Anisakis: when fish has to be frozen, when cooking is enough - and why vinegar and lemon don't help

Anchovies in vinegar, tataki, tartare, ceviche. If you make them at home from fresh fish, vinegar, salt and lemon won't protect you from anisakis. This parasite lives in fish and in cephalopods - squid, octopus and cuttlefish - and only two things kill its larvae: enough heat or enough cold.

Live larvae can cause a digestive illness known as anisakiasis, as well as allergic reactions, sometimes severe ones. The risk lies mainly in raw fish and in preparation methods that don't destroy the parasite.

Heat: 60 degrees at the centre

Spain's food safety agency (AESAN) requires the whole piece, including the centre, to reach at least 60 °C for one minute. That applies to roasting, frying, grilling and boiling. A nicely seared crust doesn't mean the inside is hot enough. Tuna or bonito seared only on the outside, and tataki or salmon with a raw centre, are considered insufficiently cooked - and need to be frozen first, just like raw fish.

Cold: four days, but count five

For home conditions, AESAN specifies at least four days at -15 °C or lower. Because fish takes time to freeze all the way through, it's safer to count at least five days from the moment you put it in the freezer. And check your appliance: freezers with three or four stars reach around -18 °C, those with one or two don't. If you're not sure, buy fish that's already frozen. Write down the date, thaw it in the fridge and don't refreeze it.

Vinegar, salt and lemon don't kill the larvae. Homemade pickled anchovies, tartare, carpaccio, ceviche and home-dried or smoked fish all require fish that has been frozen first. Shop-bought ready-made versions are frozen by the producer. Because of anisakis there's no need to freeze oysters, clams, mussels, freshwater fish or semi-preserved anchovies - but that exemption applies to this parasite only.

Ask the fishmonger to clean and gut the fish, or do it as soon as you get home: after the fish dies, the larvae can move from the gut into the flesh. Don't rely on your eyes, because the larvae aren't always visible. Restaurants and bars serving raw or undercooked fish are required to freeze it in advance, with a stricter treatment than a home freezer can achieve.

Whether the fish comes from a market in Skopje or a stall on the seafront, there is one rule: raw means previously frozen. And one more important thing - removing the larvae doesn't rule out reactions in people who are already sensitised. Anyone with an anisakis allergy should stick to their specialist's advice.