Block freeze concentration intensification by means of vacuum and microwave pulses

Abstract

Block  freeze  concentration  has  gained  interest  as  a  separation  technology  since  it  is  simpler  than  the  suspension  process. However, it has not been implemented at an industrial level because its separation efficiency is lower than that of the traditional freeze concentration process. Therefore, numerous assisting techniques are being studied around the world to overcome this deficiency. In this paper, the combination of microwave heating and vacuum separation is being studied and compared with convection heating and gravity separation. Separation efficiency was measured using the cumulative concentration factor (CumCI) and the area under the curve defined by yield (Y) as a function of the thawed fraction (f). It has been observed that all treatments that used vacuum as separation method showed a higher efficiency than those in similar processing conditions that used gravity as the separation method. Regarding the effect of microwave pulses, it has been observed that pulses below 2.4 kJ increased the separation efficiency when combined with the hydrodynamic effect generated by the vacuum pulses.