Cold Cooking Fish

• Many cultures around the world have a tradition of cooking fish without heat. Poke is a traditional Hawaiian dish featuring cubed tuna marinated in sea salt and soy sauce. Gravlax -- salmon cold cured with salt, sugar and dill -- comes from Northern Europe. Rumored to have been a favorite among the ancient Incas, the most widely used dish featuring citrus-cooked fish is ceviche. Cool and tangy, ceviche has taken over global cuisine and inspired renowned chefs and home cooks.

Marinating Replaces Cooking With Heat

• By definition, cooking is the process of heating different combinations of ingredients for consumption. Technically, a dish cannot be cooked without heat. But the process of marinating fish in acid or salt is referred to as cooking, because protein molecule structures are altered, similarly to cooking by heat. For the home cook, marinating fish -- instead of cooking with heat -- can yield delicious results.

The Denaturation Process

• When protein molecules are heated, weaker links in their structure loosen or collapse. The complex structure of the molecules is unraveled and allowed to form anew. This process is called denaturation and also occurs when proteins are exposed to citric acid, like lime juice. The original nature of the fish is fundamentally changed or denatured. The color turns opaque and the texture becomes firmer -- similarly to when a filet is cooked with heat -- but the fresh flavor is preserved.

Preparation Tips

• When cold cooking, remember that lime or salt cannot kill all bacteria and parasites. Use only the freshest, high-quality fish and chop it into smaller chunks or cubes before adding lime juice. More pieces expose more surface area to the curing agents. Timing depends on what type of fish you choose. A mild whitefish like tilapia requires less time in lime, while a denser fish like ahi will need more. Be careful not to over-marinate, as fish will become tough.