Effect of Prepackage and Postpackage Pasteurization on Postprocess Elimination of Listeria monocytogenes on Deli Turkey Products

Abstract

Surface pasteurization for inactivation of Listeria monocytogenes was evaluated for radiant heat prepackage pasteurization, submersed water postpackage pasteurization, and combinations of the two techniques on various types of ready-to-eat deli turkey products obtained from at least four different manufacturers. Products were inoculated either by in-package liquid inoculum or surface sponge-contact with approximately 10⁹ CFU of L. monocytogenes. Additional testing of radiant heat pasteurization was performed with low-level inoculation of product undersides with approximately 100 CFU of L. monocytogenes followed by enrichment recovery after pasteurization. Prepackage pasteurization provided 2.0 to 2.8 log reductions when processed for 60 s and 2.8 to 3.8 log reductions when processed for 75 s. An improved radiant oven provided 3.53 (60 s) and 4.76 (75 s) log reductions of L. monocytogenes. No positive samples were detected after enrichment when 40 samples of deli turkey (4 to 4.5 kg) undersides were inoculated at low levels and processed for 75 s. Submersed water postpackage pasteurization provided 1.95 to 3.0 log reductions when processed for 2, 3, 4, or 5 min, and combinations of the two processes gave 3.0 to 4.0 log inactivation of L. monocytogenes using either 60 + 60 s or 60 + 90 s for the prepackage and postpackage pasteurization processes, respectively. These processes, either individually or in combination, can provide postprocess elimination of bacteria for the manufacture of safe ready-to-eat deli meats.