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Chapter 15 - Low-Acid and Acidified Low-Acid Foods in Hermetically Sealed Containers (Canned Foods)
15.9 Incubation
Spoilage of canned goods is generally due to growth of microorganisms after heat processing, either from under processing, faulty cooling or post processing contamination via leakers.
Microbial growth within the can often, but not always, results in production of gas and a consequent loss of vacuum. If gas production continues flippers or blown cans result.
Note that growth of C. botulinum may occur without gas production. The incubation test alone cannot be relied for product safety or replace close control of each processing step; however, incubation of cans after processing provides a simple means to routinely check for processing defects.
It is the duty of the inspection staff to monitor the incubation procedure and to ensure that it is done as described in this section.
15.9.1 Incubation Facilities
The establishment shall provide incubation facilities which include a thermometer, a temperature/time recording device, a means for the circulation of the air inside the incubator to prevent temperature variations, and a means to prevent unauthorized entry into the facility. An employee designated by the operator shall be responsible for the security of the incubator.
15.9.2 Product Requiring Incubation
Shelf stable product requiring incubation includes:
- low acid products; and
- acidified low acid products.
15.9.3 Incubation Samples
- From each load of product processed in a batch type thermal processing system (still or agitation) the operator shall select at least one container per retort basket for incubation.
- For continuous rotary retorts, hydrostatic retorts, or other continuous type thermal processing systems, the operator shall select at least one container per 1000 for incubation.
- Only normal-appearing containers shall be selected for incubation.
- The operator shall identify the selected containers to ensure they are incubated for the required period of time.
15.9.4 Incubation Temperature and Time
The required samples for shelf stable products shall be tested by incubation for at least 10 days at 37 ± 1°C.
15.9.5 Incubation Checks and Records Maintenance
A designated person shall visually check all containers under incubation each working day and the inspector shall be notified when abnormal containers are detected. For each incubation test the establishment shall record at least the product name, container size, container code, number of containers incubated, in and out dates, and incubation results. The establishment shall retain such records, along with copies of the temperature/time recording charts for at least three years.
15.9.6 Abnormal Containers
The finding of abnormal containers among incubation samples is cause to officially retain at least the code lot involved.
Note: When abnormal containers are detected by any means other than incubation, the operator shall inform the inspector and the affected lot(s) shall not be shipped until the inspector is satisfied that the product is safe and fit for human consumption.
15.9.7 Shipping
In those instances where a good record of proper canning procedures has been demonstrated and routine incubation tests have proven negative, the operator may be permitted to ship product to another registered establishment or to a distribution warehouse for storage, without awaiting the results of the incubation tests for the particular lot, provided that the inspector is advised of the product destination, and the product is not offered for sale until the results are known.
Where product leaves the originating establishment prior to incubation being complete, the operator must maintain a detailed record of product codes, amount shipped and destinations, in case a recall is initiated.
