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Raw oysters and other bivalve shellfish such as mussels, clams and scallops are becoming increasingly popular. Because of their excellent nutritional value, people are becoming more interested in eating them raw. In response to rising demand, restaurants have added them to their menus. However, offering raw shellfish in restaurants is not without risk for restaurant owners. Many disease-causing pathogens and biotoxins are found in shellfish and eating them raw has been associated with an increased risk of shellfish poisoning and various food-borne diseases, the most common of which is Vibriosis.  Customers in high-risk groups such as the elderly, small children, pregnant women and those with compromised immune systems are more likely to get shellfish-borne diseases. Restaurants that serve raw shellfish must take food safety precautions to ensure that the shellfish they serve is safe for the customers. The risk of shellfish-borne diseases is mostly determined by how the shellfish is sourced, stored, shucked and served.

Shellfish are categorized as potentially hazardous food (PHF) which requires time and temperature control to ensure their safety for human consumption. In this article, we will look at how restaurant operators can employ safe food handling practices to reduce the risks associated with serving raw oysters and other bivalve shellfish such as clams, mussels and scallops.

Purchasing Controls

Procuring fresh and high-quality shellfish is the first step toward safe shellfish service. Restaurants must develop standard purchase specifications for all types of shellfish they offer and follow them consistently when purchasing shellfish from vendors. This assures that shellfish is purchased in accordance with the quality requirements outlined in the purchase specifications. Always buy shellfish from reputable and licensed vendors who have a track record of supplying safe seafood products. Buying shellfish from licensed and trusted suppliers provides a number of advantages. It assures that the shellfish is safe and free of contamination, that it is harvested commercially and legally from approved beds, and that it can be traced back to its source during food poisoning investigations. Shellfish harvested from unapproved beds contain high levels of marine biotoxins that are harmful to humans especially when consumed raw. Worse, some of these toxins cannot be neutralized by cooking.

Receiving Controls

Receiving is another critical stage that influences the safety of shellfish. Restaurants must work with the shellfish vendor to develop a delivery schedule that allows for adequate inspection and timely storage of the shellfish delivered. If shellfish is delivered at times when adequate inspection is not possible, it will have a direct influence on the safety of the shellfish. Receiving clerks should be trained on how to inspect shellfish deliveries to ensure they are fresh, delivered in sanitary conditions and at the correct temperature. Only accept those shellfish that are fresh and alive. Check that oysters, clams, mussels, and scallops are received at 45°F air temperature and an internal temperature of no more than 50°F. If they arrive in melted ice and at temperatures above the safe minimum temperature, they must be rejected. Accept shellfish that has shiny shells, as this indicates freshness. If the shellfish is open, lightly tap it. If it closes the shell, this indicates that the shellfish is alive and safe to eat. If it does not, it is dead and it should be rejected. In such cases, it is difficult to determine when it died, under what conditions (In cold storage or outside of cold storage) and hence there is a possibility of contamination. When a scallop dies, for example, due to unfavourable environmental conditions, the roe deteriorates faster than the rest of the scallop, making it unsafe to eat. When live shellfish are kept in colder temperatures, they often become cold and sleepy and do not always respond to being tapped by closing their shells. Allow about a minute for their response before deciding whether to accept or reject them. Shellfish with cracked shells die quickly, making them unsafe and must be discarded. Shellfish tags are important documents that can assist in tracing the origins of the shellfish during illness investigations. Check that live Shellfish have legible tags attached to identify the name, address and certification number of the dealer and the shipper, the date and location of the harvest and the type and quantity of shellfish. The statement “This tag must be attached until the container is empty or retagged and then kept on file for 90 days” must be printed on tags. The receiving clerk should sign the delivery note only after all safety and quality requirements have been met.


Oysters, mussels and clams contain a lot of sand and grit because they spend the majority of their lives buried in gavel, sand or mud. They should be thoroughly cleaned before storing and serving because sand or sediment deposits in the shell contain pathogens that can cause food poisoning. Scrub them with a brush under cold running water to remove dirt and grit on the outside shell and soak them for about an hour in a bowl of cold water mixed with salt and cornmeal to remove sand and debris from the inside their shells. When shellfish filter water containing cornmeal, they spit out the debris and sand that they have ingested. Scallops should not be soaked in water since it will ruin their flavour and make them soggy. To remove grit and sand, rinse them thoroughly under cool running water. Shellfish die when exposed to warm or hot water, so never use hot or warm water to clean them. Mussels, for example, have hair-like fibers attached to the outer shell that must be removed before service. Mussels die when they are not debearded properly. To remove the beard without harming the mussel, gently pull it toward the hinged side rather than the opening end. To be safe, debeard mussels as close to the service as possible, but no later than an hour before service.

We hope you enjoyed the first part of our two-part serieson serving raw oysters and bivalve shellfish safely; what restaurant operators need to know.  Keep an eye out for the final installment.

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