"Tuna's Red Glare? It Could Be Carbon Monoxide"
Seems the US and other countries agree the process is harmless, but Japan, Canada, and the EU have banned it because it might lead to the deceptive sale of otherwise bad tuna.
Not sure what I would think of brown tuna if it were served to me, but it is sometimes amusing what great lengths the market goes through to preserve appearances for the consumer. In another instance, I remember hearing that McDonald's was considering using genetically-modified potatoes that do not brown---simply because kids (and adults?) find pure-white fries more desireable....
Excerpts:
Tuna quickly turns an unappetizing brown (or chocolate, as it is called in the industry), whether it is fresh or conventionally frozen and thawed.
Carbon monoxide, a gas that is also a component of wood smoke, prevents the flesh from discoloring. It can even turn chocolate tuna red, according to some who have seen the process. ...
Just because a slice of tuna is brown, it does not mean it is not fresh. And other factors determine the color, including the fat content, species and cut. The finest fresh bluefin, which sells for up to $40 a pound at Tokyo's wholesale fish markets, is not a deep red but a pale pink because of the fine web of white fat that permeates the red flesh. Top-quality toro is often a brownish red. ...
Tuna treated with carbon monoxide is bright red when first defrosted, and fades within a couple of days to a watermelon pink. But "you could put it in the trunk of your car for a year, and it wouldn't turn brown," said one sales representative at Anova Foods, a distributor in Atlanta, who spoke on condition of anonymity. ...
What does all this mean at the market? Any tuna that is hot pink has probably been treated with carbon monoxide. Tuna that is bright red may be extremely fresh, and therefore very expensive, or may have been treated with the gas.
Not sure what I would think of brown tuna if it were served to me, but it is sometimes amusing what great lengths the market goes through to preserve appearances for the consumer. In another instance, I remember hearing that McDonald's was considering using genetically-modified potatoes that do not brown---simply because kids (and adults?) find pure-white fries more desireable....
Excerpts:
Tuna quickly turns an unappetizing brown (or chocolate, as it is called in the industry), whether it is fresh or conventionally frozen and thawed.
Carbon monoxide, a gas that is also a component of wood smoke, prevents the flesh from discoloring. It can even turn chocolate tuna red, according to some who have seen the process. ...
Just because a slice of tuna is brown, it does not mean it is not fresh. And other factors determine the color, including the fat content, species and cut. The finest fresh bluefin, which sells for up to $40 a pound at Tokyo's wholesale fish markets, is not a deep red but a pale pink because of the fine web of white fat that permeates the red flesh. Top-quality toro is often a brownish red. ...
Tuna treated with carbon monoxide is bright red when first defrosted, and fades within a couple of days to a watermelon pink. But "you could put it in the trunk of your car for a year, and it wouldn't turn brown," said one sales representative at Anova Foods, a distributor in Atlanta, who spoke on condition of anonymity. ...
What does all this mean at the market? Any tuna that is hot pink has probably been treated with carbon monoxide. Tuna that is bright red may be extremely fresh, and therefore very expensive, or may have been treated with the gas.
// 10/06/2004 
