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  Home > JCE Print > Journal of Chemical Education > Issues > 2000  > August  >
Chemistry for Everyone
The Other Double Helix--The Fascinating Chemistry of Starch
Robert D. Hancock and Bryon J. Tarbet
Research Department, Power Engineering, 364 West 600 North, Salt Lake City, UT 84301
Cover
August 2000
Vol. 77 No. 8
p. 988
Abstract
Current textbooks deal only briefly with the chemistry of starch. A short review with 21 references is presented, describing the structure of starch and indicating the double helix structure of A-type and B-type starch. The structure of the starch granule is examined, pointing out the existence of growth rings of alternating crystalline and noncrystalline starch, with growing amylopectin molecules extending from the hilum (point of origin) to the surface of the starch granule. The swelling of starch granules in water, above the gelatinization temperature of about 60 °C, is discussed. The process of gelatinization involves unraveling of the starch helix and a manyfold increase in volume of the starch granule as water is imbibed and bound to the unraveled starch polymer by hydrogen bonding. Baking bread or pastries causes unraveling of the starch helix, and the process by which these products become stale corresponds primarily to the re-forming of the starch helix. The importance of this phenomenon in food science is discussed. The absorption of nonpolar linear molecules such as I2, or linear nonpolar portions of molecules such as n-butanol or fats and phospholipids, by the C-type helix of starch is examined. The way in which starch is structurally modified to retard staling is discussed in relation to food technology.
More Information
*  Citation
 Hancock, Robert D.; Tarbet, Bryon J. J. Chem. Educ. 2000 77 988.
*  Keywords
 Bioorganic Chemistry; Carbohydrates; Food Science; Organic Chemistry; Stereochemistry; Introductory/High School Chemistry
*  History
 Created:
Last Updated:		 July 5, 2000
April 15, 2005
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