Amorphous state and delayed ice formation in sucrose solutions

TLDR

Differential scanning calorimetry was used to study phase transitions of amorphous sucrose and sucrose solutions (20–100 % sucrose), linking them to viscosity and delayed ice formation. Glass transition temperature decreases with increasing water content, while ice formation and freeze concentration raise apparent Tg; Tg can be predicted from component weight fractions, and the WLF relation describes viscosity above Tg; time‑dependent water crystallization above Tg and annealing of solutions with <80 % sucrose at –35 °C produce a maximally freeze‑concentrated state with a glass transition at –46 °C and ice melting at –34 °C, providing a useful state diagram for thermal behavior.

Abstract

Summary Phase transitions of amorphous sucrose and sucrose solutions (20–100% sucrose) were studied using differential scanning calorimetry, and related to viscosity and delayed ice formation. Glass transition temperature (Tg) was decreased by increasing water content. Ice formation and concurrent freeze concentration of the unfrozen solution increased apparent Tg. Tg could be predicted weight fractions and Tg values of components. Williams–Landel‐Ferry (WLF) relation could be used to characterize temperature dependence of viscosity above Tg. Crystallization of water above Tg was time dependent, and annealing of solutions with less than 80% sucrose at –35°C led to a maximally freeze‐concentrated state with onset of glass transition at –46°C, and onset of ice melting at ‐34°C. The state diagram established with experimental and predicted Tg values is useful for characterization of thermal phenomena and physical state at various water contents.