Kirsten Lawson

Food Standards Australia New Zealand is calling for submissions on banning the use of carbon monoxide to improve the appearance of fish for sale.

Agency head Steve McCutcheon refrred to reports that some producers use carbon monoxide to maintain the red colour of fish, which can hide its age..

"CO reacts irreversibly with the dark muscle tissue of tuna and similar fish, resulting in the fish becoming bright cherry red," he says. "CO prevents oxidation and discoloration, preserving the bright red tissue for an extended period of time, making it look fresher than it is."

Carbon monoxide was currently allowed as a "general purpose processing aid", but processing aids are not supposed to have any "ongoing technological function" - in this case colouring, or colour fixing, he says.

Unlike other gases commonly used in fish and meat packaging, such as  nitrogen, carbon monoxide is not inert and its effects are not reversible, the agency says. "Internationally it has been of concern because of its ability to hide the age of fish and potential food safety issues associated with poorly handled tuna."

"As a change in colour is used by consumers as a primary assessment of quality, carbon monoxide treatment has the potential to make inferior quality fish appear aesthetically more pleasing to consumers or to mask decomposition resulting in an increased risk of histamine fish poisoning.

"On this basis, the use of carbon monoxide as a food additive to colour tuna is considered to pose a food safety issue."

Using carbon monoxide gas in fish processing is already banned in Singapore, Canada, the European Union and Japan, with labelling required in the United States, but it has been used for more than a decade in some parts of the world, the agency says, pointing to a story in the New York Times: nytimes.com/2004/10/06/dining/06TUNA.html

It is not aware of any Australian or New Zealand processors using carbon monoxide, but says about 100 tons a month of imported fish, worth $12 million a year, especially tuna, is carbon-monoxide treated. This would be prohibited.

Submissions close on February 11, 2013.