REMOVAL OF BACTERIA FROM BEEF TISSUE BY SPRAY WASHING AFTER DIFFERENTTIMES OF EXPOSURE TO FECAL MATERIAL

This study examined the effect of exposure time of beef-fat fascia to an inoculated fecal paste on the efficiency of removal of bacteria by spray washing or rinsing. Brisket fat (obtained <15 min postmortem) sa mples (10 by 10 by 2 cm) were inoculated, in the geometric center of t heir fascia surface, with four 0.64-cm diameter loops of a bovine feca l paste containing an inoculum (10(8) CFU/g) of streptomycin-resistant Escherichia coli ATTC 11370. Triplicate samples were spray washed wit h water (35 degrees C, 20.7 bar) and then rinsed with solutions of 2% acetic acid, 5% hydrogen peroxide, or 12% trisodium phosphate, or spra y washed with water at 35 degrees C or 74 degrees C (20.7 bar), in an automated spray-washing cabinet for 12 s, after 0, 2, or 4 h of exposu re to the inoculated fecal paste. The samples were analyzed for strept omycin-resistant bacterial counts. Washing or washing/rinsing at time 0 (immediately after exposure to the inoculated fecal paste) with tris odium phosphate; 35 degrees C water, hydrogen peroxide, acetic acid, a nd 74 degrees C water removed 3.04 +/- 0.40, 3.52 +/- 0.55, 3.62 +/- 0 .67, 3.69 +/- 0.72 and 4.17 +/- 0.55 log CFU/cm(2), respectively. Appl ying the spray-washing treatments 2 or 4 h after exposure to the fecal paste resulted in significantly (P < 0.05) less removal (1.76 to 3.89 log CFU/cm(2) after 2 h and 0.94 to 2.58 log CFU/cm(2) after 4 h) of bacteria. Thus, the time of exposure to fecal contamination affected t he attachment of bacteria to beef-carcass tissue, as indicated by the decreasing numbers of bacteria removed by spray washing with increasin g time of exposure, regardless of the washing treatment. The most effe ctive washing agent was 74 degrees C water at all washing times.