Avoid hysteria about listeria

Cleanliness in any facility is important to protect product, reputation and revenue.

However the need for effective cleaning regimes in food manufacturing facilities goes way beyond this, potentially being a matter of life and death. Neil Brown, technical director of Hygiene Group explains how en effective cleaning, disinfection and maintenance programme can help to mimise risks

Contamination during processing can cause huge problems for manufacturers, but can cause an even bigger problem for the consumer. Among the worst of these contaminants is Listeria. So common that it cannot be eradicated completely, there are measures that can be taken to ensure levels are reduced to the point where it is unlikely to cause infection and disease.

Listeria is a rod-shaped bacterium, widely found wherever there is standing water in both food factories and the wider environment.

Transferred easily, Listeria can be carried into manufacturing facilities on equipment, or on the boots and clothing of operatives. While most of the thousands of species of Listeria are of no clinical significance in humans, two or three serotypes of monocytogenes are commonly implicated in the human illness listeriosis.

The symptoms of listeriosis range from those that we associate with a severe cold or mild food poisoning to septicaemia. Listeriosis can be life-threatening, particularly among pregnant women and people with reduced immunity such as the elderly and the very young. Death rates of 20 to 30 per cent are often quoted.

Facilities which process liquids such as unpasteurised milk are probably the most susceptible to Listeria contamination, as are facilities that wash produce and as a result have excess water pooling.

Food is self-protecting to a point, particularly food with a high salt or sugar content. But food with high water content, such as cooked meats, can be high-risk even when refrigerated as Listeria can grow in cool temperatures.

Time to get dry? Keeping areas dry and eliminating the presence of unnecessary water can significantly reduce the risk of contamination. Rinse water left on the floor and pooling inside equipment should be cleaned up where possible. However, standing water inside drains can harbour Listeria, and this cannot be taken away. It is important, therefore, that careful cleaning processes are implemented to minimise the risk, along with terminal disinfection.

Drains and covers should be cleaned carefully and then coated with a foam disinfectant which can be left to work. Floors should be cleaned and dried carefully to avoid water pooling.

Because of their physical characteristics, Biofilms on surfaces harbour many microorganisms, including Listeria monocytogenes, and are particularly difficult to clean, requiring a particular combination of chemicals to remove.

Disinfect thoroughly Effective cleaning then needs to be followed by total coverage with a fine spray of disinfectant, ensuring that this covers and penetrates the entire surface. Residues of disinfectants left on the top of sprayer tips and bottles need to be removed as, when dry, those left by quats and amphoterics can actually support microbial growth, so adding another source of infection.

While chiller evaporators need frequent cleaning, the condensate lines are easily forgotten. After cleaning the body of the evaporators, biocides should be pumped into the condensate tray and allowed to drain through the condensate line. It is even better if the lines can be temporarily blocked, to extend contact time.

Another forgotten place that can harbour Listeria is the very fabric of the building. Walls and dividers that sandwich insulation, if damaged, can absorb contaminated water from the floor and lift it as high as three to four feet within the fabric. The walls then become a reservoir for infection, and this cannot be cleaned. It is therefore not just the cleaning that is important, but the maintenance of the building itself.

Despite the press hype surrounding well publicised cases of Listeriosis in humans, the bacterium can be destroyed easily with biocides. The potential risks in food factories, though considerable, can be minimised relatively simply through planning and implementing an effective programme of cleaning, disinfection and maintenance.