Fundamental knowledge of physical state of materials gives practically important information for food, biological and pharmaceutical industry. Based on Williams-Landel-Ferry (WLF) equation, the strength concept was introduced. This concept provides a simple parameter, S, to express resistance of solids to flow above the glass transition temperature. To develop this approach, miscible trehalose-maltodextrin (0:100; 20:80; 40:60; 60:40; 80:20 and 100:0) systems with different ratios of components were used in the present study. Such systems represent various food products including infant formula and many nutritional formulations. Amorphous solids were prepared from 20% solids in water solutions by freeze-drying. Fractional water sorption analysis of trehalose-maltodextrin miscible systems allows control of water content at high water activities. Glass transition temperatures were measured by DSC. DMA and DEA in a multi-frequency mode allowed determination of corresponding α-relaxation temperatures at various structural relaxation times. Volume rheology gives structural relaxation time - temperature dependence for high water content systems. The strength showed linear dependence on maltodextrin concentration and its value decreased significantly with increasing water content in miscible systems.
Keywords: Maltodextrin; Structural relaxation; Trehalose; WLF; “Strength” parameter.
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