The water-glycine-sucrose system was studied by DTA and X ray diffract
ion at various cooling and heating rates. The following transitions we
re 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; devi
trification, which is the secondary crystallization of ice + beta-glyc
ine in water-rich samples, and sucrose + glycine crystallization in lo
w-moisture samples. The solid-liquid state diagram has been described
by polynomial approximations to the data describing the lines and surf
aces of the glass-transition, the mechanical glass-transition, and dev
itrification. Use of these data to describe the freeze-drying pathway
is presented. (C) 1994 Academic Press, Inc.