Abstract:

The content of freezable water in frozen wet gluten was determined by means of differential scanning calorimetry （DSC） to reveal the thermodynamic mechanism of ice crystallization during the ultrasonic-assisted food freezing. The shape and size distribution of ice crystals in the frozen wet gluten were also studied by means of scan- ning electron microscopy. It is found that  the freezable water contents （relative to the total water content） of wet gluten frozen respectively with an ultrasonic-assisted process respectively at 360 W, 440 W and a liquid nitrogen freezing process, namely 67.3% , 70.8% and 77.0% , are higher than that with the traditional freezing process （56. 9% ） ;  the samples frozen in different conditions are of different thermodynamic characteristics;  ultrasonic with suitable power accelerates the freezing of wet gluten and weakens the interaction between gluten and water molecules;  both the ultrasound-assisted and the liquid nitrogen freezing processes result in well-distributed ice crystals with a small size less than 4 μm, thus reducing the deterioration of gluten network ; and  as compared with the liquid nitrogen freezing process with high energy consumption, the ultrasound-assisted freezing process is more practical for food quality improvement.

Key words: wet gluten, ultrasonic, freezing, ice crystal, freezable water