Organic acids and their salts as dipping solutions to control listeria monocytogenes inoculated following processing of sliced pork bologna stored at 4 degrees C in vacuum packages.

Postprocessing contamination of cured meats with Listeria monocytogenes has become a major concern for the meat processing industry and an important food safety issue. This study evaluated aqueous dipping solutions of organic acids (2.5 or 5% lactic or acetic acid) or salts (2.5 or 5% sodium acetate or sodium diacetate, 5 or 10% sodium lactate, 5% potassium sorbate or potassium benzoate) to control L. monocytogenes on sliced, vacuum-packaged bologna stored at 4 degrees C for up to 120 days. Organic acids and salts were applied by immersing (1 min) in each solution inoculated (10(2) to 10(3) CFU/cm2) slices of bologna before vacuum packaging. Growth of L. monocytogenes (PALCAM agar) on inoculated bologna slices without treatment exceeded 7 log CFU/cm2 (P < 0.05) at 20 days of storage. No significant (P > 0.05) increase in L. monocytogenes populations occurred on bologna slices treated with 2.5 or 5% acetic acid, 5% sodium diacetate, or 5% potassium benzoate from day 0 to 120. Products treated with 5% potassium sorbate and 5% lactic acid were stored for 50 and 90 days, respectively, before a significant (P < 0.05) increase in L. monocytogenes occurred. All other treatments permitted growth of the pathogen at earlier days of storage, with sodium lactate (5 or 10%) permitting growth within 20 to 35 days. Extent of bacterial growth on trypticase soy agar plus 0.6% yeast extract (TSAYE) was similar to that on PALCAM, indicating that the major part of total bacteria grown on TSAYE agar plates incubated at 30 degrees C was L. monocytogenes. Further studies are needed to evaluate organic acids and salts as dipping solutions at abusive temperatures of retail storage, to optimize their concentrations in terms of product sensory quality, and to evaluate their effects against various other types of microorganisms and on product shelf life. In addition, technologies for the commercial application of postprocessing antimicrobial solutions in meat plants need to be developed.