Enthalpy relaxation in sucrose-maltodextrin-sodium citrate bioglass

摘要

Glass transition characteristics of sucrose (SC)-maltodextrin (MD)-sodium citrate (NaCit) bioglass system were investigated using differential scanning calorimetry. Samples were formulated with different SC:MD (7:3, 5:5 and 3:7 by mass) and NaCit/SC (0, 0.1 and 0.2 by mole) ratios, and were equilibrated to residual moisture contents of 0.27-035 %wb. Isothermal aging experiments were conducted with the degree of undercooling from 12 to 57 degrees C and aging times of 8, 20, 47 and 71 h. In general, the Kohlrausch-Williams-Watts (KWW) decay function fit well with the experimental enthalpy relaxation data. The enthalpy relaxation time ((KWW)(T)) and the time required for 50% completion of theoretical possible maximum enthalpy relaxation at constant temperature (t(phi(t)=0.5)) increased with increasing MD content; lowering the aging temperature had similar effects on (KWW)(T) and t(phi(t)=0.5). In the system with high SC and NaCit concentrations (SC:MD = 7:3 and NaCit/SC = 02), a substantial increase in (KWW)(T)and t(phi(t)=0.5) were observed when aging temperature decreased slightly; these systems also exhibited the greatest apparent activation energy. The findings reveal that NaCit can enhance the stability of low -moisture bioglass by primarily interacting with SC and form large less-mobile clusters, which helps to improve glass transition temperature and restrict the matrix mobility. (C) 2017 Elsevier Ltd. All rights reserved.