title: Use of steam condensing at subatmospheric pressures to reduce Escherichia coli O157:H7 numbers on bovine hide.
abstract: This study used a laboratory-scale apparatus to apply subatmospheric steam to bovine hide pieces inoculated with Escherichia coli O157:H7 in maximum recovery diluent (MRD) and in high-liquid content and low-liquid content fecal suspensions (HLC fecal and LLC fecal, respectively). The survival of the organism in fecal clods, which were stored for 24 days in a desiccated state, was assessed. Inoculated fecal clods were also treated with subatmospheric steam. Steam treatment at 80 +/- 2 degrees C for 20 s reduced E. coli O157:H7 concentrations on hide inoculated to initial concentrations of approximately 7 log10 CFU/g by 5.46 (MRD inoculum), 4.17 (HLC fecal inoculum), and 5.99 (LLC fecal inoculum) log10 CFU/g. The reductions achieved in samples inoculated with LLC feces were larger than in samples inoculated with HLC feces (P < 0.05). Treatment at 80 +/- 2 degrees C for 10 s resulted in significantly smaller reductions (P < 0.05) on hide pieces of 2.54 (MRD), 1.94 (HLC fecal), and 2.15 (LLC fecal) log10 CFU/g. There were no significant differences among the reductions observed in all inoculum types in samples treated for 10 s. E. coli O157:H7 inoculated in fecal clods to 7.78 log10 CFU/g and stored at 4 or 15 degrees C survived for at least 24 days. Steam treatment (20 s) of 3-day-old clods reduced surviving E. coli O157:H7 numbers from 4.20 log10 CFU/g to below the limit of detection of the assay used (1.20 log10 CFU/g). This study shows that steam condensing at or below 80 +/- 2 degrees C can reduce E. coli O157:H7 when present on bovine hide, reducing the risk of cross contamination to the carcass during slaughter and dressing.
authors.affiliation: Teagasc, The National Food Centre, Castleknock, Dublin, Ireland. j.mcevoy@nfc.teagasc.ie
authors.forename: J M
authors.initials: JM
authors.lastname: McEvoy
authors.forename: A M
authors.initials: AM
authors.lastname: Doherty
authors.forename: J J
authors.initials: JJ
authors.lastname: Sheridan
authors.forename: I S
authors.initials: IS
authors.lastname: Blair
authors.forename: D A
authors.initials: DA
authors.lastname: McDowell
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000254:growth & development*; D005243:Feces / Q000382:microbiology; D005506:Food Contamination / Q000517:prevention & control*; D006358:Hot Temperature; D011312:Pressure; D012867:Skin / Q000382:microbiology*; D013227:Steam; D013997:Time Factors; D014867:Water
chemical_list: D013227:Steam; D014867:Water