Thermal evaluation of sucrose-maltodextrin-sodium citrate bioglass: Glass transition temperature

Sucrose-maltodextrin-sodium citrate (SC-MD-NaCit) bioglass model systems were studied using modulated differential scanning calorimetry (DSC) to test the hypothesis that addition of salt to a complex amorphous carbohydrate system at low level of moisture content will significantly affect its glass transition properties. Samples were formulated with different SC/MD ratios (7: 3, 5: 5 and 3: 7, by mass) and NaCit/SC ratios (0, 0.1 and 0.2, by mole) and two levels of residual moisture content, low (0.27 -0.35%wb) and high (2.83-4.40% wb). The glass transition characteristics of these systems were strongly dependent on the moisture content and other constituents. On average, glass transition temperature (T-g) of the 7: 3, 5: 5 and 3: 7 SC/MD systems were approximately 77, 84 and 101 degrees C, respectively. The T-g values tended to increase when NaCit was added, with a noticeable increase occurring in the 7: 3 SC/MD system at low moisture content. The increase in moisture content from low to high level had a significant plasticization effect on the bioglass as elucidated based on the decrease in the T-g from approximately 106 to 67 degrees C. The DSC thermograms suggested that water molecules may interfere with intermolecular interactions between the glass-forming molecules causing changes in the molecular mobility of the bioglass matrix. The findings reveal that addition of NaCit can enhance the stability of low-moisture bioglass by primarily interacting with SC and forming large, less-mobile clusters, which helps to improve the T-g and restrict matrix mobility. (C) 2016 Elsevier Ltd. All rights reserved.