Guide to Inspections of Low Acid Canned Food 38
Manufacturers - 2
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Cascading water retorts manufactured by Lubeca and Stock in Germany differ from the Steriflow in that they offer heating by direct steam injection into the water, or by plate heat exchanger as a customer option. Cooling is by addition of cooling water to the retort or by indirect cooling through a heat exchanger. A method of recovering process water may be provided if cooling water is added to the retort.
The FMC Universal and Convenience Food sterilizers differ from the other cascading water retorts in that they utilize a weir arrangement (a small dam used to direct water flow) in the container basket to force the heated water to flow over the containers in a uniform manner from top to bottom or from one side to the other depending upon the container type. The water then overflows the basket and falls back into the bottom of the retort where it is picked up by a circulation pump and recirculated through a steam injector to reheat the water.
When any of these systems are encountered it is important to determine if the retort system is being operated under the same conditions used during temperature distribution testing. The areas of concern for these systems are similar to those for the Steriflow, and also includes control probe location.
SPRAY WATER RETORT SYSTEMS
Equipment and procedures for processing in spray water retorts are not specifically covered in the lacf regulations. These systems are covered by 21CFR 113.40(j), Other Systems. "Other" systems are required to conform to the applicable requirements of the lacf regulations.
Spray Water retort systems are known to be manufactured by the Food Processing Machinery Division of FMC U.S.A. (FMC Surdry), Surdry S.L. in Spain (Surdry Convac) and in Japan by Hisaka Works Inc. The Hisaka retort is sold in the U.S. by Advanced Retort Systems, Inc.
Spray water retort systems may be either static or rotary batch, (end-over-end) systems, depending upon the make or model. These retorts are designed to process a wide variety of packages including: glass, metal, rigid plastic and flexible pouches. They are normally operated with a compressed air over-pressure to maintain container integrity during thermal processing.
Spray water retorts differ from the cascading water retort (in which the water falls or is sprayed over the top of the containers) in that the water is sprayed over the containers, from several different angles to atomize the air used for over-pressure.
In the Surdry retort the spray nozzles are located on four to six manifolds on the top and along the sides of the retort. A small amount of water in the bottom of the retort is heated by the addition of steam through two steam spreaders located in the bottom of the retort. The water is pumped through the system by a high capacity pump. The water sprays circulate the steam/air mixture in the retort. The containers are cooled after processing by the addition of cooling water to the retort. Instrumentation is normally located in the shell of the retort. The MIG thermometer and the temperature recorder probe are located to sense the temperature of the steam/air/water mixture in the retort.
In the Hisaka retort, spray nozzles are located on manifolds along the sides and in the top of the retort. The spray nozzle banks in these retorts can oscillate (back and forward and up and down). The water in the retort is heated by means of a heat exchanger using steam. When the thermal process has been completed the water and condensate in the retort is cooled by the external heat exchanger to cool the product.
The areas of concern with spray water retort systems are similar to those for the water cascade type retort system.
- The process must be designed to provide for adequate temperature distribution. The cold spot in the retort must be determined. This may vary with container type and arrangement in the retort. Temperature distribution studies should be performed on each retort model, each product produced, each container type used, each crate or racking configuration used and on each individual retort installation.
- Care should be taken to determine the location of the control and recording instruments. The recording sensing probe must be located where it will provide an accurate record of the thermal process. The MIG thermometer must be installed where it will indicate the true thermal processing temperature in the retort.
- Water flow may not normally be directly controlled as a critical factor. A water flow measuring device is recommended to provide a more accurate measurement of actual water flow in the system. Water flow in the system must be the same as that used during temperature distribution studies in the retort.
- The holes in the water distribution sprays may become plugged through clogging with product, and through the buildup of mineral deposits. There should be a program in place for routine maintenance and cleaning of the water sprays and water filter screens if present. During the inspection of these systems the water distribution sprays should be examined to determine if the
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