EFFECTS OF ACETIC-LACTIC ACID TREATMENTS APPLIED TO BEEF TRIM ON POPULATIONS OF ESCHERICHIA-COLI O157-H7 AND LISTERIA-MONOCYTOGENES IN-GROUND BEEF

The efficacy of organic acid sprays for eliminating Escherichia coli O 157:H7 and Listeria monocytogenes from beef trim used in a model groun d beef production scheme was determined. Beef trim pieces with ca. 20% fat inoculated with E. coli O157:H7 or L. monocytogenes (ca. 3 log(10 ) CFU/g) were utilized as controls or treated by spraying with 2 or 4% acetic and lactic acids. Propylene glycol (20%) was the carrier for e ach treatment. Following acid treatment, intact pieces were stored at 4 degrees C for 12 or 24 h, ground, divided into 4 100-g retail packag es and stored at 4 degrees C for 0, 1, 2, or 4 days, at which time sur viving populations of E. coli O157:H7 or L. monocytogenes were enumera ted. High populations (>2.6 log(10) CFU/g) of the pathogens persisted in all treatments. The 2% acid spray reduced (P < 0.01) the E. coli O1 57:H7 population by only 0.1 log(10) CFU/g. The 2 and 4% acid sprays r educed (P < 0.001) the L. monocytogenes populations by 0.36 and 0.44 l og(10) CFU/g, respectively. Storing beef trim intact prior to grinding resulted in lower populations of E. coli O157:H7, and storage followi ng grinding did not affect populations of either pathogen. The acid tr eatments tested were only slightly effective as sanitizers for beef tr im destined for ground beef production.