Vapour Pressure above the Glassy Trehalose Solution and Glass Relaxation.

BACKGROUND: Data are scarce on thermophysical properties of the glassy trehalose solution at low temperatures. OBJECTIVE: Water vapor pressure above the glassy trehalose solution and the relaxation behavior were studied at temperatures from -57°C to -40°C and at concentrations from 71% to 78% (w/w). MATERIALS AND METHODS: Glassy trehalose solutions were prepared by quenching in liquid nitrogen. Vapour pressure was measured using the static method. RESULTS: Vapour pressure above the glassy trehalose solution was slightly lower than above the glassy sucrose solution. The relaxation of the glassy state can be described by the stretched exponential Kohlrausch-Williams-Watts (KWW) function. The characteristic times of water relaxation (Τp) were compared with those of enthalpy relaxation (Τe). When the difference (∆T) between the glass transition temperature (Tg) and ageing temperature was relatively small, i.e. ∆T ≤ 10 K, Τp is close to Τe. If ∆T ≥ 15 K, Τe will be much greater than Τp. CONCLUSION: The difference of water vapor pressure above the trehalose glassy solution and sucrose glassy solution could lead to significant distinction between their drying kinetics.