Guide to Inspections of Low Acid Canned Food 32
Manufacturers - 2
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the filed scheduled process.
DISCONTINUOUS AGITATING WATER IMMERSION RETORTS
Equipment and procedures for processing in discontinuous agitating water immersion retorts are covered by 21CFR 113.40(e) of the lacf regulations.
These are batch retort systems which provide for continuous product agitation by movement of the head space bubble during thermal processing. Agitation in these systems is normally induced through end over end rotation of the container (Attachment 8) as opposed to the axial rotation of the container in the FMC continuous and orbital retorts previously discussed. Because of the rotational axis of various containers in the baskets during processing, the containers against the outside walls of the basket may receive more agitation than those in the center of the basket.
Discontinuous agitating water immersion retorts are manufactured by Allpax Products Inc. in the United States under an agreement with the Maskinfabrikken Phoenix subsidiary of the Klinge group in Denmark. Known manufacturers of these systems in Europe include: Herman Stock in Germany, Lubeca in Germany, and Phoenix in Denmark. All of these systems are or have been available for installation in the United States through U.S. distributors. The Stock Rotomat is one is one which has been distributed for a number of years, with numerous installations in the U.S. and world wide.
The majority of these systems operate in a similar manner. These systems can be found with a wide variety of valve types and plumbing arrangements. The valves and plumbing may be changed for custom installation by the manufacturer or installer of the equipment to provide additional functions or for better operation of the system. Many of the early Rotomat retorts were equipped with on/off steam control valves which have been replaced with modulating steam control valves to provide for better control of the retort temperature. Retort systems now entering the U.S. are often modified to meet the U.S. requirements for MIG thermometers and instrumentation, and to replace the control valves on the retort. The configuration of the retort must be carefully reviewed during inspection of these systems.
Discontinuous agitating water immersion retorts can be used for the processing of numerous container types including: metal cans, glass jars, and plastic containers and unusual container shapes such as semi-rigid plastic bottles, flexible pouches and half-steam table trays.
The processing system consist of two pressure shells or drums, one sitting on top of the other. The top drum is used to store and preheat the processing water. The lower drum is the processing drum (Attachment 8).
Containers are loaded into crates or specially designed racking systems depending upon the container type. The crates are then loaded into a reel within the lower retort shell and locked into place during processing.
Water in the upper drum is heated by steam prior to processing. The temperature of the stored water is dependent upon the type of container to be processed, and may range from several degrees above the thermal processing temperature for metal cans to only a few degrees above the initial temperature of glass containers. Storage drum temperature may be critical to achieving adequate temperature distribution. To achieve correct temperature distribution in the retort, the firm must meet the the minimum temperature requirement.
Processing in the Rotomat retort system is designed to proceed through a series of programmed phases which may consist of several steps within each phase. The steps normally encountered include:
- Heating of the upper storage drum
- Sterilization I - in older models this includes dropping the heating water and heating the water to processing temperature, in later models this involves only dropping the processing water.
- Sterilization II - in earlier models this is the sterilization (hold) phase, in later models this is the heating phase to processing temperature.
- Sterilization III - this the sterilization phase in later models.
- Pressure cool I - this is the initial cooling phase where the process water is recaptured.
- Pressure cool II - this is the final cooling stages
- Open door - retort is ready to unload
The phases and steps used may vary with the make of retort system used, the model of retort used, the control system used, and the product being processed. It is important to determine the retort steps and sequencing during the inspection. This information should be compared to the information in the filed scheduled thermal process.
These retorts may be equipped with a wide range of control systems depending upon the manufacturer, model and customer specifications including: manual controls, semi-automatic electronic relay controls, electronic card readers, electronic pre-programmed logic controls and microprocessor controls.
At the beginning of the sterilizing cycle, water
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