title: Inactivation of acid-adapted and nonadapted Escherichia coli O157:H7 during drying and storage of beef jerky treated with different marinades.
abstract: The inactivation of both acid-adapted and unadapted Escherichia coli O157:H7 during the processing of beef jerky was studied. Following inoculation with the pathogen, beef slices were subjected to different predrying marinade treatments, dried at 60 degrees C for 10 h, and stored at 25 degrees C for 60 d. The predrying treatments evaluated were as follows: (i) no treatment (C), (ii) traditional marinade (TM), (iii) double-strength TM modified with added 1.2% sodium lactate, 9% acetic acid, and 68% soy sauce with 5% ethanol (MM), (iv) dipping into 5% acetic acid for 10 min followed by application of TM (AATM), and (v) dipping into 1% Tween 20 for 15 min and then into 5% acetic acid for 10 min followed by TM (TWTM). Bacterial survivors were determined during drying and storage using tryptic soy agar with 0.1% pyruvate, modified eosin methylene blue agar, and sorbitol MacConkey agar. Results indicated that bacterial populations decreased during drying in the order of TWTM (4.9 to 6.7 log) > AATM > MM > C > or = TM (2.8 to 4.9 log) predrying treatments. Populations of acid-adapted E. coli O157:H7 decreased faster (P < 0.05) in AATM and TWTM than nonadapted cells during drying, whereas no significant difference was found in inactivation of acid-adapted and nonadapted inocula in C and TM samples. MM was more effective in inactivating the nonadapted than the adapted inoculum. Bacterial populations continued to decline during storage and dropped below the detection limit (-0.4 log10 CFU/cm2) as early as day 0 (after drying) or as late as day 60, depending on acid adaptation, predrying treatment, and agar medium. The results indicated that acid adaptation may not increase resistance to the hurdles involved in jerky processing and that use of additional antimicrobial chemicals or preservatives in jerky marination may improve the effectiveness of drying in inactivating E. coli O157:H7.
authors.affiliation: Center for Red Meat Safety, Department of Animal Sciences, Colorado State University, Fort Collins 80523, USA.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Calicioglu
authors.forename: John N
authors.initials: JN
authors.lastname: Sofos
authors.forename: John
authors.initials: J
authors.lastname: Samelis
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Kendall
authors.forename: Gary C
authors.initials: GC
authors.lastname: Smith
mesh_terms: D019342:Acetic Acid; D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000254:growth & development / Q000502:physiology*; D000431:Ethanol; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D008461:Meat Products / Q000382:microbiology*; D019354:Sodium Lactate; D013025:Glycine max; D013696:Temperature; D013997:Time Factors
chemical_list: D000431:Ethanol; D019342:Acetic Acid; D019354:Sodium Lactate