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

The Use of Organic Acids (Lactic and Acetic) as a Microbial Decontaminant during the Slaughter of Meat Animal Species: A Review

Wild ungulate species provide a much-needed protein source to many communities in developed and developing countries. Frequently, these game meat animals are slaughtered, and the meat is unknowingly contaminated by microorganisms and released to the unsuspecting public. This review investigates the global usage of organic acids (lactic and acetic acids) as microbial decontamination strategies during slaughter. The results show that there is a more open-minded approach to adopting possible decontamination plans as a tool to improve meat safety during slaughter. Developed countries continue to adopt these strategies, while developing countries are lagging behind. While decontamination of carcasses can lead to a reduction of microbial load on these carcasses, this strategy must not be seen as a replacement of hygiene management during the animals’ slaughter.

Beef abattoir interventions in a risk-based meat safety assurance system

In risk-based meat safety assurance system, the use of interventions is intended to accomplish the meat safety targets on chilled carcasses, particularly in situations when an abattoir is unable to sufficiently reduce risks arising from specific farms/animal batches by using process hygiene alone. Furthermore, interventions are considered whenever food safety authorities identify meat production processes associated with high risks for consumers. This paper overviews the role of beef interventions in a risk-based, meat safety assurance system. Cattle hide interventions (chemical hide washes and microbial immobilisation treatment with shellac) and beef carcass interventions (pasteurisation treatments with hot water and/or steam and organic (lactic) acid washes), show consistent reduction effects of aerobic bacteria and faecal indicators and reduced prevalences of naturally present VTEC and Salmonella. The review also identified interventions where there was a lack of data and further research was needed, and other contextual factors to inform the risk management decisions for further development of risk-based meat safety assurance system.

Application of chlorine dioxide and peroxyacetic acid during spray chilling as a potential antimicrobial intervention for beef carcasses

Enteric pathogens such as Shiga-toxin producing Escherichia coli (STEC) and Salmonella spp. continue to be a major food safety concern for the beef industry. Currently, no single method is completely effective in controlling these pathogens during carcass processing. Previous research, however, suggested that STEC might become more susceptible to oxidative damage when exposed to carcass chilling (King et al., 2016). We aimed to test that hypothesis by evaluating the antimicrobial effects of an oxidant (chlorine dioxide, ClO₂ or peroxyacetic acid, PAA) on beef meat during a simulated spray chilling process (sprayed for 4 s every 15 min for 36 cycles) and/or when applied (sprayed for 144 s) prior to spray chilling with water. In all experiments, the inactivating effects of oxidants were greatest on fat surfaces and much less effective on lean surfaces. ClO₂ at 15 ppm, a non-lethal level for E. coli under optimal growth conditions, caused higher log reductions in E. coli numbers (approximately 3-log reduction) when applied during spray chilling than when applied immediately prior to 'normal' spray chilling (approximately 1-log reduction). This confirms the hypothesis that E. coli are more susceptible to oxidative stress during spray chilling. In subsequent studies, both ClO₂ and PAA at lethal levels (at ≥20 and ≥ 200 ppm, respectively) applied during spray chilling resulted in pronounced inactivation of both E. coli and Salmonella enterica strains, achieving a ≥4-log reduction at the end of chilling. These results indicate that an oxidant-based application during spray chilling as an antimicrobial intervention could be effective to minimise the problems associated with enteric pathogen contamination on beef meat.

In-Plant Validation Study of Harvest Process Controls in Two Beef Processing Plants in Honduras

Imported meat in the United States can become a food safety hazard if proper food safety programs are not fully implemented in foreign meat processing plants. Thus, exporting countries' food safety inspection systems must be equivalent to the U.S. federal inspection system to become eligible to export meat to the United States. The objective of this study was to validate the beef harvest Hazard Analysis and Critical Control Points and food safety programs of two beef processing plants in Honduras operating under U.S. equivalency standards by evaluating the presence of Salmonella (plant A) and Shiga toxin-producing Escherichia coli (STEC; plant B) on hides. Additionally, evaluating pathogen transfer from hides to carcasses, as detected by preevisceration sampling, and the mitigation of transferred pathogens, by application of carcass spray interventions and determination of Salmonella presence in lymph nodes, was also conducted. In plant A, the presence of Salmonella on hides ( n = 30 of 687; 4.4%) was significantly greater ( P < 0.10) than on carcasses swabbed at preevisceration ( n = 7 of 687; 1.0%), after intervention ( n = 13 of 678; 1.9%), and in lymph nodes ( n = 14 of 691; 2.0%). In plant B, Salmonella was not detected on hide samples; therefore, data could not be used for validation of the harvest Hazard Analysis and Critical Control Points program. Alternatively, STEC presence on hides ( n = 21 of 85; 24.7%) was greater ( P < 0.10) than on carcasses at preevisceration ( n = 3 of 85; 3.5%) and after intervention ( n = 1 of 85; 1.2%). Pathogen presence in plant B did not differ ( P = 0.306) between carcasses in preevisceration and postintervention stages; both, however, were substantially low. Both plants' controls effectively reduced Salmonella and STEC presence in postintervention carcasses.

Evaluation of Electrolytically-Generated Hypochlorous Acid ('Electrolyzed Water') for Sanitation of Meat and Meat-Contact Surfaces

'Electrolyzed water' generators are readily available in the food industry as a renewable source of hypochlorous acid that eliminates the need for workers to handle hazardous hypochlorite concentrates. We applied electrolyzed water (EW) directly to multi-strain cocktails of Listeria monocytogenes, E. coli O157:H7, and Salmonella sp. at 250 ppm free available chlorine (FAC) and achieved greater than 6-log reductions in 2 min. Lower EW values were examined as antimicrobial interventions for fresh meat (beef carcasses), processed meats (frankfurters), and food contact surfaces (slicing blades). Little or no reduction relative to controls was observed when generic E. coli-inoculated beef carcasses or L. monocytogenes-inoculated frankfurters were showered with EW. Spray application of EW (25 and 250-ppm FAC) onto L. monocytogenes-inoculated slicing blades showed that greater reductions were obtained with 'clean' (3.6 and 5.7-log reduction) vs. 'dirty' (0.6 and 3.3-log reduction) slicing blades, respectively. Trials with L. monocytogenes-inoculated protein-EW solutions demonstrated that protein content as low as 0.1% is capable of eliminating FAC, reducing antimicrobial activity against L. monocytogenes. EW appears better positioned as a surface sanitizer with minimal organic material that can otherwise act as an effective reducing agent to the oxidizing solution rendering it ineffective.

Postharvest intervention technologies for safety enhancement of meat and meat based products; a critical review

Globally, the demand for safe, healthy and nutritious meat and allied products possesses improved taste with extended shelf life is mounting. Microbial safety is among the imperative challenges that prevails in meat products because they provide an ideal medium for the growth of microorganisms particularly pathogenic bacteria. The incidence of these microbes can result quality deterioration of products leading towards food borne diseases when consumed by peoples. Several preservation technologies like chemical and biological interventions are effective to retard or inactivate the growth of micro-organisms most commonly related to food-borne diseases. Despite these, innovative approaches like hydrostatic pressure processing, active packaging, pulse electric field, hurdle approach and use of natural antimicrobials can be deployed to enhance the safety of meat and meat products. The objective of review is to describe the current approaches and developing technologies for enhancing safety of meat and allied meat products.

Effects of Plant-Derived Extracts, Other Antimicrobials, and Their Combinations against Escherichia coli O157:H7 in Beef Systems

The antimicrobial effects of thyme oil (TO), grapefruit seed extract (GSE), and basil essential oil, alone or in combination with cetylpyridinium chloride (CPC), sodium diacetate, or lactic acid, were evaluated against Escherichia coli O157:H7 in a moisture-enhanced beef model system. The model system was composed of a nonsterile beef homogenate to which NaCl (0.5%) and sodium tripolyphosphate (0.25%) were added, together with the tested antimicrobial ingredients. Beef homogenate treatments were inoculated (ca. 3 log CFU/ml) with rifampin-resistant E. coli O157:H7 (eight-strain mixture) and incubated at 15 °C (48 h). The most effective individual treatments were TO (0.25 or 0.5%) and GSE (0.5 or 1.0%), which immediately reduced (P < 0.05) pathogen levels by ≥ 3.4 log CFU/ml. Additionally, CPC (0.04%) reduced initial E. coli O157:H7 counts by 2.7 log CFU/ml. Most combinations of the tested plant-derived extracts with CPC (0.02 or 0.04%) and sodium diacetate (0.25%) had an additive effect with respect to antibacterial activity. In a second study, antimicrobial interventions were evaluated for their efficacy in reducing surface contamination of E. coli O157:H7 on beef cuts and to determine the effect of these surface treatments on subsequent internalization of the pathogen during blade tenderization. Beef cuts (10 by 8 by 3.5 cm) were inoculated (ca. 4 log CFU/g) on one side with the rifampin-resistant E. coli O157:H7 strain mixture and were then spray treated (20 lb/in(2), 10 s) with water, GSE (5 and 10%), lactic acid (5%), or CPC (5%). Untreated (control) and spray-treated surfaces were then subjected to double-pass blade tenderization. Surface contamination (4.4 log CFU/g) of E. coli O157:H7 was reduced (P < 0.05) to 3.4 (5% CPC) to 4.1 (water or 5% GSE) log CFU/g following spray treatment. The highest and lowest transfer rates of pathogen cells from the surface to deeper tissues of blade-tenderized sections were obtained in the untreated control and CPC-treated samples, respectively.

Characterization of an extremely heat-resistant Escherichia coli obtained from a beef processing facility

AIMS

This study aimed to determine the survival of Escherichia coli strains during steam and lactic acid decontamination interventions currently used by the beef-processing industry, and to determine their heat resistance.

METHODS AND RESULTS

Strains were grouped into cocktails of five strains each differing in their RAPD patterns for subsequent identification. Steam and lactic acid treatments on meat reduced cell counts of E. coli strain cocktails by 90-99%. The 20 slaughter plant isolates exhibited only minor variation in their resistance to steam and lactic acid treatments but were more resistant than reference strains (three strains) or isolates from live cattle (seven strains). D(60) values of strains from live cattle, and reference strains ranged from 0·1 to 0·5 min, in keeping with literature data. However, D(60) values of current slaughter plant isolates ranged between 15 for E. coli DM18.3 and 71 min AW 1.7. Cell counts of E. coli AW 1.7 were reduced by <5 log(10) CFU g(-1) in ground beef patties cooked to an internal temperature of 71°C.

CONCLUSIONS

Strains of E. coli that survive cooking of ground beef to the recommended internal temperature of 71°C can be isolated from beef-processing facilities.

SIGNIFICANCE AND IMPACT OF THE STUDY

Pathogen interventions in current commercial beef slaughter may select for extremely heat-resistant strains of E. coli.

Thermal inactivation D- and z-values of multidrug-resistant and non-multidrug-resistant Salmonella serotypes and survival in ground beef exposed to consumer-style cooking

There has been speculation that multidrug-resistant (MDR) strains are generated by subtherapeutic antibiotic use in food animals and that such strains result in increased resistance to lethality by food processes such as heat and irradiation. The objective of this study was to evaluate the heat resistance of 20 strains, namely an MDR and a non-multidrug-resistant (NMDR) strain of each of 10 Salmonella serotypes isolated from cattle or cattle environments. MDR and NMDR Salmonella serotypes studied included Montevideo, Typhimurium, Anatum, Muenster, Newport, Mbandaka, Dublin, Reading, Agona, and Give. For phase I, stationary-phase cultures of the strains were aliquoted into sterile capillary tubes and immersed in a temperature-controlled water bath at 55, 60, 65, and 70 degrees C for appropriate times. Survivor curves were plotted for each temperature, and a best-fit linear regression was derived for each temperature. D-values (decimal reduction times) and z-values (changes in temperature required to change the D-values) were calculated for each strain. Although there was no overall significant difference in the heat resistance of MDR and NMDR serotypes, NMDR serotypes generally appeared to have slightly higher heat resistance than NMDR serotypes, especially at 55 and 60 degrees C. The highest relative heat resistance (highest z-values) was exhibited by Salmonella Anatum. Notably, the relative heat resistance of NMDR Salmonella Agona was similar to that of NMDR Salmonella Anatum and had the highest D-values at all four temperatures. For phase II, three serotypes (regardless of resistance profile) with the highest relative heat resistance and their drug-resistant counterparts were selected for thermal inactivation in ground beef patties cooked to endpoint temperatures. Salmonella Agona was able to survive in ground beef cooked to an internal temperature of 71 degrees C. Results of these studies suggest drug resistance does not affect the heat resistance of Salmonella and that serotype or strain is an important consideration in risk assessment of the pathogen with regard to survival at cooking temperatures.

Food as a vehicle for transmission of Shiga toxin-producing Escherichia coli

Contaminated food continues to be the principal vehicle for transmission of Escherichia coli O157:H7 and other Shiga toxin-producing E. coli (STEC) to humans. A large number of foods, including those associated with outbreaks (alfalfa sprouts, fresh produce, beef, and unpasteurized juices), have been the focus of intensive research studies in the past few years (2003 to 2006) to assess the prevalence and identify effective intervention and inactivation treatments for these pathogens. Recent analyses of retail foods in the United States revealed E. coli O157:H7 was present in 1.5% of alfalfa sprouts and 0.17% of ground beef but not in some other foods examined. Differences in virulence patterns (presence of both stx1 and stx2 genes versus one stx gene) have been observed among isolates from beef samples obtained at the processing plant compared with retail outlets. Research has continued to examine survival and growth of STEC in foods, with several models being developed to predict the behavior of the pathogen under a wide range of environmental conditions. In an effort to develop effective strategies to minimize contamination, several influential factors are being addressed, including elucidating the underlying mechanism for attachment and penetration of STEC into foods and determining the role of handling practices and processing operations on cross-contamination between foods. Reports of some alternative nonthermal processing treatments (high pressure, pulsed-electric field, ionizing radiation, UV radiation, and ultrasound) indicate potential for inactivating STEC with minimal alteration to sensory and nutrient characteristics. Antimicrobials (e.g., organic acids, oxidizing agents, cetylpyridinium chloride, bacteriocins, acidified sodium chlorite, natural extracts) have varying degrees of efficacy as preservatives or sanitizing agents on produce, meat, and unpasteurized juices. Multiple-hurdle or sequential intervention treatments have the greatest potential to minimize transmission of STEC in foods.

Effectiveness of trisodium phosphate, acidified sodium chlorite, citric acid, and peroxyacids against pathogenic bacteria on poultry during refrigerated storage

The effects of dipping treatments (15 min) in potable water or in solutions (wt/vol) of 12% trisodium phosphate (TSP), 1,200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), and 220 ppm peroxyacids (PA) on inoculated pathogenic bacteria (Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Salmonella Enteritidis, Escherichia coli, and Yersinia enterocolitica) and skin pH were investigated throughout storage of chicken legs (days 0, 1, 3, and 5) at 3 +/- 1 degrees C. All chemical solutions reduced microbial populations (P < 0.001) as compared with the control (untreated) samples. Similar bacterial loads (P > 0.05) were observed on water-dipped and control legs. Type of treatment, microbial group, and sampling day influenced microbial counts (P < 0.001). Average reductions with regard to control samples were 0.28 to 2.41 log CFU/g with TSP, 0.33 to 3.15 log CFU/g with ASC, 0.82 to 1.97 log CFU/g with CA, and 0.07 to 0.96 log CFU/g with PA. Average reductions were lower (P < 0.001) for gram-positive (0.96 log CFU/g) than for gram-negative (1.33 log CFU/g) bacteria. CA and ASC were the most effective antimicrobial compounds against gram-positive and gram-negative bacteria, respectively. TSP was the second most effective compound for both bacterial groups. Average microbial reductions per gram of skin were 0.87 log CFU/g with TSP, 0.86 log CFU/g with ASC, 1.39 log CFU/g with CA, and 0.74 log CFU/g with PA for gram-positive bacteria, and 1.28 log CFU/g with TSP, 2.03 log CFU/g with ASC, 1.23 log CFU/g with CA, and 0.78 log CFU/g with PA for gram-negative bacteria. With only a few exceptions, microbial reductions in TSP- and ASC-treated samples decreased and those in samples treated with CA increased throughout storage. Samples treated with TSP and samples dipped in CA and ASC had the highest and lowest pH values, respectively, after treatment. The pH of the treated legs tended to return to normal (6.3 to 6.6) during storage. However, at the end of storage, the pH of legs treated with TSP remained higher and that of legs treated with CA remained lower than normal.

Efficacy of a peroxyacetic acid formulation as an antimicrobial intervention to reduce levels of inoculated Escherichia coli O157:H7 on external carcass surfaces of hot-boned beef and veal

The efficacy of a peroxyacetic acid formulation (POAA) at reducing Escherichia coli O157:H7 contamination on external carcass surfaces of hot-boned beef and veal with a commercial spray apparatus was determined. Hot-boned external carcass surfaces were inoculated with either a high dose (10(6) CFU/cm2) in fresh bovine feces or with a low dose (10(3) CFU/cm2) in diluent of laboratory-cultured E. coli O157:H7. Treatments included a water wash, a POAA (180 ppm) wash, or a water plus POAA wash. Samples were extracted from the external carcass surface with a cork borer to determine the numbers of viable E. coli O157:H7 remaining on the carcass surface after treatment. Although a water wash alone resulted in a 1.25 (94.4%) and a 1.31 (95.1%) mean log reduction on veal and beef inoculated with a high dose of E. coli O157:H7, the POAA treatment resulted in a substantially greater mean log reduction of 3.56 and 3.59 (>99.9%). The water wash only resulted in a 33.9% reduction on veal and 62.8% on beef inoculated with a low dose of E. coli O157:H7, whereas POAA treatment greatly improved pathogen reduction to 98.9 and 97.4% on veal and beef, respectively. The combination of a water wash followed by a POAA treatment resulted in a similar E. coli O157:H7 reduction to that achieved by POAA treatment alone. In conclusion, POAA treatment significantly reduced viable E. coli O157:H7 numbers on experimentally contaminated beef and veal carcasses, which justifies its use as a chemical intervention for the removal of this human pathogen.

Fate of inoculated Escherichia coli O157:H7, cultured under different conditions, on fresh and decontaminated beef transitioned from vacuum to aerobic packaging

This study evaluated the behavior of Escherichia coli O157:H7 during aerobic storage, after storage in vacuum packages, on beef inoculated with cultures prepared (35 degrees C, 24 h) in tryptic soy broth without dextrose (TSB), nonacid hot water carcass decontamination runoff fluids (washings; pH 6.0; WASH), cells from biofilms formed on stainless steel coupons in WASH (WETB), or WETB dried (25 degrees C, 12 h) before harvesting of cells (DRYB). These inocula were applied to fresh beef pieces (40 cm2), which were then left untreated or treated by immersion in hot water (75 degrees C) followed by 2% lactic acid (55 degrees C; hot water/lactic acid [HW/LA]), for 30 s each. Inoculated samples were vacuum packaged and stored at 0 (30, 60, or 90 days), 4 (7 or 14 days), or 12 degrees C (4 or 8 days) and subsequently transferred to retail packages for aerobic storage at 7 degrees C for 5 days. Populations of E. coli O157:H117, regardless of inoculum type, remained generally unchanged (P > 0.05) after aerobic storage (7 degrees C, 5 days) of untreated or HW/LA-treated beef samples previously stored in vacuum packages at 0 or 4 degrees C. However, reductions in E. coli O157:H7 levels were generally obtained when vacuum packaged, untreated beef samples previously stored at 12 degrees C were transitioned to aerobic conditions. Additionally, despite similar (P > 0.05) levels of E. coli O157:H7 cells of TSB, WASH, WETB, and DRYB origin on vacuum-packaged, untreated samples after 8 days of storage at 12 degrees C, subsequent aerobic storage resulted in larger (P < 0.05) reductions of cells of WETB and DRYB origin than for cells of TSB and WASH origin. For HW/LA-treated beef previously stored at 12 degrees C in vacuum packages, populations of E. coli O157:H7 remained largely unchanged after aerobic storage in retail packages. Results thus indicated that aerobic storage of beef (7 degees C, 5 days) previously stored in vacuum packages at 0 or 4 degrees C did not lead to E. coli O157:H7 population changes, whereas transition from vacuum packages stored under mildly abusive temperature (12 degrees C) to aerobic storage may have caused injury and death to the pathogen.