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Thermophysical properties of model systems of hydrocolloids and sugars

Thermophysical properties of model systems of hydrocolloids (0.6% of guar or xanthan) and sugars (30, 40, 50% trehalose or sucrose) were studied with differential scanning calorimetry (DSC). DSC scans were used to determine behaviour of model systems in temperature range (from - 60 °C to 140 °C), i.e. as a base for determining onset and midpoint glass transition temperatures (Tgo and Tgm), change of specific heat capacity (Δcp), melting temperatures (Tmo - onset, Tmp - peak and Tme - endset) and enthalpy of melting (ΔHm). Samples were investigated with the two different methods, depending on starting temperature of measurement (25 °C or -60 °C). Tg, Tm and ΔHm values decreased as the sugars concentrations increased, which is more pronounced in samples with sucrose. For example, Tgm in model systems of xanthan and trehalose decreased for 2 °C with increase of trehalose amount. In guar samples with addition of trehalose these decrease was 1.3 °C. In the systems with addition of sucrose decrease was 6.2 °C and 6.7 °C, for xanthan and guar, respectively. There were no significant differences in the DSC parameters between investigated hydrocolloids.

guar ; xanthan ; trehalose ; sucrose ; thermophysical properties

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