How to Determine Critical Limits

So you can now determine critical control points (CCPs) for your HACCP plan. The next step is to identify critical limits. Critical limits are the boundaries or limits of acceptability and unacceptability for the processing parameter being measured. For example, the critical limit for a canned vegetable may be to cook it no less than at 250^oF for 30 minutes. Below this temperature/time combination, there would be no assurance of food safety. Above this limit the product would be safe, but may lack quality such as having a poor texture. Food manufacturers establish limits to ensure that hazards are controlled while quality is preserved.

In order to control significant hazards at CCPs, critical limits have been established for such factors as time, temperature, pH, water activity, moisture, acidity, visual defects, sanitizer concentration, operation of metal detector, salt concentration and flow rate. The HACCP team will need to decide the appropriate limits to effectively manage hazards at each CCP. The team cannot rely simply on their experience or common sense on this matter. Only a science-based decision is acceptable. Two approaches are to either base the decision on in-plant research data, or on published validated scientific research data.

Using Your Own Research Data

Conducting your own in-plant research can be done if you have the time, resources and expertise. You will need to follow scientific validated experimentation and statistical methods with adequate trials and product testing to achieve reliable and valid results. Common examples of experiments that you could run include heat penetration studies, temperature distribution studies, thermal death time studies, and  microbial challenge studies. Make sure that individuals conducting these experimentations are qualified processing experts and that you maintain adequate data on file for regulatory review.

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Using Validated Research Data

Even if you have the resources to do your own research, there is no point reinventing the wheel. You can use validated research data to establish your critical limits. These data can be sourced from scientific research journals, regulatory performance guidelines, trade association guides, processing authority, and university extension publications. Equipment manufacturers, consultants and experts can also provide you with information on appropriate critical limits. However, while it is okay to adopt control points based on validated research data, it is recommended that you conduct in-plant verification tests to demonstrate that you are able to maintain the critical limits and that by adhering to these limits, you are able to reduce significant hazards in your product to a safe level.

Reference: Scott, V. N. & Stevenson, K. E. (2006). HACCP – A systematic approach to food safety, 4th edition. Washington, DC: Grocery Manufacturers Association.