Regulations are in place to ensure the control of critical parameters in the canning of foods. The U.S. Federal Food, Drug and Cosmetic Act prohibits the distribution and sale of foods that carry disease-causing contaminants as well as a list of undesirable elements categorized as "filth." Two episodes with botulism in the canning industry in 1971 led to a petition from the National Canners Association, now the National Food Processors Association (NFPA), to the U.S. FDA proposing a statement of policy that was handled as a proposal for regulation. After receiving comments, the FDA published minimum good manufacturing practice (GMP) regulations. After various revisions and comment periods since that time, the FDA now has published several GMP regulations that pertain to canned foods in the Code of Federal Regulations (CFR).
"Current Good Manufacturing Practice in Manufacturing, Packing, or Holding Human Food" (21 CFR 110) sets forth general requirements for maintaining sanitary conditions in food establishments, such as design and maintenance of facilities and equipment, and pest control. More specific requirements are set forth in an additional series of regulations in Title 21 of the CFR. "Thermally Processed Low-Acid Foods Packaged in Hermetically Sealed Containers" (Part 113) defines low-acid foods, requires design of a scheduled process by a process authority, defines commercial sterility for low-acid canned foods, and specifies design, control, and instrumentation for retorting systems. This regulation also specifies record keeping requirements, procedures for process deviations, and container closure inspection procedures. "Acidified Foods" (Part 114) defines acidified foods and procedures for acidification; this part describes requirements for process determination, corrections for process deviations, and record keeping. "Emergency Permit Control" (Part 108) describes procedures for exemptions from and compliance with registering an establishment when requirements for operation are not being met.
The U.S. Department of Agriculture (USDA) has published regulations for canning of meat (21 CFR 318.300) and poultry (21 CFR 381.300) products, "Canning and Canned Products." The U.S. Meat Inspection Act and the Poultry Products Inspection Act authorize regulation of canned products by the USDA Food Safety and Inspection Service. The canning regulations for the two products are essentially the same and contain requirements similar to those for low-acid canned foods regulated by the FDA.
Canning regulations recognize the importance of people in maintaining the integrity of the canning process, in addition to food, process design, and equipment concerns. All retort (canner), container closure, and inspection operations must be performed under the supervision of trained supervisors. Supervisors of low-acid and acidified foods operations are required by regulations in Parts 108, 113, and 114 to satisfactorily complete instruction in a school or training approved by the FDA. These courses have become known as Better Process Control Schools, developed in cooperation with the NFPA's educational arm, the Food Processors Institute (FPI). Instructors for these schools are selected from the FDA, selected universities, the FPI, the NFPA, and industry. Regulations for canned meat and poultry products (Parts 318 and 381) specify that the supervisor of canning operations must attend a school generally recognized as adequate for properly training supervisors of canning operations.
Food regulations also allow for protection from unsafe imported thermally processed foods. Foreign food processors of low-acid canned foods and acidified foods must register their establishments with the FDA before exporting products to the United States. The FDA assigns each establishment a number that helps track the registration and processing records. Imported low-acid canned foods and acidified foods are subject to all the requirements tinder the U.S. Federal Food, Drug, and Cosmetic Act and the Fair Packaging and Labeling Act. The processing of low-acid and acidified foods must also comply with GMP regulations in 21 CFR Parts 113 and 114, respectively. Canning processes must be determined by a thermal process authority and filed with the FDA before being exported.
The microbiology of the can environment during storage is an extremely important consideration in the safety of canned foods. The objective in food canning is to produce a food and container interior that are commercially sterile. This is accomplished through the application of heat alone or in combination with adjusted parameters of water activity, chemicals, or acidity (usually measured as pH). Commercial sterility results from destruction of all viable microorganisms of public health significance as well as those capable of reproduction at normal nonrefrigerated temperatures during storage and distribution.
Generally, the residual oxygen content of canned foods is minimized. Microorganisms that require an environment with oxygen (obligate aerobes) would not be expected to present spoilage or health hazards. (Special consideration would have to be given to products where oxygen is not completely removed and mild heat treatments are used in conjunction with other preservation means, such as curing salts in canned, cured meat products.) Of greatest concern, then, in the anaerobic environment of canned foods is the pH of the food, as acidity does affect the ability of microorganisms to reproduce and survive destruction by heat.
The foremost health concern with canned foods is survival of the pathogenic Clostridium botulinum bacteria. C. botulinum is a spore-forming anaerobe. Destruction of the spores in canned low-acid foods is essential to prevent germination and toxin formation during nonrefrigerated storage. It is an accepted generalization that spores of C. botulinum can germinate into vegetative cells that multiply, with the ultimate production of toxin if the pH of the canned food product is higher than 4.6. Therefore, the pH value of 4.6 is one delineating factor between low-acid and acid or acidified categories of canned foods. A low-acid food means any food, other than alcoholic beverages, with a finished equilibrium pH greater than 4.6 and a water activity greater than 0.85.
There are some extremely heat-resistant spore-forming bacteria that may survive a process for commercial sterility. These bacteria do not present a health hazard, however, and do not present a spoilage problem under normal, recommended conditions of storage. These are thermophilic, or heat-loving, bacteria that require high temperatures to germinate. If this happens, they may produce acid with little or no gas, or gases that swell cans. It is generally recommended that canned foods be quickly cooled below 105°F in thermal processing and then stored below 95°F to prevent problems from these surviving thermophiles.
Critical factors influencing the process needed to obtain commercial sterility include:
1. The composition and nature of the food (eg, pH, sauce viscosity, starch content, particle tendency to mat or clump)
2. Initial number of microorganisms on the food, also called bacterial load
3. The microorganism(s) of concern with the particular food and the heat resistance of those organisms
4. Pack style, or preparation of the food as it affects particle size, viscosity, solids-to-liquid ratio, acid-to-low-acid ratio (for acidified foods) and others depending on the product
5. Jar size and conformation
6. Fill weight
7. Initial (or fill) temperature of the food
8. Retort temperature and style (eg, rotating or still)
Designing a thermal process (canning schedule) that takes into account all the critical factors that can influence safety of the finished product requires the use of specific scientific methods. It requires knowledge and data about the microorganisms of concern in that food and the rate at which they are destroyed by heat in the product and container. Process design also requires and involves collecting data showing heat penetration into the food product in its container, under the conditions used during production. These pieces of information are used to calculate a theoretical process that is then tested by inoculated pack studies, to test that the calculated process does provide commercial sterility.
Regulations for all canned foods state that the food processor must obtain scheduled processes established by a competent processing authority. The regulations do not specifically define acceptable process authorities; there are generally recognized organizations, such as the NFPA, members of the Institute for Thermal Processing Specialists, faculty at certain universities, and a number of consultants recognized as having this expertise. The regulations also do not specify actual procedures for thermal process design. Again, the NFPA provides guidance in how to conduct heat penetration tests as well as performing the tests itself. The Institute for Thermal Processing Specialists has also developed protocols for thermal process design.
Critical details of the process used to can a low-acid or acidified food product must be filed with the FDA. The process time, temperature, and other factors critical to adequacy of the process must be filed for each product and product style in each container type and size. Critical factors that influence the integrity of the process in addition to processing time and temperature include: type of processing equipment used; minimum initial temperature of the food; sterilizing value of the process (F0) or other evidence of process adequacy; pH; water activity; and factors affecting heat penetration such as formulation, fill weight, drained weight, and headspace. The filing of a scheduled process with all necessary parameters delineated shall be done not later than 60 days after registration of the establishment and before any new product is packed. The FDA then edits all processing information filed for questionable, incomplete, or incorrectly filed information, and returns forms needing clarification or completion. The FDA does not certify or approve processes; it is the responsibility of the processor and thermal processing authority to produce a safe process.
Scheduled processes determined through testing must be applied under equivalent conditions in commercial practice. The regulations contain specifications for equipment design and management to ensure that critical controls important to a thermal process are in place. The regulations regarding equipment and procedures are detailed, and for actual requirements, the reader should consult the CFR. However, the following is a summary of the controls required to ensure the safety of canned foods.
Equipment design features are prescribed for various types of retorts (equipment used for the canning process). They include type and placement of temperature- and pressure-indicating devices and of temperature-recording devices. Because the steam supply affects maintenance of the temperature in the retort, requirements for steam controllers, the steam inlet to the retort, and steam spreaders are also described. Size and positioning of steam bleeders are specified for certain retorts. Air and water supply and drainage are also critical components discussed. Much attention is given to the placement of retort vents and venting processes; removal of air from the retort is critical to the temperature obtained for steam pressure processing.
All raw materials and ingredients that are susceptible to microbiological contamination must be suitable for use in processing. Specifications for suppliers should be in place to ensure their wholesomeness and quality. Receiving procedures should ensure adequate examination, especially so as to determine their microbiological condition. If stored before use, they should be examined again immediately prior to processing.
Raw agricultural products should be cleaned to remove excess soil from the surfaces. All raw materials should be stored or held in a manner that prevents contamination, increases in microbiological loads, and loss of quality. Physical characteristics of the product may also affect the thermal process. Product size, texture, and condition can affect heat penetration. Raw product controls important to maintain are sorting and grading for the purposes of size and quality.
The water supply must be of sufficient quality for the intended use and from an acceptable source. Any water that contacts food or food-contact surfaces shall be safe and sanitary. Water must be able to be delivered at appropriate temperatures suitable for its use at different locations in the establishment. The residual chlorine content of water needs to be checked and adjusted at various steps in the process and plant operations.
Blanching is often done. It helps inhibit enzymatic action, which may later alter the characteristics of the goods.
Blanching also expels respiratory gases and oxygen, a step that assists in control of headspace in the container and allows a greater vacuum to be achieved. Softening of food to enable easier packing, setting of flavors and colors, and cleaning are some additional benefits from blanching. Finally, blanching may allow peeling, dicing, cutting, and other steps to be done more easily.
Blanchers must be operated in such a way as to minimize thermophilic bacterial growth and contamination. Rapid heating is preferred. Blanchers should be operated at temperatures in the 190 to 200°F range to control thermophilic growth. Lower temperatures may be used, but the procedures must be evaluated for the growth of organisms. If the product is not to be immediately packed and processed after blanching, it should be rapidly cooled after heating. Potable water must be used on blanched foods washed before filling.
Product formulation must be controlled; starches, gums, sugars, and other thickening agents are particularly critical factors in heat penetration. Inspectors should determine if changes have been made, and if so, if the scheduled process was tested and changed accordingly if needed. Rehydration of dry ingredients, such as beans, rice, peas, and potatoes also affects thickening and heat penetration. Rehydration should be controlled. Viscosity of packing mediums must also be controlled, and inspectors should check for deviations from the original formulations.
Containers must be appropriate to the product being processed. They must be appropriately cleaned and even sanitized, if required. The filling operation should be inspected to ensure that no contamination occurs during the filling, such as might occur from a ventilator used to prevent trapped air in the product.
Filling of the container prior to the canning process may also be a critical control. Filling requirements specified in the process must be followed. Fill weights and ratio of solids and liquids must be controlled. Headspace may be critical, especially for agitated products that need a gas bubble to achieve movement of the product. Headspace is normally controlled by the fill weight or volume. Too little headspace may result in underprocessing of the product as well as a low vacuum. After filling, exhausting of containers to remove air from the headspace shall be controlled to meet conditions specified in the scheduled process. This is usually accomplished by hot filling, mechanical methods, steam injection, or gas flushing.
Container closing operations are another area requiring safety considerations. Intact, properly formed seams and seals are essential to successful canning and food safety. They are so essential, in fact, that careful examination of can seaming operations and frequent inspection of seals at the end of retorting and after cooling are required by regulations (see "Container Evaluations"). To avoid container leaks, can seaming equipment or other sealing equipment must be properly maintained and operated. Unacceptable practices at this stage are overfilling and using cans with defective flanges or jars with damaged lugs or threads. Food must not overhang or rest in seal areas.
Holding filled containers in the growth range of microorganisms for long periods of time before processing can lead to spoilage before canning takes place. This is known as incipient spoilage. It may increase the microbiological load before processing and reduce the vacuum obtained. Steps to eliminate incipient spoilage include controlling microbial growth on the raw material, during production, and in the container prior to processing. Holding time before processing should be minimized or carefully controlled to prevent growth. Incipient spoilage does not always result in a health hazard, but may occur, particularly with contamination from staphylococci which produces an en-terotoxin.
Operations in the thermal processing area, often called the "cook room," are vital to safety of the canned food and are heavily regulated. Retort operating procedures and venting procedures to be used for each food and container size must be readily available to the retort operator and the inspector. As discussed earlier, the design of the retorts and their critical operating components are described in detail in regulations for low-acid foods. The operator should be sure all aspects are operating properly before processing food. A system must be established and used that ensures that no product moves through the processing room without being retorted. Labels or other visual indicators should be used to provide indication that the containers have been exposed to the retort process.
All sealed containers must be marked with a code that is permanently visible. The code must identify the establishment; the product; and the year, day, and period when packed. Coding is critical to having a means for isolating and/or recalling questionable product.
The initial temperature of the container contents is a critical safety factor. These temperatures should be measured and recorded with sufficient frequency to be sure that the minimum initial temperature specified in the scheduled process is obtained. This is another reason why lag time between filling and processing should be minimized. Initial temperature is normally determined using a handheld thermometer. (Glass stem thermometers are not used due to potential breakage.) For batch retort loads, a container may be removed from the load going into a retort and set aside where it is not subject to extreme temperature change. When the retort lid is closed and steam turned on, the initial temperature is determined. When retort systems use water to cushion or hold containers, the temperature of that water is a critical concern so the initial food temperature is not lowered. The initial temperature is determined by shaking or stirring the container contents prior to measuring; it is the average temperature of the contents.
Other critical factors during processing are measurements, meters, and devices. Equipment must be accurate, and pressure gauges and thermometers must be located for ease in reading. Timing devices that record process information are to be in place and accurate. Venting of the steam retort is extremely important to achieving the desired processing temperature. Placement of containers in the retort must be consistent with conditions of the scheduled process and must not block venting of the retort.
Deviations from the intended process may occur. A line breakdown may occur at several locations and for many reasons. Procedures should be in place to provide direction for continued use or disposition of the product. Full records must be kept of any reprocessing. Product may be set aside for evaluation by a competent processing authority as to whether it may be used or should be destroyed. Records of evaluation procedures, reasons for the deviation, and actions taken must all be recorded and filed.
During inspection, all these factors of processing operations must be determined, and at least one complete cycle of retort operation should be observed.
Cooling of containers after the retort processing must be controlled to prevent recontamination and damage to seams or seals. It also should be done quickly to prevent growth of thermophilic organisms, as well as overcooking, although the latter is usually detrimental only to quality and not to safety.
Containers may be air or water cooled. Water used for cooling must be of good sanitary quality. Cooling water must be chlorinated or otherwise sanitized. The level of free chlorine in the water must be checked and care given to where the samples are taken for this testing. After processing, the sealing compound used in containers is softened, and as it cools, small amounts of cooling water may be drawn into the container. The sealing compound may then set and seal the leak without loss of vacuum. If contaminated cooling water is used, spoilage and possible danger to the consumer may result.
The time required and the temperature to which retorted foods are cooled must be checked. Cans are generally cooled to 95 to 105°F to leave enough heat in the cans to dry them (when water cooled) but not enough to permit the growth of thermophilic organisms. At this temperature the cook is also stopped, preventing overcooking of the product.
Some cooling procedures may result in damaged seams. Precautions should be taken to prevent buckling of metal containers or damage to seals in glass and other packages. If pressure is reduced too quickly during cooling, buckling may occur from the inability of seams to withstand the change. Buckling is a problem due to the potential for the can seams to be pulled apart enough to leak, and contamination of the contents may occur.
Steps to maintain the integrity of container seals must be continued into postcooling container handling. Bacterial contamination can occur in seam and seal areas if handling lines are not sanitary. Moisture present on containers or the can handling equipment can suspend the organisms and allow them to grow. Rough handling can also damage seals. Crates and baskets used to transfer containers should not have sharp edges or protrusions that damage packages. Leaks from dents or defective seams can result in postprocessing contamination of the commercially sterile product. Cleaning and sanitizing procedures should be in place for all crates, racks, conveyors, belts, and machinery.
Before product is stored prior to distribution, it must be sufficiently cooled to prevent growth of thermophilic organisms (105°F). The storage area must be clean with no product stored directly on the floor. Storage temperatures should not exceed 95°F.
Rust should be prevented or it may lead to damaged seams and seals. If the temperature of the warehouse is too high, the cans may sweat and the moisture will lead to rusting. Rust on the can exteriors may be due to other reasons, including improper operation of retort vents, too long come-up time in retort, or steam containing moisture. Failure to remove the surface water or chemical composition of the cooling water may cause rust.
Regular observations and examinations are made to determine that container closures are not defective. The establishment's personnel responsible for these procedures and the inspector need equipment that is used to conduct "tear-down" examinations of the can and its seams. Tear-down of cans to determine seam integrity must be done by a trained individual. Samples shall be taken from each seaming station not more than every 4 hours. During tear-down, measurements are made on cover and body "hooks" of the double seam. Thickness, tightness, and width are measured or observed. Can seam terminology and procedures are the subject of specialized training in the canning industry, due to the importance of producing and maintaining hermetic seals for food safety.
Sampling of containers for closure evaluation is also done during production runs. At this time, gross closure defects can be observed and corrected. Any defects and corrective actions must be recorded. Measurements and recordings should be made no more than every 30 minutes. Additional inspections of closures are made immediately following a jam in a closing machine, after any adjustment to closing machines, or following a prolonged shutdown before a machine is started up.
One of the protections provided for by canning regulations is inspection of a canning establishment. The regulations recognize that there are certain critical elements or steps common to every canning process, and low-acid canning process in particular, that must be controlled to prevent a health hazard. It is the responsibility of the inspection authority (eg, FDA for low acid canned foods) to monitor a firm's compliance with these preventive principles.
The FDA and the USDA publish inspection guidance documents that explain procedures to be followed. These documents may be consulted for detailed information about standards. Changes are being made as needed to keep these procedures updated; for example, they must be consistent with Hazard Analysis Critical Control Points (HACCP) regulatory systems being implemented in various segments of the food processing industry in the 1990s. Although the HACCP system has its origin in the industry's quality control functions of the 1960s, its emphasis is food safety and prevention of health hazards. The use of HACCP systems for regulatory purposes is growing in the 1990s; however, the current GMPs covering low-acid canned foods and acidified foods already have their origins in the HACCP principles presented at the 1971 Conference on Food Protection.
Before an inspection, the investigators should become familiar with the firm's scheduled processes and all critical control factors. A critical factor is defined in 21 CFR 113.3(f) as any property, characteristic, condition, aspect, or other parameter, variation of which may affect the scheduled process and the attainment of commercial sterility. Regulations state that critical factors specified in the scheduled process must be measured and recorded in processing records. The inspector must review documentation at the firm to determine all critical factors are being controlled.
Another safeguard in regulation of the canning industry is the provision for recalls. The FDA and USDA have the authority and responsibility to issue recalls for potentially harmful foods. A company may discover defective product on its own and issue a recall. In other instances, the FDA or USDA finds a problem, informs the company, and suggests or requests a recall. Recalls may then be done voluntarily by the processor in cooperation with the governing agency. However, it the company does not comply with a requested recall, the agency can seek a court order authorizing seizure of the product.
The FDA and USDA have guidelines on how to conduct a recall for companies to follow. There are three classes of recalls according to the level of hazard involved. The strictest procedures are in place to ensure appropriate follow-through for recalls presenting the greatest hazard.
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