Dairy processing: Aseptic processing and packaging systems
Cooling section
This section of the sterilizer uses chilled water and /or glycol to cool the hot product down to packaging and filling temperature. Since the flow diversion device is located downstream from this section, the cooling section may become contaminated with potentially unsterile product during divert, and will need to be re-sterilized as part of the thermal limit controller sequence logic after a divert event.
Flash coolers are sometimes installed on the divert line to prevent injury to by-standers if a divert event occurs during the re-sterilizing of the holding tube and cooling section, when there is no cooling turned on.
General conditions
- Is clean and in good condition
- during operation, there are no leaks at gaskets, seals, or connections
- Is constructed of stainless steel or other corrosion resistant and easily cleanable material
- Has a design that allows easy cleaning, and does not entrap product in crevices, joints, seams or openings
- Establish a routine program to monitor the condition of plates and tubes (for example, pin holes in plates, gasket condition, cracks, tube clamps)
- if pin holes are found in any plate, check all plates of the same age
- Check the integrity of all food contact heat exchange surfaces at least once per year (for example by dye penetration, permanganate recirculation, pressure retention, Helium testing, etc.)
- if there are problems with heat exchanger integrity, implement a more frequent inspection program to verify that the problem has been remedied
- Keep records to show testing has occurred
- also document the age of all the plates and which ones are replaced, the cause of the holes (for example, age, compression, metal fatigue)
Pressure differentials
- Maintain pressure on the sterilized product side of the plates at least 14 kPa (2 psi) higher than on the cooling medium side of the plates during the following conditions:
- forward flow
- diverted flow conditions
- shutdown
This reduces the possibility of chemical contamination in the event a pinhole leak develops in the plates.
- Use an automated mechanism to achieve the correct pressure relationship
- Use pressure gauges that are clean and in good condition
- check gauges for accuracy upon installation and at least once per year
- Locate pressure differential controller sensors and pressure gauges at the cooling media inlet and at the sterilized product outlet
Cooling medium
- Check cooling medium (usually sweet water or water-glycol mixture) at least monthly for microorganisms (for example, coliforms, psychrotrophs)
- keep records of the microbial testing results
- Use cooling water additives and cooling media products that are safe for use in dairy processing
- keep documents that demonstrate their safety
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