some foods may be packed with vacuums as low as two to six in. Hg. The normal range is from 10 to 20 in. Hg. Some foods may be packed with higher vacuums of up to 26 in. Hg. In Europe very low to no vacuums are sometimes used to pack products such as small fish which are filled at room temperature into small low profile containers. The lack of a vacuum in these containers may at times place the lot under suspicion when containers appear to be abnormal.
Containers may be exhausted by several methods including:
- Hot filling: filling the container with hot product. The length of time that the product is heated and the temperature to which the product is heated have an effect on the final vacuum.
- Exhaust box: the product is filled into the container and then heated by passing the filled container through a steam or hot water exhaust box.
- Mechanically: the container is filled, the lid is attached by a clinching machine which lightly attaches the lid with out forming an air tight seal, the container is then passed into a vacuum chamber where the vacuum is drawn on the container and the container is sealed.
- Steam injection: live steam is injected into the container headspace just prior to application of the container closure. The steam drives the air out of the headspace. When the steam condenses a vacuum is formed.
- Combination: for some products with large volumes of trapped air a combination of heating followed by injection of steam into the headspace may be used to create a vacuum in the container.
- Gas Flush: an inert gas such as nitrogen is used to flush the air out of the headspace. The addition of an inert gas may also be used to create an internal pressure in the container to maintain the container profile during handling.
Incipient spoilage involves the spoilage of canned food prior to the time it is thermally processed. Incipient spoilage can take place at any time prior to the thermal process. This microbiological growth may challenge the thermal process designed for the product. Holding filled containers of lacf in the growth range of microorganisms for excessive periods of time (as short as one hour) may allow microbiological growth in the container. Incipient spoilage in the container may, in addition to increasing the microbiological load, reduce the vacuum in the container. Incipient spoilage is indicated by the presence of non-heat resistant organisms in product microbiological smears with no viable organisms present in the product.
Incipient spoilage is eliminated by controlling the growth of microorganism on the raw materials, during production, and in the final container prior to the thermal process. The firms procedure for handling filled containers prior to processing and when extended holding times may be required due to equipment failure, should be evaluated during a lacf inspection. If a situation occurs in which filled containers are held for extended periods of time, and the firm takes precautions such as refrigeration to inhibit microbial growth, report the details of the incident for review by CFSAN, to ensure the thermal process was adequate for the situation, e.g., lower initial temperature or change in product characteristics. Incipient spoilage must be evaluated on an individual case by case basis and varies by product, process and plant procedures.
Incipient spoilage does not normally create a health hazard, but may result in one if there is contamination with staphylococci. If conditions for growth are favorable, the enterotoxin will be produced. This is most likely to occur when there is human handling of the product (the source of most staphylococci) with improper sanitary or hygienic practices, or evidence of employees with respiratory problems. This microorganism does not cause apparent spoilage nor produce gas.
OPERATIONS IN THE THERMAL PROCESSING AREA
21 CFR 113.87 requires that a lacf manufacturer post the operating processes and venting procedures to be used for each product and container size being packed in a conspicuous place near the processing equipment, or place the processes where they are readily available to the retort operator and to the FDA Investigator. During the lacf inspection the investigator must remember that the firms operating process may be different than the firms scheduled process for the same product. Many firms employ an operating process of one to two degrees above their filed scheduled process temperature and one to two minutes longer then the filed process time to compensate for minor fluctuations in the steam supply and possible improper employee setting or reading of timing devices. This process is called the firm's operating process. If the operating process exceeds the scheduled process, a drop of time or temperature below the operating process is not a process deviation if the drop is not below the scheduled process. This is defined in 21 CFR 108.35(c)(2)(ii)