Continuous HTST pasteurization of liquid foods with plate heat exchangers: Mathematical modeling and experimental validation using a time–temperature integrator Original Research Article

The continuous thermal processing of liquid foods with a three-section plate heat exchanger (PHE), heat integration and a non-isothermal holding tube was modeled to derive the temperature history of the product and the lethality distribution. Sequential linear temperature changes were assumed along the process and plug-flow was considered with three options for residence time: space time (bulk velocity), experimental mean residence time and minimum residence time (theoretical or experimental). In order to validate and test the model, it was used to simulate the operation of a laboratory-scale plate pasteurizer processing an enzymic time–temperature integrator (TTI) at four temperature conditions (70, 75, 80 and 85 °C). Previous studies of residence time distribution and heat transfer in the equipment provided important parameters for the simulation. Predicted results of temperature distribution were in excellent agreement with experimental values and the simulated process lethality was close to the value assessed with the TTI. A case study showed the effect of the adopted residence time and the over-processing associated with a non-isothermal holding tube with tubular connections.