starchs

Starch refers to a family of carbohydrate polymers produced by plants as a way to store energy. In plants, starch is stored in specialized organelles called amyloplasts and exists as granules that vary in size. The two main components of starch are amylose (mostly linear chains) and amylopectin (highly branched). The proportion of these components, along with granule structure, determines properties such as gelatinization, viscosity, and digestibility. Starches are found in many staple foods, including corn, potatoes, wheat, rice, and tapioca (cassava). They also occur in other seeds and roots and are produced commercially from these sources.

When heated with water, starch granules undergo gelatinization: granules swell, amylose leaches out, and the paste thickens. Upon cooling, retrogradation can occur, leading to gel formation and possible syneresis. The functional properties of a starch are influenced by its botanical source, amylose-to-amylopectin ratio, and granule structure. Some starches are modified to improve stability under heat, shear, or freezing; examples include cross-linked, oxidized, or pregelatinized starches.

Starches serve as thickeners and texturizers in food products, as well as binders in pills and paper products. In nutrition, starches contribute digestible energy; portions vary in digestibility, and a portion known as resistant starch behaves more like dietary fiber in the digestive tract.