9-2 |
Ice nucleating polysaccharides |
J. N. BEMILLER, Whistler Center for Carbohydrate Research, Purdue Univ., 1160 Food Science Bldg., West Lafayette, IN 47907-1160 Plants use different mechanisms for freeze and freeze-thaw tolerance. One mechanism involves synthesis of polysaccharides that inhibit ice crystal growth. Another involves synthesis of ice-nucleating polysaccharides. Examined for ice-nucleating activities were fluid samples from 4 species of giant senecio and 10 species of giant lobelia. The 4 most effective ice-nucleators were examined in detail. That some were modified pectins was indicated. The modified pectins secreted and impounded in the leaf rosettes of 3 of the 4 species were surprisingly similar. Fluids from Dendrosenecio brassiformis, Lobelia gregoriana, and L. deckenii contained two principal polysaccharides, with one fraction being essentially neutral and the other acidic. However, the most distinctive and effective polysaccharide was that from L. telekii which was composed of 77% galacturonic acid, the remaining sugars being similar to those in rhamnogalacturonans, but which chromatographed as a neutral polysaccharide, indicating a high degree of esterification.
Session 9, Function of carbohydrates in frozen and refrigerated foods
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