Abstract

Starch is the principal food reserve of plants and is commercially derived from grains and tubers. Starch is a mixture of two polysaccharides (glucans). The smaller of the two, amylose, is essentially a linear polymer composed of -D-glucopyranosyl units linked (). The larger polymer is amylopectin which contains ( linkages and ) branch points. These polymers occur naturally in small structures known as starch granules. Many of the chemical and physical properties of starch depend on its granular nature.

Starch hydrolysis leading to molecular fragments varying from large molecular weights down to small oligosaccharides and D-glucose may be accomplished by acids, enzymes, or a sequence of the two. Commercially important sweeteners, corn syrup and high fructose corn syrup, are produced by starch hydrolysis and in the case of HFCS its partial isomerization. Less severe acidic treatment produces acid-modified (thin-boiling) starch. Other common starch modifications include pregelatinized and oxidized starch.

Because of the high number of hydroxyl groups, starches may be chemically derivatized to produce hydroxyalkyl starch ethers, cationic starches, starch phosphates, and starch acetates. Depending on the derivative and the degree of substitution, these starches may have various food and nonfood uses. In foods they are used to thicken, gel, or otherwise control texture, whereas in nonfood uses they are important as sizing and finishing agents in both paper and textiles.