Ultrasonic freezing of polymers of various compositions before freeze drying: Effect of ultrasound on freezing kinetics and ice crystal size

The process of freezing (crystallization under cooling) is the preliminary preparation of samples for vacuum freeze drying. At this stage, the structure of the product is formed, which depends on the size of the resulting ice crystals. One of the most interesting and cost-effective ways to intensify the freezing stage and controlled nucleation is ultrasonic treatment. The effect of ultrasound with a power of 50 W and a frequency of 40000 Hz on the freezing kinetics and ice crystals size distribution were studied for polymers of various nature: sodium alginate, chitosan, polyvinyl alcohol, and a cross-linked polyelectrolyte complex of alginate-chitosan. Cryoscopic temperatures for these polymers were determined. A mathematical model for calculating the kinetics of freezing and size distribution of ice crystals was implemented in Python.