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Potato starch is a starch extracted from potatoes. It should not be confused with potato flour.
Potato starch is made by crushing high-starch potatoes and straining out the pulp to produce a liquid. The starch is extracted from the liquid and dried to produce powdered potato starch. This starch may sometimes be further treated to make "modified" potato starch, which has different properties from the standard unmodified potato starch most commonly available to consumers.
Potato starch is a fine white powder with an amylose content of about 22% and an amylopectin content of about 75-79%. When mixed with water and heated it thickens and forms a gel. When cooled, mixtures thickened with potato starch tend to remain viscous and flowing rather than stiff.
Compared to other common cooking starches, potato starch has a higher granule size. This makes it thicken quicker, although it is less fine in consistency. It also has a relatively low gelatinization temperature of 140-149°F (60-65°C), which contributes to its rapid thickening capacity. However, prolonged heating will reduce its thickening power and it should not be heated for long after it has thickened. Highly acidic mixtures can also decrease the thickening powder, and these will require more starch to thicken. Modified potato starch is generally more tolerant of pH changes and prolonged heat exposure.
Potato starch-containing gels tend to have a more neutral flavor than those thickened with cornstarch. They can also have a smoother mouthfeel than those thickened with grain-based starches.
Like many starches, potato starch can be used to thicken substances like soups, gravies, puddings, and sauces. It may also be incorporated into baked goods to modify their texture. Because it can bind more water than wheat starch, incorporating some potato starch in baked goods may make them easier to handle and slow the staling process. Potato starch is often incorporated into gluten-free flour blends to help compensate for the lack of wheat flour.
To prevent clumping, potato starch should be mixed with a neutral or cold liquid before heating.