Bivalve Mollusc Safety

Bivalve molluscs have specific hygiene requirements in order to ensure their safety. Specific hygiene considerations are needed to ensure that the risks posed by microbiological contamination and biotoxins are reduced to an absolute minimum. Some bivalve molluscs, particularly oysters, are consumed raw without any processing treatment, so precautions have to be in place to make sure they are safe to eat.

Classification of harvesting areas

Controls are in place to improve substantially the safety of bivalve molluscs intended for consumption. European Hygiene Regulations, which came into force in January 2006, state that shellfish business operators are responsible in ensuring that bivalve molluscs meet strict food safety standards. The Food Standards Agency, in compliance with European regulations, has classified harvesting areas and beds from which shellfish are gathered on the basis of the level of E.coli in the mollusc flesh:

  • Class A grounds are areas where mollusc flesh has less than 230 cfu of E.coli per 100g of flesh. Molluscs may be sent straight to the market without any intervention. From 1 January 2017, one sample in five may exceed the 230 cfu E.coli limit but not exceed 700 cfu.
  • Class B grounds area areas where mollusc flesh has E.coli levels between 230 and 4,600 cfu per 100g of flesh. Molluscs must be relayed to cleaner waters and purified through an approved depuration unit or heat treated before they can be sold for human consumption.
  • Class C grounds are areas containing bivalve molluscs whose flesh contains between 4,600 and 46,000 cfu per 100g of flesh. Molluscs must be relayed to designated cleaner waters for a minimum of two months, or purified or heat-treated, in order to meet Class A or Class B standards.
  • Prohibited areas are areas from which molluscs may not be harvested for human consumption.

Most UK mollusc harvesting areas are class B, which means that the molluscs must be purified before being sold to consumers. All molluscs sold on the UK market must contain less than 230 cfu of E.coli per 100g of flesh. 

Delivering safer bivalve molluscs

Controls are in place to mitigate against potential viral and biotoxin contamination of bivalve molluscs. To ensure best practice guidelines are followed Seafish has produced a series of industry guidance notes for fishermen and shellfish farmers.

Regulatory limits for biotoxins in bivalve molluscs are detailed in European Regulation 853/2004 and summarised here.

Seafish have produced the Live Bivalves Workbook, which is a set of Good Manufacturing Practice guidelines. This is a step-by-step guide to good live bivalve preparation for the market. End product testing standards (EPT) are in Appendices 2 and 3 of the Workbook, and see also this EPT guidance.

And the legislation...