Jay-lin Jane

　　Department of Food Science and Human Nutrition

　　Iowa State University, Ames, Iowa, USA

　　Starch is the second largest biomass next to cellulose produced on earth and is the major energy source for food, feed, and industrial applications.  Starch consists of two major types of glucan, amylopectin and amylose, and is synthesized in granular form with semi-crystalline structures.  Starch isolated from a specific botanical source consists of characteristic morphology, amylose content, amylopectin branch-chain length, phosphate monoester derivative, and lipid content.  Diameters of starch granules vary from sub-microns to ca. 100 microns, and the shape of starch granules can be spherical, oval, polygonal, lentil (disk), kidney, and elongated.  Thus, the starch displays characteristic functional properties and is desirable for selected applications.  In addition to be consumed in rice, wheat, and potato, as an energy source for human and animals, isolated starch is conventionally used in the paper industry, as a sizing agent and a binding agent, in the textile industry, as a sizing agent, and in the food industry, as a thickening agent, a texturizer, a carbon source for fermentation, and an anticaking agent.

　　Depending on unique granular structures, chemical compositions, pasting and gelling properties, and enzyme digestibility, starch has been developed for other innovative applications.  Examples are as follows:

　　Carbonless copy paper – Large A-granules of wheat starch have a disk shape.  The disk shaped starch granules can protect carbon beads in carbonless copy paper.

　　Fat replacement and instant sizing agent – Small-granular starch, such as amaranth starch and small-particle starch made from hydrolysis and attrition of common starch, which have dimeters around 2 microns, gives a mouth feeling resembling fat micelles and is also suitable for instant sizing agents.

　　Starch films and molded products – High amylose maize starch with chemical modifications can be blowing extruded into films that display good mechanical properties and can stop oxygen penetration as a packaging material.

　　Resistant starch – High-amylose cornstarch and/or its fatty acid complex, chemically modified starch, and retrograded starch are resistant to enzyme hydrolysis.  Ingesting foods made from these starches can reduce the glycemic response, prevent Type-2 diabetes, and prevent colon cancer.