The American Society for Quality defines calibration as follows: “The comparison of a measurement instrument or system of unverified accuracy to a measurement instrument or system of known accuracy to detect any variation from the required performance
specification.”1
Calibration is really a verification activity. Processors are ensuring that the instruments they use to ensure food safety, food quality, and legal issues are functioning and accurate. A range of instruments require calibration, including but not limited to: temperature monitoring
devices, pH meters, pressure gages, water activity meters, belt speeds, product flowmeters, metal detectors, and refractometers. Failure to properly maintain and manage your monitoring instruments can result in serious problems including product recalls, foodborne
illness, or injury.
In 2007, a botulism outbreak was attributed to chili sauce produced by Castleberry’s.2,3,4 In the investigation, it was discovered that a temperature indicating device was reading high. Such a scenario can adversely affect the overall lethality of a thermal process. When I teach HACCP, the example I like to use that shows the importance of a well-designed and well-maintained calibration program involves acidified bell peppers in California. During the season, the company produced red, green, yellow, and orange peppers using different cuts (sliced and diced, for example) and packed them in can sizes ranging from 1 lb. to institutional (603 × 700 size cans). Over the course of the season, the company produced hundreds of lots, all of which were determined to be at pH of 4.6 or below. Toward the end of the season, a regulator visited the facility to run tests on finished product and found that several lots exceeded the pH 4.6 limit.
The regulator reviewed the company records and found that, although the pH values were recorded as being adequate, there were no records showing that the pH meters had been calibrated. The company swore that it calibrated its meters regularly, but no record of this work existed. In other words, “If it is not written down, it never happened.” The Food and Drug Administration (FDA) embargoed the entire season’s pack and asked the company to create a sampling plan to clear the lot. The plan that was accepted would have entailed a great deal of testing and expense. The company decided to destroy the entire lot—all because it neglected to record calibration data.
Purpose of a Calibration Program
The goal of a calibration program is to ensure that all instruments used to monitor food safety, quality, and issues related to regulatory compliance have been properly calibrated and are operating effectively. The first step in the process is to conduct an inventory of all instruments
and equipment used for food monitoring. This may include, but need not be limited to: temperature measuring devices, temperature indicating devices, pressure gauges, meters (e.g., pH meter, refractometer), flowmeters, scales and load cells, metal detectors, standards, magnets, and laboratory testing devices. Each of these instruments should be placed into a Master Calibration Schedule (Figure 1).
The Master Calibration Schedule serves as an easy reference for the calibration program. The header “SQL” refers to whether the instrument is being used for food safety, food quality, or legal issues. Third-party auditors appreciate having this schedule on hand, as it summarizes
the entire calibration program.
Figure 1. Example of a Master Calibration Schedule
| Date | Type of Instrument | Serial no. | Location | Frequency | SQL* | Method | Points for Calibration | Standards Used | Responsible Person/Group | Comments |
| *SQL: Safety, Quality, or Legal (select one) | ||||||||||
Ideally, the company should conduct a risk assessment on all of the instruments requiring calibration and determine which are most critical for ensuring food safety and quality. This risk assessment should be carried out by the food safety team. These instruments will receive the highest priority when it comes to establishing calibration schedules. The food safety team may determine that instruments used for high-risk measurements, such as critical control points (CCPs), be calibrated more frequently.
KLM HIGH-giene SOLUTIONS can assist with the calibration of various instruments used in the food production facilities used for monitoring food safety and quality. You can contact us for more information and/or quotation
Article by Richard F. Stier, M.S.