Since she was using very fresh salmon with every test—and only changing the way she cooked the cakes—it made her wonder:
Could the way you cook (or even reheat) an oily fish such as salmon impact how fishy it tastes?
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Why Does Fish Smell Fishy?
First, it helps to know that there are two different kinds of “fishy.”
One can be a sign of spoilage; the flesh of all fish contains an odorless, nonvolatile chemical called trimethylamine oxide or TMAO (it is often noticeable in packaged seafood meat).
During storage, bacteria on the surface of the fish convert TMAO into a volatile compound called trimethylamine (TMA), which produces an unmistakably fishy odor the longer the fish is stored.
The second fishy smell in cooked salmon (and other fatty fish such as mackerel and tuna) comes from a different source. Salmon fat is highly unsaturated, which makes it susceptible to oxidation when cooked. Oxidation causes the breakdown of the fatty acids into strong-smelling aldehydes, which are the source of salmon’s characteristic flavor.
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How to Control Salmon’s Fishiness with Cooking
To determine if she could control some of the fishiness of her salmon cakes by changing up her cooking method, Andrea made salmon cakes three ways.
One was with flaked precooked fish that she then pan-fried, another with chopped raw fish that she baked in the oven, and a third with chopped raw fish she briefly seared until just cooked through.
Cooking the salmon twice resulted in very thoroughly cooked fish and thus a high level of aldehydes.
Baking the cakes had a similar effect because the ambient heat of the oven also cooked the fish relatively thoroughly.
But the pan-fried cakes were mildest because the least amount of the fat had oxidized. So the results were in—the fat in salmon oxidizes when it is exposed to the air as well as to heat, so the longer the cook (or re-cook), the stronger the flavor.
No-Heat Ways to Eat Leftover Cooked Salmon
Instead of risking that your leftover fish will get fishier by reheating it, try using it in one of the following ways.
1. Sub it in for the tuna in Salade Niçoise or turn that salad into a wrap.
3. Make fish tacos topped with vegetable slaw.
4. Flake it over a hearty green dinner salad instead of using smoked salmon.
How to Control Salmon’s Fishiness with a Milk Bath
You can also lessen salmon’s strong flavor by soaking it in a milk bath for 20 minutes and then draining it and patting it dry before cooking. The casein in milk binds to the TMA, and when drained away, it takes the culprit that causes fishy odor with it. Read more about this technique here.