Effects of different freezing methods on the damage in potato tissues impregnated with trehalose

In this study, four freezing methods were evaluated: −40 °C contact plate freezing (−40°C-CPF), −80 °C contact plate freezing (−80°C-CPF), liquid nitrogen freezing (LNF), and vacuum freezing (VF). Potato slices treated with trehalose impregnation underwent freeze-thaw experiments to compare their freezing characteristics, water status, cell activity, and microstructure. The treatment/control groups were denoted as −40°C_Tre/CK, −80°C_Tre/CK, LNF_Tre/CK, and VF_Tre/CK, respectively. The results showed that the addition of trehalose significantly increased the freezing rate of VF, while VF had greater freezing damage. The −40°C_Tre sample had a lower drip loss, a lower relative electrical conductivity, and a greater hardness. After freeze-thawing, the change in the peak area proportion of the −40°C_Tre sample was found to be minimal, which was beneficial for the retention of water, as evidenced by low-frequency nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) analyses. Observing the microstructure, it was found that the cell structures of the −40°C_Tre sample was relatively complete, with good preservation of cell wall morphology. In addition, the presence of cell membranes was clearly observed in the −80°C_Tre and LNF_Tre samples. Under freezing conditions of −40°C-CPF, potatoes treated with trehalose showed minimal freezing damage.