Purpose: To determine the effect of moisture, pH, and cultured sugar-vinegar blend combinations to inhibit Listeria monocytogenes or Leuconostoc mesenteroides in uncured turkey stored at 4 °C for 16 weeks.
Methods: Twenty uncured deli-style turkey breast treatments were generated using a central composite design for three variables, moisture (53.7-86.3%), pH (5.6-6.6) and cultured sugar-vinegar blend (0-5.79%) with five levels for each variable (center point treatment replicated 5 times). Sliced cooked products were surface inoculated with 3 log CFU/g of L. monocytogenes or L. mesenteroides (5-strain mix), vacuum packaged (100 g/package), and stored at 4 °C for up to 16 weeks. Triplicate samples per treatment were assayed at 0, 1, 2, 4, 6, 8, 12, 14, and 16 weeks by enumerating on Modified Oxford or APT agars. Finished products were analyzed for moisture, pH, NaCl and aw.
Results: Treatments in this study had a greater inhibitory effect on L. monocytogenes than L. mesenteroides. The replicates of the center point (70% moisture, 3.75% antimicrobial and pH of 6.1) supported <1-log increase of L. monocytogenes at 16 weeks whereas all replications supported >2-log increase of L. mesenteroides at 2 weeks. Five of the 20 treatments supported >1-log increase of L. monocytogenes during 16 weeks of storage; the pH was ≥6.4 in four of those five treatments. Sixteen of 20 treatments supported growth of L. mesenteroides within 2 weeks. L. mesenteroides was inhibited in three treatments with ≥5.0% cultured sugar-vinegar blend.
Significance: A predictive model based on the interaction between moisture, pH and cultured sugar-vinegar blend will be developed to help meat processors identify formulations to inhibit L. monocytogenes and spoilage microbes.