Why Is Tomato Paste Sautéed in Oil?

Raw tomato paste is a concentrated purée made by boiling tomatoes and evaporating their water, and it has a sharp acidity along with a slightly metallic, raw aroma. If it is thinned with water and added directly to the pot, it transfers that flavor to the dish as is; the dish tastes sour, looks pale, and has a flat flavor. Sautéed in oil, the paste becomes something else. The raw aroma disappears, the acidity recedes, and a sweet, roasted depth takes its place.

Heat causes this change. During sautéing, the water in the paste evaporates quickly, and the paste comes into direct contact with the hot surface of the pan. The sugars and proteins in the paste brown on contact; the same reactions seen in bread crust and seared meat happen on a small scale in the paste. Compounds that give tomatoes their flavor also become more concentrated with heat. As a result, the same amount of paste gives a much fuller, deeper flavor when sautéed. Sautéed paste also adds sweetness to a dish, so a dish made with it needs less sugar than one made with raw paste.

Color is another purpose of sautéing. The compounds that give tomato paste its red color dissolve in oil, not water. Sautéed in oil, the paste releases its color into the oil, which turns orange-red and carries an even color throughout the dish. With paste thinned in water, the color does not disperse through the liquid and the dish stays paler. Red oil collecting on the surface of a dish made with sautéed paste is one sign the paste was sautéed properly. The more evenly the paste disperses into the oil, the more even the color will be; that is why tomato paste added to the pan is mashed with a spoon to loosen it in the oil.

You can judge when the paste is ready by sight and smell. It is usually added to the pot after the onions are sautéed, then sautéed over medium heat, stirring constantly, for 1–3 minutes. During this time, it darkens by a shade, changing from bright red to dark red; its sour smell disappears, and it starts to stick slightly to the pan. At that point, add water, broth, or tomatoes to stop the sautéing. Moisture released by the onions keeps the paste from burning right away; in an empty, dry pan, it burns much faster.

You can tell immediately when it has gone too far. Paste that darkens, turns deep brown, and gives off a sharp burnt smell has burned; that bitterness spreads throughout the dish and cannot be corrected later. Pepper paste burns faster than tomato paste and needs less sautéing because of its sugar and thick consistency. Some dishes deliberately do not use sautéed paste: when a light-colored, fresh-tasting sauce is wanted, the paste is thinned with water and added. That is a preference; in a dish where the paste is not sautéed, its acidity remains more noticeable.