The Alginate Demonstration: Polymers, Food Science, and Ion Exchange
submitted by: Amy Sue Waldman, Linda Schechinger, Geeta Govindarajoo, and James S. Nowick Department of Chemistry, University of California at Irvine, Irvine, CA 92697-2025
submitted by: Louis H. Pignolet Department of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431
Checked by: Ted Labuza Department of Food Science and Nutrition, 136 ABLMS University of Minnesota, St. Paul, MN 55108
We have recently devised a polymer demonstration involving the crosslinking and decrosslinking of alginate, a polysaccharide isolated from seaweed. The polymer is composed of D-mannuronic acid and L-guluronic acid subunits and is a component of cell walls. It is commonly used as a thickener in foods such as ice cream and fruit-filled snacks. For the demonstration, a 2% solution of sodium alginate is poured into a 1% solution of calcium chloride. Nontoxic calcium alginate "worms" form due to crosslinking of the polymer. Alternatively, the commercially available antacid Gaviscon can be used as a source of sodium alginate. The crosslinks can then be broken by shaking the worms in brine. The demonstration is a fine addition to any chemical educator's repertoire of polymer experiments.
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Waldman, Amy Sue; Schechinger, Linda; Govindarajoo, Geeta; Nowick, James S.; Pignolet, Louis H. J. Chem. Educ.1998 75 1430.
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