Modification of Starches

Starches are inherently unsuitable for most applications and, therefore, must be modified chemically and/or physically to enhance their positive attributes and/or to minimize their defects. Starch derivatives are used in food products, in papermaking, as adhesives, for warp sizing of textiles, and for glass fiber sizing. Modified starches are used in tableting and cosmetic formulations. The properties required for a particular application, availability of the starch, and economics play an important role in selecting a particular native starch for subsequent chemical and/or physical modification. Chemical modification of starch generally involves esterification, etherification, or oxidation of the available hydroxyl groups on the α-D-glucopyranosyl units that make up the starch polymers. While these methods allow higher substitution, salts and modifying reagent by-products remain in the final product. Chemical modification provides improved stability and film-forming properties to partially-degraded starches used in paper surface sizing or coating, textile warp sizing, and adhesives. In food applications, these modifications can be combined with crosslinking treatments to provide a range of products with a range of properties. Starch polymers are often partially depolymerized to produce products that generate less viscosity on cooking a unit weight of starch; such products are known as fluidity or thinned starches.