The objective of this study was to identify ingredients that inhibit Listeria monocytogenes in natural, organic, or clean-label ready-to-eat meat and poultry products. Fourteen ingredients were screened in uncured (no-nitrate-or-nitrite-added), traditional-cured (156 ppm of purified sodium nitrite), cultured (alternative cured, natural nitrate source, and Staphylococcus carnosus), or preconverted (alternative cured, natural nitrite source) turkey slurries. Slurries were cooked, cooled, inoculated to yield 3 log CFU/ml L. monocytogenes, stored at 4°C, and tested weekly for 4 weeks. Three antimicrobial ingredients, 1.5 % vinegar-lemon-cherry powder blend, 2.5 % buffered vinegar, and 3.0 % cultured sugar-vinegar blend, were incorporated into alternative-cured ham and uncured roast beef and deli-style turkey breast. Controls included all three meat products without antimicrobial ingredients and a traditional-cured ham with 2.8 % sodium lactate-diacetate. Cooked, sliced products were inoculated with 3 log CFU/g L. monocytogenes, vacuum packed, and stored at 4 or 7°C, for up to 12 weeks. For control products without antimicrobial agents stored at 4°C, a 2-log L. monocytogenes increase was observed at 2 weeks for ham and turkey and at 4 weeks for roast beef. Growth (>1-log increase) in the sodium lactate-diacetate was delayed until week 6. Compared with the control, the addition of either vinegar-lemon-cherry powder blend or buffered vinegar delayed L. monocytogenes growth for an additional 2 weeks, while the addition of cultured sugar-vinegar blend delayed growth for an additional 4 weeks for both ham and turkey. The greatest L. monocytogenes delay was observed in roast beef containing any of the three antimicrobial ingredients, with no growth detected through 12 weeks at 4°C for all the treatments. As expected, L. monocytogenes grew substantially faster in products stored at 7°C than at 4°C. These data suggest that antimicrobial ingredients from a natural source can enhance the safety of ready-to-eat meat and poultry products, but their efficacy is improved in products containing nitrite and with lower moisture and pH.

The objective of this study was to identify concentrations of sorbate, benzoate, and propionate that prevent the growth of Listeria monocytogenes on sliced, cooked, uncured turkey breast and cured ham. Sixteen test formulations plus a control formulation for each product type were manufactured to include potassium sorbate, sodium benzoate, or sodium propionate, used alone and combined (up to 0.3% [wt/wt]), or with sodium lactate-sodium diacetate combinations. Products were inoculated with L. monocytogenes (5 log CFU/100-g package) and stored at 4, 7, or 10 degrees C for up to 12 weeks, and triplicate samples per treatment were assayed biweekly by plating on modified Oxford agar. Data showed that 0.1% benzoate, 0.2% propionate, 0.3% sorbate, or a combination of 1.6% lactate with 0.1% diacetate prevented the growth of L. monocytogenes on ham stored at 4 degrees C for 12 weeks, compared with greater than a 1-log increase at 4 weeks for the control ham without antimicrobials. When no nitrite was included in the formulation, 0.2% propionate used alone, a combination of 0.1% propionate with 0.1% sorbate, or a combination of 3.2% lactate with 0.2% diacetate was required to prevent listerial growth on the product stored at 4 degrees C for 12 weeks. Inhibition was less pronounced when formulations were stored at abuse temperatures. When stored at 7 degrees C, select treatments delayed listerial growth for 4 weeks but supported significant growth at 8 weeks. All treatments supported more than a 1-log increase in listerial populations when stored at 10 degrees C for 4 weeks. These results verify that antimycotic agents inhibit the growth of L. monocytogenes on ready-to-eat meats but aremore effective when used in combination with nitrite.

Listeria monocytogenes growth can be controlled on ready-to-eat meats through the incorporation of antimicrobial ingredients into the formulation or by postlethality kill steps. However, alternate approaches are needed to provide options that reduce sodium content but maintain protection against pathogen growth in meats after slicing. The objective of this study was to determine the inhibition of L. monocytogenes by propionic acid-based ingredients in high-moisture, cured turkey stored at 4 or 7°C. Six formulations of sliced, cured (120 ppm of NaNO2 ), deli-style turkey were tested, including control without antimicrobials, 3.2% lactate-diacetate blend (LD), 0.4% of a liquid propionate-benzoate-containing ingredient, or 0.3, 0.4, and 0.5% of a liquid propionate-containing ingredient. Products were inoculated with 5 log CFU L. monocytogenes per 100-g package (3 log CFU/ml rinsate), vacuum-sealed, and stored at 4 or 7°C for up to 12 weeks; and populations were enumerated by plating on modified Oxford agar. As expected, the control without antimicrobials supported rapid growth, with >2 log average per ml rinsate increase within 4 weeks of storage at 4°C, whereas growth was observed at 6 weeks for the LD treatment. For both replicate trials, all treatments that contained liquid propionate or propionate-benzoate limited L. monocytogenes growth to an increase of <1 log through 9 weeks storage at 4°C. Sporadic growth (>1-log increase) was observed in individual samples for all propionate-containing treatments at weeks 10, 11, and 12. As expected, L. monocytogenes grew more rapidly when products were stored at 7°C, but trends in relative inhibition were similar to those observed at 4°C. These results verify that propionate-based ingredients inhibit growth of L. monocytogenes on sliced, high-moisture, cured turkey and can be considered as an alternative to reduce sodium-based salts while maintaining food safety.

Fermentation-derived nitrite (NO2) from vegetable sources is increasingly used as a "clean label" alternative to conventional NaNO2. Previous results suggested that processed meats cured with NO2 derived from a "natural" source had lower antimicrobial activity than did meats produced with chemical NaNO2; however, the differences were likely due to NO2 concentration rather than source. The objective of this study was to compare the antilisterial properties of traditional and clean label alternative curing approaches when combined with antimicrobials in deli-style turkey. Listeria monocytogenes inhibition by NO2 from synthetic and natural sources was validated in deli-style turkey (73 to 74% moisture, 1.8% salt, pH 6.4). Products were prepared with 0, 80, or 120 mg/kg NO2 using purified NaNO2 or cultured celery powder. Additional treatments were supplemented with 3.8% lactate-diacetate blend (LD) or 1% cultured sugar-vinegar blend (DF). Sliced cooked products were surface inoculated with L. monocytogenes at 3 log CFU/g, vacuum packaged, and stored at 4°C for 12 weeks. Results revealed an average 2.4-log increase in L. monocytogenes at 3 weeks in the control without antimicrobials, a 1.3-log increase at 4 weeks for both 80 mg/kg NO2 treatments, and a 1.5-log increase at 6 weeks for the 120 mg/kg NO2 treatments. No significant difference (P > 0.05) in growth inhibition was found between NO2 sources when equivalent concentrations were added. In uncured turkey with 3.8% LD or 1% DF, growth was delayed until 6 weeks, whereas supplementation with LD or DF and 80 mg/kg NO2 from either source delayed listerial growth through 12 weeks. This study confirmed that the concentration of NO2, rather than the source, is a primary factor in enhancing the safety of ready-to-eat meats. Both conventional NO2 treatments and a clean label solution consisting of a fermentation-derived antimicrobial combined with 80 mg/kg naturally derived NO2 inhibited L. monocytogenes through 12 weeks of storage at 4°C.