Cascade control of HTST milk pasteurization process with and without pre-cooling stage

The milk pasteurization is a multivariable interacting process where it is required to maintain the temperature profile of the milk precisely at each stage to inactivate the bacteria as well as to retain the nutritional content of the milk. The existing methodology involves the use of a pre-cooling stage which adds up considerable cost to the milk pasteurization plant. The objective function of the proposed work aims at reduction of the cost involved which is achieved by eliminating the pre-cooling stage. Individual cascade controllers have been designed to maintain the temperature of the milk at heating and cooling stages of the milk pasteurization process at optimum levels. Simulink models developed for the milk pasteurization plant with and without pre-cooling stage have been analyzed and compared. The obtained results proved that it is possible to maintain the performance of the milk pasteurization plant, even after eliminating the pre-cooling stage with slight increase in the speed of the compressor.