ABSTRACT The viability of Shiga toxin–producing Escherichia coli (STEC), Salmonella, and Listeria monocytogenes within plant- and beef-based burgers was monitored during storage and cooking. When inoculated (ca. 3.5 log CFU/g) into 15-g portions of plant- or beef-based burgers, levels of STEC and Salmonella decreased slightly (≤0.5-log decrease) in both types of burgers when stored at 4°C, but increased ca. 2.4 and 0.8 log CFU/g, respectively, in plant-based burgers but not beef-based burgers (≤1.2-log decrease), after 21 days at 10°C. For L. monocytogenes, levels increased by ca. 1.3 and 2.6 log CFU/g in plant burgers after 21 days at 4 and 10°C, respectively, whereas pathogen levels decreased slightly (≤0.9-log decrease) in beef burgers during storage at 4 and 10°C. Regarding cooking, burgers (ca. 114 g each) were inoculated with ca. 7.0 log CFU/g STEC, Salmonella, or L. monocytogenes and cooked in a sauté pan. Cooking plant- or beef-based burgers to 62.8°C (145°F), 68.3°C (155°F), or 73.9°C (165°F) delivered reductions ranging from ca. 4.7 to 6.8 log CFU/g for STEC, ca. 4.4 to 7.0 log CFU/g for L. monocytogenes, and ca. 3.5 to 6.7 log CFU/g for Salmonella . In summary, the observation that levels of all three pathogens increased by ca. 1.0 to ca. 2.5 log CFU/g in plant-based burgers when stored at an abusive temperature (10°C) highlights the importance of proper storage (4°C) to lessen risk. However, because all three pathogens responded similarly to heat in plant-based as in beef-based burgers, well-established cooking parameters required to eliminate STEC, Salmonella, or L. monocytogenes from ground beef should be as effective for controlling cells of these same pathogens in a burger made with plant-sourced protein. HIGHLIGHTS Cooking parameters validated for beef burgers will eliminate pathogens in plant burgers. Pathogen viability during cold storage is generally better in plant- than beef-based burgers. Values for pH, salt, carbohydrate, and nitrite were appreciably higher for plant burgers. Cooking temperatures were achieved in less time for plant- than beef-based burgers. Levels of indigenous flora were generally higher in beef- than plant-based burgers.

We evaluated high pressure processing to lower levels of Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes inoculated into samples of plant or beef burgers. Multi-strain cocktails of STEC and L. monocytogenes were separately inoculated (ca. 7.0 log CFU/g) into plant burgers or ground beef. Refrigerated (i.e., 4°C) or frozen (i.e., -20°C) samples (25-g each) were subsequently exposed to 350 MPa for up to 9 or 18 min or 600 MPa for up to 4.5 or 12 min, respectively. When refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of STEC were reduced by ca. 0.7 to 1.3 log CFU/g. However, when refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of L. monocytogenes remained relatively unchanged (ca. ≤0.3 log CFU/g decrease) in plant burger samples, but were reduced by ca. 0.3 to 2.0 log CFU/g in ground beef. When refrigerated plant or beef burger samples were treated at 600 MPa for up to 4.5 min, levels of STEC and L. monocytogenes were reduced by ca. 0.7 to 4.1 and ca. 0.3 to 5.6 log CFU/g, respectively. Similarly, when frozen plant and beef burger samples were treated at 350 MPa up to 18 min, reductions of ca. 1.7 to 3.6 and ca. 0.6 to 3.6 log CFU/g in STEC and L. monocytogenes numbers, respectively, were observed. Exposure of frozen plant or beef burger samples to 600 MPa for up to 12 min resulted in reductions of ca. 2.4 to 4.4 log and ca. 1.8 to 3.4 log CFU/g in levels of STEC and L. monocytogenes, respectively. Via empirical observation, pressurization did not adversely affect the color of plant burger samples, whereas appreciable changes in color were observed in pressurized ground beef. These data confirm that time and pressure levels already validated for control of STEC and L. monocytogenes in ground beef will likely be equally effective towards these same pathogens in plant burgers without causing untoward effects on product color.

ABSTRACT A total of 514 raw pork samples (395 ground or nonintact and 119 intact samples) were purchased at retail stores in Pennsylvania, Delaware, and New Jersey between July and December 2017. All raw pork samples were screened for serogroup O26, O45, O103, O111, O121, O145, or O157:H7 cells of Shiga toxin–producing Escherichia coli (STEC-7) using standard microbiological and molecular methods. In short, 21 (5.3%) of the 395 ground or nonintact pork samples and 3 (3.4%) of the 119 intact pork samples tested positive via the BAX system real-time PCR assay for the stx and eae virulence genes and for the somatic O antigens for at least one of the STEC-7 serogroups. However, none of these 24 presumptive-positive pork samples subsequently yielded a viable isolate of STEC displaying a STEC-7 serogroup-specific surface antigen in combination with the stx and eae genes. These data suggest that cells of STEC serogroups O26, O45, O103, O111, O121, O145, or O157:H7 are not common in retail raw pork samples in the mid-Atlantic region of the United States. HIGHLIGHTS None of the 514 retail raw pork samples were positive for STEC-7. Four of 514 raw pork samples harbored E. coli of unknown serogroup containing stx and eae . STEC-7 are uncommon in retail raw pork samples in the U.S. mid-Atlantic region.

ABSTRACT Meat bars are dried snacks containing a mixture of meat, berries, and nuts. To explore consumer awareness of meat bars, we conducted two online, nationally representative surveys and established that 70.8% (743 of 1,050) of U.S. citizens were unfamiliar with this product. When asked to check all answers that applied, most of the 545 respondents (who were recruited based on their familiarity with meat bars) preferred beef ( n = 385) as the protein source, followed by chicken ( n = 293), pork ( n = 183), and turkey ( n = 179). Most meat bars were purchased from grocery stores ( n = 447), followed by online orders ( n = 130) and outdoor stores ( n = 120). When asked specifically whether they made their own meat bars, 17.8% of respondents (97 of 545) replied “yes,” the majority (52 of 97, 54%) of which obtained recipes online. Some 69.1% (67 of 97) measured the internal temperature of the meat during dehydration, but only 10.3% (10 of 97) confirmed the internal temperature by using a thermometer. Given the paucity of information available on the fate of pathogenic or spoilage bacteria associated with meat bars, as another component of this study, batter was prepared with or without encapsulated citric acid (ECA; 0.74%) added to a formulation of ground beef (65%; 90% lean, 10% fat), chopped pecans (15%), golden flaxseed flour (9.7%), chopped cranberries (5.0%), chopped sunflower seeds (3.1%), sea salt (1.1%), black pepper (0.8%), and celery powder (0.35%). Batter was inoculated (ca. 6.5 log CFU/g) with Shiga toxin–producing Escherichia coli (STEC), portioned by hand (40 ± 0.1 g each), and then dried in a commercial dehydrator. Regardless of the drying treatment, inclusion of ECA in the batter resulted in a pH decrease from ca. 5.5 to ca. 4.7 to 5.0 in the finished product. Without ECA, when meat bars were dried at 62.8°C for 6 h, 71.1°C for 4 h, or 62.8°C for 2 h and then 71.1°C for 2 h, levels of STEC decreased by ca. 6.2, 6.3, or 5.2 log CFU/g, respectively. With ECA, STEC decreased by ca. 6.0, 6.6, or 6.0 log CFU/g in meat bars dried at 62.8°C for 6 h, 71.1°C for 4 h, or 62.8°C for 2 h and then 71.1°C for 2 h, respectively. Our results confirmed that a ≥5.0-log reduction in STEC could be achieved in meat bars formulated with or without ECA under all dehydration conditions tested.

ABSTRACT The effect of heating times and temperatures on inactivation of Salmonella in pâté made from chicken liver was evaluated. Raw chicken liver (ca. 1 kg) was blended in a food processor with two hard-boiled eggs (ca. 100 g total) plus a mixture of sautéed white onions (100 g), salt (5.0 g), black pepper (2.5 g), and butter (112 g). The tempered (ca. 15°C) raw pâté batter was inoculated with a nine-strain cocktail (ca. 6.5 log CFU/g) of Salmonella, and then ca. 25-g portions were aseptically transferred into sterile 50-mL polypropylene conical tubes. One set of tubes was completely submerged in a thermostatically controlled, circulating water bath set at 74.9°C and cooked to target instantaneous internal temperatures ranging from 60 to 73.9°C. An otherwise similar set of tubes was cooked at 60 to 73.9°C, with holding times of 3 to 30 min, in a water bath set at 1°C above each target endpoint cooking temperature. Regardless of the cooking process, when pâté was cooked to a target instantaneous internal temperature of 60 to 73.9°C, pathogen numbers decreased by ca. 1.9 to ≥6.4 log CFU/g; additional reductions of ca. 0.6 to 1.3 log CFU/g were observed when pâté was cooked to a target instantaneous internal temperature of 60 to 68°C and then held for 3 to 30 min. In related experiments, pâté was prepared as described above, but with inoculated chicken livers (500 g; ca. 5.5 log CFU/g) that were cooked in a frying pan maintained at ca. 140°C for 3 to 8 min with a mixture of sautéed onions, salt, black pepper, and butter and then blended with a hard-boiled egg. Pathogen numbers within liver cooked in a frying pan decreased by ca. 1.0 to 4.9 log CFU/g. Collectively, these findings may be useful for establishing cooking guidelines for pâté and thus for lowering the risk of illness if chicken liver is contaminated with Salmonella and the attendant batter is not handled or cooked properly. HIGHLIGHTS Cooking may reduce the potential risk of salmonellosis associated with liver pâté. A 5-log reduction was achieved when inoculated pâté was cooked to an internal temperature of ≥73.8°C. A 5-log reduction was achieved when pâté was made with inoculated liver fried for >8 min at 140°C. Findings of this study may be useful for establishing cooking guidelines for liver and pâté.

ABSTRACT We surveyed chicken livers from various sources for the presence and levels of Salmonella . The pathogen was recovered from 148 (59.4%) of 249 chicken livers purchased at retail stores in Delaware, New Jersey, and Pennsylvania over about a 9-month period. Positive samples harbored Salmonella at levels of 6.4 most probable number (MPN)/g to 2.4 log CFU/g. The percentage of Salmonella -positive livers purchased at retail outlets in New Jersey (72%, 59 of 82 livers) was significantly higher ( P < 0.05) than the percentage for livers purchased in Delaware (48%, 36 of 75 livers); however, this percentage was not significantly different ( P > 0.05) from that for livers purchased in Pennsylvania (57.6%, 53 of 92 livers). The pathogen was also recovered more often ( P = 0.019) from livers that were packaged by retailers (81 of 121 livers, 66.9%) than from livers packaged directly by processors (67 of 128 livers, 52.3%). In related studies, 12 (5.8%) of 207 chicken livers harvested from birds on a research farm tested positive for Salmonella at levels of 0.4 to 2.2 MPN/g. The recovery rate of Salmonella was 4.4% (6 of 135 livers) from livers with the gall bladder attached and 8.3% (6 of 72 livers) from livers when the gall bladder was removed at harvest on the research farm. We also quantified the levels of a nine-strain cocktail (ca. 6.5 log CFU/g) of Salmonella strains inoculated externally onto or internally into livers both before and after extended cold storage. Storage for at least 2 days at 4°C or 15 days at −20°C resulted in a decrease of about 1.0 log CFU/g in pathogen levels. Given the relatively high recovery rate (ca. 6.0 to 60.0%) and high (possibly illness causing) levels (0.4 MPN/g to 2.4 CFU/g) of Salmonella associated with chicken livers in the present study, further interventions for processors are needed to lower the prevalence and levels of this pathogen on poultry liver.

ABSTRACT All-pork mortadella, an Italian-style deli meat, was produced by a local artisanal meat producer with or without 1.0 or 1.5% liquid buffered vinegar (LBV), 0.4, 0.6, or 1.0% dry buffered vinegar (DBV), or a 2.5% blend of potassium lactate and sodium diacetate (KLac). In each of three trials, mortadella was sliced (ca. 1.5 cm thick, ca. 30 g) and surface inoculated with 250 μL per side of a five-strain mixture of Listeria monocytogenes (ca. 3.8 log CFU per slice). The packages were vacuum sealed and then stored at 4 or 12°C. In the absence of antimicrobials, L. monocytogenes levels increased by ca. 2.6 and 6.0 log CFU per slice after up to 120 or 28 days at 4 or 12°C, respectively. With inclusion of 1.0 or 1.5% LBV, 1.0% DBV, or 2.5% KLac as ingredients, pathogen levels decreased by ca. 0.3 to 0.7 log CFU per slice after 120 days at 4°C, whereas with inclusion of 0.4 or 0.6% DBV, L. monocytogenes levels increased by ca. 1.2 and 0.8 log CFU per slice, respectively. After 28 days at 12°C, inclusion of 2.5% KLac, 1.0 or 1.5% LBV, or 0.4 or 0.6% DBV resulted in a ca. 1.4- to 5.7-log increase in L. monocytogenes levels. When 1.0% DBV was included in the formulation, pathogen levels remained unchanged after 28 days at 12°C. However, product quality was lessened at this abusive storage temperature (12°C) for all treatments by the end of storage. Thus, inclusion of LBV or DBV, as clean-label ingredients, in mortadella is equally effective as KLac for controlling L. monocytogenes during storage at 4°C without adversely affecting product quality.

ABSTRACT Scalding of hide-on bob veal carcasses with or without standard scalding chemical agents typically used for hogs, followed by an 82.2°C hot water wash and lactic acid spray (applied at ambient temperature) before chilling, was evaluated to determine its effectiveness in reducing Shiga toxin–producing Escherichia coli surrogate populations. A five-strain cocktail of rifampin-resistant, nonpathogenic E. coli surrogates was used to inoculate hides of veal carcasses immediately after exsanguination (target inoculation level of 7.0 log CFU/100 cm 2 ). For carcasses receiving no scalding treatments, spraying with 82.2°C water as a final wash resulted in a 4.5-log CFU/100 cm 2 surrogate reduction, and an additional 1.2-log CFU/100 cm 2 reduction was achieved by spraying with 4.5% lactic acid before chilling. Scalding hide-on carcasses in 60°C water (no chemicals added) for 4 min in a traditional hog scalding tank resulted in a 2.1-log CFU/100 cm 2 reduction in surrogate levels, and a subsequent preevisceration 82.2°C water wash provided an additional 2.9-log CFU/100 cm 2 reduction. Spraying a 4.5% solution of lactic acid onto scalded, hide-on carcasses (after the 82.2°C water wash) resulted in a minimal additional reduction of 0.4 log CFU/100 cm 2 . Incorporation of scalding chemicals into the scald water resulted in a 4.1-log CFU/100 cm 2 reduction (1.9 log CFU/100 cm 2 greater than scalding without chemicals) in the surrogate population, and the first 82.2°C wash provided an additional 2.5-log CFU/100 cm 2 reduction. Application of antimicrobial interventions did not affect the carcass temperature decline during chilling, the pH decline, or the color characteristics of the ribeye or the flank of the bob veal carcasses.

ABSTRACT In total, 115 marinade samples (58 fresh marinades and 57 spent marinades) were collected over 12 months from specialty retailers (four individual stores) near Raleigh, NC. These marinades were screened for total mesophilic aerobic plate count (M-APC), total psychrotrophic aerobic plate count (P-APC), and Enterobacteriaceae . These marinades were also screened for the seven regulated serogroups of Shiga toxin–producing Escherichia coli . Stores A and B used immersion to marinade raw beef cuts, whereas stores C-1 and C-2 used vacuum tumbling. In general, marinade temperatures at the stores ranged from 1.8 to 6.6°C, and beef cuts were marinated from a few minutes to up to 3 days. Regardless of the process used to marinade meat, levels of M-APC and P-APC in fresh marinades ranged from 3.4 to 4.7 and 1.4 to 1.8 log CFU/mL, respectively, whereas Enterobacteriaceae were not detected in any fresh marinades, even after enrichment. However, levels of M-APC, P-APC, and Enterobacteriaceae in spent marinades collected from stores C-1 and C-2 (ca. 3.6 to 7.1 log CFU/mL) were significantly higher ( P < 0.05) compared with levels of these same types of bacteria enumerated from spent marinades collected at stores A and B (ca. ≤0.7 to 4.9 log CFU/mL). None of the 115 marinade samples tested positive for Shiga toxin–producing E. coli by using a BAX system real-time PCR assay. No significant ( P > 0.05) association was observed between microbial levels (i.e., M-APC, P-APC, and Enterobacteriaceae ) and the temperature or duration of the marination process. Levels of M-APC, P-APC, and Enterobacteriaceae in spent marinades were significantly affected by the marination method ( P < 0.05), with levels, in general, being higher in marinades used for tumbling. Thus, retailers must continue to keep marinade solutions and meat at a safe temperature (i.e., ≤4°C) and to properly and frequently sanitize the equipment and environment in both the processing area and deli case.

ABSTRACT The efficacy of an electrostatic spraying system (ESS) and/or the sprayed lethality in container (SLIC) method to deliver antimicrobial agents onto the surface of beef subprimals to reduce levels of Shiga toxin–producing Escherichia coli (STEC) was evaluated. Beef subprimals were surface inoculated (lean side; ca. 5.8 log CFU per subprimal) with 2 mL of an eight-strain cocktail comprising single strains of rifampin-resistant (100 μg/mL) STEC (O26:H11, O45:H2, O103:H2, O104:H4, O111:H − , O121:H19, O145:NM, and O157:H7). Next, inoculated subprimals were surface treated with lauric arginate (LAE; 1%), peroxyacetic acid (PAA; 0.025%), or cetylpyridinium chloride (CPC; 0.4%) by passing each subprimal, with the inoculated lean side facing upward, through an ESS cabinet or via SLIC. Subprimals were then vacuum packaged and stored at 4°C. One set of subprimals was sampled after an additional 2 h, 3 days, or 7 days of refrigerated storage, whereas another set was retreated via SLIC after 3 days of storage with a different one of the three antimicrobial agents (e.g., a subprimal treated with LAE on day 0 was then treated with PAA or CPE on day 3). Retreated subprimals were sampled after 2 h or 4 days of additional storage at 4°C. A single initial application of LAE, PAA, or CPC via ESS or SLIC resulted in STEC reductions of ca. 0.3 to 1.3 log CFU per subprimal after 7 days of storage. However, when subprimals were initially treated with LAE, PAA, or CPC via ESS or SLIC and then separately retreated with a different one of these antimicrobial agents via SLIC on day 3, additional STEC reductions of 0.4 to 1.0 log CFU per subprimal were observed after an additional 4 days of storage. Application of LAE, PAA, or CPC, either alone or in combination, via ESS or SLIC is effective for reducing low levels (ca. 0.3 to 1.6 log CFU) of STEC that may be naturally present on the surface of beef subprimals.

ABSTRACT To better understand how consumers perceive food safety risks in retail food store settings, a survey was administered to 1,041 nationally representative participants who evaluated possible food safety risks depicted in selected photographs and self-reported their perceptions, attitudes, and behaviors. Participants were shown 12 photographs taken at retail stores portraying either commonly perceived or actual food safety contributing factors, such as cross-contamination, product and equipment temperatures, worker hygiene, and/or store sanitation practices. Participants were then asked to specifically identify what they saw, comment as to whether what they saw was safe or unsafe, and articulate what actions they would take in response to these situations. In addition to the survey, focus groups were employed to supplement survey findings with qualitative data. Survey respondents identified risk factors for six of nine actual contributing factor photographs >50% of the time: poor produce storage sanitation (86%, n = 899), cross-contamination during meat slicing (72%, n = 750), bare-hand contact of ready-to-eat food in the deli area (67%, n = 698), separation of raw and ready-to-eat food in the seafood case (63%, n = 660), cross-contamination from serving utensils in the deli case (62%, n = 644), and incorrect product storage temperature (51%, n = 528). On a scale of 1 to 5, where 1 was very unsafe and 5 was very safe, a significant difference was found between average risk perception scores for photographs of actual contributing factors (score of ca. 2.5) and scores for photographs of perceived contributing factors (score of ca. 2.0). Themes from the focus groups supported the results of the survey and provided additional insight into consumer food safety risk perceptions. The results of this study inform communication interventions for consumers and retail food safety professionals aimed at improving hazard identification.

ABSTRACT A multiyear interagency Listeria monocytogenes Market Basket Survey was undertaken for selected refrigerated ready-to-eat foods purchased at retail in four FoodNet sites in the United States. Food samples from 16 food categories in six broad groups (seafood, produce, dairy, meat, eggs, and combination foods) were collected weekly at large national chain supermarkets and independent grocery stores in California, Maryland, Connecticut, and Georgia for 100 weeks between December 2010 and March 2013. Of the 27,389 total samples, 116 samples tested positive by the BAX PCR system for L. monocytogenes, and the pathogen was isolated and confirmed for 102 samples. Among the 16 food categories, the proportion of positive samples (i.e., without considering clustering effects) based on recovery of a viable isolate of L. monocytogenes ranged from 0.00% (95% confidence interval: 0.00, 0.18) for the category of soft-ripened and semisoft cheese to 1.07% (0.63, 1.68) for raw cut vegetables. Among the 571 samples that tested positive for Listeria -like organisms, the proportion of positive samples ranged from 0.79% (0.45, 1.28) for soft-ripened and semisoft cheese to 4.76% (2.80, 7.51) for fresh crab meat or sushi. Across all 16 categories, L. monocytogenes contamination was significantly associated with the four states ( P < 0.05) but not with the packaging location (prepackaged by the manufacturer versus made and/or packaged in the store), the type of store (national chain versus independent), or the season. Among the 102 samples positive for L. monocytogenes, levels ranged from <0.036 most probable number per g to 6.1 log CFU/g. For delicatessen (deli) meats, smoked seafood, seafood salads, soft-ripened and semisoft cheeses, and deli-type salads without meat, the percentage of positive samples was significantly lower ( P < 0.001) in this survey than that reported a decade ago based on comparable surveys in the United States. Use of mixed logistic regression models to address clustering effects with regard to the stores revealed that L. monocytogenes prevalence ranged from 0.11% (0.03, 0.34) for sprouts (prepackaged) to 1.01% (0.58, 1.74) for raw cut vegetables (prepackaged).

ABSTRACT We investigated the effects of deep-frying or oven cooking on inactivation of Shiga toxin–producing cells of Escherichia coli (STEC) in meatballs. Finely ground veal and/or a finely ground beef-pork-veal mixture were inoculated (ca. 6.5 log CFU/g) with an eight-strain, genetically marked cocktail of rifampin-resistant STEC strains (STEC-8; O111:H, O45:H2, O103:H2, O104:H4, O121:H19, O145:NM, O26:H11, and O157:H7). Inoculated meat was mixed with liquid whole eggs and seasoned bread crumbs, shaped by hand into 40-g balls, and stored at −20°C (i.e., frozen) or at 4°C (i.e., fresh) for up to 18 h. Meatballs were deep-fried (canola oil) or baked (convection oven) for up to 9 or 20 min at 176.7°C (350°F), respectively. Cooked and uncooked samples were homogenized and plated onto sorbitol MacConkey agar with rifampin (100 μg/ml) followed by incubation of plates at 37°C for ca. 24 h. Up to four trials and three replications for each treatment for each trial were conducted. Deep-frying fresh meatballs for up to 5.5 min or frozen meatballs for up to 9.0 min resulted in reductions of STEC-8 ranging from ca. 0.7 to ≥6.1 log CFU/g. Likewise, reductions of ca. 0.7 to ≥6.1 log CFU/g were observed for frozen and fresh meatballs that were oven cooked for 7.5 to 20 min. This work provides new information on the effect of prior storage temperature (refrigerated or frozen), as well as subsequent cooking via deep-frying or baking, on inactivation of STEC-8 in meatballs prepared with beef, pork, and/or veal. These results will help establish guidelines and best practices for cooking raw meatballs at both food service establishments and in the home.

ABSTRACT Viability of Listeria monocytogenes was monitored during refrigerated (4°C) and/or frozen (i.e., deep chilling at −2.2°C) storage on casing-cooked hams that were commercially prepared with and without potassium lactate and sodium diacetate (1.6%), buffered vinegar (2.2%), buffered vinegar and potassium lactate (1.7%), or a blend of potassium lactate, potassium acetate, and sodium diacetate (1.7%). A portion of these hams were subsequently surface treated with lauric arginate ester (LAE; 44 ppm). In phase I, hams (ca. 3.5 kg each) were sliced (ca. 0.7 cm thick, ca. 100 g), inoculated (ca. 4.0 log CFU per slice), surface treated with LAE, and stored at either 4°C for 120 days or at −2.2°C for 90 days and then at 4°C for an additional 120 days. In phase I, without antimicrobials, the population of L. monocytogenes increased by ca. 5.9 log CFU per slice within 120 days at 4°C; however, pathogen levels increased only slightly (ca. 0.45 log CFU per slice) for hams formulated with potassium lactate and sodium diacetate and decreased by ca. 1.2 log CFU per slice when formulated with the other antimicrobials. For slices held at −2.2°C and then stored at 4°C, but not treated with LAE, L. monocytogenes increased by ca. 4.5 log CFU per slice for controls, whereas when formulated with antimicrobials, pathogen levels decreased by ca. 1.4 to 1.8 log CFU per slice. For product treated with LAE, L. monocytogenes increased by ca. 4.0 log CFU per slice for controls, whereas when formulated with antimicrobials, pathogen levels decreased by ca. 0.9 to 1.9 log CFU per slice. In phase II, whole hams (ca. 1.0 kg each) containing antimicrobials were inoculated (6.8 log CFU per ham) and then stored at −2.2°C for 6 months. Pathogen levels decreased by ca. 2.0 to 3.5 log CFU per ham (without LAE treatment) and by ca. 4.2 to 5.2 log CFU per ham (with application of LAE via Sprayed Lethality in Container) when product was held at −2.2°C. In general, deep chilling hams was listericidal, and inclusion of antimicrobials in the formulation suppressed outgrowth of L. monocytogenes during extended cold storage.

Boneless beef rib eye roasts were surface inoculated on the fat side with ca. 5.7 log CFU/g of a five-strain cocktail of Salmonella for subsequent searing, cooking, and warm holding using preparation methods practiced by restaurants surveyed in a medium-size Midwestern city. A portion of the inoculated roasts was then passed once through a mechanical blade tenderizer. For both intact and nonintact roasts, searing for 15 min at 260°C resulted in reductions in Salmonella populations of ca. 0.3 to 1.3 log CFU/g. For intact (nontenderized) rib eye roasts, cooking to internal temperatures of 37.8 or 48.9°C resulted in additional reductions of ca. 3.4 log CFU/g. For tenderized (nonintact) rib eye roasts, cooking to internal temperatures of 37.8 or 48.9°C resulted in additional reductions of ca. 3.1 or 3.4 log CFU/g, respectively. Pathogen populations remained relatively unchanged for intact roasts cooked to 37.8 or 48.9°C and for nonintact roasts cooked to 48.9°C when held at 60.0°C for up to 8 h. In contrast, pathogen populations increased ca. 2.0 log CFU/g in nonintact rib eye cooked to 37.8°C when held at 60.0°C for 8 h. Thus, cooking at low temperatures and extended holding at relatively low temperatures as evaluated herein may pose a food safety risk to consumers in terms of inadequate lethality and/or subsequent outgrowth of Salmonella , especially if nonintact rib eye is used in the preparation of prime rib, if on occasion appreciable populations of Salmonella are present in or on the meat, and/or if the meat is not cooked adequately throughout.

Thermal inactivation of Shiga toxin–producing Escherichia coli (STEC) cells within knitted/cubed beef steaks following cooking on a nonstick griddle was quantified. Both faces of each beef cutlet (ca. 64 g; ca. 8.5 cm length by 10.5 cm width by 0.75 cm height) were surface inoculated (ca. 6.6 log CFU/g) with 250 μl of a rifampin-resistant cocktail composed of single strains from each of eight target serogroups of STEC: O26:H11, O45:H2, O103:H2, O104:H4, O111:H − , O121:H19, O145:NM, and O157:H7. Next, inoculated steaks were (i) passed once through a mechanical tenderizer and then passed one additional time through the tenderizer perpendicular to the orientation of the first pass (single cubed steak; SCS) or (ii) passed once through a mechanical tenderizer, and then two tenderized cutlets were knitted together by passage concomitantly through the tenderizer two additional times perpendicular to the orientation of the previous pass (double cubed steak; DCS). SCS and DCS were individually cooked for up to 3.5 min per side in 30 ml of extra virgin olive oil heated to 191.5°C (376.7°F) on a hard-anodized aluminum nonstick griddle using a flat-surface electric ceramic hot plate. Regardless of steak preparation (i.e., single versus double cubed steaks), as expected, the longer the cooking time, the higher the final internal temperature, and the greater the inactivation of STEC cells within cubed steaks. The average final internal temperatures of SCS cooked for up 2.5 min and DCS cooked for up to 3.5 min ranged from 59.8 to 94.7°C and 40.3 to 82.2°C, respectively. Cooking SCS and DCS on an aluminum griddle set at ca. 191.5°C for 0.5 to 2.5 min and 1.0 to 3.5 min per side, respectively, resulted in total reductions in pathogen levels of ca. 1.0 to ≥6.8 log CFU/g. These data validated that cooking SCS (ca. 0.6 cm thick) or DCS (ca. 1.3 cm thick) on a nonstick aluminum griddle heated at 191.5°C for at least 1.25 and 3.0 min per side, respectively, was sufficient to achieve a 5.0-log reduction in the levels of the single strains from each of the eight target STEC serogroups tested.

We evaluated the efficacy of potassium levulinate (KLEV; 0.0, 1.0, 1.5, and 2.0%) with and without a blend of potassium propionate (0.1%) and potassium diacetate (0.1%) (KPD) versus a blend of potassium lactate (1.8%) and sodium diacetate (0.125%) (KLD) for inhibiting Listeria monocytogenes on commercially prepared, uncured turkey breast during refrigerated storage. Product formulated with KLD or KLEV (1.5%) was also subsequently surface treated with 44 ppm of a solution of lauric arginate (LAE). Slices (ca. 1.25 cm thick and 100 g) of turkey breast formulated with or without antimicrobials were surface inoculated on both the top and bottom faces to a target level of ca. 3.5 log CFU per slice with a five-strain cocktail of L. monocytogenes , vacuum sealed, and then stored at 4°C for up to 90 days. Without inclusion of antimicrobials in the formulation, pathogen levels increased by ca. 5.2 log CFU per slice, whereas with the inclusion of 1.0 to 2.0% KLEV pathogen levels increased by only ca. 2.9 to 0.8 log CFU per slice after 90 days at 4°C. When 1.0% KLEV and KPD were included as ingredients, pathogen levels increased by ca. 0.8 log CFU per slice after storage at 4°C for 90 days, whereas a decrease of ca. 0.7 log CFU per slice was observed when 1.5 or 2.0% KLEV and KPD were included as ingredients. When used alone, KPD was not effective (≥5.8-log increase). As expected, KLD was effective at suppressing L. monocytogenes in uncured turkey breast. When uncured turkey breast was formulated with KLD or KLEV (1.5%) or without antimicrobials and subsequently surface treated with LAE, pathogen levels decreased by ca. 1.0 log CFU per package within 2 h; no differences ( P ≥ 0.01) were observed in pathogen levels for product surface treated with or without LAE and stored for 90 days. Our results validate the use of KLEV to inhibit outgrowth of L. monocytogenes during refrigerated storage of uncured turkey breast. KLEV is at least as effective as KLD as an antilisterial agent.

Preflattened veal cutlets (ca. 71.5 g, ca. 0.32 cm thick) were surface inoculated with ca. 6.8 log CFU/g of a multistrain cocktail of Escherichia coli O157:H7 (ECOH) or a cocktail made of single strains of serogroups O26, O45, O103, O104, O111, O121, and O145 of Shiga toxin–producing E. coli (STEC) cells and then were mechanically tenderized by passing once through a “Sir Steak” tenderizer. For each cooking time, in each of at least three trials, three inoculated and tenderized cutlets, with and without breading, were individually cooked in 15 or 30 ml of canola oil for 0.0, 0.75, 1.0, 1.25, 1.5, 1.75, or 2.25 min per side on an electric skillet set at 191.5°C. The temperatures of the meat and of the skillet were monitored and recorded using a type J thermocouple. Regardless of the breading or volume of oil used to cook the meat, the longer the cooking times, the higher was the internal temperature of the meat, along with a greater reduction of both ECOH and STEC. The average final internal temperature of the meat at the approximate geometric center ranged from 56.8 to 93.1°C. Microbial reductions of ca. 2.0 to 6.7 log CFU/g and ca. 2.6 to 6.2 log CFU/g were achieved for ECOH and STEC, respectively. Our data also revealed no differences in thermal inactivation of ECOH relative to the volume of oil used to cook nonbreaded cutlets. However, when cooking breaded cutlets, the use of more (30 ml) compared with less (15 ml) cooking oil resulted in greater reductions in pathogen numbers. To deliver about a 5.0-log reduction of ECOH and STEC, and to achieve the recommended internal temperature of 71.1°C, it was necessary to cook mechanically tenderized veal cutlets for at least 1.5 min per side on a preheated electric skillet set at 191.5°C and containing 15 ml of cooking oil. These data also established that cooking times and temperatures effective for inactivating serotype O157:H7 strains of E. coli in tenderized veal are equally effective against the additional six non-O157 Shiga toxin–producing strains investigated herein.

We determined the viability of Listeria monocytogenes on uncured turkey breast containing buffered vinegar (BV) and surface treated with a stabilized solution of sodium chlorite in vinegar (VSC). Commercially produced, uncured, deli-style turkey breast was formulated with BV (0.0, 2.0, 2.5, or 3.0%), sliced (ca. 100 g and ca. 1.25 cm thick), and subsequently surface inoculated (ca. 4.3 log CFU per slice) in each of two trials with a five-strain cocktail of L. monocytogenes . Next, 1 ml per side of a 2 or 10% solution of VSC was added to each package before vacuum sealing and storing at 4 or 10°C. Without antimicrobials, L. monocytogenes numbers increased by ca. 6.2 log CFU per slice after 90 and 48 days of storage at 4 or 10°C, respectively. At 4°C, L. monocytogenes numbers increased by ca. 0.4 to 1.9 log CFU per slice on turkey breast formulated with 2.0 or 2.5% BV and treated or not with 2% VSC, whereas when treated with 10% VSC, L. monocytogenes levels remained relatively unchanged over 90 days. However, when turkey breast was formulated with 3.0% BV and treated or not with VSC, pathogen numbers decreased by ca. 0.7 to 1.3 log CFU per slice. At 10°C, L. monocytogenes numbers increased by ca. 1.5 to 5.6 log CFU per slice after 48 days when formulated with 2.0 to 3.0% BV and treated or not with 2% VSC. When formulated with 2.0% BV and treated with 10% VSC, L. monocytogenes numbers increased by ca. 3.3 log CFU per slice, whereas when formulated with 2.5 or 3.0% BV and treated with 10% VSC, L. monocytogenes decreased by ca. 0.3 log CFU per slice. Inclusion of BV as an ingredient in uncured turkey breast, alone or in combination with VSC added to the package, appreciably suppressed outgrowth of L. monocytogenes during an extended refrigerated shelf life.

Both high-fat and low-fat ground beef (percent lean:fat = ca. 70:30 and 93:7, respectively) were inoculated with a 6-strain cocktail of non-O157:H7 Shiga toxin–producing Escherichia coli (STEC) or a five-strain cocktail of E. coli O157:H7 (ca. 7.0 log CFU/g). Patties were pressed (ca. 2.54 cm thick, ca. 300 g each) and then refrigerated (4°C, 18 to 24 h), or frozen (−18°C, 3 weeks), or frozen (−18°C, 3 weeks) and then thawed (4°C for 18 h or 21°C for 10 h) before being cooked on commercial gas or electric grills to internal temperatures of 60 to 76.6°C. For E. coli O157:H7, regardless of grill type or fat level, cooking refrigerated patties to 71.1 or 76.6°C decreased E. coli O157:H7 numbers from an initial level of ca. 7.0 log CFU/g to a final level of ≤1.0 log CFU/g, whereas decreases to ca. 1.1 to 3.1 log CFU/g were observed when refrigerated patties were cooked to 60.0 or 65.5°C. For patties that were frozen or freeze-thawed and cooked to 71.1 or 76.6°C, E. coli O157:H7 numbers decreased to ca. 1.7 or ≤0.7 log CFU/g. Likewise, pathogen numbers decreased to ca. 0.7 to 3.7 log CFU/g in patties that were frozen or freeze-thawed and cooked to 60.0 or 65.5°C. For STEC, regardless of grill type or fat level, cooking refrigerated patties to 71.1 or 76.6°C decreased pathogen numbers from ca. 7.0 to ≤0.7 log CFU/g, whereas decreases to ca. 0.7 to 3.6 log CFU/g were observed when refrigerated patties were cooked to 60.0 or 65.5°C. For patties that were frozen or freeze-thawed and cooked to 71.1 or 76.6°C, STEC numbers decreased to a final level of ca. 1.5 to ≤0.7 log CFU/g. Likewise, pathogen numbers decreased from ca. 7.0 to ca. 0.8 to 4.3 log CFU/g in patties that were frozen or freeze-thawed and cooked to 60.0 or 65.5°C. Thus, cooking ground beef patties that were refrigerated, frozen, or freeze-thawed to internal temperatures of 71.1 and 76.6°C was effective for eliminating ca. 5.1 to 7.0 log CFU of E. coli O157:H7 and STEC per g.