Carbon monoxide treated fish, (aka tasteless smoke, filtered wood smoke, CO treated) refers to a process by which tuna loins are treated with the gas to prevent oxidation and thereby alter the cosmetic appearance of the meat. Normally, a fresh piece of tuna will lose its red color and turn brown over a period of a few days when exposed to the air. The same piece when treated with CO retains an artificial watermelon red appearance indefinitely. So treating tuna with CO not only brightens the color of the meat, but it also allows the meat to retain its “fresh-looking” color even after it begins to deteriorate.
Here's a few things to keep in mind when you see "treated with carbon monoxide to preserve freshness"
Because a 3 week old piece of carbon monoxide treated tuna will be as bright and vibrant as a 3 day old piece, it’s difficult for the average consumer to know what it is they’re getting. Furthermore, since most CO treated fish is imported, there is often no record of how that fish was handled prior to landing in the US. The combination of these factors has had some serious consequences for the consuming public. In 2015, a major salmonella outbreak that spread to 9 states was linked to imported tuna treated with carbon monoxide. This wasn’t an isolated case either. This has happened numerous times over the last decade. And of course the recent Hepatitis A outbreak in Hawaii linked to imported scallops has once again brought food safety issues regarding foreign supply chains into question.
Unfortunately, when such outbreaks are reported the public doesn't always discern between the foreign imports that are responsible for the problem and the domestic fisheries which comply with the very regulations designed to prevent such an occurrence. Countries like Japan, Canada, European Union have all banned CO treatment in fish, while the US continues to condone the practice despite public health repercussions. The bottom line is that with imported tuna products, it’s hard to tell exactly what you’re getting.
Know Your Source
The best way to ensure that you're getting a quality product is to ask where the fish is from, how it's caught, and the handling methods used to get it to you. Beware of suspicious bright colors when sourcing tuna. If it looks too good to be true and unnaturally red it's probably gassed. Fresh, domestic caught tuna is probably going to be more expensive than an imported, frozen product, but at the end of the day the difference in value is rather explicit. You get what you pay for. At Hawaiian Fresh Seafood we take great pride in offering our customers the best of the best. We never use CO treated products and because we own and operate our own fleet, we can trace every fish we sell back to the boat that caught it. We know exactly how that fish was handled from the time it was hooked to the time it’s shipped to your door. So don't sell yourself short when it comes to sourcing quality and freshness. Carbon monoxide treated fish and other low quality imports just don't compare.