STUDY OF THE SOLID-LIQUID STATE DIAGRAM OF THE WATER-GLYCINE-SUCROSE SYSTEM

The water-glycine-sucrose system was studied by DTA and X ray diffraction at various cooling and heating rates. The following transitions were the most distinctive of those observed during heating of the frozen and freeze-dried samples: the glass-transition, T-G, which is due to an abrupt change of heat capacity; the mechanical glass-transition (''ante-melting'') T-AM (T-AM > T-G), which is related to the appearance of viscous-flow in the amorphous phase, caused by its own weight; devitrification, which is the secondary crystallization of ice + beta-glycine in water-rich samples, and sucrose + glycine crystallization in low-moisture samples. The solid-liquid state diagram has been described by polynomial approximations to the data describing the lines and surfaces of the glass-transition, the mechanical glass-transition, and devitrification. Use of these data to describe the freeze-drying pathway is presented. (C) 1994 Academic Press, Inc.