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Is this techno tuna - carbon monoxide and tuna?

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I love tuna and for the past few years have pretty consistently had seared tuna or poke for dinner nearly at least once a week. I used to buy it at H Mart when I was there to buy other things. It has always tasted fine and been cheaper than the other store in my area at which sashimi grade tuna is available so it was often a destination trip. However, with the recent winter, my motivation to go to H Mart 30 miles away has waned and so I've been spending the extra few dollars to buy at Whole Foods. Recently, I had purchased tuna at H Mart but SO and I were quite hungry so wanted to pick up more and only had time to go to Whole Foods. I always noticed that the tuna at Whole Foods and H Mart were different colors, but didn't think too much of it until I recently learned about the use of carbon monoxide to keep tuna a nice pink color. In the picture below, the H Mart filet is on top and is definitely a brighter pink which makes me think that it's the so called "techno tuna." I think it's also pretty consistent with my occasional experiences with freezing - I have frozen the H Mart tuna a few times and the color remains pretty much the same whereas the one time I froze the Whole Foods tuna it turned a lovely shade of brown as you would expect from oxidation.

I just wanted to see if anyone knew if this was the reason for the color difference, and if not is there a reason?

Also, do you avoid the "techno tuna" or don't bother as it doesn't affect the taste or so they say?

 
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  1. Yellowfin tuna has a range of colors that occur naturally (mostly based on the size of the fish - larger is darker red), so color alone tells you little about the fish. The frozen saku tuna blocks that many sushi restaurants use tends to be on the pinker side. Again, not an indication of lesser quality, just that it's a loin that's flash frozen (something you can't do at home - home freezing is slow and allows the cell walls to break down resulting in mushy texture)very soon after it's caught (and is generally thawed just before it's sold - or left frozen). Carbon monoxide treatment is purely cosmetic but the risk is that you may be buying a fish that has started to go bad. So the rule - as always - is to know your seller.

    1. Not oxidation, the opposite. the color is due to myoglobin, the oxygen binding protein in muscle. When oxygen is bound, it is red when carbon monoxide binds it is pinker and CO binds more tightly to myoglobin than oxygen (and hemoglobin in your blood) and hence the tuna stays pink. It's also why carbon monoxide kills you as you cannot get sufficient oxygen to your tissues. When myoglobin releases its oxygen it turns browner. Agree with ferret, purely cosmetic.