Starch is a vital polysaccharide that serves as the primary energy storage molecule in plants. It is composed mainly of amylose and amylopectin and typically appears as a white, granular, tasteless powder that is insoluble in cold water or alcohol. Its general chemical formula is (C₆H₁₀O₅)_n.

Molecular Structure

Starch consists of two glucan polymers: linear amylose (20–25%), linked by α-1,4 glycosidic bonds, and branched amylopectin (75–80%), which includes additional α-1,6 branch points. These polymers form semi-crystalline granules whose characteristics vary by plant source. For example, wheat starch exhibits disk-like A-type granules larger than 15 μm, while potato starch contains granules ranging from 10–100 μm. Amylopectin is the primary driver of granule architecture, and even high-amylose starches generally do not exceed ~60% amylose to maintain structural integrity.

Physical and Functional Properties

Starch exhibits a range of functional properties, including high viscosity, swelling capacity, iodine-binding, and gelling behavior—each influenced by the amylose-to-amylopectin ratio. It functions as a thickener, emulsifier, and stabilizer in various applications. Properties such as gelatinization, retrogradation, and freeze–thaw stability can be enhanced through specific modifications. In native form, starch contributes moisture retention and anti-staling effects in food products.

Modifications and Industrial Uses

Physical, chemical, and enzymatic modification techniques are widely used to improve starch functionality, such as reducing oil uptake, enhancing stability, or producing sweeteners like maltodextrin and fructose. Modified and native starches find extensive use in the food industry—including bakery products, sauces, dairy applications, and confectionery—as thickeners, stabilizers, and bulking agents. Beyond foods, starch is also utilized in non-food industries as a binder, encapsulant, and moisture-control agent. In processed meats, soups, and frozen foods, modified starches play key roles in improving texture and controlling water retention.