Dairy Establishment Inspection Manual – Chapter 14 - Aseptic Processing and Packaging Systems
1.14.05 Regeneration

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The regenerator section on aseptic systems may either be of milk-to-milk or milk-to-heat transfer medium-to-milk type. The cold raw product is warmed by hot sterilized product flowing in a counter current direction on the opposite sides of thin stainless steel plates or tubes. The sterilized product will in turn, be partially cooled.

The basic requirements for the regeneration section are:

  1. That it is installed and operated in such a way that the proper pressure relationship exists between the raw product or media and sterilized product in forward and divert flow conditions
  2. Proper sanitary design and construction
  3. Clean and in good condition, with no cracks, pinholes or leaks

1.14.05.01 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 shall be of sanitary design, constructed of stainless steel or other corrosion resistant material, and must be without pin holes, cracks or leaks. The plates or tubes must be clean with no presence of milk remnants, milk-stone, mineral scale build-up, or foreign materials. If plates are used, the plate gaskets must be equipped with leakage grooves and must not be compressed or otherwise show signs of wear.

A routine program to monitor the condition of plates and tubes (pin holes, gasket condition, cracks, etc.) must be established by plants, taking into consideration the design specifications, operating conditions and hours of operation, wear and the history of the plates and gaskets. The integrity of all food contact heat exchange surfaces must be checked at least once per year by an acceptable method (e.g. dye recirculation, dye check, pressure retention, Helium Testing etc.). However, if the plant has experienced problems with heat exchanger integrity (plate or gasket issues), a more frequent inspection program must be implemented to verify that the problem has been remedied. Appropriate records must be kept to show proper testing has occurred. These records should also document the cause of any failure (e.g. age, compression, metal fatigue, etc.). If pin holes are found in any plate in any section then all plates in the same section should be checked.

1.14.05.02 Pressure Differentials

This task will only assess the differential pressure. The equipment used to monitor pressure (PDC recorder and gauges) will be assessed under the task Pressure differential recorder controllers (PDC recorder).

As previously discussed, raw milk or media and sterilized milk are separated in the regenerator section only by thin metal plates or tubes and a system of gaskets. In milk-to-milk type regenerators, the raw side of the regenerator must, at all times, be under lower pressure (at least 14 kPa or 2 psi) than the sterilized milk.

In milk-to-heat transfer medium-to-milk type regenerators, the sterilized milk section must be under greater pressure by at least 14 kPa (2 psi) than the heat transfer medium at all times. The protection is on the sterilized milk side of the system and is engineered to allow sterilized product to leak into the heat transfer medium in case of regenerator plate (or tubular) failures. In this type of system, the heat transfer medium (e.g. hot water) must be from a safe source. Locations of the pressure sensors for these controls are a) at the heat transfer medium inlet on the aseptic side of the regenerator and, b) at the sterilized product outlet of the regenerator. Failure to maintain the required pressure differential in the sterilized milk section of the regenerator shall cause the FDD to assume the divert flow position.

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