Effect of various chemical decontamination treatments on natural microflora and sensory characteristics of poultry

Regulation (EC) No. 853/2004 of the European Parliament and of the Council provides a legal basis permitting the use of antimicrobial treatments to remove surface contamination from poultry. This paper reports the results of research into the effects on natural microflora, pH, and sensorial characteristics achieved by dipping chicken legs (15 min, 18+/-1 degrees C) into solutions (wt/vol) of 12% trisodium phosphate (TSP), 1200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), 220 ppm peroxyacids (Inspexx 100; PA), and water. Samples were collected immediately after evisceration, subjected to the treatments listed or left untreated (control) and tested after 0, 1, 3 and 5 days of storage (3 degrees C+/-1 degrees C). For most microbial groups similar counts were observed on water-dipped and on untreated legs. All the chemical compounds were effective in reducing microbial populations throughout storage, with TSP, ASC and CA showing the strongest antimicrobial activity. The average reductions (mean+/-standard deviation) relative to untreated samples caused by chemical treatments when considering simultaneously all storage days ranged (log(10) cfu/g skin) from 0.53+/-0.83 (PA) to 1.98+/-0.62 (TSP) for mesophilic aerobic counts, from 0.11+/-0.89 (PA) to 1.27+/-1.02 (CA) (psychrotrophs), from 1.34+/-1.40 (PA) to 2.15+/-1.20 (CA) (Enterobacteriaceae), from 1.18+/-1.24 (PA) to 1.98+/-1.16 (CA) (coliforms), from 0.66+/-0.99 (PA) to 1.86+/-1.80 (TSP) (Micrococcaceae), from 0.54+/-0.74 (TSP) to 2.17+/-1.37 (CA) (enterococci), from 0.72+/-0.66 (TSP) to 2.08+/-1.60 (CA) (Brochothrix thermosphacta), from 0.78+/-1.02 (PA) to 1.99+/-0.96 (TSP) (pseudomonads), from 0.21+/-0.61 (PA) to 1.23+/-0.60 (TSP) (lactic acid bacteria), and from 1.14+/-0.89 (PA) to 1.45+/-0.61 (ASC) (moulds and yeasts). The microbial reductions throughout storage increased, decreased, or did not vary, in accordance with microbial group and chemical involved. Similar pH values were observed for untreated samples and for those dipped in PA and water on all sampling days. ASC-treated samples showed a lower pH than controls to day 1. TSP-treated legs exhibited the highest pH values and CA-treated ones the lowest, throughout storage. Hedonic evaluation (nine-point structured scale, untrained panellists) showed similar colour, smell and overall acceptability scores for dipped and untreated samples on day 0 and day 1. From day 3 sensorial attributes scored lower for untreated, PA- and water-dipped legs, as compared to legs treated with TSP, ASC and CA. Only for these three groups of samples were average scores higher than 6 (shelf-life limit value) observed by the end of storage. Results from the present study suggest that the treatments tested improve the microbial quality of chicken without adverse sensorial effects.     

Effectiveness of trisodium phosphate treatment against pathogenic and spoilage bacteria on poultry during refrigerated storage

To determine the efficacy of trisodium phosphate (TSP) against pathogenic and spoilage bacteria on poultry and to assess the influence of the bacterial combination of inoculum on TSP effect, chicken legs were coinoculated with similar concentrations of a pathogenic (Salmonella enterica ser. Enteritidis or Listeria monocytogenes) and a spoilage (Pseudomonas fluorescens or Brochothrix thermosphacta) bacteria. Samples were dipped in TSP (12%, 15 min) or were not treated (control). Microbiological analysis and pH determinations were carried out at 0, 1, 3, and 5 days of storage (3 degrees C). Significant bacterial reductions (marked in gram-negative species) were observed on TSP-treated samples throughout refrigerated storage. Inoculum composition scarcely influenced the TSP effect against gram-positive bacteria. However, greater reductions were observed on gram-negative bacteria (Salmonella Enteritidis and P. fluorescens) when samples were coinoculated with B. thermosphacta and L. monocytogenes, respectively. Values of pH were higher in TSP-treated than in control samples at all sampling times. The combination of bacteria in inocula did not have a significant influence on pH values.     

Effects of Trisodium Phosphate and Sodium Chloride Dipping on the Microbial Quality and Shelf Life of Refrigerated Tray-packaged Chicken Breasts

Effects of trisodium phosphate (TSP) and/or sodium chloride (NaCl) dipping on microbial quality and shelf life of chicken breasts were investigated during refrigeration. Chicken breasts were dipped in aqueous solution (w/v) of 10% TSP, 10% NaCl, combination of TSP and NaCl (7.5% + 7.5%) or distilled water (control) for 10 min, followed by tray-packaging storage at 2 degrees C. During storage, chicken breasts dipped in TSP maintained almost constant pH, while pH of control or NaCl-treated samples significantly increased (P<0.05). TSP dipping resulted in initial reduction of 0.48 and 0.91 log(10) CFU/g in aerobic plate counts and Enterobacteriaceae count, respectively, when compared with control. By storage day 6, APC of control chicken breasts reached 6.91 log(10) CFU/g, while TSP-treatment either alone or in combination with NaCl significantly delayed microbial growth (P<0.05) and extended shelf life of refrigerated chicken breasts up to 12 days, at which APC were 6.87 and 6.39, respectively, versus 9.58 log(10) CFU/g for control. Significant reductions in psychrotrophic and Enterobacteriaceae count were detected at the end of storage period in chicken breasts treated with TSP alone or in combination with NaCl, whereas such treatments had no significant effects on lactobacilli or mold and yeast populations.     

Physicochemical,microbial, and sensory evaluation of cook-chilled Korean traditional rice cake (<Emphasis Type="Italic">Backseolgi</Emphasis>) during storage via various packaging methods

Backseolgi is a Korean traditional rice cake, which is prepared by steaming the rice flour. After cook-chilling processing, backseolgi samples packaged by a modified atmosphere package (MAP), top sealing package (TSP), and linear low density-polyethylene package (LDPA; control) were evaluated in regard to microbial safety and sensory characteristics during storage. During storage at 30°C, the cell numbers of aerobic, psychrophilic, and anaerobic bacteria for the MAP sample increased to below 2 log CFU/g for 10 days, whereas the control and TSP samples increased more than 5.0 log CFU/g after 4 days. After 50 days of storage at 3°C, the cell numbers in the MAP sample were below 1.0 log CFU/g, whereas they were approximately 3.0 log CFU/g in the control and TSP samples. In the case of the sensory evaluation, the MAP sample score was above 5.0, whereas the scores of the CON and TSP samples were 1.0. As a result, MAP was identified as the most effective packaging method for increasing microbial safety while maintaining the sensory characteristics of the cook-chilled backseolgi.     

Effects of diacetyl and carbon dioxide on spoilage microflora in ground beef

The effect of CO2 and diacetyl, alone or in combination, on spoilage microflora in ground beef was determined. Ground beef was treated with 20, 30, or 40% CO2 for 22 days (study I); 20, 50, or 100 microg/g diacetyl for 26 days (study II); or a combination of 20% CO2 and 100 microglg diacetyl for 40 days (study III). Antimicrobial effectiveness was determined by aerobic plate counts (log10 CFU/g) using plate count agar (total aerobic bacteria), deMan Rogosa Sharpe (MRS) Lactobacillus agar (gram-positive bacteria), MacConkey agar (gram-negative bacteria), pH, and informal organoleptic assessments (by appearance and by odor). In study I, total bacteria and pH increased by day 4 in control meat samples. For all CO2 levels, gram-negative bacteria decreased and gram-positive bacteria increased compared with untreated controls. The pH remained constant for CO2-treated meat. Control samples had an off-odor and a brown appearance, while CO2-treated samples had no off-odor but did have a brown appearance. For samples treated with diacetyl (study II), spoilage was evident by day 7 for samples treated with 0, 20. and 50 microg/g diacetyl for all parameters examined. Ground beef treated with 100 microg/g diacetyl was spoiled on day 12. Diacetyl was detected (by odor) in samples that were treated with 100 microg/g diacetyl and had a brown appearance. Meat samples treated with the combination of CO2 and diacetyl (study III) showed that the addition of diacetyl did not have an additive effect on microbial growth. Combination-treated meat maintained a red appearance and no off-odor. Diacetyl and CO2 could be used in combination to maintain a red color and inhibit spoilage microorganisms.     

Inactivation of Salmonella during drying and storage of Roma tomatoes exposed to predrying treatments including peeling, blanching, and dipping in organic acid solutions

The objective of this study was to evaluate the influence of predrying treatments, i.e., peeling, blanching prior to inoculation, and dipping in organic acid solutions, on inactivation of Salmonella during drying (60 degrees C for 14 h) and aerobic storage (25 degrees C for 28 days) of inoculated (five-strain composite, 7.1 to 7.4 log CFU/g) Roma tomato halves. Four predrying treatments groups were established. One group received no treatment (C). In the other three groups, unpeeled-unblanched, unpeeled-blanched (steam blanched at 88 degrees C for 3 min), peeled-unblanched, and peeled-blanched tomato halves were immersed for 10 min in water (W), ascorbic acid solution (AA; 3.40%, pH 2.48), or citric acid solution (CA; 0.21%, pH 2.51). Appropriate dilutions of homogenized tomato samples were spread plated on tryptic soy agar with 0.1% pyruvate and XLT4 agar for bacterial enumeration during drying and storage. Ten minutes of immersion in W, AA, or CA reduced bacterial populations by 0.7 to 1.6 log CFU/g. After 14 h of dehydration, total log reductions in the populations of bacteria were 3.2 to 4.5 (C), 3.7 to 4.9 (W), > 5.6 to > 6.1 (AA), and 4.5 to 5.5 (CA) log CFU/g, depending on type of agar used and condition of tomato samples. During drying and storage, the order of pathogen inactivation for predrying dipping treatments was AA > CA > W > C, with AA and CA rendering bacterial populations below detectable levels ( < 1.3 log CFU/g) prior to storage and between 7 and 14 days of storage, respectively. The results also indicated that peeling and blanching of tomatoes prior to inoculation may not necessarily affect destruction of Salmonella during the drying process. Use of predrying acid dipping treatments of tomatoes, especially in AA, may improve destruction of Salmonella during the dehydration process.     

Efficacy of trisodium phosphate solutions in reducing Listeria monocytogenes populations on chicken skin during refrigerated storage

Chicken skin inoculated with l0(8) CFU/ml of Listeria monocytogenes was dipped for 15 min in sterile water (control) and in 8, 10, or 12% trisodium phosphate (TSP) solutions. Skin samples were stored at 2 degrees C for 5 days, with microbial monitoring on days 0, 1, 3, and 5 after treatment. Compared to the water dip, all TSP treatments significantly (P < 0.05) reduced L monocytogenes populations on chicken skin. The concentration of the TSP was a significant factor in reducing the populations of the bacteria at days 0, 1, 3, and 5 of refrigerated storage. For all sampling times, the best outcomes were attained with the highest TSP concentration studied (12%). Bacterial reductions in counts during the first day of storage were between 1.52 and 2.70 log10 cycles for 8 and 12% TSP-treated samples, respectively. Significantly greater reductions were observed from the third day of refrigerated storage onward. This occurred largely because populations of L. monocytogenes on control samples increased somewhat, but on TSP-treated samples the pathogen remained practically constant. Differences between L monocytogenes counts in skin samples immersed in water and those treated with TSP ranged from 2.10 (8% TSP-treated samples) and 3.63 (12% TSP-treated samples) log10 cycles on day 5 of storage. These results indicated that TSP is effective against L. monocytogenes in chicken meat, especially after several days of refrigerated storage.     

Effectiveness of trisodium phosphate against Listeria monocytogenes on excised and nonexcised chicken skin

The influence of sample type (i.e., excised versus nonexcised chicken skin) on the efficiency of trisodium phosphate (TSP) solutions in reducing Listeria monocytogenes populations and inhibiting their growth during refrigerated storage was studied. Whole chicken legs and excised chicken leg skin fragments inoculated with 10(8) CFU of L. monocytogenes per ml were dipped for 15 min in sterile tap water (control) or in a solution containing 8, 10, or 12% TSP. L. monocytogenes counts were determined after 0, 1, 3, and 5 days of refrigerated storage (2 degrees C). The decontamination effect of TSP was greater for excised skin than for whole legs. Microbial differences between control and TSP-treated samples were significantly larger for excised skin than for whole legs for 9 (75%) of 12 tested combinations of TSP concentrations and storage times. These differences varied from 1.05 +/- 0.26 log10 cycles (day 1) to 3.30 +/- 0.14 log10 cycles (day 5) for nonexcised-skin samples (whole legs) and from 1.54 +/- 0.48 log10 cycles (day 1) to 4.28 +/- 0.86 log10 cycles (day 5) for excised-skin samples. Significantly larger reductions were observed from the third day of refrigerated storage onward. The TSP concentration was a significant factor in the reduction of L. monocytogenes populations. These results suggest that bacteria are more readily accessible to TSP in excised than in nonexcised chicken skin and that the type of sample used to ascertain the efficacy of antimicrobial surface treatments may influence the findings of this type of study.     

ACIDIFIED SODIUM CHLORITE, TRISODIUM PHOSPHATE AND POPULATIONS OF CAMPYLOBACTER JEJUNI ON CHICKEN BREAST SKIN

The present study was designed to determine the effects of acidified sodium chlorite (ASC) and trisodium phosphate (TSP) antimicrobial treatments. Chicken skin samples inoculated with Campylobacter jejuni ATCC 33291 and C. jejuni pc10 (isolated in our laboratory from chicken carcasses) were separately dipped into sterile tap water (control), 0.1% ASC, 10% TSP, 0.1% ASC followed by 10% TSP and 10% TSP followed by 0.1% ASC for 15 s at 25 ± 1C. Campylobacter jejuni counts and pH values were determined after 0, 1, 3 and 5 days of storage at 4 ± 1C. On day 0, reductions were between 1.1–2.5 log for C. jejuni ATCC 33291 and 1.4–2.4 log for C. jejuni pc10, while the reduction effects of all antimicrobials increased (P < 0.001) during the storage period and the bacterial counts reached undetectable levels (<1.0 × 10² cfu/g) on day 5 of storage at 4 ± 1C. The results of this study suggest that introduction of the antimicrobial treatments ASC, TSP and ASC followed by TSP into poultry processing systems could provide an added measure of safety.     

Prewashing with acidified sodium chlorite reduces pathogenic bacteria in lightly fermented Chinese cabbage

Efficacy of prewashing with acidified sodium chlorite (ASC) for the sanitation of lightly fermented Chinese cabbage was evaluated. The population of the natural microflora on the cabbage leaves was reduced about 2.0 log CFU/g just after washing with ASC, a significant reduction compared with the control distilled water wash (P < or = 0.05). In the control experiment, viable aerobic bacteria increased gradually when incubated at 10 degrees C; however, ASC-washed cabbage maintained a lower microbial concentration. The treatment of Chinese cabbage with ASC reduced the population of artificially inoculated Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes by 2.4 log CFU/g. The sanitation efficacy of ASC was 1.6 log CFU/g higher than that of distilled water washing. The viable cell counts of all pathogenic bacteria tested remained constant during 8 days of storage at 10 degrees C for both washing treatments, with the exception of L. monocytogenes, whose viable cell counts increased gradually with time for both treatments. No significant differences in color, odor, taste, and texture in raw leaves were observed after the ASC wash compared with after the distilled water wash. These results indicate that prewashing with ASC could control bacterial growth in lightly fermented Chinese cabbage without changing the product quality.     

ACIDIFIED SODIUM CHLORITE, TRISODIUM PHOSPHATE AND POPULATIONS OF SALMONELLA TYPHIMURIUM AND STAPHYLOCOCCUS AUREUS ON CHICKEN-BREAST SKIN

The present study was designed to determine the individual and combined effects of acidified sodium chlorite (ASC) and trisodium phosphate (TSP) antimicrobial treatments. Chicken‐skin samples inoculated with Salmonella typhimurium and Staphylococcus aureus were separately dipped into sterile tap water, 10% TSP, 0.1% ASC, 0.1% ASC followed by 10% TSP and 10% TSP followed by 0.1% ASC for 15 s at 25C ± 1. On day 0, reductions were 1.4–1.6 log for S. Typhimurium and 1.1–2.1 log for S. aureus, while they were 1.8–2.9 and 0.7–1.7 log, respectively, on day 5 of storage. Results indicated that treatment with ASC solution alone was more effective than treatment with ASC and TSP solutions combined in reducing S. aureus populations on chicken skin during the entire storage period. Similarly, treatment with TSP solution alone was more effective than treatment with ASC and TSP solutions combined in reducing S. typhimurium populations on chicken skin on days 1, 3 and 5 of storage.     

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).     

Impacts of broadband and selected infrared wavelength treatments on inactivation of microbes on rough rice

This study investigated the effects of broadband and selected infrared (IR) wavelength treatments of rough rice on microbial inactivation. Rough rice was treated at different IR wavelengths and product-to-emitter distances (110, 275, and 440 mm) followed by tempering at 60°C for 4 hr. The total mold and aerobic plate counts (APC) on non-treated and treated samples were determined. Significant total mold reductions of 1.14 and 3.11 log CFU/g were obtained after IR heating using broadband and selected wavelengths, respectively (p < .05). The most significant reduction of APC using selected IR wavelength was 1.09 log CFU/g; the broadband IR wavelength had no effect on the mean APC. The IR treatments followed by tempering step resulted in greater reductions of total mold counts and APC (4.03 and 3.50 log CFU/g) in comparison to IR treatments without tempering (3.11 and 1.09 log CFU/g). Overall, bacteria showed more resistance to IR treatments than molds.     

Bacterial contamination in an egg-breaking factory and its control

From January to November, 2003, bacterial contamination was surveyed in a small egg-breaking factory that produced non pasteurized liquid egg. Test egg samples were taken at various stages of the egg processing operation. Salmonella Enteritidis was isolated from liquid egg yolk and liquid egg white on October, but was not found in any other samples (50 liquid egg samples, 21 containers and 94 attached production facilities and gloves). The data suggest that the contamination rate (3.8%) is lower than those reported previously. Levels of bacterial standard plate counts, gram-positive bacterial counts and gram-negative bacterial counts were in the ranges of 2 to 5 log CFU/g, 2 to 3 log CFU/g, 2 to 5 log CFU/g, respectively. Liquid egg containers returned from customers was contaminated with bacteria at the level of 8 log CFU per container. However, washing and application of a sanitizer containing sodium hypochlorite reduced the bacterial counts.     

Effects of post-packaging pasteurization process on microbial,chemical, and sensory qualities of ready-to-eat cured vacuum-packed Turkey breast

Ready-to-eat (RTE) cured vacuum-packed turkey breast was pasteurized (80°C, 5.5 min) and stored at 8°C (like supermarkets refrigerator temperature). After 42 days (current shelf life of this product), in control group (RTE cured vacuum-packed turkey breast), the number of mesophilic, anaerobic, lactic acid bacteria, mold and yeast, coliform, and psychrotrophic increased 5.82, 6.85, 5.85, 4.75, 1.49, and 5.57 log CFU/g, respectively. However, in the pasteurized samples, the number of mesophilic, anaerobic, and lactic acid bacteria increased 1.86, 2.12, and 2.28 log CFU/g, respectively, and mold and yeast, coliform, and psychrotrophic bacteria were under the detection limit. The effects of post-packaging pasteurization on the reduction of total mesophilic, anaerobic and lactic acid bacteria counts on Day 42 of storage was 7.04 ± 0.33, 4.73 ± 0.11, and 5.58 ± 0.11 log CFU/g, respectively. Sensory quality of treated samples was significantly better than the control's (p < .05). Post-packaging pasteurization (PPP) significantly inhibited the reduction in the pH and the increase in TVB-N, TBARS, titratable acidity, and drip loss (p < .05). This study shows the effectiveness of PPP on microbial, chemical, and sensory quality of cured vacuum-packed turkey breast during cold storage.     

Combined antimicrobial effect of oregano essential oil and caprylic acid in minced beef

Oregano essential oil (OEO) and caprylic acid (CA) are highly aromatic natural antimicrobials with limited individual application in food. We proved their combined additive effect when used in meat. Application of 0.5% CA and 0.2% OEO (v/w) with 0.1% of citric acid in vacuum packed minced beef inoculated with Listeria monocytogenes at a concentration of 5 log cells/g reduced counts of lactic acid bacteria by 1.5 log CFU/g and counts of psychrotrophic bacteria and L. monocytogenes by more than 2.5 log CFU/g at the end of storage at 3 °C for 10 days. In sensory evaluation the samples with OEO showed during the whole experiment statistically better scores than control, whereas the samples treated with CA showed worse colour attributes.     

Inactivation of pathogens on pork by steam-ultrasound treatment

The objective of the study was to evaluate a new pathogen inactivation concept that combines application of pressurized steam simultaneously with high-power ultrasound through a series of nozzles. On skin and meat surfaces of pork jowl samples, counts of total viable bacteria were reduced by 1.1 log CFU/cm(2) after treatment for 1 s and by 3.3 log CFU/cm(2) after treatment for 4 s. The mean reduction of 1.7 to 3.3 log CFU/cm(2) on the skin surface was significantly higher than the reduction of 1.1 to 2.5 log CFU/cm(2) on the meat surface. The inactivation of Salmonella Typhimurium, Salmonella Derby, Salmonella Infantis, Yersinia enterocolitica, and a nonpathogenic Escherichia coli was studied on inoculated samples that were treated for 0.5 to 2.0 s. With one exception, no significant differences in reduction were observed among the bacterial types. After treatment for 0.5 s, the 0.9-to 1.5-log reductions of E. coli were significantly higher than the 0.4- to 1.1-log reductions for Salmonella and Y. enterocolitica. Overall, reductions increased by increasing treatment time; reductions were 0.4 to 1.5 log CFU/cm(2) after treatment for 0.5 s and 2.0 to 3.6 log CFU/cm(2) after treatment for 2 s. Reductions on the skin (1 to 3.6 log CFU/cm(2)) were significantly higher than reductions on the meat surface (1 to 2.5 log CFU/cm(2)). The reduced effect on the meat surface may be explained by greater protection of bacteria in deep structures at the muscle surface. No significant difference in reduction was observed between samples inoculated with 10(4) CFU/cm(2) and those inoculated with 10(7) CFU/cm(2), and cold storage of samples for 24 h at 5°C after steam-ultrasound treatment did not lead to changes in recovery of bacteria.     

Reducing levels of Listeria monocytogenes contamination on raw salmon with acidified sodium chlorite

The antimicrobial activity of acidified sodium chlorite (ASC) against Listeria monocytogenes in salmon was studied. Raw salmon (whole fish and fillets) inoculated with L. monocytogenes (10(3) CFU/cm2 or 10(4) CFU/g) were washed with ASC solution (50 ppm) for 1 min and stored at -18 degrees C for 1 month (whole salmon) or in ice for 7 days (fillets). L. monocytogenes populations were determined for whole salmon after frozen storage and for fillets on days 1, 3, 5, and 7 of storage. A wash with ASC solution followed by ASC glazing did not reduce L. monocytogenes on the skin of whole salmon during frozen storage. However, the wash resulted in an L. monocytogenes reduction of 0.5 log CFU/g for salmon fillets. The populations of L. monocytogenes in fillets increased slowly during ice storage, but the growth of these populations was retarded by ASC ice. By day 7, the populations were 0.25 log units smaller in fillets stored in ASC ice and 0.62 log units smaller in fillets that had been washed with ASC solution and stored in ASC ice than in control fillets. Treatment with ASC also reduced total plate counts (TPCs) by 0.43 log CFU/cm2 on the skin of whole salmon and by 0.31 log CFU/g in fillets. The TPCs for skin decreased during frozen storage but increased gradually for fillets stored at 5 degrees C or in ice. However, TPCs of ASC-treated samples were lower than those for controls at any point during the study. Washing with ASC solution significantly (P < 0.05) reduced TPCs on the skin of whole salmon and in fillets, as well as L. monocytogenes in fillets. The antimicrobial activity of ASC was enhanced when salmon was washed with ASC solution and stored in ASC ice.     

Effects of cetylpyridinium chloride, acidified sodium chlorite, and potassium sorbate on populations of Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus on fresh beef

The effects of selected food-grade antimicrobial agents at decreasing the number of pathogenic bacteria on fresh beef were determined. Beef cubes inoculated with Escherichia coli O157:H7, Listeria monocytogenes, or Staphylococcus aureus were sprayed with 0.5% cetylpyridinium chloride (CPC), 0.12% acidified sodium chlorite (ASC), 0.1% potassium sorbate (PS), or an equal mix of any two solutions. The beef samples were placed on absorbent tray pads sprayed with each single or mixed solution, wrapped with polyvinyl chloride film, heat sealed, and stored at 4 degrees C for 2 weeks. Surface sanitization using CPC, ASC, or an equal mix of these two agents effectively reduced microbial numbers on the beef during storage. At day 0, ASC and the CPC-ASC mix reduced the number of E. coli O157:H7 by 2.50 and 1.58 log CFU/cm2, respectively. CPC demonstrated a 3.25-log reduction of L. monocytogenes and a 4.70-log reduction of S. aureus at 14 days. The CPC-PS mix reduced E. coli O157:H7 numbers by 1.46, L. monocytogenes by 2.95, and S. aureus by 4.41 log CFU/cm2 at 14 days. PS alone and the mixed solutions, CPC-ASC, CPC-PS, or ASC-PS, were not as effective as ASC or CPC alone. To effectively reduce E. coli O157:H7, L. monocytogenes, or S. aureus numbers, higher (> 0.1%) concentrations of PS were necessary. Loss of redness and light color of beef surfaces consistently coincided with decreases in pH for ASC-treated beef samples.     

Acidified sodium chlorite treatment for inhibition of Listeria monocytogenes growth on the surface of cooked roast beef

The effects of acidified sodium chlorite (ASC) against Listeria monocytogenes on the surface of cooked roast beef were investigated. L. monocytogenes, strain V7, serotype 1/2a, was inoculated at numbers of 6.0 log CFU/g onto 5-g cubes of cooked regular or spicy roast beef. The samples were allowed to air dry for 1 h. The cooked roast beef samples were dipped into ASC or sprayed with ASC solutions of 250, 500, 750, or 1,000 ppm, then placed in bags with or without a vacuum and refrigerated at 4 degrees C. L. monocytogenes counts were determined after 0, 7, 14, 21, and 28 days of storage by spread plating roast beef samples onto Oxford agar plates that were incubated at 37 degrees C for 48 h. At day 28, the number of L. monocytogenes on the > or = 500 ppm ASC-treated spicy roast beef samples had count reductions that were >4.0 log CFU/g, whereas the same concentrations of ASC-treated regular roast beef samples had approximately a 2.5 log CFU/g reduction in L. monocytogenes counts when compared with the untreated samples. No significant differences (P > 0.05) were observed in L. monocytogenes counts between the vacuum- or nonvacuum-packaged ASC-treated cooked roast beef samples. Sensory evaluation showed no significant differences (P > 0.05) between ASC-treated and untreated roast beef. ASC can be used as a processing aid in the form of a dip or spray treatment to control L. monocytogenes on the surface of cooked roast beef.