Process validations and food production

How can you keep potentially harmful bacteria (like Salmonella, Listeria monocytogenes, or Toxin-producing E. coli), that come into your plant with raw ingredients, from getting into your finished products?

“…it is essential that a validation be performed using parameters that represent the worst case scenario for the process.”
-Deibel Laboratories

Where do the microbes come from?

There are many types of bacteria that are commonly found on raw agricultural products, food ingredients and products, and in the soil itself.  The vast majority of these organisms are not pathogenic (i.e. harmful), but there is always a good chance of pathogen contamination.  Pathogen contamination is usually a result of exposure to environmental conditions or animals, such as rodents, birds, or insects, but also from the manufacturing facility itself.  The number of microbes on raw products can likewise be increased by transportation, storage and post-harvest practices.

What is a process validation?

A process validation is a scientific study that determines the total potential pathogen reduction in the food manufacturing process, often expressed as a “log reduction” strategy.  In practical terms, a process validation is a scientific study in which product samples are inoculated either with a pathogen of concern (i.e. lab level) or a surrogate culture (i.e. in the manufacturing facility; more on this later) and exposed to a kill process.  Samples are analyzed, along with positive and negative controls, and the overall log reduction of the inoculated microbe(s) is determined.  Simply put, a log reduction is a reduction of the bacterial population by a power of 10.  So, a drop from 1,000 to 100 is a one-log reduction, and a drop from 1,000 to 10 is a two-log reduction.  The log reduction required for a process depends on the particular regulatory or customer expectations.  For example, in the U.S., there is an expectation for a 2 log reduction of E. coli 0157:H7 in sausage, a 4-5 log reduction of Salmonella in roasted almonds, and a 6.5 log reduction of Salmonella and Listeria in cooked meats, poultry, and seafood.

How are process validations done?

An effective process validation relies on the manufacturer already having an effective HACCP plan, solid GMP’s, effective sanitation and pest control, calibrated equipment, and good overall control of the process.  Once these are established, the process validation can be done one of two ways.

In the first type of validation, the untreated product is sent to the laboratory.  The product is inoculated with the pathogen of concern, such as Salmonella, and the product is allowed to stabilize to its original moisture level.  Once the product is stabilized, multiple samples of the product are subjected to multiple runs of the kill step in question (heating, fumigation, etc.).  Stabilization of the microbes within the product matrix is the key step a successful process validation; over the years we have perfected the stabilization process for a host of surrogates to many common food pathogens as well as the pathogenic organisms themselves. Samples are then analyzed and compared against inoculated, untreated samples (that had not gone through the kill step), and the log reduction is calculated.  This type of in-lab process validation is only effective when the kill step can be accurately reproduced in the laboratory.  Some processes, like oil roasting, lend themselves well to lab simulation; while others (i.e. spray drying) do not simulate effectively.  Where the process can not be replicated in the lab, an in-plant surrogate validation is required.

For an in-plant validation, product is sent to the lab, but instead of being inoculated with the pathogen of concern, a surrogate culture is used.  A surrogate is a non-pathogenic microbe that is used in lieu of the pathogen.  Use of a surrogate culture is essential because it is never appropriate to introduce bacterial pathogens to a food processing environment.  An effective surrogate is one whose resistance to the kill step is well known relative to the pathogen of concern.  Once the lab has inoculated and stabilized the product with the surrogate culture, it is retuned to the plant where a trained professional introduces inoculated samples into the process flow and recovers them after the kill step is complete.  It is essential that the inoculated samples are introduced into a full process load (e.g., a full bed on a belt roaster, or a full fumigation chamber).  Running the inoculated samples through an otherwise empty process is not effective because it does not adequately represent processing conditions.  Several “processed” samples are then sent back to the lab to be analyzed and the log reduction of the surrogate (and subsequently the pathogen) is calculated.

What are the important considerations for process validations?

As stated above, it is meaningless to conduct a process validation in a manufacturing environment where there is an ineffective HACCP system, inconsistent adherence to GMP’s, sanitation and/or pest control procedures.  It is essential that a validation be performed using parameters that represent the worst case scenario for the process.  For example, in a heat process, cooking temperatures should be at their absolute lowest, exposure time should be at its absolute quickest, and product throughput should be at its greatest volume.  This ensures that any parameters you run during normal processing are more effective than those that were validated.  The parameters established during the process validation can then serve as validated critical limits in your HACCP plan.  Process validations run using only normal processing parameters often lead to a breach of critical limits as a result of normal process variation.

Even though process validations are a critical part of ensuring product safety, a significant challenge to the industry is the prevention of post-process contamination.  This places extreme importance on plant air quality, moisture control, traffic control, hand sanitation, prevention of cross-contamination, and microbiological testing of environmental swabs, raw materials, and finished products.  At Deibel Labs, we can assist you with all of these important tasks, in addition to process validations.  Please contact a Deibel Labs representative for more information, including our newest laboratory in Milano, Italy.