A multilayer freezer for freeze concentration of liquid milk

Abstract Over the past few decades, much progress has been made in the development of freeze concentration technology, and commercial freeze concentration plants have been established around the world. However, high costs still limit its use in many potential applications. A continuous, multilayer freezer was designed, constructed, and operated under different conditions. This process used a series of chambers, mounted as layers in a column, with individual coolant jackets for controlling ice crystal growth and heat removal. Mixing effects and specific gravity differences between ice and liquid concentrate generated a natural counter-current flow, providing suitable conditions for ice crystal growth and ice-liquid separation. The multilayer freezer was operated at different process conditions to evaluate operation efficiency. Both coolant temperature and stir rate influenced efficiency of ice crystallization, with coolant temperature having a larger influence. The results show that freeze concentration in the multilayer freezer was feasible for low concentration (10–17%) skim milk, but further research at the pilot-scale level would be required to develop this process to a commercial system.