Essential elements of a processing environment monitoring program have been identified by an expert group of the International Life Sciences Institute (ILSI) Europe.

The aim is to help industry and regulators with targeted environmental monitoring by covering information on outbreaks, pathogens in low moisture foods, and knowledge on indicators.

Past outbreaks have shown the role of the environment as a contamination pathway. However, there are still questions and a lack of clarity on how to set up a program to provide early warnings of potential product contamination, said the study published in the International Journal of Food Microbiology.

The majority of outbreaks and recalls involving low moisture foods such as nuts, spices and infant food, have been because of Salmonella, with only a few related to Bacillus cereus, Cronobacter, Listeria monocytogenes and E. coli.

Design of program
Two recent infant formula outbreaks linked to Salmonella environmental contamination highlight the importance of monitoring the factory space, researchers said. In 2019, rice-based infant formula was behind a Salmonella Poona outbreak that affected more than 30 infants. In 2017-18, a Salmonella Agona outbreak linked to infant formula sickened 40 youngsters.

Salmonella Poona was not found in food products or the processing environment, while Salmonella Agona was confirmed in the food. The two incidents were caused by an isolate confirmed by whole genome sequencing to be similar to a strain previously implicated in outbreaks from the same facilities more than a decade before.

Researchers said processing environment monitoring programs should be designed to identify critical points to be routinely sampled and to seek and destroy pathogens of concern. They need to be managed and updated. A hazard analysis should be done to identify relevant pathogens for the process and product.

Controls include hygienic zoning with segregation of production areas, hygienic design of equipment, cleaning and disinfection and utility controls.

Processing environment monitoring through surface swabbing is a proactive approach to anticipate product contamination. Finished product testing is of limited value to identify low prevalence contamination, which is mainly the case for low moisture foods, as it does not reveal where problems might have occurred.

Sampling should consider product proximity and priority depending on hygienic conditions and place in the process such as before or after heat treatment. Sampling systems, target organisms, methods, areas, frequencies, and corrective actions depend on the product hazard and local conditions.

Need for follow-up
Monitoring microbial contamination in the processing environment should be followed by corrective and preventive action plans. Molecular tools help with these plans by providing information such as adherence capability potential, resistance to cleaning agents and heat and biofilm formation.

Genetic characterization of isolates provides insights to understand the difference between resident and sporadic strains in a processing environment, according to the experts.

Tests for indicator organisms can provide information about process failures, possible contamination sources or toxin formation and the overall hygiene level, including verification of cleaning and disinfection, and they could allow for corrective actions before pathogens can emerge. However, they are not a replacement for pathogen testing, the scientists cautioned.

Action limits or thresholds for acceptable and unacceptable results are often applied to indicators. This allows for warning signs before an actual safety or quality issue occurs. Setting actions limits requires establishing a baseline beforehand. This can be done by multiple sample rounds after and before cleaning as well as during production and account for seasonal variations.

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