61A-13 |
Glass transition of amorphous trehalose-sucrose mixtures |
K. D. ROE and T. P. Labuza. Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, MN 55108 A great deal of experimental data has shown the glass transition temperature (Tg) of trehalose to be higher than that of sucrose, although the degree to which this is true is not well-agreed upon. The variance of reported dry Tgs for both sucrose and trehalose is most likely due to considerable plasticization effect small amounts of moisture has on this property. Little data, however, has been reported on the glass transition of sugar mixtures at various moistures, and no work as yet has been done on sucrose-trehalose mixtures in this regard. We propose that the presence of trehalose in high-sucrose foods will significantly raise the glass transition temperature and lower the rate of sucrose crystallization, which has been thought to effect the texture and shelf-life of food products. Our objective was to quantify Tg values for a range of amorphous sucrose-trehalose mixtures at various moisture contents. Samples were freeze-dried under vacuum and then placed in desiccators over various saturated salt solutions for humidification. Differential scanning calorimetry was used to obtain Tg values for all mixtures and pure sugars. Glass transition of pure dry trehalose was found to be 106º C, while sucrose had a Tg of 60º C. Glass transition, as expected, occurred at an intermediate temperature for sucrose-trehalose mixtures. Of the dry samples, only those containing less than 16% trehalose crystallized during scanning. These data show that trehalose may indeed be a useful crystallization inhibitor in foods with high sucrose content, although small amounts of trehalose did not significantly raise the Tg. Since trehalose is roughly half as sweet as sucrose, and more expensive, mixtures of less than 20% trehalose are of special importance to practical applications. Therefore it is significant to see the most profound crystallization effect of mixing occurring in this region.
Session 61A, Carbohydrate
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