Starch-based thickeners

Starch-based thickeners, like cornstarch, flour, arrowroot, and tapioca, are common agents that thicken liquids and foods by swelling with heat, creating web-like structures that trap water and fats, ideal for sauces, gravies, and desserts, often used in a slurry (starch mixed with cold liquid) to prevent lumps for a smooth finish.
Common Starch Thickeners
Cornstarch: A very efficient thickener, giving a glossy, translucent finish, used in slurries or rouxs.
Wheat Flour: Often used with fat to create a roux, it’s a popular everyday thickener.
Arrowroot & Tapioca: Gluten-free options that provide a clear, smooth texture and are great for fruit pies and sauces.
Potato Starch: Another root starch that thickens effectively, often used in gluten-free baking.
How They Work (Gelatinization)
Swelling: Starch granules absorb liquid and swell when heated.
Unraveling: Heat causes the granules to unravel and form a network.
Trapping: This network traps water and fat molecules, increasing viscosity (thickness).
Application Techniques
Slurry: Mix starch with a small amount of cold liquid (water, milk) first to prevent lumps, then whisk into hot liquid.
Roux: Cook flour with fat (butter, oil) before adding liquid; provides richness.
Beurre Manié: Knead raw flour and butter together and whisk into a sauce at the end.