Swordfish is a popular fish available year round. Swordfish from Canada and the North Atlantic is almost always caught sustainably according to the Monterey Bay Aquarium. But most swordfish served in restaurants and cooked at home is tough and dry. In fact, until recently, we avoided it because it is usually overcooked. However, once we had properly cooked swordfish served to us at Galley Beach restaurant in Nantucket, we became interested in how you can cook and serve this fish at home.
Swordfish is usually available as steaks, and may be fresh or have been frozen. It is most frequently cooked by broiling in the oven or over a grill.
Most cookbooks don’t say much about swordfish that is very helpful. Mark Bittman’s venerable tome, How to Cook Everything is more helpful than most:
“Check the fish for doneness by peeking between the layers of flesh with a thin bladed knife-- when the knife meets little resistance and just a touch of translucence remains, the swordfish is done.”
This is specific, but really hard to execute. We looked among internet recipes for temperature details. Several sites (here and here, for example) recommend cooking it to 125º F, so we took that as a first recommendation.
Following Bittman’s (and several others’) recipes, we brushed the fish with a little olive oil, and then put it under our oven broiler for 4 minutes on the first side, then turned it and broiled the second side for 3 more minutes.
Then we tested the internal temperature with an instant read thermometer. Depending on the thickness of the steaks (usually 1” to 1.5”) the swordfish will probably be at about 105-115 by this time.
We returned the fish to the broiler and broiled it another minute or two depending on thickness of the pieces until the internal temperature was between 120ºF and 125ºF.
At this temperature, the fish is cooked through, warm and still tender and juicy as shown in the photos.
To see what would happen as the fish is cooked further, we cooked one piece to about 130ºF and again to 140ºF.
At 130º, the fish was still pretty moist and tasted fine, but it had begun to develop a more pronounced grain or fibrous texture, as shown in the photos.
At 140º, the fish was dry, much more fibrous and had developed a pronounced lemony taste. You can see the difference in the photos. This is the way it is served at second-rate or careless restaurants, and we called it pretty inedible.
So our conclusion is that you want to cook your swordfish to no more than 125º under a broiler. A hot charcoal fire may actually reduce these cooking times, so monitor the cooking carefully.
Swordfish usually comes with the skin still on the sides of the steaks. Swordfish skin is tough and inedible: you should cut it off after cooking and before serving.
We note that a number of recipes suggest that you marinate the fish briefly in, say, lime juice and soy sauce, but we didn’t find it had much effect. We’ll give you some serving suggestions in a subsequent column.