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  4. Guide to Inspections of Low Acid Canned Food 25
  1. Inspection References

Guide to Inspections of Low Acid Canned Food 25

Guide to Inspections of Low Acid Canned Food 25

Manufacturers - 2

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3/16 47-62 81-108 111-148 183-244 260-346
1/4 27-36 45-60 62-84 102-137 147-196
3/8 -------- 21-28 28-37 45-60 66-88
1/2 -------- 11-15 15-20 26-36 36-48

*Inside Diameter

Vents must be installed in such a way that all air is removed from the retort before timing of the process begins. Vents are normally controlled by a gate, plug cock or ball valve, which must be fully open during venting. Vents must be installed so that a back pressure is not created during venting. Vents must not be connected directly to a closed drain system. Vent pipe(s) exits cannot be submerged under water during venting. On those retort systems where more than one retort vent pipe from a single retort connects to a manifold, the manifold must be of a size that the cross sectional area of the manifold is greater than the cross sectional area of all of the connecting vents. The manifold may be controlled by one free flowing valve. Where vents from more than one retort or manifold pipes are connected to a header the header must have a cross sectional area at least equal to the cross sectional area of the connecting pipes from the maximum number of retorts to be vented at one time. The header must not be controlled by a valve. Venting installations may differ from the above specifications if the firm has evidence in the form of heat distribution data that adequate venting of air is accomplished.

Bleeders are openings in retorts used to remove air entering the retort with the steam, and to promote circulation of the steam in the retort. The lacf regulations require that all retort bleeders, except thermometer well bleeders, have an inside diameter of no less than 1/8 inches when fully opened. Thermometer well bleeders are required to have an inside diameter of no less than 1/16 inch when fully opened. Bleeders must be wide open and emit steam continuously during the entire process including the come-up time. The operator must be able to observe the operation of the bleeders during processing. If the retort has the steam entry in the top of the retort, a bleeder of adequate size must be installed in the bottom of the retort to remove the condensate from the retort during processing. The condensate bleeder has to be installed in a manner that allows the operator to observe its function.

Vertical still retorts are required to have at least one bleeder opposite the steam entry. Horizontal retorts are required to have at least one bleeder opening within one foot of the outermost location of containers at each end of the retort, and at intervals of no less than 8 feet along the top of the retort.

As previously noted, each retort system must be equipped with a MIG thermometer, a temperature-recording device and an automatic steam controller. The sensing bulbs for the MIG thermometer and the temperature recording device may be installed within the retort shell or in an external well attached to the retort. External wells or pipes must be connected to the retort through at least a 3/4 inch diameter opening, and be equipped with at least a 1/16 inch diameter bleeder to provide for a free flow of steam past the thermometer sensing bulb.

Air may be supplied to the still steam retort to provide overpressure during the water cooling of containers in the retort. Considerable pressure is built up in the container during thermal processing. To prevent buckling (the container ends become permanently distorted) of the container overpressure from air or steam is provided during cooling. Air overpressure is more easily controlled as the steam tends to collapse in the retort headspace. The overpressure must be controlled within limits, as too great a pressure or cooling for too long will panel (permanently distort the side panels) the containers. The air supply line must be equipped with a tight fitting valve (e.g. globe or ball) to prevent air leaking into the retort during thermal processing. Generally pressure cooling is needed when processing container sizes with diameters above 401 (4 1/16 inches) at temperatures greater than 240° F. Smaller containers processed at higher temperatures may also require pressure cooling.


Equipment and procedures for crateless retorts, which are still steam retorts (see above), are covered by 21CFR 113.40(a) of the lacf regulations.

Crateless retort systems are manufactured by Malo Inc., by the FMC Corp. and by others. Crateless retort systems are still steam retorts in which the containers are fed directly into the retort from a continuous belt (see Attachment 5). Crateless systems are normally operated in a series of from 2 to 6 or more retorts depending upon the firms requirements. One operator can normally operate several crateless retorts at one time. Crateless retorts may be up to 8 feet high and 6 feet in diameter. The capacity of the retort is several times that of the normal 3 crate vertical retort (over 10,000 cans for some smaller containers). Container size is not limited by the retort design. Prior to filling the retort with containers, the retort is filled to approximately half full with preheated cushion water at a temperature which will not lower the product temperature below the minimum specified in the scheduled process. When used, the automatic conveyor system is then set to feed the preset

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