Processing under spotlight as flaws revealed in shellfish toxin testing

The European food safety watchdog also declared that one of the major test methods used to determine the level of some marine toxins in shellfish was fundamentally flawed and said other techniques must be developed.

A further finding of the body’s panel on contaminants in the food chain (CONTAM) showed that exposure to some marine biotoxins at levels previously considered safe could cause health problems.

It has made a series of recommendations for further action to plug what it describes as “knowledge/ data gaps”​

Commission request​

EFSA delivered its findings yesterday following a request from the European Commission to summarise the outcome of the adopted opinions on marine biotoxins - poisonous substances produced by different algae that can accumulate in shellfish - currently regulated under EU legislation. These were the opinions on okadaic acid (OA) and analogues, azaspiracid (AZA)-group toxins, yessotoxin (YTX)-group toxins, saxitoxin (STX)-group toxins, pectenotoxin (PTX)-group toxins and domoic acid (DA). EFSA was asked to examine current EU limits with regard to human health and methods of analysis.

Processing and toxin concentrations​

The safety body raised concerns over the influence of processing of shellfish on intensifying concentrations of lipophilic toxins; OA-,AZA, YTX- and PTX- group toxins that may be present.

“Processing of shellfish could lead to an approximate two-fold increase in the concentration of lipophilic marine biotoxins”,​ said the panel, while noting the conclusion was based on “limited information”.​

The experts added: “Since the limit values for marine biotoxins in shellfish meat are meant to protect the consumer, the effect of processing (cooking, steaming, autoclaving) should be considered when testing shellfish in official control. Shellfish that contains levels of lipophilic toxins below the regulatory limits may reach, after processing levels that are higher than regulatory limits.”​

Testing method failings​

EFSA also pointed out that the mouse bioassay (MBA), which is used as the official reference for lipophilic biotoxins, is not fit for purpose. The test method has “shortcomings and is not considered an appropriate tool for control purposes because of the high variability in results, the insufficient detection capability and the limited specificity​”, said the panel.

Of particular concern was the MBA’s ability to detect OA- toxin groups at current EU limits, which was labelled as “inadequate, leading to false negative results in official controls”.​

It added that MBA was incapable of detecting concentrations considerably below EU levels and therefore could not be used to monitor the effects of commercial processing on lipophilic biotoxins.

Consumption levels​

For each toxin the panel established the amount which can be consumed within a 24-hour period without any appreciable health risk (the acute reference dose). These were then compared with shellfish consumption and occurrence data from a number of EU countries in order to assess the EU limits. The experts identified 400g as a realistic estimate of a large portion of shellfish and used this in assessing current permitted levels of the toxins.

“Based on these calculations, however, people eating a smaller portion of shellfish contaminated with toxins from the okadaic acid, azaspiracid, saxitoxin or domoic acid groups could also experience ill effects, such as diarrhoea and vomiting,”​ said an EFSA statement.

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Recommendations​

The panel made a raft of recommendations which included identifying knowledge and data gaps – including calling for more information on the effects of processing on levels of marine biotoxins. In March, 2009, EFSA said there was “a need for harmonisation of sample pre-treatment practices (i.e. cooking versus non-cooking) before the actual analysis of lipophilic marine biotoxins is carried out​”.

This task will need to be done by the EC and member states, EFSA told FoodProductionDaily.com.

It also called systems for collecting information about incidences of illnesses connected to eating shellfish and the database on shellfish consumption to be improved.

More accurate and sensitive testing methods to measure concentrations of marine biotoxins in shellfish as well as establishing better characterisation of their performance characteristics are also needed, said the report.