Use of Nonpathogenic, Green Fluorescent Protein–Marked Escherichia coli Biotype I Cultures To Evaluate the Self-Cleansing Capabilities of a Commercial Beef Grinding System after a Contamination Event

Inoculated beef trim containing a cocktail of green fluorescent protein–marked Escherichia coli biotype I cultures as surrogates for E. coli O157:H7 was introduced into two large, commercial grinding facilities capable of producing 180,000 kg of ground product in 1 day. Three repetitions were performed over 3 days. Sampling occurred at three different points within the process: postprimary grind, postsecondary grind-blender, and postpackaging. Resulting data show that, as the inoculated meat passes through the system, the presence of the marked surrogate quickly diminishes. The depletion rates are directly related to the amount of product in kilograms (represented by time) that has passed through the system, but these rates vary with each step of the process. The primary grinder appears to rid itself of the contaminant the most quickly; in all repetitions, the contaminant was not detected within 5 min of introduction of the contaminated combo bin into the system, which in all cases, was prior to the intro...