Effectiveness of supercooled freezing in suppressing ice recrystallization during frozen storage

Ice recrystallization often occurs during frozen food storage, an undesirable occurrence that can cause further damage to food cells and tissues. One factor that triggers its occurrence is the initial structure of the ice crystals formed during the freezing phase. During frozen storage, small ice crystals may recrystallize due to their high surface-to-volume ratio and excess free energy. In this study, the ice recrystallization of supercooled frozen tofu was evaluated during a 12-week frozen storage period and compared with that of slowly and rapidly frozen tofu. The storage temperature was at − 10 ± 2 ℃. Slow freezing at − 10 ℃ static air has produced large crystals up to 0.6 mm before storage and tended not to grow further. Rapid freezing at − 80 ℃ static air with elongated ice crystals exhibits the highest recrystallization rate, especially on the surface of the sample, where the maximum ice crystals grew from 0.23 mm before storage to 0.45 mm after 12 weeks. Supercooled freezing has produced small and homogeneous ice crystals, the largest being 0.15 mm, but their spherical shape tends to have a low affinity for recrystallization, which has allowed the crystals to maintain their size and structure during the frozen storage.