In most countries, tomato sauce is a cooking sauce that is often a base for other sauces. The simplest tomato sauce is an uncooked, cold sauce, such as the Italian checca sauce. Other sauces are cooked, including the Italian arrabbiata sauce or marinara sauce. Generally, cooks prefer meaty, flavorful tomatoes, such as plum tomatoes, because juicier tomatoes tend to make watery sauces. Grocers sell tomato sauce in cans or jars, and home cooks often bottle tomato sauces or seal it in jars.
The tomato is actually a fruit, although many people consider it a vegetable. It is a New World native, so European and Asian cooks did not incorporate tomato into their cuisine until after the 1600s. One of the first countries to use tomato sauce was Italy, especially in southern Italy, where it remains a very popular pasta dressing.
There are several ways to make tomato sauce. The Italian sauce checca is an uncooked sauce similar to salsa. The cook finely dices tomatoes and mixes them with other ingredients, including olive oil and flavorings, such as basil. Another method is to use tomato paste and thin it with water. The most common method is to cook peeled, chopped tomatoes until they reach the desired consistency.
One of the most popular tomato sauces is ketchup, or catsup, which is a very popular condiment in some countries. Other popular sauces are pasta toppers, such as arrabbiata sauce that is similar to the ancient South American tomato sauces. Arrabbiata means "angry" in Italian, and this sauce is spicy because of the addition of dried chili pepper flakes during the cooking process. Tomato sauces are basic cooking sauces, and cooks often add their own combination of flavorings to liven up the sauces.
Sailors created marinara sauces because early ships lacked refrigeration. The tomato's high acid content kept the sauce fresh. The practice of not refrigerating low-acid tomato sauces is risky because bacteria begin to breed within minutes after a food reaches room temperature. Most tomato-based condiments, such as ketchup and steak sauces, have added acid to keep them fresh and add flavor.
A notable difference between tomato sauce and ketchup is that ketchup is a condiment, and sauces usually are integral parts of recipes. Although the sauces are tomato-based, sometimes cooks add other vegetables, such as zucchini, onions and carrots. In different regions, people call them gravies. In some places, including southern Africa and Great Britain, tomato sauces are ketchup-like condiments.