Glass transition sucrose-water

Kouassi, K., Roos, Y.H. Glass transition and water effects on sucrose version in non-crystalline carbohydrate food systems. Food Res. Int. 34, 895-901, 2001... 

Kouassi K, Roos YH. Glass transition and water effects on sucrose inversion by invertase in a lactose-sucrose system. / Agric Food Chem 2000 48(6) 2461-2466. 

To illustrate this more quantitatively, consider the hypothetical sucrose example discussed by Ahlneck and Zografi [80]. Assuming that all the sorbed water is taken up by the amorphous portion of material, 0.1% total moisture would correspond to approximately 20%, 10%, 4%, and 2% moisture content in the amorphous material, respectively, for 0.5%, 1%, 2.5%, and 5% of amorphous solid. The glass transition temperatures for the amorphous portions... 

Chen, Y.H., Aull, J.L., and Bell, L.N. 1999. Invertase storage stability and sucrose hydrolysis in solids as affected by water activity and glass transition. J. Agric. Food Chem. 47, 504-509. 

Glass Transition Temperature (Tg) of Amorphous Sucrose versus Water Content... 

Table 1.6.1 Glass transition temperature Tg and crystallization temperature Tc for amorphous sucrose, trehalose, lactose, raffinose and amorphous sucrose in the presence of absorbed water...

Fig. 1.27.1. DTA measurement of a 24% sucrose-6% NaCI solution during slow rewarming after quick (200 °C/min) freezing. 1, Glass transition at = 78 °C 2, growth of crystals (exothermic) at =52 °C 3, increase of c water is formed between the crystals 4, ice melts at = 7 °C (Figure 1 from [1.25])...

Both lactose and sucrose have been shown to crystallize in an amorphous form at moisture contents close to the glass transition temperature (Roos and Karel 1991a,b Roos and Karel 1992). When amorphous lactose is held at constant water content, crystallization releases water to the remaining amorphous material, which depresses the glass transition temperature and accelerates crystallization. These authors have done extensive studies on the glass transition of amorphous carbohydrate solutions (Roos 1993 Roos and Karel 1991d). 

Maltodextrins of varying molecular weights are plasticized by water and decrease the glass transition temperature. Maltodextrins retard the crystallization of amorphous sucrose and at high concentrations totally inhibit sucrose crystallization (Roos and Karel 1991c). 

For example. Figure 7.2 shows the glass transition temperature versus water activity relationship for lactose, sucrose and mixtures of sucrose-fructose and sucrose-Amioca, demonstrating that Tg decreases with increasing water activity (Roos and Karel 199Id). 

Fig. 12 The effect of residual water on the glass transition temperatures of sucrose and trehalose. (From Ref...

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