Controlling Listeria monocytogenes in Natural, Ready-to-Eat Meat and Poultry Products

The study identified ingredients to suppress growth of Listeria monocytogenes in ready-to-eat (RTE), deli-style, meat and poultry products that meet “natural” or organic requirements defined by USDA.

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Objectives

• To screen a variety of natural flavorings, plant extracts, and microbial fermentation byproducts for antilisterial activity in model uncured and “naturally” cured meat systems (turkey slurries)
• To determine the effect of natural antimicrobial systems on flavor for meat/poultry products
• To compare the antilisterial activity of “natural antimicrobial” systems in naturally cured ham, uncured beef, and uncured deli-style turkey with that for traditional cured ham prepared with lactate-diacetate.

Conclusions

This study identified several commercial ingredients (1.5% lemon/cherry/vinegar blend, 2.0% buffered vinegar and 3.0% cultured cane sugar/vinegar blend) which can be used to inhibit growth of L. monocytogenes in natural ham, turkey, and roast beef without significant adverse effect on sensory attributes. The addition of “natural nitrite” through the use of preconverted vegetable powder enhanced the effect of the antimicrobials tested in ham compared with uncured turkey. Since the antilisterial effect of nitrite is dose dependent, and nitrite levels contributed by preconverted vegetable powder are typically lower than those found in traditionally cured products, naturally cured products logically have reduced microbial inhibition compared with traditional products. Overall, inhibition of L. monocytogenes in naturally cured ham supplemented with certain adjunct natural antimicrobials was similar to that of lower salt (1.6-1.8% NaCl), traditionally cured ham with lactate-diacetate blend. However, even the most effective turkey and ham treatments supported a 2-log increase of L. monocytogenes within 6 weeks storage at 4°C. It should be noted that listerial growth in beef was significantly delayed compared to the ham and turkey. The additional delay in beef may be attributed to either the relatively small differences in product moisture and pH compared to the other two product types or to other unidentified factors. These data suggest that certain natural growth inhibitors can improve the safety of natural and organic ready-to-eat meat and poultry products, but their efficacy is enhanced in the presence of nitrite, in products with lower moisture and pH, and when stored at strict refrigeration temperatures.

Deliverable

Although the natural ingredients delay growth compared with the No-Antimicrobial Control treatments, L. monocytogenes can still grow within 6 weeks storage at 4°C in natural ham and turkey, as well as lower salt, no phosphate traditional ham. Data further emphasize that storage at 4°C or lower is a critical factor in controlling growth of L. monocytogenes in ready-to-eat meat and poultry products regardless of antimicrobial addition. These results demonstrate the need to incorporate additional hurdles in natural meat and poultry products as well as when producing reduced-sodium traditional products.