeks. Norway's Directorate of Health advises pregnant women and people with weak immunity not to eat it. Botulism outbreaks came from home batches with too little salt or too warm storage.

Hazards the sources name: Listeria monocytogenes (detected from time to time; linked to listeriosis outbreaks); Clostridium botulinum (historic outbreaks from home batches with too little salt or too warm storage).

History and sources

Every number is labelled with how it is known. How this atlas is made

Rakfisk is named in documents from Jämtland, then Norwegian, in 1348. Valdres sold it at markets from at least 1600, and farmed rainbow trout has been used since 1965.

  1. [valdres-pgi] Mattilsynet 2006, Forskrift om beskyttelse av produktbetegnelsen Rakfisk fra Valdres som beskyttet geografisk betegnelse, FOR-2006-10-27-1196 (Lovdata; copy in FAOLEX)spec
  2. [bjerke2019] Bjerke G.A., Rudi K., Avershina E., Moen B., Blom H., Axelsson L. 2019, Exploring the brine microbiota of a traditional Norwegian fermented fish product (rakfisk) from six different producers during two consecutive seasonal productions, Foods 8(2):72paper
  3. [axelsson2020] Axelsson L., Bjerke G.A., McLeod A., Berget I., Holck A.L. 2020, Growth behavior of Listeria monocytogenes in a traditional Norwegian fermented fish product (rakfisk), and its inhibition through bacteriophage addition, Foods 9(2):119paper
  4. [wp] Wikipedia, Rakfisk (serving only)wiki