Full-bodied, rich and thick are words that describe a quality spaghetti sauce. Thin and watery are not appealing qualities for the sauce you toss with your pasta. Simply cooking tomatoes for a short period of time with a little Italian seasoning, garlic and onions, and even beef, yields a meat or marinara sauce with little substance.
Typically, to make spaghetti sauce, you saute garlic and onions for a few minutes in olive oil, add crushed tomatoes and some herbs and spices. This process only takes 10 minutes or so to heat through, but to thicken the sauce more, simmer it for at least 45 minutes to help reduce some of the moisture from the tomatoes and consolidate the flavors.
Sweeten and thicken your sauce by adding pureed carrots. Cook the onions, garlic, any meat and tomatoes as your recipe requires. In a separate pan, cook one large carrot, chopped, in olive oil and enough chicken broth to cover it. Simmer until the carrot is soft, and then puree it in a food processor or blender. Add the carrot mixture to the tomato mix along with any seasonings. Simmer for 10 to 15 minutes, or until thickened to your liking.
As it cooks, pasta releases starch, which you can use to thicken your spaghetti sauce. The key is, don’t rinse the pasta before you sauce it. When you rinse the spaghetti, sauce slips right off and you lose any lingering starch that can help with thickening. Instead, to coat your noodles, pull them out of the pot of boiling water with a slotted spider or tongs and add them immediately to the sauce. Cook for two to three minutes, as you stir, coating the spaghetti completely.
Add a tablespoon or two of tomato paste to thicken the sauce, stirring it along with the other tomato ingredients and giving it time to cook. Keep in mind that it might make your sauce taste too heavily of canned tomato. If it does, you’ll have to adjust the other seasonings accordingly.
Do not use flour or cornstarch to thicken the sauce. Flour will add a pasty consistency and taste that is inappropriate for a good, tomato-based sauce. Cornstarch will also add an off-taste to your sauce and won’t thicken well due to the acidity of the tomatoes. Save flour or cornstarch for gravies, Asian dishes and desserts.