In the ready-to-eat food industry, Listeria control is mandatory to ensure the food safety of the products since its presence could cause a disease called listeriosis. The objective of the present study was to carry out a challenge test to verify the efficiency of different combinations of natural antimicrobial ingredients against Listeria monocytogenes to be used in ready-to-eat foods. Six different formulations of cooked ham were prepared: a control formulation and five different formulations. An initial inoculation of 2 log cycles was used in the different products, and the growth of Listeria was monitored at different temperatures and times (4 °C for 17 w and 7 °C for 12 w). Control samples showed a progressive growth, reaching 5-6 log after 3 or 4 weeks. The rest of the samples showed constant counts of Listeria during the entire study. Only samples containing 100 ppm nitrite + 250 PPM ascorbic acid + 0.7% PRS-DV-5 did not control the growth of Listeria at 7 °C after 7 w of storage. The results obtained allowed us to classify the cooked ham prepared using natural ingredient combinations as a "Ready-to-eat food unable to support the growth of L. monocytogenes other than those intended for infants and for special medical purposes".
Keywords: Listeria monocytogenes; challenge test; food safety; natural ingredients combinations.