Effect of immersion freezing on water migration in Huangguan pears

The effect of immersion freezing on water distribution and calcium ion migration in pears was studied. The samples were frozen at -20 °C and -40 °C. Results showed that the -40 °Ccombined immersion freezing (-40IF-T) was better in inhibiting sample browning and sensory quality, compared with other groups. Water activity and freezable water content were closer to that of the unfrozen sample. Compared with -20IF, the freezing time of -40IF-T was reduced by 74.90%. Both the drip loss and calcium ion content showed that -40IF-T was better than other groups. Low-field nuclear magnetic resonance results showed that -40IF-T reduced water migration during freezing, indicating a more uniform distribution of water in -40IF-T tissues. The results of relative conductivity showed that -40IF-T could effectively reduce the damage of cell membrane caused by freezing. In conclusion, low temperature and cryoprotective fluid can be used as effective methods to maintain sample quality.