Dairy processing: Aseptic processing and packaging systems
Regeneration section

General conditions

Since the physical distance between the various liquids in the sterilization plates or tubes is extremely small, the liquids have the potential to move through the plates or tubes and cross-contaminate the product if pin holes, cracks or leaks exist.

• The plates or tubes are of sanitary design, constructed of stainless steel or other corrosion resistant material, and are without pin holes, cracks or leaks
• The plates or tubes are clean with no presence of milk remnants, milk-stone, mineral scale build-up, or foreign materials
• If plates are used, the plate gaskets are equipped with leakage grooves and are not compressed or otherwise showing signs of wear
• Establish a routine program to monitor the condition of plates and tubes (for example, pin holes, gasket condition, cracks), taking into consideration the design specifications, operating conditions and hours of operation, wear and the history of the plates and gaskets
• Check the integrity of all food contact heat exchange surfaces at least once per year (for example, dye recirculation, dye check, pressure retention, helium testing)
  • if there are problems with heat exchanger integrity (plate or gasket issues), implement a more frequent inspection program to verify that the problem has been remedied
  • if pin holes are found in any plate in any section, check all plates in the same section
  • document the cause of any failure (for example, age, compression, metal fatigue)
• Keep records to show testing has occurred

Pressure differentials

• Maintain the pressure on the sterilized side of the regenerator at least 14 kPa (2 psi) higher than on the raw or heat transfer medium side of the regenerator during the following conditions:
  • forward flow
  • divert flow
  • shutdown

This protects the sterilized milk side of the system since sterilized product will leak into the raw milk (or heat transfer medium) in the case of regenerator plate (or tubular) failures.

• In "milk-to-heat transfer medium-to-milk" type regenerators:
  • use a safe source for the heat transfer medium (for example, potable hot water)
  • locate the pressure sensors for these controls:
    • at the heat transfer medium inlet on the aseptic side of the regenerator
    • at the sterilized product outlet of the regenerator

Failure to maintain the required pressure differential in the sterilized milk section of the regenerator causes the flow diversion device to assume the divert flow position.