Understanding FDA 21 CFR Part 113: A Guide to Thermally Processed Low-Acid Canned Foods

by Tim Arrowsmith March 31, 2026

Food processors who manufacture low-acid canned foods face strict regulatory requirements designed to prevent foodborne illness, particularly botulism. FDA 21 CFR Part 113 sets the federal standard for thermally processed low-acid canned foods and is non-negotiable for any facility producing shelf-stable canned products in the United States. Understanding this regulation and implementing proper thermal verification is critical to maintaining consumer safety and avoiding costly recalls or regulatory action.

What Is FDA 21 CFR Part 113?

21 CFR Part 113 is the Code of Federal Regulations section governing the production of thermally processed low-acid canned foods intended for human consumption. The regulation applies to any facility that heats low-acid foods in hermetically sealed containers to achieve commercial sterility—a condition in which the product and its container are free of all viable microorganisms, including spores of Clostridium botulinum.

Low-acid foods are those with a final pH greater than 4.6 and water activity (Aw) greater than 0.85. Common examples include vegetables, meats, fish, and mixed dishes. These foods lack the natural antimicrobial properties of acidic foods and therefore require heat treatment to eliminate pathogenic spores.

The regulation mandates that each processing establishment establish and maintain a Scheduled Process—a documented thermal treatment designed to achieve a specific level of lethality against target pathogens. This process must be established by a Processing Authority or equivalent expert, and every batch of product must be processed according to this schedule with rigorous monitoring and documentation.

Who Must Comply With 21 CFR Part 113?

Any facility that manufactures, packs, or holds low-acid canned foods intended for sale in the United States must comply with 21 CFR Part 113. This includes:

• Traditional canneries and canning operations
• Food manufacturers who produce canned components or finished products
• Co-packers processing low-acid foods in thermal equipment
• Specialty food producers manufacturing shelf-stable canned items
• In-house institutional kitchens that produce canned foods for distribution

Even small-scale or artisanal producers are required to comply if their products are intended for commercial sale or distribution outside their own household.

Critical Control Points in 21 CFR Part 113

The regulation identifies several critical control points that must be monitored and documented:

Temperature and Processing Time

The scheduled process specifies a minimum temperature (measured in degrees Fahrenheit) and duration that must be achieved in the coldest point of the product (the cold spot). The standard reference process for most low-acid canned foods is 250°F (121°C) for a specified time depending on container size and product characteristics. Retort equipment must be capable of achieving and maintaining this temperature uniformly throughout the chamber.

Equipment Calibration

Temperature measurement devices used to monitor the retort must be calibrated at regular intervals against a standard thermometer traceable to NIST (National Institute of Standards and Technology). Inaccurate temperature readings can result in underprocessing, which leaves pathogens viable.

Product Temperature Monitoring

During processing, the actual temperature inside containers must be verified. This is traditionally done using thermocouples placed in representative containers, but thermal indicators provide an independent verification that the product reached the required temperature.

Documentation and Recordkeeping

Every thermal process must be documented with process time, retort temperature, container size, product type, and date. Records must be retained and made available to regulatory authorities upon inspection.

How Thermal Indicators Support 21 CFR Part 113 Compliance

Irreversible thermal process indicators, such as Thermal Process Checks, serve as a visual, independent verification that containers reached the required processing temperature. These indicators:

• Provide a physical record: Unlike electronic data, a color change on the indicator provides permanent, visible proof that proper temperature was achieved
• Validate cold spots: Indicators can be placed in locations likely to be the last to reach temperature, confirming that even the coldest part of the load was adequately processed
• Detect equipment failures: If a batch of indicators shows incomplete color change, it signals a processing failure before product is released to market
• Support regulatory documentation: Indicators provide tangible evidence during FDA inspections that your facility maintains rigorous thermal verification

Thermal indicators complement datalogger systems and thermocouple measurements; they do not replace them. Together, these tools create a comprehensive verification system that demonstrates commitment to food safety and regulatory compliance.

The Role of Processing Authorities

21 CFR Part 113 requires that the scheduled process be established by an expert designated as a Processing Authority. This person must have formal training in thermal processing and microbiology. Many facilities contract with independent laboratories or process development companies to establish their scheduled processes and validate their equipment.

Processing Authorities conduct studies to determine the exact time and temperature needed to achieve the required level of microbial reduction (typically a 12-decimal reduction, or a "12D" process, for C. botulinum spores in low-acid foods). Once established, the process is filed and must be strictly followed.

Common Pitfalls and Best Practices

Underestimating equipment validation: Retort equipment must be proven capable of achieving uniform temperatures throughout. Many facilities discover discrepancies only during formal validation studies.

Inadequate cold spot identification: Knowing where the coldest point in your retort or product is crucial. Using thermal indicators in potential cold spots reveals whether processing conditions are truly uniform.

Poor record organization: FDA inspectors will request thermal processing records. Maintain clear, chronological documentation with batch numbers, process parameters, and indicator results.

Neglecting equipment maintenance: Regular maintenance of retorts, vents, and steam systems is essential. Malfunctioning equipment can lead to temperature variations that compromise food safety.

Frequently Asked Questions

Q: What is the difference between a scheduled process and a tested process?

A scheduled process is established by a Processing Authority through scientific study and defines the exact conditions needed to achieve commercial sterility. A tested process is one that has been experimentally validated using actual equipment and products to confirm the scheduled process is effective.

Q: Can I use thermal indicators instead of thermocouples?

No. Thermal indicators are a complementary verification tool but cannot replace the primary measurement methods required by the regulation. Use indicators alongside thermocouples and dataloggers as part of a comprehensive monitoring system.

Q: How often must retort equipment be validated?

Validation frequency varies depending on equipment type and regulatory guidance. Many facilities conduct formal validations annually or after major maintenance. Your Processing Authority can recommend the appropriate schedule.

Q: What happens if a batch fails thermal indicator inspection?

A failed batch (where indicators show incomplete color change) must be held, investigated, and either reprocessed or destroyed. The failure must be documented and reported to your Processing Authority.

Q: Is 21 CFR Part 113 enforcement by the FDA alone, or are there other regulators?

State health departments often conduct parallel inspections and enforcement of 21 CFR Part 113. Federal, state, and local authorities work together on food safety oversight.

About Retort Checks

Retort Checks is the US division of Temperature Indicators Ltd, a UK-based manufacturer of irreversible temperature indicating labels and thermal process indicators. Our products are used globally in food processing, canning, sterilization, and cold chain monitoring. Visit retortchecks.com to browse our full range.

Legal Disclaimer

The information in this article is provided for general informational purposes only and does not constitute professional advice. Always consult qualified food safety professionals and follow applicable FDA regulations and your facility's HACCP plan.

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