title: Effect of simulated spray chilling with chemical solutions on acid-habituated and non-acid-habituated Escherichia coli O157:H7 cells attached to beef carcass tissue.
abstract: Samples (10 by 20 by 2.5 cm) of beef carcass tissue were inoculated (10(4) to 10(5) CFU/cm2) with Escherichia coli O157: H7 that was either non-acid habituated (prepared by incubating at 15 degrees C for 48 h in inoculated filter-sterilized composite [1:1] of hot and cold water meat decontamination runoff fluids, pH 6.05) or acid habituated (prepared in inoculated water fluids mixed with filter-sterilized 2% lactic acid [LA] runoff fluids in a proportion of 1/99 [vol/vol], pH 4.12). The inoculated surfaces were exposed to conditions simulating carcass chilling (- 3 degrees C for 10 h followed by 38 h at 1 degree C). Treatments applied to samples (between 0 and 10 h) during chilling included the following: (i) no spraying (NT) or spraying (for 30 s every 30 min) with (ii) water, (iii) cetylpyridinium chloride (CPC; 0.1 or 0.5%), (iv) ammonium hydroxide (AH; 0.05%), (v) lactic acid (LA; 2%), (vi) acidified sodium chlorite (ASC; 0.12%), (vii) peroxyacetic acid (PAA; 0.02%), (viii) sodium hydroxide (SH; 0.01%), or (ix) sodium hypochlorite (SC; 0.005%) solutions of 4 degrees C. Samples were taken at 0, 10, 24, 36, and 48 h of the chilling process to determine changes in E. coli O157:H7 populations. Phase 1 tested water, SH, PAA, LA, and 0.5% CPC on meat inoculated with non-acid-habituated pathogen populations, whereas phase 2 tested water, SC, AH, ASC, LA, and 0.1% CPC on meat inoculated with acid- and non-acid-habituated populations. Reductions in non-acid-habituated E. coli O157:H7 populations from phase 1 increased in the order NT = water = SH < PAA < LA < CPC. Reductions from phase 2 for acid-habituated cells increased in the order NT = water = SC < ASC = LA = AH < CPC, whereas on non-acid-habituated cells the order observed was NT = water = SC < AH = ASC < LA < CPC. Previous acid habituation of E. coli O157:H7 inocula rendered the cells more resistant to the effects of spray chilling, especially with acid; however, the trend of reduction remained spray chilling with water = non-spray chilling < spray chilling with chemical solutions.
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523-1171, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Stopforth
authors.forename: Y
authors.initials: Y
authors.lastname: Yoon
authors.forename: K E
authors.initials: KE
authors.lastname: Belk
authors.forename: J A
authors.initials: JA
authors.lastname: Scanga
authors.forename: P A
authors.initials: PA
authors.lastname: Kendall
authors.forename: G C
authors.initials: GC
authors.lastname: Smith
authors.forename: J N
authors.initials: JN
authors.lastname: Sofos
mesh_terms: D000818:Animals; D002417:Cattle / Q000382:microbiology*; D003080:Cold Temperature; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004202:Disinfectants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development*; D005506:Food Contamination; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D005525:Food-Processing Industry / Q000592:standards*; D006863:Hydrogen-Ion Concentration; D013997:Time Factors
chemical_list: D004202:Disinfectants