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Guide to Inspections of Low Acid Canned Food 12

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Devices used to time retort thermal processes must be accurate. Pocket and wrist watches are not considered satisfactory for timing purposes. Even though wrist and pocket watches may be accurate, one problem noted with the use of wrist watches is that several people involved in separate portions of the thermal process may use wrist or pocket watches with different times of the day. When this happens the thermal processing records do not correspond to each other. A large wall clock which can be read from all areas of the thermal processing room is the best method for timing thermal processes. If more than one clock is used in the thermal processing area they both should be set to the same time of day. During the inspection of lacf manufacturers the accuracy of the timing clock should be checked with an accurate stop watch.

21 CFR 113.87(d) states digital clocks may be used if the operating process and the venting schedule have a 1 minute or greater safety factor over the scheduled process and venting schedule. If the digital clock reads out to the second this requirement is not necessary.

When timing clocks are read, the method used must be conservative to insure that the time of vent, come up time, the time of thermal processing, and other operations are carried out for the required time interval. Except in those instances where automatic equipment is used to record times, the operator normally records operations in the thermal processing area in full minutes (e.g., 7:15). If time is not recorded to the second that the operation takes place then the operator must record the time for the beginning of the operation at the next full minute and the time for the end of the operation to the last full minute to insure that the full required time for an operation is achieved (e.g., if the retort vent is turned on at 07:10:15, the operator would record 07:11 and if the retort vent was turned off at 07:10:15, the operator would enter 07:10). Operations in the retort room must be monitored during the inspection to insure that timing of the operations are accurate. Use of a stop watch by the investigator insures that accurate time intervals are measured.


Traffic in the retort room and processing area must be controlled to prevent unprocessed lacf from circumventing the thermal process. The retort area should be designed so that product enters one end of the processing area and leaves the opposite end. This can be done in several ways depending upon the retort system in use. For batch retort systems a routine procedure should be designed by the firm to stage unprocessed product in an area separate from processed product. When multiple vertical retorts are arranged in rows or rings, the product should enter the row or ring at a different location than product exits the ring or row. In systems using continuous conveyors or chains to move the product through the retort system the entry and exit of product should be physically separated if possible to prevent the mixing of processed and unprocessed containers. Containers which are found to be on the floor or off of normal conveying equipment should be destroyed.

Crates and containers of lacf products must be identified in a manner which will readily identify the status of the product. One method of identifying the status of lacf product containers is through the use of thermal indicators. Thermal indicators are placed on the containers, on one container in a retort crate, or on the retort crate itself. Thermal indicators may be impregnated onto a paper tag to be attached to a retort crate, painted onto the surface of a container or crate, incorporated into a tape to be placed onto a container or crate, or incorporated into an ink jet spray which is applied by the can manufacturer or canning firm. Some container manufacturing firms incorporate thermal ink into a container manufacturing code which is placed on each container. Thermal indicators can be purchased to meet the temperature range of the thermal process being used. Thermal indicators do not however indicate that an adequate thermal process has been applied to the lacf product, only that the product has been subjected to a heat source. The thermal indicators should be examined following processing and written records of changes in thermal indicators should be made. In lieu of thermal indicators the firm can use other effective means of visually distinguishing between processed and unprocessed containers.


Although other methods of heating lacf are being developed steam is the predominant heating medium used to process lacfs. The steam may be used to directly or indirectly heat the products or containers. Steam in modern canneries is normally produced in remote steam boilers. Two common types of steam boilers or generators found in canneries are the fire-tube and water-tube. Smaller boilers of the "packaged" boiler type are almost always fire-tube boilers, and in physical appearance are unusually long and relatively low. Such boilers are often referred to as "scotch-marine" or "marine" type boilers. Larger boilers which have been constructed in place are almost always water-tube boilers, and are usually nearly square and quite high,

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