How to avoid Listeria in meat production

To guarantee food safety, good hygiene during food production is essential. Cleaning and disinfection play an important role, but also moisture control as water, moist, is the breeding ground for microorganisms and pathogens.

In the food industry, much attention is paid to cleaning and disinfection,but cleaning alone is not enough. During cleaning and disinfection, water is used and water is the breeding ground of molds, viruses and bacteria. As concluded in our last article discussing how to minimize the risk for microorganisms in meat production, it’s critical to keep the humidity levels under control.

Cleaning agents and disinfectants have a limited duration of action. Once they have worn off and the cleaned surfaces are still wet, microorganisms and pathogens can start growing again. Microorganisms will therefore survive, multiply and eventually even form a biofilm that is more resistant to most cleaning agents. Drying after cleaning is therefore essential.

Moisture control to avoid Listeria in meat production

Research by the University of Paris (France) has shown that the death rate of Listeria monocytogenes increases in four days from an average of Log 2.5 with only cleaning and disinfection to >Log 7 with cleaning, disinfection and quick drying by an air dryer (Log=time the bacterium needs to multiply). See figure 1.

^{Figure 1: Cleaning, disinfection & dehumidification reduces potential for microbial growth in 4 days}.

The higher death rate of Listeria is the result of the so-called water stress cycle, which consists of the following three steps: Osmotic stress, i.e. that the moisture is withdrawn from the cell, -> Re-hydration stress, i.e. that after drying, the cell takes up water again, -> Oxidative stress, i.e. that repeated drying and re-hydration weakens the cell wall, which means the cell is exposed to oxygen more often. 

"Drying reduces cell viability in Listeria because it damages the cell membrane,"
explains air treatment expert André van Zutphen from Munters.

Humidity control is crucial for hygiene and efficiency

Micro-organisms in food production and storage areas are best controlled by drying rapidly after cleaning and disinfection, and by controlling the air humidity during production. Most pathogens and viruses have in common that they thrive poorly at a relative humidity of about 50-60%.

Controlling relative humidity during production is hence crucial. With high relative humidity, some bacteria (such as Listeria) will still multiply even at low temperatures.

An additional advantage of such low humidity is that maintenance of buildings and equipment is needed less often and materials and (electronic) equipment wear out less quickly. It is also much more pleasant for people to work in a drier atmosphere.

Would you like to speak to one of Munters experts on humidity control, please find your local representative here.