A custom built ultrasound-assisted immersion freezer
(Ningbo Scientz Biotechnology Co. Ltd.) was used to carry out
the experiments. Schematic diagram of this immersion
freezer is presented in Fig. 1. A blend of ethylene glycol
(C2H6O2) and water (50%:50%, v/v) was used as immersion
fluid/coolant. Six piezoelectric transducers were evenly
attached to the bottom of the stainless steel freezer cavity
(30 cm 24 cm 25 cm) through which a continuous flow
(1 L min1) of coolant was maintained by a low temperature
circulation pump. Coolant level was maintained at 15 cm in
freezer cavity during each freezing run and the temperature of
the coolant was set at 25 C.