Corn Starch

About This Product

Corn starch, also called maize starch, is extracted from the endosperm of Zea mays by wet milling, in which the steeped grain is separated into starch, protein, fibre and germ. It carries CAS number 9005-25-8 and is supplied as a fine white powder. Chemically it is a mixture of two glucose polymers: amylose, a largely linear chain making up roughly a quarter of the starch, and amylopectin, a highly branched molecule making up the rest.

In its native state the starch is packed into semi-crystalline granules that are insoluble in cold water. Heating a suspension past about 62 to 72 degrees Celsius breaks the hydrogen bonds holding those granules together; they absorb water, swell dramatically and eventually rupture, releasing the polymer chains into solution. That process, gelatinisation, is what thickens a sauce, and it is irreversible. On cooling and standing the linear amylose chains realign and force water out again, a second process called retrogradation, which is why a starch-thickened sauce becomes cloudy and weeps on refrigeration and why bread goes stale. Prolonged heating, high acidity or shear will break the chains and thin the system.

It is used as a thickener in soups, sauces, gravies and desserts, in bakery and confectionery, as a binder and dusting agent, and as feedstock for glucose, maltodextrin and modified starches.

Bio Green Foods supplies food-grade corn starch to specification on moisture, starch content, protein, ash, pH, whiteness and sulphur dioxide.