DEAR DR. BLONZ: Should I be concerned that there is a great difference in the fishy odor level in the cans of tuna that I open? I'll typically have several cans of solid albacore from the same major brand, but when I open one, it's very smelly, while another identical can will have a very mild odor. Recently I considered throwing out the contents since the fishy odor was so pronounced. Any thoughts on this issue? Any safety concerns? -- F.M., via email
DEAR F.M.: "Solid" types of tuna come from blocks cut from different parts of the fish muscle. They often rely on larger fish for the solid tuna, as the muscle mass will be larger, but this also means you are getting your tuna from an older fish. All, of course, depends on the quality control of the manufacturing process, which includes the tolerances set for what gets included as solid or chunk tuna.
Other possible issues are how the particular cans were processed and stored. If the tuna spent more time in a warmer environment between its time in the ocean and being opened in your home, this could increase the tendency to develop "off" odors that presage the actual breakdown of the tissue and the spoilage process. Fish, especially cold-water fish, have this tendency by virtue of their content of certain fats and amino acids that break down to malodourous substances. All goes well if they remain chilled, but enough time away from the cold, and you have an insult to the senses.
I am of the mind that whenever you crack a can of anything and it has an "off" smell, you should not eat it. You have the option of contacting customer support at the manufacturer and telling them your story (there should be contact information on the tin). Likely they will also tell you to toss the stuff (they might ask for the lot identifiers first), and I would predict they will send you some coupons for a replacement product. Another option is to take it back to the store where you bought it and get your replacement can that way.
As long as we are talking about tuna, you should be alert to the issue of mercury. Albacore tends to have higher levels of mercury than chunk light, which usually comes from skipjack -- a smaller-sized, shorter-lifespan breed. Tuna tend to bio-accumulate mercury and the older the tuna, the greater the risk.
The main reason for this is that albacore tend to live longer and are moderately large among the breeds used for canned tuna. As such, bigger albacore caught for large commercial canners tend to come from deep waters and will have a higher risk of mercury. There are brands, such as Wild Planet (wildplanetfoods.com), that catch younger, smaller tuna. Their fishing methods include pole-and-line or trolling, and those result in fish with a lower risk of mercury. You can do some additional research at tinyurl.com/d464hdm before you buy.
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