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Researchers find pig DNA in seafood products

18 November 2019 | Research - Impact

Prawn balls yielded pig DNA in samples tested by the NUS team

NUS researchers have uncovered one of the worst cases of food mislabelling in Singapore, with pig DNA being found in seafood and expensive ingredients being swapped out for cheaper substitutes.

Their discoveries regarding seafood bought in supermarkets and restaurants in Singapore have been published as a preprint. The manuscript has also been submitted for formal review.

Pig DNA in cuttlefish and prawn balls

“Arguably, the most serious case of mislabelling for a multi-religious society like Singapore involved pig DNA in cuttlefish and prawn balls. We initially suspected lab contamination, but the same seafood brand repeatedly yielded pig DNA in five samples which were bought at different times and places,” wrote the team from NUS Biological Sciences.

This is a serious problem given that many people avoid pork for religious, ethical, or health reasons such as allergies, added the team which was led by Professor Rudolf Meier.

“Fortunately, the samples were not labelled as halal or kosher, but such cases do highlight the need for regular testing of heavily processed, multi-species seafood samples,” the researchers added.

High-value products were mislabelled

The team also found that about 7.6 per cent of single-species seafood samples were clearly mislabelled. Higher-value products — such as prawn roe, wild-caught Atlantic salmon and halibut — were replaced with lower-value ingredients including fish roe, Pacific salmon and arrowtooth flounder.

Though the percentage is “comparatively low”, the “low rates are somewhat deceptive” because of the widespread use of vague common species names that do not allow for a precise assessment of the expected ingredients, the researchers said.

Increased demand has created incentives for seafood fraud via mislabelling. Such fraud is particularly common for fillets and heavily processed seafood products because they are not readily identifiable by eye.

The problem was worse for mixed-species products, where 38.5 per cent of samples were mislabelled. For example, all mixed samples labelled as containing crustaceans — crab, prawn or lobster — only yielded fish DNA.

“Increased demand has created incentives for seafood fraud via mislabelling. Such fraud is particularly common for fillets and heavily processed seafood products because they are not readily identifiable by eye,” noted the researchers.

The team added that most fraud appears driven by the desire to maximise profit because profit margins can be significantly increased by substituting expensive and desirable food species with less desirable and cheaper ones. They concluded that there is a need for more regular testing of seafood samples.

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