Food processors monitor many different parameters to ensure that the foods, beverages, or ingredients they are manufacturing meet safety, quality, and legal requirements. Perhaps the most important of these parameters is temperature. However, temperature does not stand alone. It goes hand-in-hand with time. Think of all the processes that entail the monitoring of both temperature and time: aseptic processes; processes for low-acid foods; nuts for roasting, dry roasting, oil production, or other processes; bakery processes; and fermentations in the food, beverage, and pharmaceutical industries, to name a few.

Temperature monitoring is more than just tracking changes in temperature. It entails the following additional tasks: 

• Establishing the proper parameters to ensure that safety, quality, and legal standards and specifications are met
• Ensuring the temperature monitoring devices are fit for purpose and have been properly calibrated
• Confirming that the persons doing the monitoring are properly educated on how to use and interpret results from the equipment
• Compiling forms or electronic systems to record results
• Setting up programs to quickly address measurements that are out of compliance. 

The bottom line is that temperature monitoring is more than just a line on a specific procedure that might read, for example, "The operator shall monitor and record the temperature of the mercury-in-glass thermometer at 15-minute intervals."

So, let us take a look at these different elements. Establishing the proper parameters for heating is a task for a processing authority or the research and development team. Safety is the number-one consideration. Thermal processes must be established to ensure that potential pathogens are controlled. When the Preventive Controls for Human Foods rule¹ (21 CFR Part 117) was enacted, processors expended a great deal of effort reevaluating traditional processes, such as baking and frying, to validate that they not only yielded quality products but that they also provided an adequate kill step. They also worked to update their food safety programs to ensure that they met the requirements of the rule. As an example, this work showed that traditional baking processes were adequate to ensure safety and quality. However, cookies or brownies with inclusions such as nuts or chocolate nibs presented a different challenge. The inclusions did not receive as much heat as the dough, so the emphasis was now on ensuring that the ingredients themselves received a kill step by the supplier.

All instruments that are used to monitor temperature must be properly calibrated and suitable for the task. How often an instrument is calibrated depends upon the instrument itself and should be determined by the Hazard Analysis and Critical Control Points (HACCP) team. A supplier of a handheld thermometer might recommend that the instrument be calibrated monthly. If the measurements being made are critical for safety, then the HACCP team might recommend more frequent calibrations. 

The Low-Acid Canned Foods regulation in 21 CFR Part 113.40(a) states the following:

(1) Temperature-indicating device. Each retort shall be equipped with at least one temperature-indicating device that accurately indicates the temperature during processing. Each temperature-indicating device shall have a sensor and a display. Each temperature-indicating device and each reference device that is maintained by the processor shall be tested for accuracy against a reference device for which the accuracy is traceable to a National Institute of Standards and Technology (NIST), or other national metrology institute, standard reference device by appropriate standard procedures, upon installation and at least once a year thereafter, or more frequently if necessary, to ensure accuracy during processing. Each temperature-indicating device and each reference device that is maintained by the processor shall have a tag, seal, or other means of identity.²

Processors of low-acid canned foods have the option of replacing the mercury-in-glass thermometer with another instrument of equivalent accuracy, and many are doing so simply because they do not want mercury or glass on the processing floor. Processors should adopt the requirements highlighted above for their own calibration programs—i.e., maintaining records of the accuracy checks and tagging the instrument so that it is clear when the instrument was last tested for accuracy. This applies to all instruments including recorder charts, handheld devices, infrared thermometers, and any others. Calibration may be done internally or by a competent metrics company and, in some cases, must be done by regulatory agencies. 

The next step is to make sure that any person assigned to monitor temperature understands not only how to do the job, but also why they are doing it and why it is important. Educating personnel requires that procedures be developed and properly documented and that the educational process focuses on the written procedures. It is a bad idea to conduct training or education programs without using documented protocols. Why? The session may miss a point or fail to emphasize something important. Remember the old parlor game in which someone whispers something to someone in a group, and that person passes it on to the next person, and so on around the table. The message received by the last person is usually vastly different from the original message. 

The educational sessions should also include hands-on work on the floor. These sessions often employ more experienced and/or longer-employed staff as mentors and evaluators. Programs often mandate that the more experienced staff "sign off" on the trainee's competence. The procedures and training sessions should emphasize the following:

1. Records should be recorded immediately on the form or electronically. Results should never be recorded on a separate piece of paper for transfer at a later time.
2. If using hard copy forms, neatly record results and the time of the observation. Sign or initial the records neatly.
3. The operator should check the recorder chart at regular intervals and neatly sign or initial the form and note the time of the observation. 

It is important to routinely check the recorder charts for several reasons. If the temperature begins to drop, then the operator may be able to make an adjustment, thereby preventing a deviation. Regular checks will also let the operator know that the chart recorder still has ink. If the recorder runs out of ink, then any time period that is blank would be deemed a deviation. 

One last point regarding education: it may be helpful to send all retort operators and those responsible for monitoring temperature to a Better Process Control School. The focus of the course is low-acid and acidified foods, but the principles are applicable to all types of processed foods.

Remember, the recorder is not the official monitoring device. A now-defunct business named Castleberry's had a botulism issue a number of years ago.^3,4 Missing temperature monitoring devices on retorts was one of the problems that contributed to the botulism outbreak. In total, 14 people in seven U.S. states contracted botulism poisoning from consumption of the company's "Hot Dog Chili Sauce" and other products that were under-processed. The outbreak ultimately led to the closure of the company's Georgia canning operations in in March 2008.

Recordkeeping forms should be designed for ease of use. Ensure there is adequate space to record all results so that they are easily visible to reviewers and auditors. If an incorrect result is inadvertently entered on a form, that number should be lined out, initialed, and dated, and the correct value should be entered. The operator should then make a note on the form explaining the correction. The incorrect entry should never be erased or covered up. Such an action would be deemed a falsified record. Another useful addition to any recordkeeping form for temperature monitoring is to include the target temperatures and what to do in the event of a deviation. If those values are on the form and easily visible, then there should be no question about what is and is not an acceptable value.

Part of the educational process must include how the operator should handle deviations. How a deviation is handled depends upon the product and process. For products that are processed using high-temperature/short-time processes such as pasteurized foods and beverages, aseptic puddings, juices, and sauces, temperature drops are detected and diverted by a flow diversion valve. The low-temperature product usually goes back to a surge tank, from which it circulates until the proper temperature is achieved. If a system has a flow diversion valve, then the startup process should include a test while running water through the system. If the temperature drops below the target, it will divert, indicating that the flow diversion valve is functioning. Any procedure that addresses how to handle deviations should include notification of management. The management team is ultimately responsible for making the decision on the product in question. 

The bottom line is that temperature monitoring is more than writing numbers on a form or entering data into a spreadsheet. Operators and recorders must be properly educated on not only how to do the work, but also why it is important—as well as the ramifications of failing to properly do the work. Remember Castleberry.

References

1. U.S. Food and Drug Administration (FDA). Code of Federal Regulations. Title 21, Ch. I, Subpart B, Part 117. "Current Good Manufacturing Practice, Hazard Analysis, and Risk-Based Preventive Controls for Human Food." https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-117?toc=1.
2. FDA. Code of Federal Regulations. Title 21, Ch. I, Subpart B, Part 113.40. "Equipment and Procedures." https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-113/subpart-C/section-113.40. 
3. Falkenstein, Drew. "The 2007 Castleberry Farms Botulism Outbreak." Food Poison Journal. February 25, 2015. https://www.foodpoisonjournal.com/foodborne-illness-outbreaks/the-2007-castleberry-farms-botulism-outbreak/.
4. Centers for Disease Control and Prevention (CDC). "Botulism Associated with Commercially Canned Chili Sauce—Texas and Indiana, July 2007." Morbidity and Mortality Weekly Report. July 30, 2007. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm56d730a1.htm. 

Acknowledgment

The author thanks Richard Kimball, former President of the Institute for Thermal Processing Specialists (IFTPS), for his help in reviewing this manuscript.