Pre-Chill Spray of Chicken Carcasses to Reduce Salmonella typhimurium

The efficacy of sodium acid sulfate on controlling Listeria monocytogenes on apples in a water system with organic matter

During fresh apple packing, wash water in the dump tank and flume systems is reused during daily production, resulting in high levels of organic matter in the wash water. This study evaluated the antimicrobial efficacy of sodium acid sulfate (SAS), a Generally Recognized as Safe compound, against Listeria monocytogenes on fresh apples in a water system with high organic load. SAS at 1.0% reduced L. monocytogenes population in water with 1000 ppm chemical oxygen demand (COD) by more than 5.0 Log₁₀ CFU/ml in 5 min, 2.0-3.0% SAS reduced L. monocytogenes to undetectable levels (10 CFU/ml) within 2 min regardless of organic levels. When applied on apples, a 2-min wash with SAS at 1.0, 1.5, 2.0, and 3.0% reduced L. monocytogenes by ~1.3, 1.9, 2.3, and 3.0 Log₁₀ CFU/apple in clean water, respectively. High organic load in wash water up to 4000 ppm COD had no impact on the bactericidal effect of SAS against L. monocytogenes on fresh apples regardless of SAS concentrations. Shortening the contact time from 2 min to 30 s significantly reduced the antimicrobial efficacy of 25 ppm chlorine and 1.0-2.0% SAS but not that of 3.0% SAS. In addition, SAS at 1.0% demonstrated a better efficacy than 25 ppm chlorine in reducing fruit-to-water cross-contamination regardless of organic matter. SAS also showed a comparable efficacy as 25 ppm chlorine in reducing fruit-to-fruit cross-contamination in water with organic matter. The collective data indicate that SAS, as an enviroment-friendly compound, has the potential to be used as an alternative antimicrobial washing aid in dump tank process water intervention in apple packing facilities.

Efficacy of Lactic Acid and Modified Atmosphere Packaging against Campylobacter jejuni on Chicken during Refrigerated Storage

The present study was conducted to evaluate the combined effect of lactic acid washing and modified atmospheres packaging on the counts of Campylobacter jejuni on chicken legs stored at 4 °C. In experiment 1, inoculated chicken legs were washed with either 1% or 2% lactic acid solution for 5 min or distilled water (control). The treatment with 2% lactic acid reduced C. jejuni counts 1.42 log units after treatment (day 0). In experiment 2, inoculated samples were packaged under different conditions: air, 100%N2, vacuum, 20%CO2/80%N2, or 40%CO2/60%N2. C. jejuni counts were higher in samples packaged under vacuum or atmospheres containing CO2 than in air. In experiment 3, inoculated chicken legs were washed with a 2% lactic acid solution for 5 min or distilled water (control). Samples were packaged under different conditions: air, vacuum, 20%CO2/80%N2, or 40%CO2/60%N2. C. jejuni counts were lower in samples treated with lactic acid than in samples non-treated. However, C. jejuni counts were higher in chicken legs treated with lactic acid and packaged in modified atmospheres than in those treated and packaged in air. Immersion of chicken legs in a solution containing 2% lactic acid can reduce C. jejuni counts on fresh chicken packaged in modified atmosphere.

Prioritization of Chicken Meat Processing Interventions on the Basis of Reducing the Salmonella Residual Relative Risk

Protecting public health by controlling Salmonella in chicken meat products continues to be a challenge to both industry and policymakers. Studies evaluating the combined use of commercially available antimicrobial interventions are scarce. The aim of this work was to develop a risk-based prioritization framework to rank chicken meat processing interventions that achieve the greatest Salmonella relative risk reduction. A baseline model characterizing the current U.S. broiler industry food safety intervention practices was created from direct observation of processes and expert elicitation. Results showed the combination of chlorine at the bird wash station and peroxyacetic acid at the on-line reprocessing and chill stages as the most common U.S. processing scenario. Irradiation at packaging and acidified sodium chlorite at evisceration were the most effective single processing interventions (98.8 and 91.6% risk reduction, respectively); however, no single intervention was able to comply with the current Food Safety and Inspection Service Salmonella postchill performance standards. The combination of peroxyacetic acid in at least one of the chicken processing stages with the current set of U.S. baseline interventions achieved >99% Salmonella relative risk reduction and ensured Food Safety and Inspection Service compliance. Adding more than one intervention to the U.S. current practice did not enhance (<2%) the overall Salmonella risk reduction. This study can help poultry processors to prioritize food safety interventions to maximize Salmonella reduction and public health protection.

The Efficacy of Sodium Bisulfate Salt (SBS) Alone and Combined With Peracetic Acid (PAA) as an Antimicrobial on Whole Chicken Drumsticks Artificially Inoculated With Salmonella Enteritidis

The presence of Salmonella spp. on poultry products is one of the leading causes of foodborne illness in the United States. Therefore, novel antimicrobial substances are being explored as potential interventions in poultry processing facilities. The objective of the current study was to evaluate the efficacy of varying concentrations of sodium bisulfate salt, SBS, alone or in combination with peracetic acid, PAA, in 15 s whole part dips. Ninety six drumsticks (4 replications, 8 treatments, 3 days) were inoculated separately in a 400 mL solution of nalidixic resistant (NA) Salmonella Enteritidis (10⁷ CFU/mL) and allowed to adhere for 60 to 90 min at 4°C for a final concentration of 10⁶ CFU/g. The experimental treatments included: a no treatment (control), and 15 s dips in 300 mL of tap water alone (TW) or with the addition of 1; 2; and 3% SBS; 1; 2; and 3% SBS+PAA. After treatment, drumsticks were stored at 4°C until microbial sampling was conducted. On d 0, l, and 3, drumsticks were rinsed in 150 mL of nBPW for 1 min, 100 μL of rinsate was serially diluted, spread plated on XLT4+NA (20 μg/mL), and incubated aerobically at 37°C for 24 h. Log-transformed counts were analyzed using a randomized complete block design (day) using One-Way ANOVA, polynomial contrasts, and pairwise comparisons with means being separated by Tukey's HSD with a significance level of P ≤ 0.05. A treatment by day interaction (P = 0.14071) was not substantial. Thus, the treatment effect was investigated separately by days. Over time, a linear trend was observed in S. Enteritidis concentration when SBS was increased (1 < 2 < 3%). The concentration of S. Enteritidis was different between 1% SBS and 1% SBS+PAA on d 0. However, the level of S. Enteritidis was not different among drumsticks treated in 2 and 3% SBS and 2 and 3% SBS+PAA across d 0, 1, 3. The application of 3% SBS alone or in combination with 200 ppm of PAA is capable of reducing the presence of Salmonella over a 3-d refrigeration period; potentially increasing the safety of poultry products for consumers.

Effectiveness of Several Antimicrobials Used in a Postchill Decontamination Tank against Salmonella and Campylobacter on Broiler Carcass Parts

New microbial performance standards for chicken parts necessitate postchill antimicrobial interventions to make poultry parts safer for consumers. This research was conducted to determine the effectiveness of antimicrobials (0.003% chlorine; 0.07% acidified sodium chlorite [ASC], 0.07 or 0.1% peracetic acid [PAA], and 0.35 or 0.60% cetylpyridinium chloride [CPC]) when used in a postchill decontamination tank to reduce Salmonella and Campylobacter on broiler chicken parts (including breasts, thighs, wings, and drumsticks) and to determine the sensory attributes of the treated samples. Samples ( n = 90, 9 treatments × 5 samples × 2 replications) were inoculated with Salmonella Typhimurium (10⁸ CFU/mL) and Campylobacter jejuni (10⁸ CFU/mL). After a 30-min attachment time, chicken parts were rinsed with various antimicrobials in a decontamination tank for 23 s. Salmonella and Campylobacter reduction was determined by sampling parts after the treatments were applied. Sensory evaluation of skin-on (drumettes) and skin-off (breast meat) parts were conducted by untrained panelists by using an 8-point hedonic scale. CPC (0.35 or 0.60%), provided a reduction of 2.5 or 3.5 log CFU/mL on Salmonella and a reduction of 4 or 5 log CFU/mL on Campylobacter, respectively. Both concentrations of PAA (0.07 or 0.1%) provided a 1.5-log reduction on Salmonella and Campylobacter. Chlorine at 0.003% and ASC at 0.07% were the least effective antimicrobials, providing <1-log reduction for both pathogens, which did not differ from the reduction provided by a water rinse alone. Sensory attributes were unaffected in drumettes, and skinless breast fillets received the most acceptable scores ( P ≤ 0.05) for texture, juiciness, and overall acceptability when treated with 0.07% PAA and 0.35% CPC. Results from this study indicated that using PAA and CPC in a postchill decontamination tank are effective treatments for reducing Salmonella and Campylobacter on chicken parts, with minimal effects on product quality.

Sodium bisulfate and a sodium bisulfate/tannin mixture decreases pH when added to an in vitro incubated poultry cecal or fecal contents while reducing Salmonella Typhimurium marker strain survival and altering the microbiome

The objective of the present study was to investigate the ability of animal feed-grade sodium bisulfate (SBS) and a mixture of sodium bisulfate/tannin to inhibit the growth of Salmonella using an anerobic in vitro mixed cecal culture to mimic the conditions within the chicken cecum. An initial inoculum of Salmonella Typhimurium was introduced to an anerobic dilution solution containing 1/3000 diluted cecal bacteria and solids consisting of ground chicken feed and different percentages of solid SBS or SBS/tannin, and surviving organisms were enumerated. Two different experimental designs were employed. In the "unadapted" treatment, the S. Typhimurium was added at the beginning of the culture incubation along with cecal bacteria and chicken feed/SBS or chicken feed/SBS/tannin. In the "adapted" treatment, S. Typhimurium was added after a 24 hour pre-incubation of the cecal bacteria with the chicken feed/SBS or chicken feed/SBS/tannin. Adding SBS resulted in reduction of pH in the cultures which paralleled with the reduction of S. Typhimurium. The SBS alone was found to be inhibitory to S. Typhimurium in the adapted treatment at all concentrations tested (0.25, 0.5, and 0.75%), and the degree of inhibition was concentration-dependent. Salmonella Typhimurium was completely killed in the adapted culture with 0.5% SBS after 24 and 48 h. The SBS/tannin mixture was less inhibitory than SBS alone at the same concentrations in side-by-side comparisons. Testing at a 0.5% SBS concentration, chicken age had little or no effect on log reduction of S. Typhimurium relative to age-matched control cultures without SBS, but age did affect the absolute number of S. Typhimurium surviving, with the greatest decreases occurring at 2 and 4 weeks of age (approx. 10³ S. Typhimurium surviving) compared to 6 weeks of age (approx. 10⁵ Salmonella surviving). Microbiome analysis with an Illumina MiSeq platform was conducted to investigate bacterial compositional changes related to the addition of SBS. The relative abundance of Firmicutes (at the phylum level) was decreased, and genera Lactobacillus and Faecalibacterium were increased when SBS was added to the anaerobic mixed culture containing either fecal or cecal material. The antimicrobial action of feed-grade SBS may represent a potential pre-harvest control measure for Salmonella in poultry production.

Antimicrobial Efficacy of a Sulfuric Acid and Sodium Sulfate Blend, Peroxyacetic Acid, and Cetylpyridinium Chloride against Salmonella on Inoculated Chicken Wings

Studies were conducted to evaluate the efficacy of a commercial blend of sulfuric acid and sodium sulfate (SSS) in reducing Salmonella on inoculated whole chilled chicken wings and to compare its efficacy to peroxyacetic acid (PAA) and cetylpyridinium chloride (CPC). Wings were spot inoculated (5 to 6 log CFU/ml of sample rinsate) with a five-strain mixture of novobiocin- and nalidixic acid-resistant Salmonella and then left untreated (control) or treated by immersing individual wings in 350 ml of antimicrobial solution. An initial study evaluated two treatment immersion times, 10 and 20 s, of SSS (pH 1.1) and compared cell recoveries following rinsing of treated samples with buffered peptone water or Dey/Engley neutralizing broth. In a second study, inoculated wings were treated with SSS (pH 1.1; 20 s), PAA (700 ppm, 20 s), or CPC (4,000 ppm, 10 s) and analyzed for survivors immediately after treatment (0 h) and after 24 h of aerobic storage at 4°C. Color and pH analyses were also conducted in the latter study. Recovery of Salmonella survivors following treatment with SSS (10 or 20 s) was not (P ≥ 0.05) affected by the type of cell recovery rinse solution (buffered peptone water or Dey/Engley neutralizing broth), but there was an effect (P < 0.05) of SSS treatment time. Immersion of samples for 10 or 20 s in SSS resulted in pathogen reductions of 0.8 to 0.9 and 1.1 to 1.2 log CFU/ml, respectively. Results of the second study showed that there was an interaction (P < 0.05) between antimicrobial type and storage time. Efficacy against Salmonella at 0 h increased in the order CPC , SSS , PAA; however, after 24 h of aerobic storage, pathogen counts of SSS- and PAA-treated wings did not differ (P ≥ 0.05). Overall, the results indicated that SSS applied at pH 1.1 for 20 s was an effective antimicrobial intervention to reduce Salmonella contamination on chicken wings.

Synthesis and disinfection effect of the pyridine-4-aldoxime based salts

A set of new quaternary ammonium compounds based on pyridine-4-aldoxime was synthesized, characterized with analytical data (NMR, EA, HPLC, MS) and tested for in vitro antimicrobial activity (antibacterial, antifungal) and cytotoxicity. Quaternary pyridinium-4-aldoxime salts with length of alkyl side chain from C8 to C20 and belonging to the group of cationic surfactants were investigated in this work. An HPLC experimental protocol for characterization of mixtures of all homologues has been found. Antimicrobial evaluation found that yeast-type fungi were most sensitive towards C₁₄ and C₁₆ analogues, whereas the C₁₆ analogue was completely ineffective against filamentous fungi. Antibacterial assessment showed versatility of C₁₄ and relatively high efficacy of C₁₆ against G+ strains and C₁₄ against G− strains. Notably, none of the studied compounds exceeded the efficacy and versatility of the benzalkonium C₁₂ analogue, and benzalkonium analogues also exhibited lower cytotoxicity in the cell viability assay.

Efficacy of ε-polylysine, lauric arginate, or acidic calcium sulfate applied sequentially for Salmonella reduction on membrane filters and chicken carcasses

Salmonella contamination continues to be one of the major concerns for the microbiological safety of raw poultry products. Application of more than one decontamination agent as a multihurdle intervention to carcasses in a processing line might produce greater reductions than one treatment alone due to different modes of action of individual antimicrobials. In this study, all possible two-way combinations and individual applications of ε-polylysine (EPL), lauric arginate (LAE), and acidic calcium sulfate (ACS) solutions were evaluated for their effects against Salmonella enterica serovars, including Enteritidis and Typhimurium, using a sterile membrane filter model system. The combinations that provided higher Salmonella reductions were further evaluated on inoculated chicken carcasses in various concentrations applied in a sequential manner. Sequential spray applications of 300 mg of EPL per liter followed by 30% ACS and of 200 mg of LAE per liter followed by 30% ACS produced the highest Salmonella reductions on inoculated chicken carcasses, by 2.1 and 2.2 log CFU/ml, respectively. Our results indicated that these sequential spray applications of decontamination agents are effective for decreasing Salmonella contamination on poultry carcasses, but further studies are needed to determine the effectiveness of these combinations over a storage period.

Validation of a 2 percent lactic acid antimicrobial rinse for mobile poultry slaughter operations

Poultry processing antimicrobial interventions are critical for pathogen control, and organic, mobile operations in Washington seek alternatives to chlorine. Laboratory and field studies (three replications each) evaluated lactic acid efficacy as a chlorine alternative. For the laboratory study, retail-purchased, conventionally processed chicken wings inoculated with Salmonella were randomly assigned to the following treatments: Salmonella inoculation followed by no treatment (10 wings) or by 3-min rinses of water, 50 to 100 ppm of chlorine, or 2% lactic acid (20 wings for each rinse treatment). Wings were sampled for Salmonella enumeration on xylose lysine desoxycholate agar. During pastured poultry processing at mobile slaughter units for each field study replication, 20 chicken carcasses were randomly assigned to each treatment: untreated control or 3-min immersion in lactic acid or chlorine. Whole-carcass rinses were examined for aerobic plate count (APC) on tryptic soy agar and coliforms on violet red bile agar. Untreated controls were also examined for Salmonella. In the laboratory study, lactic acid produced a significant (P < 0.01) Salmonella reduction compared with the inoculated no-rinse, water, and chlorine treatments, which were statistically similar to each other. In the field study, no Salmonella was detected on untreated controls. Lactic acid produced significant >2-log (P < 0.01) reductions in APC and coliforms, whereas chlorine resulted in slight, but significant 0.4-log reductions (P < 0.01) and 0.21-log reductions (P < 0.05) in APC and coliforms compared with untreated controls. Considering laboratory and field studies, lactic acid produced greater reductions in Salmonella, APC, and coliforms, validating its effectiveness as a chlorine alternative in mobile poultry slaughter operations.

Development of stable reporter system cloning luxCDABE genes into chromosome of Salmonella enterica serotypes using Tn7 transposon

BACKGROUND

Salmonellosis may be a food safety problem when raw food products are mishandled and not fully cooked. In previous work, we developed bioluminescent Salmonella enterica serotypes using a plasmid-based reporting system that can be used for real-time monitoring of the pathogen's growth on food products in short term studies. In this study, we report the use of a Tn7-based transposon system for subcloning of luxCDABE genes into the chromosome of eleven Salmonella enterica serotypes isolated from the broiler production continuum.

RESULTS

We found that the lux operon is constitutively expressed from the chromosome post-transposition and the lux cassette is stable without external pressure, i.e. antibiotic selection, for all Salmonella enterica serotypes used. Bioluminescence expression is based on an active electron transport chain and is directly related with metabolic activity. This relationship was quantified by measuring bioluminescence against a temperature gradient in aqueous solution using a luminometer. In addition, bioluminescent monitoring of two serotypes confirmed that our chicken skin model has the potential to be used to evaluate pathogen mitigation strategies.

CONCLUSIONS

This study demonstrated that our new stable reporting system eliminates bioluminescence variation due to plasmid instability and provides a reliable real-time experimental system to study application of preventive measures for Salmonella on food products in real-time for both short and long term studies.

Prevalence, serotype, and antimicrobial resistance of Salmonella on broiler carcasses postpick and postchill in 20 U.S. processing plants

The objective of this study was to measure the effect of broiler processing on the prevalence, serotype, and antimicrobial resistance profiles of salmonellae. Twenty U.S. commercial processing plants representing eight integrators in 13 states were included in the survey. In each of four replications, 10 carcasses from one flock were collected at rehang and 10 more carcasses were collected at postchill; each carcass was sampled by whole-carcass rinse. Salmonella organisms were isolated from carcass rinses by standard cultural techniques, serotypes were determined, and the resistance to 15 antimicrobials was measured. Overall, Salmonella was detected on 72% of carcasses at rehang (ranging from 35 to 97%) and on 20% of carcasses postchill (ranging from 2.5 to 60%). In every instance, a significant (P < 0.05) decrease in Salmonella prevalence was noted between rehang and postchill. The four most common serotypes, accounting for 64% of all Salmonella isolates, were Kentucky, Heidelberg, Typhimurium, and Typhimurium var. 5-; most isolates of Kentucky (52%), Heidelberg (79%), and Typhimurium (54%) serotypes were susceptible to all antimicrobial drugs tested. However, only 15% of the Typhimurium var. 5- isolates were pansusceptible; more than one-half of the isolates of this serotype were resistant to three or more drugs. No isolate of any serotype exhibited resistance to amikacin, ceftriaxone, ciprofloxacin, or trimethoprim-sulfamethoxazole. These data demonstrate that although processing lessens carcass contamination with Salmonella, antimicrobial-resistant isolates may still be present.

Development of bioluminescent Salmonella strains for use in food safety

BACKGROUND

Salmonella can reside in healthy animals without the manifestation of any adverse effects on the carrier. If raw products of animal origin are not handled properly during processing or cooked to a proper temperature during preparation, salmonellosis can occur. In this research, we developed bioluminescent Salmonella strains that can be used for real-time monitoring of the pathogen's growth on food products. To accomplish this, twelve Salmonella strains from the broiler production continuum were transformed with the broad host range plasmid pAKlux1, and a chicken skin attachment model was developed.

RESULTS

Salmonella strains carrying pAKlux1 constitutively expressed the luxCDABE operon and were therefore detectable using bioluminescence. Strains were characterized in terms of bioluminescence properties and plasmid stability. To assess the usefulness of bioluminescent Salmonella strains in food safety studies, we developed an attachment model using chicken skin. The effect of washing on attachment of Salmonella strains to chicken skin was tested using bioluminescent strains, which revealed the attachment properties of each strain.

CONCLUSION

This study demonstrated that bioluminescence is a sensitive and effective tool to detect Salmonella on food products in real-time. Bioluminescence imaging is a promising technology that can be utilized to evaluate new food safety measures for reducing Salmonella contamination on food products.

Recovery of bacteria from broiler carcasses after spray washing with acidified electrolyzed water or sodium hypochlorite solutions

A study was conducted to investigate the effects of spray washing broiler carcasses with acidified electrolyzed oxidizing water (EO) or sodium hypochlorite (HOCl) solutions for 5, 10, or 15 s. Commercial broiler carcasses were contaminated with 0.1 g of broiler cecal contents inoculated with 10(5) cells of Campylobacter and 10(5) cells of nalidixic acid-resistant Salmonella. Numbers of bacteria recovered from unwashed control carcasses were 6.7, 5.9, 6.3, and 3.9 log(10) cfu/mL for total aerobic bacteria, Escherichia coli, Campylobacter, and Salmonella, respectively. Washing in either EO (50 mg/L of sodium hypochlorite, pH 2.4, oxidation reduction potential of 1,180 mV) or HOCl (50 mg/L of sodium hypochlorite, pH 8.0) significantly reduced the levels of bacteria recovered from carcasses (P < 0.05). Carcasses washed with EO had slightly lower levels of total aerobic bacteria (0.3 log(10) cfu/mL) and E. coli (0.2 log(10) cfu/mL) than HOCl-treated carcasses; however, populations of Campylobacter and Salmonella were comparable after washing in either solution. Increasing the carcass washing time from 5 to 10 s lowered the levels of total aerobic bacteria (6.1 vs. 5.8 log(10) cfu/mL), E. coli (4.6 vs. 4.1 log(10) cfu/mL), Campylobacter (5.2 vs. 4.2 log(10) cfu/mL), and Salmonella (2.0 vs. 1.2 log(10) cfu/mL), but no further microbiological reductions occurred when washing time was extended from 10 to 15 s. Data from the present study show that washing poultry carcasses with EO is slightly better (total aerobic bacteria and E. coli) or equivalent to (Campylobacter and Salmonella) washing with HOCl. Washing broiler carcasses for a period equivalent to 2 inside-outside bird washers (10 s) provided greater reductions in carcass bacterial populations than periods simulating 1 (5 s) or 3 inside-outside bird washers (15 s).

Predictive models for reduction of Salmonella Hadar on chicken skin during single and double sequential spraying treatments with acetic acid

AIMS

The response surface methodology was used to evaluate the effect of acetic acid concentration, spraying time and temperature on the reduction of Salmonella Hadar on poultry skin in a laboratory spraying process, and to identify the best conditions required to develop this operation.

METHODS AND RESULTS

A comparative analysis was carried out to ascertain the effects of the application of single (SS) and double sequential decontamination (DSS) treatments on skin samples inoculated with Salm. Hadar. While on the SS treatment, the linear and quadratic acid concentration terms and the interaction of the temperature and time term of the model are statistically significant at P < or = 0.001, P < or = 0.01 and P < or = 0.05, respectively, the other terms do not significantly affect (P > 0.05) the reduction of Salm. Hadar. On the DSS model the acid concentration and time linear terms significantly affected (P < or = 0.001 and P < or = 0.01) the Salm. Hadar reduction within the experimental range assayed.

CONCLUSION

Any of the models could be used as an approach to optimize spray washing during chicken processing.

SIGNIFICANCE AND IMPACT OF THE STUDY

Neither the SS or the DSS treatment has the capability of eliminating Salm. Hadar from carcasses. However, reductions of approx. 99% initial load could be attained if DSS treatment were put into practice.

Efficacy of lactic acid against Listeria monocytogenes attached to poultry skin during refrigerated storage

AIMS

The aim of this study was to evaluate the effect of lactic acid washing on the growth of Listeria monocytogenes on poultry legs stored at 4 degrees C for 7 days.

METHODS AND RESULTS

Fresh inoculated chicken legs were dipped into either a 0.11, 0.22 mol l(-1) or 0.55 mol l(-1) lactic acid solution for 5 min or distilled water (control). Surface pH values, sensorial characteristics and L. monocytogenes, mesophiles and pychrotrophs counts were evaluated after treatment (day 0) and after 1, 3, 5 and 7 days of storage at 4 degrees C. Legs washed with 0.55 mol l(-1) lactic acid for 5 min showed a significant (P < 0.05) inhibitory effect on L. monocytogenes compared with control legs, being about 1.74 log units lower in the first ones than in control legs after 7 days of storage. Sensory quality was not adversely affected by lactic acid, with the exception of colour.

CONCLUSIONS

Treatments with 0.55 mol l(-1) lactic acid reduced bacterial growth and preserved reasonable sensorial quality after storage at 4 degrees C for 7 days. However, it was observed a reduction in the colour score within 1 day post-treatment with 0.55 mol l(-1) lactic.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrates that, while lactic acid did reduce populations of L. monocytogenes on poultry, it did not completely inactivate the pathogen. The application of lactic acid may be used as an additional hurdle contributing to extend the shelf-life of raw poultry.

Predictive model for reduction of Escherichia coli during acetic acid decontamination of chicken skin

AIMS

The response surface methodology was used to evaluate the effect of operating variables (acetic acid concentration, spraying time and temperature) on the reduction of Escherichia coli populations on poultry breast skin in a laboratory showering process, as well as to identify the best conditions that are required to develop this operation.

METHODS AND RESULTS

Skin samples were inoculated with a 24-h E. coli culture and afterwards treated according to experimental design under selected acetic acid concentration, spraying time, and solution temperature. The E. coli reduction model was significantly affected by the acetic acid concentration and spraying time (P < or = 0.05 and < or =0.01), while temperature did not show a significant effect (P > 0.05).

CONCLUSION

The predictive model obtained was validated through additional confirmatory experiments and showed to be adequate, and it could be used as an approach to optimize the acetic acid spray washes during poultry carcasses processing.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of acetic acid washes in the processing of poultry does not have the capability of eliminating E. coli populations from carcasses. However, significant reductions in the initial load could be achieved.

Microbiological impact of spray washing broiler carcasses using different chlorine concentrations and water temperatures

A study was conducted to investigate the microbiological impact of spray washing broiler carcasses with chlorinated water (0 or 50 ppm) at different temperatures (21.1, 43.3, or 54.4 degrees C). A whole carcass rinse (WCR) was performed on each carcass before (control) and after spray washing (final). After the control WCR, carcasses were inoculated with 0.1 g of cecal material containing 2 x 10(5) cells per gram of Campylobacter and 2 x 10(5) cells per gram of nalidixic acid-resistant Salmonella. Carcasses were held at room temperature for 12 min before washing in an inside-outside bird washer (80 psi for 5 s). Chlorine level and water temperature had no effect on total aerobic bacteria, Escherichia coli, or Campylobacter numbers recovered from the final WCR. Levels of bacteria found on carcasses before and after washing were 4.6, 3.6, and 3.5 log10 cfu/mL rinse for total aerobic bacteria, E. coli, and Campylobacter, respectively. Average counts for nalidixic acid-resistant Salmonella after washing were 3.1 log10 cfu/ mL rinse irrespective of water temperature or chlorine level (P < 0.05). In addition, chlorine level and water temperature had no effect on the breast skin color, with average values of L* = 66.6; a* = -0.09; b* = -0.05 (P < 0.05). Under the conditions outlined in the present study, adding chlorine and/or elevating the water temperature during spray washing in an inside-outside bird washer did not enhance the removal of bacteria from broiler carcasses and had no effect on carcass skin color.

Effect of high-temperature inside-outside spray on survival of campylobacter jejuni attached to prechill chicken carcasses

Prechill chicken carcasses, inoculated with Campylobacter jejuni, were sprayed in an inside-outside birdwasher at 20, 55, or 60 C, with or without 50 ppm chlorine, in a poultry processing pilot plant. Carcasses were sprayed for 12 s at 80 pounds per square inch (psi). Next, carcasses were placed in a chiller filled with 50 ppm chlorinated ice water at 4 C for 50 min. Most probable numbers of C. jejuni were determined based on chicken carcass wash water before and after the spray treatment. The skin color of chicken carcasses was measured. The results of this study showed that the 55 and 60 C water spray treatments significantly reduced C. jejuni by more than 0.78 log cfu/carcass compared with the 20 C water spray treatment. However, all of the 50 ppm chlorine spray treatments at three different temperatures were not significantly different. The skin color of chicken carcasses did not change significantly after the spray treatments at temperatures less than 60 C. The chilling process with 50 ppm chlorinated ice water at 4 C further reduced more C. jejuni (approximately 1 log cfu/carcass) among the water spray treatments but did not result in greater reduction of C. jejuni among the chlorine spray treatments.

Influence of poultry carcass skin sample site on the effectiveness of trisodium phosphate against Listeria monocytogenes

The aim of this study was to determine the influence of skin sample site on the efficacy of trisodium phosphate (TSP) solutions in reducing Listeria monocytogenes populations on chicken carcasses during refrigerated storage. Chicken skin samples from the legs, the breasts, and the dorsal area inoculated with L. monocytogenes (10(8) CFU/ml) were dipped for 15 min in sterile tap water (control) or in 8, 10, or 12% TSP. L. monocytogenes counts and surface pH values were determined after 0, 1, 3, and 5 days of storage at 2 degrees C. For all sampling times and TSP concentrations, the reductions in L. monocytogenes numbers in breast skin were significantly larger (P < 0.05) than those in leg skin or dorsal skin. No significant differences were found in pH values as an effect of skin site. Our results suggest that skin sampling site is an important factor that needs to be considered when decontamination protocols are developed for poultry carcasses with the TSP treatment.

Process engineering variables in the spray washing of meat and produce

Recently, much attention has been focused on the safety of fruits and vegetables. Washing is a fundamental operation in the processing of produce. Aqueous spray energy can be, and often is, used to remove mineral, chemical, or biological contaminants from produce. A few advantages of spray washing over washing by dipping, soaking, or gravity rinse are increased energy directed to contaminants, reduced volume of water use and wastewater generation, and reduced water uptake by produce. The kinetic energy of the spray droplets produces the cleaning action. Increased spray pressure increases energy. If the energy is too great, produce may be physically damaged. If the energy is too little, the surface may not be cleaned. Indeed, studies on meat have shown that water pressures ranging from 1,379 to 2,070 kPa (200 to 300 psi) are effective in reducing microbial contamination, and a water flow rate of 7.5 liters/min is recommended. Water temperature >70 degrees C has been found to reduce bacterial counts in carcass tissue by 2 to 3 log CFU/cm2. These levels are likely too high for the fragile produce; hence, the main function of spray washing in produce applications will probably shift to being a delivery system for antimicrobial agents. Several other equipment, process, and product variables are relevant to the optimization of such a system. Qualities of the spray, such as droplet spectrum, droplet velocity, angle of droplet impingement, number and orientation of nozzles, spray rate, and resident time of the produce in the sprayer, also can be manipulated to adjust the amount of energy directed to the surface. There is a need to scientifically investigate the effects of these processes and equipment parameters on the removal of microbiological contaminants on meats and produce. Such empirical investigations guided by the results from fundamental studies about produce surface characteristics and the mechanism of bacterial attachment to plant tissue surfaces would allow for the efficient development of spray washers that effectively decontaminate produce.

Effectiveness of immersion treatments with acids, trisodium phosphate, and herb decoctions in reducing populations of Yarrowia lipolytica and naturally occurring aerobic microorganisms on raw chicken

Yarrowia lipolytica, one of the predominant yeasts in raw poultry, is believed to play a role in spoilage. This study was undertaken to investigate treatments to control the growth of Y. lipolytica on raw chicken stored at refrigeration temperature. Raw chicken wings inoculated with a mixture of five strains of Y. lipolytica isolated from raw poultry were dipped in solutions containing 2, 5, or 8% lactic acid, 2% lactic acid containing 0.2, 0.4, or 0.8% potassium sorbate or sodium benzoate, and 4, 8, or 12% trisodium phosphate solution. Populations of the yeast and total aerobic microorganisms were determined before and after treatment. Immersion of wings in 2% lactic acid (with or without 0.2% potassium sorbate or sodium benzoate) or 4% trisodium phosphate caused a significant (alpha = 0.05) reduction in numbers of Y. lipolytica and aerobic microorganisms. Treatment with 2% lactic acid containing 0.4 or 0.8% preservative did not result in additional significant reductions. Treatment of chicken wings with 2% lactic acid or 8% trisodium phosphate significantly reduced numbers of Y. lipolytica by 1.47 and 0.65 log10 cfu/g, respectively, and aerobic microorganisms by 2.60 and 1.21 log10 cfu/g, respectively, compared to controls. Growth of Y. lipolytica on wings stored at 5 degrees C for up to 9 days, however, was not affected by these treatments. Significant reductions in the population of Y. lipolytica occurred when the yeast was inoculated into 100% basil, marjoram, sage, and thyme decoctions, but not in 100% oregano or rosemary decoctions, held at 5 degrees C for 24 h. Treatment of chicken wings with 100% sage or thyme decoctions significantly reduced populations of Y. lipolytica but did not control its growth during storage at 5 degrees C for up to 9 days. The small, temporary decreases in numbers of Y. lipolytica and aerobic microorganisms resulting from immersion treatment of chicken wings with sage and thyme decoctions render these treatments of questionable value as preservation interventions.

Quantitative investigation of the effects of chemical decontamination procedures on the microbiological status of broiler carcasses during processing

The effects of elevated chlorine concentrations (25 ppm) added to water in the final carcass washing equipment on total viable counts (TVCs 22 degrees C) and Escherichia coli and Enterobacteriaceae levels on poultry carcasses were investigated. Mean TVC counts on neck skin samples were significantly reduced when pre-evisceration and postwash samples were compared with log10 4.98 to 4.52 CFU/g recovered, respectively (P < or = 0.05). No significant reductions in TVC counts were observed in control samples at corresponding sampling points subjected to wash water containing 1 to 2 ppm chlorine. E. coli and Enterobacteriaceae counts were not significantly altered following final carcass washing in the processing plant. A second trial assessed the microbial decontamination capabilities of sodium triphosphate (TSP) on broiler carcasses. Neck skin samples from carcasses were obtained before final washing (control), following a 15-s dip in potable water and after dipping in a 10% TSP solution (pH 12) for 15 s. Reductions in E. coli and Enterobacteriaceae counts were all statistically significant for both water and TSP-treated samples when compared with corresponding controls (P < or = 0.01). The TSP treatment resulted in higher reductions of log10 1.95 and 1.86/g for E. coli and Enterobacteriaceae, respectively. In contrast, reductions of log10 0.37 and 0.3 l/g were observed for E. coli and Enterobacteriaceae counts when water-dipped carcasses were compared with corresponding controls. Significantly, Salmonella was not detected in any of the TSP-treated carcasses, while log10 1.92 and 1.04/g were found in control and water-dipped samples, respectively. Thermophilic Campylobacter counts were significantly lower in both treatment groups when compared with corresponding controlsresulting in log10 0.55 and 1.71/g reductions for water- and TSP-dipped carcasses, respectively (P < or = 0.01).