Serving raw fish carries an inherent risk that many food business operators underestimate: parasitic infection. Unlike bacterial hazards that dominate most food safety discussions, parasites in raw fish present a distinct biological threat that cannot be eliminated through marinades, citric acid, soy sauce, or wasabi — despite widespread misconceptions. In the UK, the law is clear: if you serve raw or lightly processed fish, you must demonstrate that parasites have been destroyed through controlled freezing. This article explains the science, the legal framework, and the practical steps every UK sushi, sashimi, or ceviche business must follow to remain compliant.
Why Freezing Is Required for Raw Fish
The two parasites of greatest concern in fish destined for raw consumption are Anisakis simplex (herring worm) and Diphyllobothrium (broad fish tapeworm). Anisakis is by far the most commonly encountered in UK and European waters. The larvae are found in the gut cavity and flesh of many wild-caught fish species, including cod, herring, mackerel, salmon, and sea bass.
When a person ingests live Anisakis larvae, the parasite can embed itself in the stomach or intestinal wall, causing intense abdominal pain, nausea, vomiting, and allergic reactions. In severe cases, surgical removal of the larvae is required. Cases of anisakiasis are rising across Europe, partly due to the growing popularity of sushi and sashimi.
Crucially, there are only two reliable methods for killing parasites in fish: cooking to a core temperature of 60°C or above, or freezing to specific time and temperature combinations. Since cooking defeats the purpose of raw fish dishes, freezing is the only viable control measure. Acidification (such as lemon juice in ceviche), smoking at low temperatures, salt-curing, and condiments such as wasabi and soy sauce do not kill Anisakis larvae. This is a persistent myth in the hospitality sector and one that Environmental Health Officers will immediately challenge.
The Legal Framework
The freezing requirement for raw fish is set out in Regulation (EC) No 853/2004, Annex III, Section VIII, Chapter III, Part D. This regulation has been retained in UK domestic law following Brexit and continues to apply in full. It states that fishery products intended to be consumed raw, or practically raw, must be frozen to destroy viable parasites.
The regulation specifies two acceptable freezing protocols:
- Option A: Freeze the product at a core temperature of -20°C or below for not less than 24 hours.
- Option B: Freeze the product at a core temperature of -35°C or below for not less than 15 hours.
It is essential to understand that these temperatures refer to the core temperature of the fish, not the air temperature of the freezer. A domestic freezer that displays -18°C on its dial will not achieve -20°C at the core of a thick piece of fish within any reasonable timeframe. Compliance requires commercial freezing equipment capable of reaching and maintaining these temperatures throughout the product. Our HACCP consultants can help you verify that your freezing process meets these requirements.
Which Fish Must Be Frozen?
As a general rule, all fish intended for raw or near-raw consumption must undergo the freezing treatment described above. This includes fish used in sushi, sashimi, tartare, carpaccio, ceviche, and cold-smoked preparations where the internal temperature does not exceed 60°C.
However, there are limited exemptions. Farmed Atlantic salmon (Salmo salar) can be exempt from the freezing requirement where the fish have been reared from smolts on a feed regime that does not include live parasites, and the food business operator has epidemiological data or supplier documentation confirming that the farming conditions do not pose a parasite risk. In practice, most reputable Scottish salmon farms can provide such certification. However, this exemption does not apply to wild-caught salmon, which must be frozen without exception.
Tuna species are generally considered low risk for Anisakis, but best practice — and the expectation of most Environmental Health Officers — is to freeze tuna as well unless you hold robust evidence to the contrary. When in doubt, freeze. The cost of freezing is negligible compared to the consequences of a parasitic infection in a customer. Our Sushi and Sashimi Food Safety Course covers these species-specific requirements in detail.
Supplier Verification and Documentation
Most sushi restaurants in the UK purchase fish that has already been frozen to specification by their supplier, rather than freezing in-house. This is perfectly acceptable — but you must be able to prove it. The burden of demonstrating compliance rests with the food business operator, not the supplier.
You should obtain and retain the following documentation from every supplier of raw fish:
- Freezing certificates — confirming the product has been frozen to -20°C for 24 hours or -35°C for 15 hours, with batch traceability.
- Supplier specifications — product data sheets confirming species, origin, and processing methods.
- Delivery temperature records — your own records confirming that fish arrived at the correct temperature (frozen or chilled as specified).
- Supplier audit records — evidence that you have assessed your supplier’s food safety management systems, ideally through a documented supplier approval process.
Retain these documents for a minimum of two years. When an Environmental Health Officer visits your premises, they will ask to see freezing certificates and traceability documentation. If you cannot produce them, you will be unable to demonstrate that your raw fish is safe — which may result in enforcement action, regardless of whether the fish was actually frozen correctly by your supplier.
What If You Freeze In-House?
Some businesses choose to purchase fresh fish and freeze it on-site before using it for raw preparations. This is permitted under the regulations, but imposes additional responsibilities on the food business operator. You must be able to demonstrate that your equipment and procedures achieve the required core temperatures for the required duration.
Key requirements for in-house freezing include:
- Commercial-grade freezer equipment capable of reaching -20°C or -35°C at the core of the product. Blast freezers are strongly recommended as they achieve target temperatures far more quickly and uniformly than static freezers.
- Core temperature monitoring — you must record the core temperature of the fish at the start and end of the freezing process, using a calibrated probe thermometer.
- Batch records — each batch of fish frozen in-house should be logged with the date of freezing, species, quantity, time placed in the freezer, time removed (or time the 24-hour hold was confirmed), and core temperatures recorded.
- Probe calibration records — your probe thermometer must be regularly calibrated (at least monthly) and calibration records retained.
If your freezer cannot reliably reach -20°C at the core of the product, you should not be freezing fish in-house for parasite control purposes. In that scenario, you must source pre-frozen fish from an approved supplier with appropriate certification. A well-written HACCP plan will clearly document which approach your business uses and the supporting procedures.
Consequences of Non-Compliance
Failure to comply with the freezing requirements for raw fish carries serious consequences. Environmental Health Officers have a range of enforcement options at their disposal, and parasite control failings are treated with particular severity because the risk to public health is direct and foreseeable.
- Improvement notices — requiring you to demonstrate compliance within a specified period, typically 14 days.
- Prohibition orders — preventing you from serving raw fish until compliance is demonstrated.
- Prosecution — under the Food Safety Act 1990, with unlimited fines in the Crown Court and potential custodial sentences for the most serious offences.
- Reputational damage — a low food hygiene rating, negative press coverage, and loss of customer trust. For a sushi business built on freshness and quality, this can be devastating.
You can learn more about the full range of enforcement measures in our guide to food safety penalties, fines and prosecution in the UK. For a thorough understanding of your obligations under Regulation (EC) 852/2004, see our detailed explainer on what the regulation means for UK food businesses.
Frequently Asked Questions
Does freezing affect the quality of sushi-grade fish?
When done correctly, freezing has minimal impact on the quality of fish used for sushi and sashimi. Blast freezing at -35°C or below is particularly effective at preserving texture because the rapid freezing process creates smaller ice crystals, which cause less cellular damage. The vast majority of premium sushi restaurants worldwide use fish that has been frozen to specification. The term “sushi-grade” is not a legal definition — it simply means the fish has been frozen to meet parasite-destruction requirements and is of suitable quality for raw consumption.
Can I buy pre-frozen fish for sushi from any supplier?
You should only purchase fish for raw consumption from approved, reputable suppliers who can provide freezing certificates and full traceability documentation. Not all frozen fish has been frozen to the required specification — standard frozen supermarket fish, for example, may have been frozen for shelf-life purposes at temperatures that do not meet the parasite-destruction threshold. Always verify that your supplier’s freezing process meets the requirements of Regulation (EC) 853/2004.
How long should I keep freezing records?
There is no single statutory retention period specified in the regulations, but best practice is to retain all freezing certificates, supplier documentation, and in-house freezing records for a minimum of two years. This ensures you can demonstrate compliance to EHOs for any product that may have been in your supply chain or storage. Some local authorities recommend retaining records for the shelf life of the product plus one year.
Is wild salmon exempt from the freezing requirement?
No. Wild salmon is not exempt. The limited exemption available for farmed Atlantic salmon exists because controlled farming conditions can eliminate the parasite risk. Wild salmon feed on natural prey that may carry Anisakis larvae, and wild fish are therefore at significant risk of parasitic infection. Wild salmon intended for raw consumption must always be frozen to the required specification before serving.
Written by Carren Amoli, BSc (Hons), RSPH Registered
