The Alginate Demonstration: Polymers, Food Science, and Ion Exchange

Louis H. Pignolet
Department of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431
Amy Sue Waldman , Linda Schechinger , Geeta Govindarajoo and James S. Nowick
Department of Chemistry, University of California at Irvine, Irvine, CA 92697-2025
Ted Labuza
Department of Food Science and Nutrition, 136 ABLMS University of Minnesota, St. Paul, MN 55108
J. Chem. Educ., 1998, 75 (11), p 1430
DOI: 10.1021/ed075p1430
Publication Date (Web): November 1, 1998

Abstract

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.

Keywords (Audience):

High School / Introductory Chemistry

Keywords (Domain):

Demonstrations

Keywords (Feature):

Tested Demonstrations

Keywords (Subject):

Food Science
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History

  • Received: August 03, 2009

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