Dairy processing: Aseptic processing and packaging systems
Aseptic surge tank
The aseptic surge tank acts as a sterilized product balance tank for the fillers. This allows both the fillers and the aseptic processor to operate independently at different flow rates.
- Install the aseptic surge tank downstream from the flow diversion device
- Protect the surge tank by one or more aseptic barriers at the flow diversion device
- filling operations can continue from the tank while the Aseptic processor is in divert
- If there are no aseptic barriers to protect the surge tank, empty and re-sterilize the fillers and aseptic surge tank after a divert event (refer to Appendix G: Preventing cross connections)
The cleanliness and operation of the aseptic surge tank are important to prevent contamination of the sterilized product.
- Use sterile air over the product in the tank
General conditions
- The aseptic surge tank and associated valves, thermometers (as examples) are clean and in good condition
- Instrumentation (temperature recording chart) are installed to record and verify pre-sterilization of the tank before production commences
Sterile air
As product is withdrawn from the surge tank, negative pressure could develop in the tank, which could cause unsterile air and bacteria to be drawn in through joints, gaskets (as examples).
- Pressurize the sterile air to prevent the development of negative pressure inside the aseptic surge tank
Sterile air is produced by incineration and/or filtration.
- Incineration:
- install a temperature sensing device monitoring system
- Sterile filter:
- monitor the specifications of the filter, filter location and number of filters
- change the filter at intervals recommended by the manufacturer or the person responsible for the scheduled process (for example a process authority), and document this on the processing records
- Maintain sterile air over-pressure on aseptic surge tanks to ensure proper operation (that is, product flow to the filler)
- in general, the person responsible for the scheduled process establishes a venting or air purge schedule for the surge tank
- Use a sterile air pressure controller or transmitter to monitor the sterile air pressure in the tank
- if the sterile air pressure drops below the value specified in the scheduled process, the filler(s) ceases operation, and the aseptic barrier located at the inlet of the unsterile tank is activated to protect the sterile product in the processing system from entering the unsterile tank
- do not resume filling operations until the aseptic surge tank, fillers and valves have been emptied and re-sterilized - unless multiple aseptic surge tanks and fillers are used and the sterility of these is maintained
- Test the accuracy of the controller/transmitter upon installation and at an interval of at least every 6 months
- use the testing methods in Critical process test procedures – Pressure differential
- Increase the frequency of testing if the calibration is consistently found to be out of adjustment
- if the calibration is consistently found to be out of adjustment, immediately identify and rectify the reason for the calibration problems
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