University of Sau Paulo
Laboratory Pasteuriser
Lab Pic
Lab Pic

Versatility of the laboratory pasteurizer expanded at the University of Sâo Paulo, Brazil

In the Food Engineering Laboratory of the University of São Paulo, Brazil, an Armfield FT43 Laboratory Pasteurizer unit has been in intensive use since its installation in 1998. Associate Professor Carmen Tadini of the Chemical Engineering Department originally acquired the FT43 unit for studying the pasteurization of orange juice. However, the unit has been used for several research projects and teaching purposes since then, as follows:

  • Study of the HTST pasteurization of orange juice, with respect to pectinesterase enzyme inactivation, sensorial quality of the product and determination of its shelf-life under refrigeration.
  • Study of the pasteurization of coconut water.
  • Study of heat transfer and pressure drop in plate heat exchangers.
  • Experimental validation of a configuration optimization method for plate heat exchangers.
  • Teaching to chemical engineering students the operation of pasteurization unit and clean-in-place procedures.
Though the FT43 was very versatile, the original unit received several modifications for expanding its capabilities: a chiller unit for supplying cold water to the cooling section of the exchanger, an additional holding tube for the coconut water processing and a higher flow rate pump for studying the heat transfer at higher Reynolds numbers. One of the most interesting modifications was a custom built set of manometers for measuring the pressure of the product stream at different points of the pasteurization process. The manometers allowed the monitoring of the pressure drop at different sections of the plate exchanger and in the holding tube.

Moreover, a custom set of washboard-corrugated plates (similar to those used on the Armfield FT74 HTST/UHT unit) with gaskets, was manufactured by an MSc student as an alternative for the original Armfield flat plates. With these it was possible to study the heat transfer augmentation induced by the plate corrugations.

The FT43 Laboratory Pasteurizer unit contains a plate heat exchanger with heating, regenerating and cooling sections mounted on a common framework, a variable speed peristaltic pump connected to a feed tank, an electrically heated hot water circulating system, an insulated holding tube, six thermocouple sensors and a temperature data recorder, which was connected to a PC for monitoring the pasteurization process. With the supplied spare plates and gaskets, different configurations of the plate heat exchanger can be tested by varying the numbers of sections, plates, passes and channels per pass.

The raw product in the feed tank is pumped into the regenerating and heating sections of the exchanger to be brought up to the desired pasteurization temperature. Then, the hot product flows through the holding tube, where most of the thermal treatment occurs (inactivation of micro organisms and enzymes), and a divert valve returns it to the feed tank if the temperature at the end of the holding tube has not reached the required value. The pasteurized product then passes back through the regenerating and cooling sections of the exchanger where it is cooled to a suitable storage temperature.