Control of Listeria monocytogenes in vacuum packaged frankfurters by generally-recognized-as-safe (GRAS) antimicrobials and electron-beam irradiation

Byelashov, Oleksandr
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The effect of sodium lactate (SL), lactic acid (LA), sodium lauryl sulfate (SLS) and electron beam irradiation on viability of Listeria monocytogenes and selected quality characteristics of vacuum-packaged frankfurters made with 2% (w/w) or without sodium lactate (SL) was evaluated. In the first study, frankfurters were immersed for 1 or 3 minute in solutions containing all combinations of 0 and 5% (v/v) LA and 0.0, 0.5 and 1 % (w/v) SLS. The treated product was surface inoculated with 10⁷CFU of a five-strain mixture of L. monocytogenes per link, vacuum packaged and stored for at 4.0° C for 90 days. In the second experiment frankfurters were dipped for 1 minute in H₂O (control) or in 1% SLS+5% LA inoculated with 10⁸ CFU of L monocytogenes and irradiated (0, 1.0, or 2.0 kGy) in vacuum packages and stored at 4.0° C. Dipping in 5% LA or 1% SLS alone reduced initial numbers of the pathogen by 0.4 to 0.7 log. In contrast, the combination of 5% LA and 1% SLS reduced numbers of the pathogens by 3.8-4.2 log CFU/link. Reduction of initial numbers of L. monocytogenes did not differ with dipping time; however there was some residual bacteriostatic effect when samples with SL were dipped for 3 minutes in LA (5%) +SLS (1% or 0.5 %). Irradiation (2 kGy) of treated frankfurters reduced bacterial numbers to non-detectable levels. Number of survivors did not increase on frankfurters that contained SL. The Hunter L-, a- and b-values were not affected by the dipping solutions, 2% SL or irradiation. The pH of the frankfurters was not changed by SL, but treatment solutions with 5% LA decreased pH of the product (P<0.05). The volatile profile of surface treated frankfurters was not different from the control, and no increase in lipid oxidation products and sulfur compounds was observed after irradiation and during the storage. Based on these results irradiation (1.0 or 2.0 kGy) of frankfurters formulated with SL (2%) and surface-treated with LA (5%) + SLS (1%) has a good potential for controlling L. monocytogenes in frankfurters without significantly affecting the quality of the product.

Food Science and Technology