Saturday, November 2, 2019

Pig DNA found in cuttlefish and prawn balls: NUS researchers

By Janice Lim

02 November, 2019

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 Mr Jonathan Ho, Ms Jayanthi Puniamoorthy, Ms Amrita Srivathsan and Mr Rudolf Meier, from the NUS department of biological sciences.

In the academic paper published on Wednesday (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.

[That's a relief. But what about Catholics abstaining from meat on Fridays?]

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.

Still, 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.

[I will be doing my own research after this. So it is a seafood brand that has fish, cuttlefish and prawn products... There are only so many seafood brands - Dodo, Bobo, LiChuan are just three that I can name off the top of my head...]

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 are “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, is 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.”

[Crabsticks are just fish. Surimi to be precise. If you are thinking you got crab at those prices... you are ready to help a Nigerian prince claim his inheritance. Didn't know about prawn or lobster sticks and balls...]

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.

[Well, I'm not fond of prawn or lobster balls/sticks. And I already know that crab sticks are just surimi... so I don't find that (imitation crabsticks) to be unacceptable. One brand even calls their product "seasticks".]


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.

[It would be good if we have an approved list of seafood for labelling. Or a rule that says anything that claims to be one product (say "prawn") needs to have at least X% (say 50% for a low standard) of the content (i.e. 50% prawn meat). Product with a lower content (say 10% to 49%) can be described as "flavoured" as in "prawn-flavoured" balls or sticks. And products with less than 9% of real content would have to be labelled "imitation". Or some such guidelines along similar lines. ]

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