Lactate Keeps Listeria in Check

N/Ats 1994 report, "Foodborne Pathogens: Risks and Consequences," The Council for Agricultural Science and Technology (Ames, IA), estimated that as many as 9,000 deaths and 6.5 to 33 million illnesses in the U.S. each year are food-related. Meat products, in particular, have a high risk of pathogenic bacteria growth that has been confirmed by recent outbreaks of Listeria. To enhance the safety of meat products, processors first must reduce the risk of pathogen contamination, then take steps to inhibit the pathogen growth during handling and storage. Using sodium or potassium lactate in meat products is one way to inhibit pathogens.

Microbial inhibitor
Sodium and potassium lactate are salts of lactic acid, which is naturally present in the animal tissue. Each takes the form of a clear, high-viscosity liquid. For easier handling, both are commercially available in a 60% aqueous solution.

Lactates inhibit the growth of pathogens such as Salmonella, Clostridium botulinum, Staphylococcus aureus and Listeria monocytogenes. They do this by increasing the lag phase, or dormant phase, of the microorganisms. In addition, both are hygroscopic and help lower water activity.

This antimicrobial action can suppress growth for extended periods to help assure a longer shelflife and increased product safety. Keep in mind, however, that lactate does not kill bacteria, nor can it be used to mask poor sanitation practices. Meat product safety depends on several factors working together such as initial bacteria load, plant sanitation, handling and storage temperatures. Nevertheless, lactates can enhance a total safety program even for microorganisms such as Listeria.

Keeping Listeria in check
Recently, many different foods have been recalled due to Listeria contamination. Listeria monocytogenes is widespread in the environment. It has been isolated from soil, silage, food processing environments, and healthy humans and animals. The ubiquitous nature of this microorganism makes it nearly impossible to avoid contamination during meat product handling. This makes it a good candidate for inhibition control using lactates.

In an inoculation study, researchers at the Kulmbach Institute in Germany, compared a control sausage formula with test samples that contained 2% and 3% sodium lactate (60% concentration). While Listeria counts in the control reached the range of 10⁸, the sausage with 2% sodium lactate extended the lag phase by 100%. The sample containing 3% lactate demonstrated effective inhibition control through 28 days of refrigerated storage at 41°F (See figure 1).

At Detroit's Wayne State University, Leora Shelef, a professor in the Department of Nutrition and Food Science conducted a test in a meat model system to determine the effect of 2% sodium chloride alone and in combination with 3.3% lactate (60%). Consisting of cooked, strained beef, the untreated meat model had a water activity of 0.986. Adding 2% salt lowered the water activity to 0.962, while the further addition of 3.3% lactate yielded a water activity of 0.972.

Shelef inoculated the meat samples with Listeria monocytogenes and incubated them at 68°F for 7 days. Although the salt had a small effect on Listeria growth, the combination of salt and lactate caused a full growth inhibition. (See figure 2.)

If sodium reduction is a product requirement, product developers can use potassium lactate. Several studies have proven that it is as effective as sodium lactate on Listeria control.

Formulating with lactates
Lactate can be applied to wide range of cured and uncured meat and poultry products. It can be found in fresh sausage, fresh marinated whole-muscle products, fajita strips, bratwurst, cooked sausage, roast beef, fat-free/low-fat franks, sliced deli items and many different poultry products.

Both spoilage and pathogenic organisms commonly found in meat are sensitive to lactates—even those that are more salt-tolerant. How well lactate performs is directly related to its concentration. At the recommended 3.3% use level, a 60% lactate solution can extend the shelflife of further processed meat products by 30% to 100%.

Lactate addition is easily incorporated into standard processing systems. Production staff may simply add lactate at the cutter stage or blend it with curing pickle.

The FDA has affirmed both sodium and potassium lactate as GRAS for use as a direct human food ingredients. USDA approves its use as a flavoring agent and flavor enhancer in various meat and poultry products. For all products covered under the 9 CFR 319.180 (emulsified products such as frankfurters, bologna, etc.) the current allowable use is 2% of actual sodium lactate (which is 3.3% of the 60% commercially available solution). For all cooked products that are hermetically sealed and not covered under the 9 CFR 319.180, the maximum use level is 4.8%, which equals 8% of the 60% commercially available solution. It should be declared in the product ingredient listing on a dry solid basis.

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