Mitigate Pathogen Risk in Frozen Foods

Dr. Wiedmann emphasized, however, that in frozen food, the vast majority of food safety issues are due to improperly designed or inconsistently or incorrectly implemented food safety systems. As such, food processors and manufacturers can and do need to have a good food safety system in place to prevent and mitigate as much as possible the potential of selling contaminated products to consumers.

For food processors and manufacturers of frozen food products, the first step is recognizing the prevalence of L. monocytogenes and understanding how this pathogen can be introduced into frozen food products.

A Ubiquitous and Persistent Pathogen in Frozen Foods

John Butts, PhD, founder and principal of FoodSafetyByDesign, LLC, advisor to Land O’Frost and a member of the Food Quality & Safety Editorial Advisory Board, underscored that food processors really need to understand the risks of the problem. “Just because it’s frozen doesn’t mean the organism isn’t present,” he says. He also emphasized the persistent nature of the pathogen, citing an experience in a meat plant in which L. monocytogenes contaminated a product 12 years after the same pathogen had resulted in the first fatality from a contaminated turkey frank.

Dr. Wiedmann detailed two primary ways pathogens can be introduced into frozen foods. The first is through the raw material if it does not go through a “kill step,” such as blanching, to inactivate the pathogen in vegetables and fruit. The second is through environmental exposure at the processing facility, which, he said, can lead to contamination of products after the “kill step” or heat treatment.

Drilling a bit deeper, Sanjay Gummalla, PhD, senior vice president of scientific affairs at the AFFI, emphasized the risk of repeated entry of L. monocytogenes as raw produce comes from fields into facilities, allowing for the potential spread within the production environment due to movement of personnel and vehicular traffic. “Frozen food facilities inherently present optimal harborage environments for Listeria growth,” he says, emphasizing the need for food manufacturers to continually address ways to prevent and limit the pathogen by improving sanitation practices, environmental monitoring programs, and investments in hygienically designed equipment and facility infrastructure. He underscores, however, the fact that food can still be contaminated in the post-lethality environment, making it imperative that facilities establish and implement good manufacturing practices.

Environmental Monitoring

Dr. Wiedmann also stresses that a key component of a well-designed and implemented food safety system is effective environmental monitoring and “seek and destroy” programs, as well as effective root cause analysis for every time a problem is detected. He emphasized the need to verify consistent implementation of validated safety practices, which means ensuring that these practices are followed consistently day in and day out.

Dr. Butts, who developed the seek and destroy process in the early 1990s, says that the process separates verification samples from process control samples. “A positive process control sample is an opportunity to celebrate because the plant has the opportunity to intervene before product or contact surfaces are involved,” he says. “The application of process control sampling helps eliminate “firefighting” and enables preventive and predictive pathogen control.”

Dr. Gummalla also emphasizes the need for kill steps (or lethality steps) to effectively reduce the presence of L. monocytogenes in facilities, and the requirement to validate these processes as mandated by the Food Safety Modernization Act (FSMA).

The need for environmental monitoring accompanied by verification programs as key components of a food safety plan was recently discussed and highlighted in an article published in the Journal of Food Protection, in which investigators surveyed food safety professionals working in frozen food manufacturing facilities. The survey found that floors, walls, and drains were the major areas of reported concerns in facilities for finding Listeria-positive results, and that most food safety programs within the facilities surveyed focused their attention on identifying the presence of Listeria in the processing environment and mitigating product contamination, while few focused on testing active raw material and finished products for Listeria. Along with environmental monitoring, the survey also reported the need by industry to improve and develop verification programs to reduce the prevalence of L. monocytogenes in environments in which frozen food products are processed.