Anisakis is the fish parasite that most concerns Spanish consumers, and rightly so: Spain is the second country in the world with the most cases of anisakiasis (after Japan). But when we talk about salted and desalted cod, the reality is very different from what most people believe. The salting process at concentrations above 20% for weeks effectively destroys anisakis larvae. Here, with scientific data, I explain what anisakis is, when it is truly dangerous, why salted cod is safe, and how to prevent any risk with any fish.
Table of Contents
- What is Anisakis: Biology of the Parasite
- How Anisakis Reaches Fish
- Symptoms of Anisakiasis in Humans
- Salted Cod: Why it's Safe
- Safety Table: Methods to Eliminate Anisakis
- The 7 Most Common Myths About Anisakis
- Spanish Regulations: What the Law Says
- Which Fish are Most at Risk and Which are Least
- Prevention in the Kitchen: Practical Guide
- Frequently Asked Questions
- Conclusions
What is Anisakis: Biology of the Parasite
Anisakis (Anisakis simplex) is a parasitic nematode, meaning a roundworm that lives in the digestive tract of marine mammals (whales, dolphins, seals). Its larvae, measuring between 1 and 3 cm long and whitish-translucent in color, are found in marine fish as part of their natural life cycle.
The life cycle of anisakis works like this:
- Eggs are expelled into the sea with the feces of infected marine mammals.
- Eggs hatch, and larvae are ingested by small crustaceans (krill).
- Fish that eat these crustaceans become infected. The larvae migrate from the fish's stomach to its musculature (the flesh we eat).
- When a marine mammal eats that fish, the larvae mature into adult worms in its stomach, completing the cycle.
Humans are an accidental host: we are not part of the natural anisakis cycle. When we eat raw or undercooked fish with live larvae, these attempt to penetrate the lining of our stomach or intestine, causing an inflammatory reaction (anisakiasis) or allergic reaction. The larva cannot complete its cycle in humans and eventually dies, but the damage it causes can be significant.
How Anisakis Reaches Fish
Anisakis is present in practically all oceans of the world. It is not a problem of contamination or lack of hygiene: it is natural marine biology. Any wild marine fish that feeds on other fish or crustaceans can carry anisakis.
Factors influencing the presence of anisakis:
- Fishing area: The North Atlantic (where cod is fished) has a high prevalence of anisakis. The Mediterranean also, especially on the western coast.
- Fish species: Predatory fish (hake, cod, bonito, mackerel) have more anisakis than herbivores.
- Size and age: Larger and older fish are more likely to be parasitized (they have eaten more prey throughout their lives).
- Part of the fish: Larvae concentrate first in the viscera (stomach, intestines) and then migrate to the musculature. Rapid evisceration after capture significantly reduces the number of larvae in the flesh.
- Wild-caught vs. farmed fish: Farmed fish fed with feed (not wild fish) have a practically zero risk of anisakis.
Symptoms of Anisakiasis in Humans
Anisakiasis manifests in two main forms:
Gastric Anisakiasis (the most common)
Occurs when the larva attempts to penetrate the stomach lining. Symptoms appear 1-12 hours after eating infected fish:
- Intense abdominal pain (colic-like)
- Nausea and vomiting
- Sometimes, diarrhea
- In severe cases, the larva can perforate the gastric wall (rare but serious)
Allergic Reaction to Anisakis
Some people develop an allergy to anisakis proteins, not to the live parasite. This is important because it means that even with dead larvae (due to cooking or freezing), they can have an allergic reaction. Symptoms include:
- Urticaria (hives on the skin)
- Angioedema (swelling of lips, eyelids)
- In severe cases, anaphylaxis (systemic allergic reaction)
Anisakis allergy is relatively common in Spain: it is estimated that up to 5-8% of the Spanish population has antibodies against anisakis (indicating previous exposure), although not all develop symptoms.
Salted Cod: Why it's Safe
Here comes the part that most interests our customers, and the answer is clear: properly processed salted cod is safe from anisakis.
The reason is scientific. Anisakis larvae need an environment with certain humidity and a low salt concentration to survive. The cod salting process creates exactly the opposite conditions:
- Salt concentration: Cod is cured in salt at concentrations of 20-25% (by weight). Scientific studies (EFSA, 2010) have shown that salt concentrations above 9% maintained for 6 weeks kill 100% of anisakis larvae. Commercial salted cod remains in salt for months.
- Dehydration: Salt extracts moisture from the fish, reducing water activity (Aw) below 0.75. Anisakis larvae need an Aw above 0.85 to survive.
- Time: Cod remains in salt for weeks or months, well beyond the time needed to eliminate any larvae.
A study published in the Journal of Food Protection (2005) confirmed that Anisakis simplex larvae in salted cod with more than 20% NaCl were completely killed in less than 21 days. Commercial cod is kept in salt much longer than that.
What about desalted cod? Desalted cod starts from salted cod (where the larvae are already dead). The desalting process in water does not "resurrect" dead larvae. Therefore, desalted cod is equally safe.
All our salted cod and desalted cod undergo industrial salting processes that far exceed food safety standards. At Bacalalo, we work only with certified suppliers who guarantee product traceability and safety from the boat to your kitchen.
Safety Table: Methods to Eliminate Anisakis
This table summarizes scientifically validated methods for eliminating anisakis larvae:
Methods that DO eliminate anisakis
- Freezing at -20 °C for 5 days: kills 100% of larvae. This is the legal standard in the EU for fish to be consumed raw or lightly cooked.
- Freezing at -35 °C for 15 hours: rapid industrial method.
- Cooking at +60 °C in the center of the product for 1 minute: sufficient to kill larvae. Most cooking methods (boiling, baking, frying) far exceed this temperature.
- Cooking at +70 °C in the center for 10 seconds: the conservative standard.
- Salting at 20%+ for 21+ days: traditional method for salted cod.
- Marinating in vinegar (6% acetic acid) for 35 days: not practical but effective.
Methods that DO NOT eliminate anisakis
- Short marinating in vinegar or lemon: anchovies in vinegar (marinated for hours or days) DO NOT kill larvae if the fish has not been previously frozen. This is a real problem in Spain.
- Cold smoking: cold-smoked salmon (below 60 °C) does not eliminate larvae. It must be frozen beforehand.
- Microwave: irregular heating, can leave cold spots where larvae survive.
- Washing fish: water does not kill larvae that are already inside the flesh.
- Acidic sauces (ceviche): the acid from lemon or lime does not kill anisakis larvae. Ceviche requires previously frozen fish.
The 7 Most Common Myths About Anisakis
Myth 1: "Salted cod has anisakis"
False. The cod salting process (salt at 20%+ for weeks/months) eliminates anisakis larvae. Salted and desalted cod is safe for consumption without the need for additional prior freezing.
Myth 2: "If I cook fish well, I don't need to freeze it"
True, but with caveats. If you cook fish above 60 °C in the center, the larvae die. The problem is that many preparations (sushi, sashimi, ceviche, carpaccio, anchovies in vinegar, tataki) do not reach that temperature. For these preparations, prior freezing is mandatory.
Myth 3: "Vinegar kills anisakis"
False in home preparations. Anchovies in vinegar marinated for hours or days do not eliminate larvae. More than 35 days in concentrated vinegar would be needed. That's why Spanish law requires freezing fish before making anchovies in vinegar.
Myth 4: "Farmed fish has anisakis"
Generally false. Farmed fish fed with processed feed (not wild fish) have a practically zero risk of anisakis. Farmed salmon, sea bream, sea bass, trout, and turbot are very safe options.
Myth 5: "If I don't see worms in the fish, it's clean"
False. Anisakis larvae are small (1-3 cm) and can be coiled inside the flesh, invisible to the naked eye. Also, they can be translucent, blending in with the fish fibers. Visual inspection reduces the risk but does not eliminate it.
Myth 6: "Anisakis is only found in cheap fish"
False. The presence of anisakis does not depend on the price but on the species, habitat, and fishing method. Premium wild salmon can have more anisakis than a sardine. An almadraba tuna can be parasitized like any other wild fish.
Myth 7: "Freezing for 24 hours at -20 °C is enough"
Insufficient according to regulations. European regulation (EC Regulation 853/2004) requires freezing at -20 °C for a minimum of 5 days (120 hours), or at -35 °C for 15 hours. Domestic freezers that do not reach a real -20 °C need more time (at least 7 days). Check that your freezer has 4 stars (****), which indicates it reaches at least -18 °C.
Spanish Regulations: What the Law Says
Spain has specific regulations on anisakis, among the strictest in Europe, motivated by the high incidence of anisakiasis in the country:
- Royal Decree 1420/2006: obliges catering establishments to pre-freeze fish that will be served raw or lightly cooked (sushi, ceviche, anchovies in vinegar, carpaccios, etc.).
- Mandatory freezing: -20 °C for at least 24 hours (the Spanish standard, more lenient than the European 5-day standard) or -35 °C for 15 hours.
- Consumer information: restaurants must inform customers about the risks of anisakis and the preventive measures taken. Many do so with a mandatory sign.
- Exceptions: fish from aquaculture fed with feed, bivalve mollusks (mussels, clams, oysters), freshwater fish, and salted products such as salted cod (provided the salt concentration is sufficient) do not require pre-freezing.
Which Fish are Most at Risk and Which are Least
Higher risk of anisakis
- Hake: one of the fish with the highest prevalence (up to 80-90% of specimens parasitized in some areas of the Cantabrian Sea)
- Fresh cod: high prevalence as a cold-water predator
- Mackerel and horse mackerel: highly parasitized, especially in summer
- Bonito and tuna: large predators with high probability
- Anchovy/sardine: high risk when consumed in vinegar without prior freezing
- Wild salmon: high prevalence
Lower risk or no risk
- Salted/desalted cod: salting process eliminates larvae
- Salted anchovies: cured in salt for months (similar process to cod)
- Bivalve mollusks (mussels, clams, oysters): not hosts for anisakis
- Cephalopods (octopus, squid, cuttlefish): very low risk
- Farmed fish with feed: salmon, sea bream, sea bass, trout, turbot
- Freshwater fish: no anisakis in freshwater
- Canned tuna: sterilized at high temperature
Prevention in the Kitchen: Practical Guide
These are the golden rules to avoid anisakis at home:
- Buy gutted fish: larvae migrate from the viscera to the flesh after the fish's death. Rapid evisceration after capture significantly reduces the number of larvae in the edible part.
- Visually inspect: examine the fish flesh for larvae (whitish threads 1-3 cm long). It is especially easy to detect them in dark-fleshed fish (mackerel, bonito). In white fish (hake), they are harder to see.
- Freeze if you are going to eat raw or lightly cooked: sushi, sashimi, ceviche, carpaccio, anchovies in vinegar, tataki, cold smoking. Minimum 5 days at -20 °C in a 4-star freezer.
- Cook to a sufficient temperature: for cooked preparations, ensure the center of the fish reaches 60 °C for at least 1 minute. A kitchen thermometer is the most reliable tool.
- Salted cod is exempt: if you buy salted cod from reliable suppliers, you don't need to freeze it or worry about anisakis.
- Salted anchovies are exempt: the curing process in salt for months (like that of our Cantabrian anchovies) eliminates any larvae.
At Bacalalo, food safety is the foundation of everything we do. Our salted cod, desalted cod, and salted anchovies undergo curing processes that guarantee the elimination of anisakis. We have been in the Mercat del Ninot in Barcelona for more than 30 years offering safe and verifiable quality products.
Frequently Asked Questions
If I am allergic to anisakis, can I eat salted cod?
This is a delicate question. Salted cod does not have live larvae, but it may contain residual proteins from dead anisakis, which are what cause the allergic reaction. In people with severe anisakis allergy (previous anaphylaxis), some allergists recommend avoiding all marine fish, even salted. If you have a diagnosed allergy, consult your allergist before consuming any marine fish.
Is anisakis visible to the naked eye?
Larvae measure 1-3 cm and are visible, but not always easy to detect. In dark-fleshed fish (mackerel, bonito), they are more easily seen as white threads. In white fish (hake, fresh cod), they can be confused with the fibers of the flesh. Visual inspection reduces the risk but does not eliminate it 100%: some larvae may be coiled within the musculature, invisible from the outside.
Are anchovies in vinegar safe?
Only if the fish has been previously frozen for a minimum of 5 days at -20 °C (or 24 hours according to Spanish regulations). Vinegar alone does not kill anisakis larvae. In Spanish bars and restaurants, the law requires pre-freezing anchovies. At home, buy already frozen anchovies or freeze them yourself before marinating.
If I cook cod pil pil, is there a risk of anisakis?
Double safety: 1) if you use salted/desalted cod, the larvae are already dead due to salting, and 2) the cooking of pil pil reaches sufficient temperatures to kill any larvae. Cod pil pil made with salted/desalted cod is completely safe. If you were to use fresh cod (unusual for pil pil), cooking at 65-80 °C would also be sufficient.
My freezer reaches -18 °C, is that enough?
A 4-star (****) freezer reaches at least -18 °C. To kill anisakis, European regulations require -20 °C for 5 days. At -18 °C, it is recommended to increase the time to 7 days for a safety margin. If your freezer only has 3 stars (***), it may not be enough: these models reach -18 °C under optimal conditions but can fluctuate. When in doubt, freeze for longer.
Do canned fish have anisakis?
No. Canned goods (canned tuna, sardines, mackerel) are sterilized at temperatures above 100 °C during the canning process, which destroys any living organisms, including anisakis larvae. Canned goods are 100% safe regarding anisakis. The same applies to anchovy semi-preserves (cured in salt for months before packaging).
Can you eat sushi in Spain without the risk of anisakis?
Yes, as long as the restaurant complies with regulations (prior freezing of fish). Japanese restaurants in Spain are legally obliged to freeze fish served raw. Good restaurants do this; those that don't are breaking the law. If you have doubts, ask the restaurant if they pre-freeze their fish. You have the right to know.
Conclusions
Anisakis is a real risk with fresh marine fish consumed raw or lightly cooked, but it is not the apocalypse that some media portray. The science is clear: proper freezing (-20 °C for 5 days), cooking above 60 °C, and prolonged salting effectively eliminate larvae.
For lovers of salted and desalted cod, the conclusion is reassuring: the salting process to which cod is subjected (salt concentrations above 20% for weeks or months) is one of the most effective methods for eliminating anisakis. When you buy salted cod from a trusted supplier, you are buying a safe product. You don't need to freeze it, you don't need to worry. You just need to cook it and enjoy it.
