33A-21 |
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Y. HUANG1, P. P. Singh2, J. Tang3, and B. G. Swanson1. (1) Dept. of Food Science & Human Nutrition, Washington State Univ., PO Box 646376, Pullman, WA 99164-6376, (2) Dept. of Food Science & Toxicology, Univ. of Idaho, Box 442201, Moscow, ID 83844-2201, (3) Dept. of Biological Systems Engineering, Washington State Univ., 213 L.J. Smith Hall, PO Box 646120, Pullman, WA 99164-6120 Commercially available gellan gums can be classified into two categories: high acyl (HA) and low acyl (LA) gellan. Most of the current studies focused on LA gellan, while the basic properties of HA gellan are not as well studied. Gelling temperature is one of the most important characteristics for food hydrocolloid gelling agents. The objectives of the study were to investigate the effects of Na+, K+, Ca++ and Mg++ cations on the sol-gel transitions of HA gellan dispersions, and to determine the gelling temperatures of HA gellan dispersions containing selected cations. Gelling temperatures of 1% HA gellan dispersions containing selected cations (monovalent cations, 10-200 mM; divalent cations, 2-80 mM) were determined using dynamic rheological analysis. Temperature ramp tests were used to determine the change in rheological properties (e.g. G’ and G”) with change in temperature from 98 ºC to 50 ºC for 1% gellan dispersions with selected concentrations of Na+, K+, Mg++ or Ca++. The gelling temperature of each gellan dispersion was identified as the intersection of the extrapolation of the rapidly increasing G’ and the temperature axis. Gelling temperatures increased with cation concentrations. Divalent cations exhibited greater effects on the gelling temperature than equivalent concentrations of monovalent cations, but the effect between the two different types of divalent cations or the two different monovalent cations were not significantly different. An equation based upon the assumption that the effects of cations on gelation mechanisms were additive fitted well with the experimental data (R2=0.98, standard error of prediction=0.58 ºC). Gellan gum is a novel polysaccharide food gelling agent secreted by microbes. Investigations on the properties of HA gellan are necessary to promote utilization of this bacterial polysaccharide in food and pharmaceutical industry.
Session 33A, Carbohydrate: General
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