Distribution of Escherichia coli O157:H7 in Beef Processed in a Table-Top Bowl Cutter†

Abstract

Beef-processing equipment can be contaminated with pathogens such as Escherichia coli O157:H7 and Salmonella spp. The bowl cutter has wide application in particle-size reduction and blending of meat products. This study was undertaken to determine (i) the distribution patterns of E. coli O157:H7 in equipment components and ground beef produced with a table-top bowl cutter under different operational conditions and (ii) the likelihood that pathogen contamination can be transferred to subsequent batches after a batch of beef contaminated with E. coli O157:H7 has been processed in the same bowl cutter. A beef trim (44.6 ± 29.5 g) inoculated with 2 log CFU of an E. coli O157:H7 mutant strain resistant to rifampicin ( E. coli O157:H7rif) was fed by hand into an uncontaminated beef-trim batch under two different batch sizes (2 and 4 kg), three processing times (60, 120, and 240 s), and two feeding modes (running and stoppage fed). There were no significant differences (P ≥ 0.05) among all the treatments for the averages of the counts of E. coli O157:H7rif distributed in the ground beef. Regardless of the processing time and the method used to feed the beef trims into the bowl cutter, the whole batch and the following subsequent batch became contaminated when previously contaminated beef was processed. Areas of the bowl cutter most likely to be contaminated with E. coli O157:H7 were (i) the material left on the top of the comb/knife guard and (ii) the knife. Material that overflowed the bowl cutter, when processing the batch with E. coli O157:H7rif, contaminated the equipment surroundings. A Pearson V probability distribution function was determined to describe the distribution of pathogenic organisms in the ground beef, a distribution that can also be applied when conducting process risk analyses on mixing-particle reduction operations for beef trims.