Author
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Lawton Jr, John |
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Submitted to: Encyclopedia of Grain Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/28/2003 Publication Date: 12/1/2004 Citation: Lawton Jr, J.W. 2004. Native starch; uses of. Encyclopedia of Grain Science. 1-3:195-202. Interpretive Summary: Starch is the primary energy source in cereal grains and tubers. These starchy plants have always been an important part of the human diet and they provide 70 to 80% of the calories consumed by humans worldwide. Due to the abundance of these starchy materials, it is not surprising that other applications have been found for starch. Starch has a long history of nonfood uses with it first being described in papyrus paper making by the Egyptians. Today, starch uses include adhesives, binders, coatings, foams, fillers, flocculents, plastics, sizings, and viscosity modifiers. Commercial starches are obtained from corn, wheat, potato and casava. Corn is the predominant commercial starch, making up about 83% of the world supply. Of the wet milled cornstarch produced in the U.S., about 54% goes to sweetners, 27% goes to manufacture fuel alcohol, and 19% is used as starch. The largest user of starch is the paper industry, which accounts for over 60% of the starch use. Food use accounts for another 15% and other nonfood uses account for the rest. Starch use in paper is in three general areas: wet end sizing, surface sizing, and coatings. Large amounts of starch is also used by corrugated board manufactures as adhesives. Starch-based adhesives also are used for the manufacture of bags and sacks. Starch-based adhesives makeup approximately 60% of the natural adhesives market. Over the last twenty years, starch-based plastics have found uses in a variety of ways, such as packing materials, mulch films, and single use articles. In the food industry, starch's primary function is to control viscosity and is used to thicken and add texture to a variety of prepared foods, ranging from canned foods to puddings. This review summarizes the uses of commercial starches. Technical Abstract: Starch is used in the production of paper, corrugated board, adhesives, plastics, and in many processed foods. Starch can contribute to adhesion, binding, viscosity, film forming, and moisture retention. Starch is also an attractive industrial material because of its abundance, low cost, ease of modification, and renewability. The variation found in different sources of starch give it great versatility in its uses. Starch is deposited as granules in plants. The size and shape of these granules varies with its botanical source. The granule is comprised of two polymers of D-glucose, consisting of amylose and amylopectin. The ratio of amylose and amylopectin varies with the source. Some starches have been found that contain no amylose and others have been found that contain up to 70% amylose. Native starch granules are partially crystalline, with the amylopectin providing the crystalinity. Gelatinization is the process of disrupting the molecular structure within the starch granule as it is heated in the presence of water. During the gelatinization process, the viscosity is increased by the granules absorbing water and swelling. Pasting is the consequence of further heating after gelatinization. Additional heating causes the granules to become distorted, with soluble starch being released into the solution and eventually, total disruption of the granules occurs. Many applications of starch rely on the rheological and textural properties of the starch paste. Using starch as an ingredient requires that its functional properties of the starch match a particular application. This review will summarize the functional properties of different commercial starches and which industries use these starches. |
