A mackerel fillet is the meat taken from the sides of a fish of the same name; a fillet has been cleaned of bones, head, tail and internal organs. The fillet is used in many recipes, including sushi dishes. There are large amounts of selenium, niacin, vitamin B12 and omega fatty acids in a mackerel fillet. The taste of such a fillet can be very strong, requiring it to be marinated before being eaten. Although there are several varieties of mackerel in the oceans, not all of them are part of the same species.
The meat of a mackerel fillet is substantial, rich and contains a lot of oil. It can stand up to many forms of cooking and is able to assert its flavor against other pungent ingredients. One drawback is that mackerel caught in the ocean must be immediately frozen; otherwise, it will become inedible within one day. Fresh mackerel, however, is prized as an ingredient in Japanese sushi.
When purchasing mackerel fillets, they should have a vibrant color and not appear gray or dried out. They also should have a fresh smell, like the ocean. Fillets that smell like ammonia or smell fishy are old and should be avoided. Pre-packaged, frozen mackerel fillets also can usually be found if there are no fresh ones available.
There are several ways to cook a mackerel fillet. One popular treatment is to cook the fish in soy sauce, because the mackerel will not overpower it. Adding vinegar and saki can add complexity to the dish. The strong flavors of the soy sauce, vinegar and mackerel can be tempered by serving it over rice.
Mackerel also can be baked. An unusual preparation is to put the mackerel fillet into a shallow pan and fill the pan with milk until the fish is half-covered. The dish is then baked until the fish is tender but done. The milk can help to tone down the fishy flavor of the mackerel and keep it tender at the same time.
Other ways to cook a mackerel fillet include rolling it around in spices and vegetables and then grilling it. It can be poached in wine or a wine and broth mixture to impart a more complex flavor to the fish. The fish also can be marinated in an Asian mix of soy sauce, ginger and garlic and then fried in a cast iron pan.
Whatever method of cooking is used for a mackerel fillet, it is important to know when it is done. The fillet is done when the flesh has just turned opaque. Overcooking mackerel can harm the flavor, so the meat should still appear a little oily when removed from the heat.