Watery red sauce or runny Alfredo does not make for an appetizing plate of pasta. Thickening a pasta sauce is not complicated but it does require knowing which ingredients to grab and which to avoid.
For red sauce
A traditional spaghetti sauce should be thick enough to stick to the pasta no matter which style of noodle you are serving. A marinara will be thinner but a spaghetti sauce should have some backbone to it. Several add-ins can help to thicken the pasta sauce.
Tomato paste is probably the number one choice for most cooks when thickening a spaghetti sauce. Tomato paste is simply a concentrated paste of pureed seedless, skinless tomatoes. It has a very strong tomato flavor. When adding as a thickening agent be careful not to add to much as it can overpower your spices and may add too much acid to the sauce. Add a few spoonfuls at a time, stirring to thicken to the desired consistency. Adjust spices as needed.
Grated cheese like parmesan can also be a flavorful thickener. Add about one-half cup to the sauce and stir. Add additional tablespoons until you reach the desired thickness of sauce. Adding the parmesan will change the flavor a bit, giving the sauce a cheesier taste.
Instant tapioca is a great thickening agent that does not change the flavor of the sauce. Instant tapioca should be used instead of regular, as the tapioca beads in instant are smaller. When using instant tapioca as a thickener there will be a texture change to your sauce, as the beads will not completely dissolve in the sauce. To eliminate the grains or beads, simply blend in a food processor until powdery before adding to sauce.
Lean ground beef or ground turkey can also be used to thicken a red sauce. Many people enjoy a meaty pasta sauce over their spaghetti or penne pasta. However, if you prefer not to have the chunky texture the meat add-in brings, consider blending the warm sauce and cooked ground meat in the blender or food processor to smooth out the sauce. The meat will also add a change of flavor, a bit of savory. Ground pork or Italian sausage may also be substituted.
For Alfredo sauce
Alfredo sauce is butter, heavy cream and parmesan blended into a rich, smooth consistency. When cooking a quick pasta meal aided by prepared Alfredo sauce, it may be a bit runny. For a thicker sauce, consider added additional heavy cream. Add about one half cup, stir over a low heat until the sauce thickens. Another option is to add about three-ounces of cream cheese as a thickener. Be sure the sauce is hot before you add the cream cheese or it will be difficult to melt and blend in. Instant tapioca or more parmesan can also be added to Alfredo sauce the same as when added to red sauce.
Basic best sauce tips
No matter what kind of pasta sauce is cooking, the best and easiest way to thicken it is to cook it slowly on a low heat, uncovered. The key is no lid! If you put a lid on your sauce, condensation will form under the lid and drip down into the sauce making it watery. Slow cooking the sauce does not mean it will take hours for you to get dinner to the table either. Always begin your pasta sauce first. Get it to simmer, without a lid, and then finish preparing the other elements of your meal. By the time you finish everything else, the pasta sauce will be savory with the perfect thickness to grip any noodle.
Avoid thickening pasta sauces with flour or cornstarch. The flavors will end up funky if you try to use these thickeners.
Thickening a pasta sauce does not have to a kitchen mystery. Remember with most cooking tasks, patience is important. Even if you choose to add a thickening agent, a bit of simmering for the pasta sauce will ensure each time a tasty dish everyone will enjoy.