Starch is a long chain of sugar molecules linked together. Starches we commonly use in the kitchen come from wheat (flour), corn (cornstarch), potato, arrowroot, and cassava (tapioca). When we add starches to liquids, they absorb water. When we apply heat, the starch granules swell and then burst, causing the release of more starch molecules into the liquid; thickening then occurs. You should not add starches directly to hot liquids. The edges of the starch will immediately gelatinize and form lumps. Thus, you should make most starches into a slurry with a small amount of cool liquid and then add it into the hot liquid.
Flour, cornstarch, and tapioca are the most common starches used for thickening sauces, gravies, puddings, and pie fillings. Starches begin to thicken around 140 degrees F. Flour and cornstarch have a high percentage of amylose, which must be boiled for three minutes to remove the raw starch flavor. Flour continues to thicken as it cools so stop cooking gravies and sauces at slightly less than their ideal consistency. Tapioca and other root starches have a high percentage of amylopectin, which thicken well without boiling. Different starches also start to lose their thickening ability depending on the amounts of heat, agitation, and acids, such as lemon juice, wine, and vinegar, which are added to the recipe. Each thickening agent also differs in its clarity, cooking characteristics, and whether they freeze and thaw well.
Flour is the most commonly used thickener. White, all-purpose flour has a higher starch content than other wheat flours, so it provides the best thickening action. However, because flour contains protein and other compounds, it has about half the thickening power of other starches. The proteins in flour make flour-thickened sauces and pie fillings look cloudy. White sauces, simple pan gravies, beef stew, chicken and dumplings, and apple pie thicken nicely with flour.
Cornstarch is a pure starch derived from corn. Cornstarch particles literally soak up the liquid and expand. You should use it also by creating a slurry first to prevent lumping and for one minute to prevent a chalky flavor. It can withstand prolonged cooking and stirring before it begins to break down. It’s frequently used for thickening pastry cream, cream pie and berry fillings, puddings, and delicate sauces. Cornstarch-thickened sauces give a translucent shimmer or an opaque quality to sauces. Cornstarch does not work well with acidic ingredients or dishes that will be frozen.
Potato starch is made from a potato variety with a very high starch content. The starch is extracted from potato pulp with tap water. Then it is dried to a powder. It is naturally white in color and thickens quickly without a pronounced flavor. It is a great fix for too-thin sauces or for people with a wheat allergy or sensitivity.
The root of the cassava plant produces the pure starch of tapioca, also known as tapioca flour. Tapioca pearls are also available. Follow the directions for use on the label for best results. Tapioca-thickened pie fillings are crystal clear and have a more jelly-like consistency. Because it thickens juices faster than flour or cornstarch, it is great for all fruit pies. Because tapioca holds liquid, the pie filling will not weep when frozen and thawed. Thus, tapioca is great for pies that will be frozen and reheated.
Arrowroot powder comes from the root of a plant of the same name. Because the starch granules are very small, arrowroot makes very smooth sauces when added to hot liquids as a slurry. It can withstand long cooking at moderate temperatures and forms a clear sauce. It thickens at lower temperatures, so it can be used at the end of cooking. High temperatures may cause it to lose its thickening ability. Arrowroot can thicken sauces, gravies, soups, jams, and pie fillings. It creates flaky, moist, baked goods. Products thickened with arrowroot freeze well. It also works well with acidic ingredients but not with milk-based cream sauces because it may curdle the sauce.
Substituting one agent for the other does not always work well but here are some recommended amounts. 2 tablespoons of flour equals 1 tablespoon of cornstarch, which equals 1 tablespoon of tapioca, which equals 1 tablespoon plus 1 1/2 teaspoons of arrowroot, which equals 1 1/2 teaspoons of potato starch.
Source: Dr. Sandra Bastin, RDN, LDN, Extension Professor, Food and Nutrition Specialist
Social media post: Are you looking for ways to thicken your gravy, fruit pie, or sauce? We have answers and suggestions for using several different starches in your kitchen.
