Ice-crystal formation during cooling and rewarming of concentrated sucrose solutions

The concentration dependence of ice-crystal formation during cooling and rewarming of sucrose solutions (51-72 wt%) was studied by differential scanning calorimetry and optical microscopy at cooling and heating rates of ±1.0-±3.0 °C/min. During cooling, ice crystals formed in solutions with concentrations of up to 60 wt%, but were not found in solutions with concentrations of ≥61 wt%. In contrast, ice-crystal at solution concentrations of 59-62 wt% during rewarming was irregular and accompanied by devitrification (T_d) and/or recrystallization (T_r). However, at ≥64 wt%, only devitrification occurred, and no ice crystals were formed at 72 wt% or higher. These results suggest that the T_d curve on the binary system state diagram exists at concentrations of ≥60 wt%, with concentrations of ≥64 wt% resulting in ice-crystal formation only via devitrification at -40 to -30 °C during rewarming at 3.0 °C/min.