Purpose: Monitor viability of Lm on uncured ham steaks and uncured pork frankfurters containing added vinegar, subjected or not to high pressure processing (HPP), during extended refrigerated storage.
Methods: One batch of freshly-manufactured, vacuum-packaged, uncured pork frankfurters and one batch of uncured ham steaks were formulated with and without dry buffered vinegar (0.74%; Verdad Powder N6) or liquid buffered vinegar (2.41%; E(lm)inate V), respectively. Products were surface inoculated with 0.5 ml of the five-strain cocktail of Lm to achieve a target level of ca. 3.5 log CFU/package. After vacuum-sealing, the packages were or were not pressurized at 600 MPa (87,000 psi) for 3 min. Ham steaks and pork frankfurters were then stored for up to 180 days at 4°C.
Results: When both products were formulated without vinegar, Lm numbers increased by ca. 6.5 log CFU/package over 180 days of storage at 4°C; however, when both products were formulated with vinegar, pathogen numbers remained relatively unchanged during extended storage at 4°C. In addition, regardless if uncured ham steaks or uncured pork frankfurters were formulated with or without vinegar, HPP delivered an initial reduction in pathogen numbers of ca. 2.2 log CFU/pack. Thereafter, pathogen numbers remained relatively unchanged after 180 days at 4°C.
Significance: Inclusion of buffered vinegar in the formulation of uncured ham steaks or uncured pork frankfurters, alone or in combination with HPP, was an effective clean label antimicrobial agent for controlling outgrowth of Lm during extended storage at 4°C.