Levels of acetic and lactic acid in RTE meat and poultry products and their association with occurrence of Listeria monocytogenes at retail

The purposes of this study were (1) to quantify the levels of acetic, and lactic acid occurring in approximately 1800 retail ready-to-eat (RTE) processed deli meat and poultry products to determine the impact of current antimicrobial lethality treatments on occurrence of Listeria monocytogenes (LM) at retail, (2) to determine if the intrinsic levels of lactic acid (LA) produced by lactic acid bacteria (LAB) of the processed RTE meat or poultry affect the extrinsic levels of lactic acid added in RTE meat and poultry products, and (3) to evaluate 2%LA for its effect as a post-lethality treatment on the survival of LM on RTE meat and poultry products. Samples were randomly selected and acetic and lactic acids were extracted and analyzed by ion exclusion HPLC. Amount of LA extracted from the samples did not change with increased LAB counts (P> 0.05) and with storage time of six weeks (P>0.05).Thus, the age of the processed RTE meat or poultry did not affect the levels of lactic acid present in RTE meat and poultry products in six weeks at 4 C. The effect of 2%LA as a post lethality treatment on LM count differed according to meat type and time of storage. However, greater than a 1 log CFU/g reduction was achieved with frankfurters, bologna, and ham after application of 2%LA . Mean concentrations of acetic acid and lactic acid in samples varied by product type and by different manufacturers and ranged from 0.51 to 5.7 m/g (0.051 - 0.57%), and 12.88 to 23.03 m/g (1.28% -2.3%). Concentrations of acetic and lactic acids varied among manufacturers (p<0.0001) and within products produced by the same manufacturer. Higher levels of AA and LA in RTE meat and poultry products were associated (p<0.01) with lower occurrence of LM.Thus, addition of acetates and lactates as antimicrobials is helpful in formulations as a part of an overall listeria control program for processed meat and poultry products; however, even high levels of LA and AA may not prevent contamination of RTE meat and poultry with LM, particularly with post-process contamination.