Enthalpy relaxation of freeze concentrated sucrose-water glass.
The enthalpy relaxation of freeze concentrated sucrose-water glass was investigated using 40% sucrose, differential scanning calorimetry (DSC) with isothermal ageing for 1-6 days at various temperatures (-70, -65, -60, and -55 degrees C). The enthalpy relaxation was observed as an endothermic peak superimposed on the endothermic step-wise change due to the glass transition around -47 degrees C. The enthalpy relaxation was found to increase with ageing time and temperature. An 80% sucrose glass was also investigated at ageing temperatures of -60 and -65 degrees C, and this material exhibited a similar glass transition and enthalpy relaxation to that observed with the frozen 40% sucrose solution. The calculated activation energy of the enthalpy relaxation of the sucrose-water glass was smaller than that reported for pure sucrose. These results suggest that the freeze concentrated sucrose-water glass could have a higher molecular mobility and less stability than pure sucrose glass.
Inoue
Chiharu
C
Unilever R&D Vlaardingen, Olivier van Noortlaan 120, 3130AC Vlaardingen, The Netherlands. Chiharu. Inoue@unilever.com
Suzuki
Toru
T
D002152:Calorimetry, Differential Scanning; D005615:Freezing; D013395:Sucrose / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D014867:Water; D013395:Sucrose