Importers can use fast test for oilfish, say researchers

Researchers at Chinese University yesterday called on fish importers to adopt a test to identify oilfish which they say is quick and cheap.

The university took 25 fish samples and, using the test, identified 10 as oilfish - a species which shops and restaurants have been selling as cod or white jade fish.

Biology professor Paul But Pui-hay said the researchers combined DNA testing and a widely used technique called thin layer chromatography (TLC) to distinguish the oilfish among the samples. Oilfish contains a high level of wax ester, which some people find hard to digest and can cause diarrhoea.

He said the combination test was reliable and highly accurate, and pointed out a TLC test could be done by a competent secondary school science student.

'The TLC test is simple, quick and cheap. It takes around 30 minutes and costs about HK$50 per test on average. The equipment is very simple,' Professor But said.

The cost of testing would drop if the volume of testing was high, he said.