Your choice of a marinade for grilling tuna fish is generally based on personal preference. There are, however, a few very important considerations. Raw tuna, and most other fish for that matter, absorb the flavors of a marinade very quickly. As a rule, a grilled tuna marinade should contain a minimum of acids, such as lemon juice. Tuna also cooks very quickly to varying degrees of preferential doneness, and corresponding taste.
Many markets do not offer a varied selection of fish suitable for grilling. The exception is tuna which is readily available throughout most of the world. Its powerful back muscles, also called its loins, provide large and thick “steak cuts” of meat. The cooked flesh is dense and firm; as a result, it will not flake and break apart on a grill.
Some people enjoy eating tuna raw and prefer grilled tuna rare. Others are fond of canned tuna and may prefer tuna that is thoroughly cooked on a grill. Your choice for the grilled tuna marinade should be influenced by this as well. Raw tuna is more subtle in flavor, and must be paired with a marinade with subtle seasonings and herbs. Fully cooked tuna is more robust, and will hold up to an aggressive marinade such as a traditional sweet and spicy tomato barbecue.
When cooking with marinades, the meat must be allowed to sit and soak up the flavors for a time. It should not take even a thick cut of raw tuna more than thirty minutes in the refrigerator to fully marinate. You can choose a grilled tuna marinade of any consistency, ranging from watery thin to pasty thick. Your main concern in a store bought bottle of marinade is acids in the label’s ingredients list. An excess of vinegar or lemon juice, will actually cook the delicate flesh of tuna halfway through just from the marinating process.
Remember, tuna cooks in very little time. A mostly raw piece with a thin outer layer of grill marks will take no more than two minutes on each side over hot coals or gas flame. A piece cooked completely through may take five minutes per side. Sugar content in your grilled tuna marinade is not an issue since it won’t be on the grill long enough to burn. Oils within the marinade is also acceptable, even preferable, because tuna is a very lean meat.
Some of the ingredients to consider in your marinade for tuna, whether it is purchased at a market or made from scratch, are Pacific Asian and Mediterranean. Examples of the former well suited to tuna include sesame oil, ginger and a Chinese sauce called hoisin. Mediterranean flavors usually include strong pastes, such as the puree of olives called tapenade. The short cooking time of tuna on a grill also means that both fresh and dried herbs, such as dill, tarragon and chervil, are good marinade ingredients.