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Pig DNA found in cuttlefish and prawn balls: NUS researchers

SINGAPORE — The genetic material of pigs was found in cuttlefish and prawn balls manufactured by a particular seafood brand in Singapore, a team of researchers from the National University of Singapore (NUS) found.

A close-up view of processed seafood such as prawn balls and crab sticks.

A close-up view of processed seafood such as prawn balls and crab sticks.

SINGAPORE — The genetic material of pigs was found in cuttlefish and prawn balls manufactured by a particular seafood brand in Singapore, a team of researchers from the National University of Singapore (NUS) found. 

Their discovery of arguably the most serious case of mislabelling of seafood products for a multi-religious society such as Singapore came about after they tested 105 samples of seafood products bought from six supermarkets and two seafood restaurants.

They also found that more premium seafood such as prawn roe, wild-caught Atlantic salmon and halibut have been replaced with lower-value ingredients such as fish roe, Pacific salmon and arrowtooth flounder respectively. 

The research team comprised Professor Rudolf Meier, Mr Jonathan Ho, Dr Amrita Srivathsan and Ms Jayanthi Puniamoorthy from the Department of Biological Sciences in NUS.

In the academic paper published on Thursday (Oct 31), they wrote: “(The pig DNA) in a seafood product is a serious problem given that many consumers avoid pork for religious, ethical or health reasons.”

Thankfully, the samples were not labelled as halal or kosher, they noted.

Their study suggested that the level of mislabelling of seafood products in Singapore is not particularly high when compared to the results from other South-east Asian countries. 

However, they argued that the discovery of pig DNA in seafood products highlighted the need for regular testing of heavily processed, multi-species food samples.


The team of researchers discovered pig DNA in all five samples of the same seafood brand, which were bought at different times and places. 

It was not found in any other seafood samples from other brands. 

That particular brand of seafood found to contain pig DNA was not identified in the paper, but TODAY has contacted the researchers to find out. 

Besides the pig DNA, they noted that about 7.6 per cent of single-species seafood products suffered from a “clear-cut” case of mislabelling. 

As for mixed-species samples, the rates were higher at 38.5 per cent.

Even though the rates of mislabelling for single-species were only 7.6 per cent, the researchers said that the low rates were “somewhat deceptive”. 

This is because of the widespread use of vague common species names that do not allow for the precise assessment of the expected ingredients. 

Among samples of flatfish — a fish category that included halibut — the researchers found that about 40 per cent of its samples were mislabelled.

Some cases of mislabelling they found among the samples included:

  • Arrowtooth flounder were sold as halibut  

  • Chum salmon were sold as wild-caught Atlantic salmon

  • Capelin roe were sold as prawn roe  

The substituted product were less valuable than the species indicated on the label. For example, arrowtooth flounder, which usually develops a soft and mushy texture when cooked, was being substituted for the more highly valued halibut. 


As for the samples of mixed-seafood species that the researchers tested, this was what they said: “Many mixed-species products were labelled as ‘crab’, ‘prawn’, or ‘lobster’ sticks or balls. Only fish were listed as ingredients in six out of eight mixed-species samples, while two more explicitly listed shrimp meat or prawn powder in addition to fish in their ingredients.

“However, we were unable to find any crustacean DNA in all eight samples. Fish DNA was abundant and we suspect that overall, many of these products do not include any or have only minuscule amounts of crustacean tissues.”

The researchers argue that such “creative labelling” misleads consumers because the main product label suggests that the seafood product contains crustacean content, yet only when the ingredient list is examined does one realise that the product does not contain crustaceans. 

“The average consumer would consider extremely low proportions of crustacean protein to be unacceptable, given that the label highlights the crustacean component,” the researchers said. 


The researchers found that the level of clear-cut mislabelling in Singapore is not high in comparison with other countries in region. Studies from Malaysia, the Philippines and Vietnam found levels of mislabelling to be at around 60 per cent. 

The main problem in Singapore, the researchers argued, is “creative labelling” especially for heavily processed products. 

This is probably due to the lack of clear regulations in the Sale of Food Act, defining which species should be included in products that are labelled with common names. 

The law states that labels need to provide a name or description which is “sufficient to indicate the true nature of the food”.

Fish is also defined as any aquatic organism commonly consumed by humans. While this does not include mammals, the definition includes crustaceans and molluscs. 

“This state of affairs is no longer in line with the expectations of today’s consumers who expect labels to be precise,” the researchers said.

They suggested that a regulatory update, benchmarked against rules set by the European Union (EU), may be required. 

The EU mandates that both the commercial and scientific name of the product should be listed on its label. The commercial names used also needs to be taken from approved lists published by EU member countries. 

The number of seafood products sold in supermarkets being mislabelled dropped from 20 per cent to 8 per cent after the implementation of these rules, the researchers noted. 

Countries with laxer laws continued to have mislabelling rates of between 20 and 30 per cent. 

“Levels of seafood mislabelling may also drop in Singapore’s supermarkets if such legislation were to be enacted,” they said.


In response to TODAY's queries, the Singapore Food Agency said it has not detected any porcine DNA in any halal-certified fishball products sold in Singapore.

"We have detected porcine DNA in fishball products which are not halal-certified. The presence of porcine DNA in these non-halal products could be due to manufacturing processes. For example, a food manufacturing plant may produce a wide range of products, including seafood and pork products," the agency said.

"As such, trace levels of porcine DNA may be introduced into the seafood products. This however is not a food safety issue."

The SFA added: "Surimi (fish) is commonly used to make seafood imitation products such as crab and lobster sticks. Such products may be named as 'crab/lobster' sticks if surimi is reflected in its statement of ingredients on the label."

The Singapore Food Regulations stipulates that all pre-packed food for sale in Singapore must be labelled with the name of food, ingredients, net content and source.

It is the responsibility of the industry to ensure that any food labelling claim made is accurate and can be substantiated, the SFA noted, adding that consumers are also advised to check the ingredient listing to ascertain the contents of the product before purchase.

The SFA investigates feedback on authenticity of food products, it added.

Attempting to pass off one species as another species is an offence (e.g. beef being sold as mutton) under the Sale of Food Act, and the offender is liable to a maximum fine of S$5,000.

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