Sedat Sayar, Department of Food Engineering, University of Mersin, Ciftlikkoy, Turkey; Pamela J. White, Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa, U.S.A.
OATS: Chemistry and Technology, Second Edition
Pages 109-122
DOI: https://doi.org/10.1094/9781891127649.007
ISBN: 978-1-891127-64-9
Abstract
Starch is the major carbohydrate reserve in plant tubers and seed endosperm. It is found as granules, each typically containing several million amylopectin molecules accompanied by a larger number of smaller amylose molecules. These two polysaccharides, amylose and amylopectin, consist of chains of (1→4)-linked α-d-glucopyranosyl units in the 4C1 conformation. Amylopectin additionally contains α-(1→6)-linked branch points. Starch granules are relatively dense and insoluble and hydrate only slightly in cold water. Modern techniques enable starch to be extracted from a variety of agricultural crops with high yield and purity, making starch the most versatile raw material used within the food industry.
The main commercial cereal starches, including corn, rice, and wheat, have been the subject of many scientific and industrial studies since the eighteenth century. These studies have resulted in extensive utilization of starch in the food and other industries. Oat starch, however, was not explored in detail until the work of C. T. Greenwood's group in the mid-1950s and Paton's group after 1974. Understanding the morphology and functionality of oat starch is essential to achieving maximum use of this cereal. Oat starches have some special and unique properties that make them different from other starches, such as small granule size (Hartunian-Sowa and White 1992, Hoover and Vasanthan 1992), high lipid content (Gudmundsson and Eliasson 1989, Hartunian-Sowa and White 1992, Gibinski et al 1993), high relative crystallinity, and small amylose chain length (Wang and White 1994a, Hoover et al 2003). These properties make the use of oat starch possible in various commercial products. Oat groats have 40–60% starch (Paton 1977, Åman 1987, Hartunian-Sowa and White 1992, Doehlert et al 2001), with a recovery yield of 70–90% (Paton 1977, Hartunian-Sowa and White 1992, Hoover and Vasanthan 1992, Lim et al 1992a). Studies comparing oat starch with other cereal starches show that oat starch has an amylose content similar to that of wheat and corn starches (MacArthur and D'Appolonia 1979, Hartunian-Sowa and White 1992, Wang and White 1994b). Oat starch exhibits relatively high water absorption in baking tests and a low gelatinization temperature (55°C) (MacArthur and D'Appolonia 1979). Paton (1977), MacArthur and D'Appolonia (1979), and Wang and White (1994c) studied the pasting properties of the starch extracted from different oat cultivars and reported that the gelatinization curves were similar to those of other cereal starches, but cooked granules appeared more sheer sensitive than those of corn, wheat, or rice starch. Differences in the behavior of oat starches on cooling were also indicated. High viscosity developed rapidly, and the cooled gels were clearer and less susceptible to retrogradation than those of other cereal starches. Doublier et al (1987) and Gudmundsson and Eliasson (1989) reported that oat starch had higher swelling power than did other cereal starches.
