CONTROL OF FOODBORNE PATHOGENS IN MEAT PRODUCTS BY SANITATION, DRYING AND ANTIMICROBIALS John N. Sofos Colorado State University

SANITIZER INACTIVATION OF ACID- ADAPTED AND NONADAPTED LISTERIA MONOCYTOGENES BIOFILMS Objective To evaluate the antimicrobial effects of sodium hypochlorite (200 ppm, pH 10.4), pH-adjusted (pH 6.8) sodium hypochlorite (200 ppm), a quaternary ammonium compound (200 ppm), and peroxyacetic acid (150 ppm) on biofilms produced by previously acid-adapted or nonadapted Listeria monocytogenes inoculated in fresh beef decontamination washings.

2 Closed symbols = acid-adapted cells; open symbols = nonadapted cells Stainless steel attached cells; fresh beef washings (15 o C, 2 days) inoculated with Listeria monocytogenes

Closed symbols = acid-adapted cells; open symbols = nonadapted cells Deattached cells; fresh beef washings (15 o C, 2 days) inoculated with Listeria monocytogenes

Conclusions Previous acid adaptation did not affect biofilm formation or inactivation. Intact biofilms were more resistant to inactivation than biofilm cells (deattached) removed into suspension. Peroxyacetic acid was more effective on the attached cells of the natural flora than those of L. monocytogenes. Peroxyacetic acid was relatively less effective on biofilm cells in suspension than on attached biofilm cells when compared with the other sanitizers. Sodium hypochlorite adjusted to pH 6.8 was more effective than when unadjusted (pH 10.4).

FATE OF LISTERIA MONOCYTOGENES IN FRESH MEAT DECONTAMINATION FLUIDS AT 4 AND 10 o C Objective To evaluate the potential for survival and growth of acid-adapted, partially acid-adapted or nonadapted Listeria monocytogenes in acid or nonacid (water) spray-washings of fresh beef at low temperatures to simulate conditions encountered in the meat industry.

Behavior of Listeria monocytogenes in meat washings

Conclusions Limited survival of L. monocytogenes for at maximum 4 days may be expected in undiluted acidic (lactate or acetate) meat decontamination washings, or mixed with water washings, when the resulting pH is less than 4.0. Acid-containing washings with a pH above 4.0 may support survival and potential growth for extended times, while in nonacid (water) washings the pathogen may increase to high numbers.

FRESH BEEF DECONTAMINATION AND POPULATIONS OF LISTERIA MONOCYTOGENES DURING VACUUM- PACKAGED STORAGE (4 o C, 10 o C) TREATMENTS Control Water (pH 6.7, 55  C) Water (pH 6.7, 75  C) Lactic acid (2%, pH 2.3, 55  C) Acetic acid (2%, pH 2.8, 55  C)

2 a a a a a a a a a a a b b bbb b b b b b b b b b Acid-adapted Listeria monocytogenes in vacuum packaged beef Not-treated:, Water (55°C):, Water (75°C):, Lactic acid (55°C): or Acetic acid (55°C):

2 d b b c a d d c a b c c b a a b b a a a c b b a a

Conclusions Application of organic acids (acetic or lactic acid) to meat can reduce levels of contamination and then inhibit growth of L. monocytogenes during storage at 4 or 10  C. Although 75  C water decreased the initial population of L. monocytogenes on meat, growth of the pathogen occurred during storage. Prior acid-adaptation of this strain did not enhance growth on meat treated with acid or water. This study emphasizes the importance of long-term residual effects of acid and water decontamination treatments and storage temperatures on meat safety.

EVALUATION OF PROCESSES TO DESTROY ESCHERICHIA COLI O157:H7 AND LISTERIA MONOCYTOGENES IN WHOLE MUSCLE HOME DRIED BEEF JERKY Objectives To determine the survival of inoculated E. coli O157:H7 populations during preparation of whole muscle beef jerky with and without marinade and acids.

Escherichia coli O157:H7 Beef Jerky o C 68.3 o C Closed symbols = TSA Open symbols = SMAC

Escherichia coli O157:H7 Beef Jerky o C 68.3 o C Closed symbols = TSA; Open symbols = SMAC

Escherichia coli O157:H7 Beef Jerky (68.3 o C) Closed symbols = TSA Open symbols = SMAC 2 Water = 94 o C, 15 secMarinate/store at 4 o C, 24 h Season/store at 4 o C, 24 hHot brine = 78 o C, 90 sec Acetic acid (2.5%), 57.5 o C 20 sec

Escherichia coli O157:H7 Beef Jerky (68.3 o C) Water = 94 o C, 15 secMarinate/store at 4 o C, 24 h Season/store at 4 o C, 24 hHot brine = 78 o C, 90 sec Acetic acid (2.5%), 57.5 o C 20 sec

Escherichia coli O157:H7 Beef Jerky (62.5 o C)

Bacterial counts (TSA+0.1% pyruvate) on jerky (dried at 60.0 o C) inoculated with E. coli 0157:H7 5.0 log reduction

Survival Of L. monocytogenes on beef jerky—(PALCAM) 5.0 log reduction

Conclusions The traditional marination procedure did not result in a 5 log reduction of either pathogen. In addition, the traditional marination procedure may provide protection/resistance of pathogens during drying. In general, application of pre-drying treatments or modified marination was more detrimental to either pathogen than the control or traditional procedures and more detrimental to Listeria monocytogenes than E. coli O157:H7. Bacterial injury may be occurring during drying.

TREATMENTS TO CONTROL POST- PROCESSING CONTAMINATION BY LISTERIA MONOCYTOGENES ON PORK FRANKFURTERS AND SLICED BOLOGNA STORED AT 4 o C IN VACUUM PACKAGES Objective To evaluate antimicrobials or their combinations in the formulation of frankfurters, or as dipping solutions for bologna slices, against surface inoculated Listeria monocytogenes after peeling/slicing and before vacuum packaging.

2 Bologna slices inoculated with Listeria monocytogenes and then immersed (1 min)

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Conclusions Listeria monocytogenes inoculated (2-3 log CFU/cm 2 ) on bologna slices before vacuum packaging reached high populations (> 7 log CFU/cm 2 ) in days of storage at 4 o C. Immersion of inoculated bologna slices in acetic acid (2.5 and 5%), lactic acid (5%), sodium diacetate (5%) or potassium benzoate (5%) inhibited Listeria monocytogenes for over 90 days at 4 o C. Lower immersion concentrations of lactic acid (2.5%) and sodium diacetate (2.5%), or immersion in sodium acetate (2.5 and 5%), and sodium lactate (5 and 10%) exhibited lower levels of inhibition.

Conclusions Results of this study revealed that post-processing contamination with L. monocytogenes may be controlled in cured meat products by post-processing exposure to solutions of acetic, lactic, benzoic or sorbic acid or their salts. Sensory evaluation studies should be performed, however to refine the concentrations needed and to determine their effects in product shelf-life before the commercial application of any of the effective treatments of this study. Evaluation of antimicrobial effects at abusive temperature is also suggested and technological innovations are needed for commercial application of the treatments.

2 Frankfurters with antimicrobials included in the formulation inoculated with Listeria monocytogenes

2 Inoculated frankfurters dipped in hot (75 o C) water; open symbols = 1 frankfurter/bag; closed symbols = 2 frankfurters/bag

2 Frankfurters with antimicrobials included in the formulation inoculated with Listeria monocytogenes

Conclusions Listeria monocytogenes inoculated (2-4 log CFU/cm 2 ) on frankfurters after peeling exceed 7 log CFU/cm 2 after day at 4 o C in vacuum packages. Permissible concentrations of sodium acetate and sodium diacetate (both at 0.25% of the total formulation weight) were inhibitory to Listeria monocytogenes inoculated on frankfurters post- processing for up to 30 days at 4 o C. The permissible concentration of sodium lactate (3% of the total formulation weight) inhibited growth of the pathogen for 50 to 70 days during storage at 4 o C under the experimental conditions.

Conclusions Increase of the permissible concentrations of sodium acetate to 0.5% did not affect growth of L. monocytogenes for more than 20 days, while by doubling their permissible concentrations, sodium diacetate and sodium lactate exhibited complete control for 120 days at 4 o C. As applied, post-packaging thermal pasteurization (75-80 o C/30-90sec) had variable effects in reducing initial contamination and was not effective or reliable in controlling growth of L. monocytogenes during storage, especially when two frankfurters were included in a package.

Conclusions The increase in the permissible concentrations of antimicrobials in frankfurters could be avoided by combining a lower level of sodium lactate (1.8%) with sodium acetate (0.25%) or sodium diacetate (0.25%); these combinations inhibited growth of the pathogen for up to 120 days at 4 o C. Post-packaging thermal treatment may enhance the inhibitory activity of the combined antimicrobials during storage at 4 o C. Use of adequate levels of antimicrobials or their combinations, in the formulation of cooked meat products, needs to be evaluated for effects on product quality and shelf-life, and for antimicrobial effects at abusive temperatures.

ACKNOWLEDGEMENTS Faculty –K.E. Belk –P.A. Kendall –J.A. Scanga –G.R. Schmidt –G.C. Smith Post Docs: –J. Samelis –J. Ikeda –M. Calicioglu Research Associate –M.L. Kain Graduate Students : –A. Abushelaibi –S. Albright –C. Anderson –T. Bacon –G. Bedie –J. Burnham –E. Derrickson –T. DiPersio –S. Lakkakula –J. Ransom –K. Segomelo –J. Stopforth –Y. Yoon Funding : USDA-CSREES Colorado Agricultural Experiment Station National Pork Producers Council