Destruction of Listeria monocytogenes by electron-beam irradiation and food-grade chemicals in vacuum-packaged frankfurters stored at 4° or 10°C
Two studies were conducted to determine the fate of Listeria monocytogenes in vacuum-packaged frankfurters when food grade chemicals and electron-beam irradiation were used as interventions. In our first study, frankfurters were formulated with 2 or 3% (w/w) sodium lactate (SL), 0.1% (w/w) sodium diacetate (SDA), or SL (2 or 3%) + SDA (0.1%). Samples of the product without SL or SDA served as controls. Frankfurters inoculated with L. monocytogenes (6.0 log CFU/frankfurter) were irradiated (0.0, 1.0, and 2.0 kGy) and stored at 4°C for 90 days or 10°C for 36 days. L. monocytogenes on control frankfurters grew rapidly and reached greater than 9.0 log CFU/frankfurter. Irradiation of frankfurters at 1.0 and 2.0 kGy reduced initial numbers of the pathogen by [difference] 1.65 and 3.0 logs, respectively. In contrast, growth of the pathogen was completely inhibited in frankfurters containing 2% or 3% SL irrespective of irradiation dose or storage temperature. The second study evaluated the antimicrobial activity of liquid smoke, sodium lauryl sulfate, and electron-beam irradiation against L. monocytogenes in vacuum packaged frankfurters. Frankfurters formulated with or without 2% (w/w) sodium lactate (SL) were immersed (2 min) in distilled water (control), 30 % (v/v) liquid smoke (LQS), 1% (w/v) sodium lauryl sulfate (SLS) or LQS + SLS. Initial numbers of L. monocytogenes were reduced by 0.66, 1.77, and 1.27 log, on samples (without SL) that were immersed in LQS, SLS, and LQS+SLS, respectively. Log reductions on samples with SL were 0.77 (LQS), 2.84 (SLS), and 2.13 (LQS+SLS). Irradiation (2.0 kGy) reduced initial numbers of the pathogen on controls by 3.52 log and produced further reductions of 4.93, 2.60 and 4.26 log respectively, on LQS-, SLS-, and LQS+SLS-treated samples with no added SL. For samples with SL, irradiation reduced numbers by 4.15, 4.54, 3.43, and 3.65 for control, LQS-, SLS-, and LQS+SLS-treated samples, respectively. Survivors were completely suppressed in all samples formulated with SL. The combination of all these interventions would insure that L. monocytogenes will be decreased substantially as opposed to using each intervention individually in this popular ready-to-eat meat product.