MICROBIAL ECOLOGY OF HUMAN PATHOGENS RELATIVE TO POULTRY PROCESSING
Location: Bacterial Epidemiology and Antimicrobial Resistance
Title: Control of Listeria monocytogenes in Ham Deli Loaves using Organic Acids as Formulation Ingredients
Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2010
Publication Date: November 1, 2010
Citation: Lloyd, T., Alvarado, C.Z., Mckee, S.R., Berrang, M.E. 2010. Control of Listeria monocytogenes in Ham Deli Loaves using Organic Acids as Formulation Ingredients. Journal of Food Safety. 30(4):793-803.
Interpretive Summary: Listeria monocytogenes is a human foodborne pathogen which has caused outbreaks due to contaminated fully cooked meat and poultry products. Foodborne listeriosis is a serious disease with a high rate of mortality relative to other foodborne diseases. The meat and poultry industry is constantly looking for more effective means to control this pathogen in product. Food grade organic acids have bactericidal activity and are attractive for use as interventions in meat and poultry processing or as an additive in product. In this study, different combinations of organic acids (potassium lactate, sodium lactate and sodium diacetate) were tested as ingredients in the raw product formulation and as post-cook dip treatments for ham deli loaves. Ham deli loaves were formulated in a pilot processing plant, cooked, cooled then inoculated with a marker strain of Listeria monocytogenes. Deli loaves were stored under refrigeration for 56 d and cultured for L. monocytogenes at one week intervals. L. monocytogenes numbers increased during storage in untreated deli loaf product while the numbers did not increase in product treated with organic acids. This demonstrates that organic acid formulation and treatment may have utility for lengthening the lag phase and controlling the growth of this deadly pathogen in processed turkey meat products. Meat and poultry processors can use this information in planning product formulations and treatments to assure continued microbiological quality of the final product.
Organic acids are popular preservatives and are utilized in the industry to inhibit the growth of Listeria monocytogenes (LM) in ready-to-eat (RTE) products. In this study, sodium lactate (SL), potassium lactate (PL) and sodium diacetate (SD) were utilized alone or in combination in the raw product and as a post-cook dip to determine their inhibitory effect on the growth of LM in ham deli loaves. The loaves were first formulated with an organic acid as an ingredient, cooked, cooled, inoculated with Streptomycin-resistant LM, and then dipped in an organic acid treatment. The treatments consisted of PL in the raw product and PL in the dip, PL with SL/PL/SD dip, SL/SD along with PL dip, and SL/SD with SL/PL/SD dip. A positive (inoculated) and negative (non-inoculated) control were dipped in distilled water. On days 0, 7, 14, 21, 28, 42, 56, loaves were sampled for LM. In the ham deli loaves, the treatments containing PL – SL/PL/SD, SL/SD – PL, and SL/SD – SL/PL/SD had similar inhibition effects on LM from day 0 to day 42. On day 56, the PL – SL/PL/SD and SL/SD – SL/PL/SD treatments were similar. The growth of LM increased immediately in the positive control, while the negative control appeared to have no growth. The PL – SL/PL/SD, SL/SD – PL, and SL/SD – SL/PL/SD treatments increased the lag phase of LM at least through day 42. Therefore, meat processors are provided with a useful method for controlling LM in RTE meat and poultry products.