Listeria monocytogenes, a facultative anaerobe, is an airborne pathogen. L. monocytogenes has been isolated in soil, silage, food processing environments, and healthy humans and animals. A variety of foods have been recalled from market shelves because of contamination with Listeria monocytogenes. Individuals with compromised immune systems, e.g., newborns, the elderly, and people with immunodeficiency syndrome, are most susceptible to listeriosis.

The widespread occurrence of Listeria makes it nearly impossible to avoid contamination during the handling of the meat products, e.g. slicing and packaging. L. monocytogenes is able to grow at low temperatures and is affected by neither high salt concentrations nor the presence of nitrite. Due to the high mortality of listeriosis, there is an increasing interest in measures aimed at controlling this pathogen. The use of lactate has proven to be effective in inhibiting the growth of Listeria monocytogenes in both cured and uncured meat products.

In a study conducted at the Kulmbach Institute in Germany, samples with 2% and 3% sodium lactate (60% concentration) were compared with a control formulation without added lactate. L. monocytogenes was inoculated into the sliced bologna at approximately 100 microorganisms per gram of product. Listeria counts in the control reached levels of 10⁸ per gram of product. In the bologna with 2% sodium lactate, the lag phase was extended by 100%. The use of 3% lactate (60%) demonstrated effective total control through 28 days of refrigerated storage at 41°F/5°C.

 

Effect of PURASAL on Listeria monocytogenes in sliced vacuum packed cooked sausages (Kulmbach Institute Germany, 1995)

 

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