Modulation of ice crystal formation behavior in pectin-sucrose hydrogel by freezing temperature: Effect on ice crystal morphology and drying properties

A model solid food system was designed to investigate the effects of freezing temperature on freezing rate, ice crystal morphology, physical properties, and drying characteristics of freeze-dried pectin cryogels. The results indicated that the fractal dimension of ice crystals was significantly reduced in gels while the mean diameter and the diameter range tended to increase as the freezing rate accelerated. The drying time is positively correlated with the fractal dimension and negatively correlated with the proportion and the mean diameter of the ice crystal. Slow freezing (at 20 °C) produced large ice crystals (0.3 mm) with a low fractal dimension (1.662), resulting in a short drying time (9.46 h) and low hardness (max positive force and positive area were 436.69 g and 717.79 g mm, respectively). This study provides reference data that could help increase freeze-drying efficiency and improve the texture quality of food products.