Bacteriological quality of broiler carcasses as affected by in-plant lactic acid decontamination

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.

Chemical additive to enhance antimicrobial efficacy of chlorine and control cross-contamination during immersion chill of broiler carcasses

Immersion chilling of broiler carcasses can be a site for cross-contamination between the occasional highly contaminated carcass and those that are co-chilled. Chlorine is often used as an antimicrobial but can be overcome by organic material. A proprietary chlorine stabilizer (T-128) based on phosphoric acid-propylene glycol was tested as a chill tank additive in experiments simulating commercial broiler chilling. In bench-scale experiments, 0.5% T-128 was compared with plain water (control), 50 ppm of chlorine, and the combination of 0.5% T-128 with 50 ppm of chlorine to control transfer of Salmonella and Campylobacter from inoculated wing drummettes to co-chilled uninoculated drummettes. Both chlorine and T-128 lessened cross-contamination with Salmonella (P < 0.05); T-128 and T-128 with chlorine were significantly more effective (P < 0.05) than the control or plain chlorine for control of Campylobacter. T-128 treatments were noted to have a pH of less than 4.0; an additional experiment demonstrated that the antimicrobial effect of T-128 was not due merely to a lower pH. In commercial broiler chilling, a pH close to 6.0 is preferred to maximize chlorine effectiveness, while maintaining water-holding capacity of the meat. In a set of pilot-scale experiments with T-128, a near-ideal pH of 6.3 was achieved by using tap water instead of the distilled water used in bench-scale experiments. Pilot-scale chill tanks were used to compare the combination of 0.5% T-128 and 50 ppm of chlorine with 50 ppm of plain chlorine for control of cross-contamination between whole carcasses inoculated with Salmonella and Campylobacter and co-chilled uninoculated carcasses. The T-128 treatment resulted in significantly less crosscontamination by either direct contact or water transfer with both organisms compared with plain chlorine treatment. T-128 may have use in commercial broiler processing to enhance the effectiveness of chlorine in processing water.

Inhibition of nalidixic acid-resistant salmonella on marinated chicken skin

Marination is widely used to enhance flavor and increase consumer acceptability of meat and poultry products. The impact of such marination on the safety and shelf life of poultry meat was evaluated in this study. A series of experiments were conducted to determine the efficacy of teriyaki and lemon pepper marinades against multiple strains of nalidixic acid (NAL)-resistant Salmonella. NAL-resistant Salmonella serovar (Typhimurium, Heidelberg, and Senftenberg) cultures were inoculated onto chicken skin at 0.6 to 3.14 log CFU/g in a 12-well titer plate. Inoculated chicken skin was exposed to teriyaki or lemon pepper marinades for up to 32 h and stored at 4 or 25°C to determine the prevalence of Salmonella. To determine Salmonella survival, a three-strain cocktail of Salmonella was inoculated at low (ca. 4 log CFU/g) and high (8 log CFU/g) levels onto chicken skin that was then marinated with either teriyaki or lemon pepper marinade for up to 32 h and stored at 4 or 25°C. Prevalence of Salmonella was significantly reduced (P ≤ 0.05) by teriyaki marinade at all levels of contamination regardless of storage temperature. Lemon pepper marinade reduced Salmonella prevalence (P ≤ 0.05) at low levels of contamination (10¹ and 10² CFU/g), whereas no significant effect (P > 0.05) was observed at higher levels of contamination. Marination of chicken skin with teriyaki marinade greatly reduced Salmonella prevalence and survival (P ≤ 0.05) regardless of the storage temperature, indicating the antimicrobial potential of this marinade for poultry and meat products.

Lactic acid as a potential decontaminant of selected foodborne pathogenic bacteria in shrimp (Penaeus merguiensis de Man)

Fresh raw shrimps were dipped for 10, 20, and 30 min at room temperature (25°C ± 1°C) in lactic acid (LA; 1.5%, 3.0%, v/v) to evaluate their antipathogenic effects against Vibrio cholerae, Vibrio parahaemolyticus, Salmonella entreitidis, and Escherichia coli O157:H7 inoculated at a level of 10(5) CFU/g. Significant reductions in the population of all these pathogenic bacteria were recorded after dipping treatments, which were correlated to the corresponding LA concentrations and treatment time. With respect to the microbial quality, 3.0% LA treatment for 10 min was acceptable in reducing the pathogenic bacteria. Additionally, sensory evaluation results revealed a 10-min dip in 3.0% LA to be more acceptable organoleptically compared with 20 and 30 min of treatments. Results of the present study are envisaged to be useful for commercial applications for effective decontamination of shrimp.

Comparative study of different surface decontaminants on chicken quality

(1) A comparative study on the effect of different surface decontaminants: hot water at 70 degrees C for one minute; 2% lactic acid for 30 s; 1200 p.p.m. acidified sodium chlorite (ASC) solution for 5 s and 50 p.p.m. chlorine solution for 5 min in the form of dips and sprays on the surface of dressed broilers for 0, 24 and 48 h of storage was conducted. (2) The variables studied were, total plate count (TPC), presumptive coliform count (PCC), pH and extract release volume (ERV). All treatments reduced TPC and PCC. (3) Lactic acid dip and hot water dip were the most effective for reducing TPC (1.36 and 1.28 log/cm2, respectively) with no significant difference between them. (4) ASC and hot water in dip could diminish PCC (1.37 and 1.34 log/cm2, respectively) and did not vary significantly. (5) No treatment affected muscle pH, water holding capacity (WHC), ERV, appearance, smell, tenderness and overall acceptability of treated broilers significantly. (6) Hot water treatment is the cheapest, most convenient and simplest decontamination technique for hygienic and wholesome poultry production.

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.

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.

Decontamination of broilers with hydrogen peroxide stabilised with glycerol during processing

Experiments were conducted to assess the effects of different concentrations of hydrogen peroxide stabilised by glycerol solution in potable water on the bacteriological and organoleptic quality of freshly slaughtered broiler carcasses. Skin-pH and colour were measured 3.5 and 24 h after treatment and compared to untreated carcasses. Bacterial colonisation was determined 3.5 and 24 h and, 7 days after treatment, carcasses being stored at 1 degrees C. None of the concentrations used affected the appearance and "bloom" of the carcasses as could be measured by colorimeter and changing of the acidity. Mean microbial counts were significantly reduced (P<0.01) when treated and control broilers were compared. Average reductions of 0.3 up to1.4 log N for the mesophilic aerobic counts were achieved and from 0.4 up to 1.2 log N for Enterobacteriaceae. A 3% w/w solution made from a commercially available stock solution (Glyroxyl), which consists of 44% hydrogen peroxide, 44% demineralised water and 12% glycerol proved to lower colonisation more effectively than a 2% solution.

A review of aerobic and psychrotrophic plate count procedures for fresh meat and poultry products

This is a review of reports that employed aerobic plate counts on fresh meat and poultry products since 1985; it lists synopses of 100 applications. A total of 15 different plating media were used, with 48 (48%) being either plate count agar (PCA) or tryptone glucose yeast extract agar. The temperature-time relations ranged from a low temperature of 20 degrees C for 120 h to 37 degrees C for 24 h. Some 29 different temperature-time combinations were used among the total of 109, with 21 (19.3%) being 35 degrees C/48 h, followed by 12 (11.0%) at 32 degrees C/48 h, 11 (10.1%) at 25 degrees C/48 h, and 9 (8.3%) at 25 degrees C/72 h. Fifty-four (49.5%) plate count applications employed incubation temperatures of 30 degrees C and below. From the 26 reports that employed psychrotrophic counts, 16 (61.5%) used PCA; 18 different temperature-time combinations were used, with 7 degrees C/10 d employed by only four. Twenty-one (80.8%) employed an incubation temperature at or <10 degrees C, and five employed an incubation temperature >10 degrees C. There is a serious need for some consensus on methodologies for aerobic and psychrotrophic counts on fresh meat and poultry products.

Validation of acid washes as critical control points in hazard analysis and critical control point systems

A 2% lactic acid wash used in a large meat-processing facility was validated as an effective critical control point (CCP) in a hazard analysis and critical control point (HACCP) plan. We examined the microbial profiles of beef carcasses before the acid wash, beef carcasses immediately after the acid wash, beef carcasses 24 h after the acid wash, beef subprimal cuts from the acid-washed carcasses, and on ground beef made from acid-washed carcasses. Total mesophilic, psychrotrophic, coliforms, generic Escherichia coli, lactic acid bacteria, pseudomonads, and acid-tolerant microorganisms were enumerated on all samples. The presence of Salmonella spp. was also determined. Acid washing significantly reduced all counts except for pseudomonads that were present at very low numbers before acid washing. All other counts continued to stay significantly lower (P < 0.05) than those on pre-acid-washed carcasses throughout all processing steps. Total bacteria, coliforms, and generic E. coli enumerated on ground beef samples were more than 1 log cycle lower than those reported in the U.S. Department of Agriculture Baseline data. This study suggests that acid washes may be effective CCPs in HACCP plans and can significantly reduce the total number of microorganisms present on the carcass and during further processing.

Antimicrobial efficacy of AvGard carcase wash under industrial processing conditions

1. The efficacy of the AvGard Trisodium Phosphate (TSP) immersion carcase wash process was evaluated during 5 industrial trials against Salmonella, Enterobacteriaceae, thermotolerant coliforms and total aerobic count. The effect against Pseudomonas was also studied in the first 3 trials. 2. Dramatic reductions in Salmonella incidence were seen using a whole carcase rinse method. In 4 of the 5 trial sites, only one positive sample was found after AvGard treatment (average 0.5% incidence), in spite of an average control incidence of 57.7%. In the 5th site, a water-chilled broiler plant, an average control incidence of 74.0% was reduced to 9.4% after AvGard treatment. 3. In the latter case, Most Probable Number (MPN) analyses were performed on some of the Salmonella positive samples taken from the control and post-treatment series; the average MPN count per carcase on controls was 115, whereas for AvGard treated birds the figure was only 0.6 per carcase, a greater than 2 log reduction. 4. In addition, AvGard treatment gave average log reductions for all trials of: Enterobacteriaceae; 2.5 log; Coliforms; 2.7 log, and Total Aerobic Count; 1.1 log, leading to carcases substantially free of Gram negative pathogens. 5. Pseudomonas was reduced by an average of 1.7 log in the first 3 trials, dramatically reducing the carcase loading of this important spoilage organism.

Identification, assessment and management of food-related microbiological hazards: historical, fundamental and psycho-social essentials

Microbiological risk assessment aimed at devising measures of hazard management, should take into account all perceived hazards, including those not empirically identified. It should also recognise that safety cannot be "inspected into" a food. Rather hazard management should be the product of intervention strategies in accordance with the approach made mandatory in the EU Directive 93/43 and the USDA FSIS Pathogen Reduction HACCP system; Final Rule. It is essential too that the inherent variability of the biological attributes affecting food safety is recognised in any risk assessment. The above strategic principles may be conceptualised as a four-step sequence, involving (i) identification and quantification of hazards; (ii) design and codification of longitudinally integrated ("holistic") technological processes and procedures to eliminate, or control growth and metabolism of, pathogenic and toxinogenic organisms; (iii) elaboration of microbiological analytical standard operating procedures, permitting validation of "due diligence" or responsible care, i.e. adherence to adopted intervention strategies. This should be supported by empirically assessed reference ranges, particularly for marker organisms, while the term "zero tolerance" is refined throughout to tolerable safety limit; (iv) when called for, the need to address concerns arising from lay perceptions of risk which may lack scientific foundation. In relation to infectious and toxic hazards in the practical context the following general models for quantitative holistic risk assessment are presented: (i) the first order, basic lethality model; (ii) a second approximation taking into account the amount of food ingested in a given period of time; (iii) a further adjustment accounting for changes in colonization levels during storage and distribution of food commodities and the effects of these on proliferation of pathogens and toxin production by bacteria and moulds. Guidelines are provided to address: (i) unsubstantiated consumer concern over the wholesomeness of foods processed by an innovative procedure; and (ii) reluctance of small food businesses to adopt novel strategies in food safety. Progress here calls for close cooperation with behavioural scientists to ensure that investment in developing measures to contain risk deliver real benefit.

Lactic acid decontamination of fresh pork carcasses: a pilot plant study

Lactic acid decontamination (LAD) was carried out in an abattoir on pork carcasses, artificially contaminated with Salmonella typhimurium in faeces suspensions. The surface contamination with S. typhimurium ranged from 1-2 log10 cfu/cm2. Before cold and hot LAD was undertaken, the inoculum was allowed to adhere to the meat surface for 20 min. Cold LAD consisted of treatment for 60 s with 2% (pH 2.3) or 5% (pH 1.9) lactic acid (LA); for hot LAD the exposure times were 30, 60, 90 and 120 s. The spray nozzle temperatures were 11 degrees C and 55 degrees C, and that of the treated meat surface 16-18 degrees C and 36-38 degrees C, respectively. Treatment with cold 2% and 5% LA for 60 s eliminated S. typhimurium from pork carcasses inoculated with ca. 1 log10 cfu/cm2, but not from those inoculated at ca. 2 log10 cfu/cm2. However, this could be achieved by hot 2% and 5% LA sprayed for 60-120 s. Also exposures of at least 30 s using these hot LA solutions eliminated S. typhimurium consistently from carcasses inoculated with ca. 1 log10 cfu/cm2. Rinsing-off contributed only marginally to contamination reduction. Application of 2% or 5% LA for 120 s led to an unacceptable deterioration of the organoleptic qualities of the meat. Addition of nicotinic and ascorbic acid as colour stabilizers to the spraying solutions reduced these changes to just acceptable levels when 2% LA was used.

The immediate bactericidal effect of lactic acid on meat-borne pathogens

The kinetics of the bactericidal effect of lactic acid decontamination (LAD) on meat-borne pathogens (Salmonella spp., Campylobacter jejuni and Listeria monocytogenes) was studied in an in-vitro model. The bactericidal effect was greatest on organisms in the lactic acid film that replaced the natural fluid on the meat surface during LAD. A stepwise increase in pH from 2.6 to 3.5 and 4.0 progressively reduced the bactericidal effect of decontamination. For treatment with 2% lactic acid for 30-90 s at 21 degrees C, the immediate death of Salmonella spp. decreased from about 0.5-2 log10 cfu at pH 2.6 to an insignificant level at pH 4.0. The immediate death for Camp. jejuni decreased from 2.6 to > 5.3 at pH 2.6 to 0.3-1.0 at pH 4.0. The decrease in bactericidal effect with increasing pH could, however, be countered by an increase in the temperature from 21 degrees C to 37 degrees C. It is suggested that 2% LAD at 37 degrees C for 30-90 s is suitable for elimination of salmonellas on meat but not for L. monocytogenes. Decontamination with 1% lactic acid at pH 3.0 and 21 degrees C for at least 30 s was effective for Camp. jejuni. Mesophilic Enterobacteriaceae were reliable indicators of the LAD-induced bactericidal effect on Salmonella spp. and Camp. jejuni.

Destruction of gram-negative food-borne pathogens by high pH involves disruption of the cytoplasmic membrane

High pH has been shown to rapidly destroy gram-negative food-borne pathogens; however, the mechanism of destruction has not yet been elucidated. Escherichia coli O157:H7, Salmonella enteritidis ATCC 13706, and Listeria monocytogenes F5069 were suspended in NaHCO3-NaOH buffer solutions at pH 9, 10, 11, or 12 to give a final cell concentration of approximately 5.2 x 10(8) CFU/ml and then held at 37 or 45 degrees C. At 0, 5, 10, and 15 min the suspensions were sterilely filtered and each filtrate was analyzed for material with A260. Viability of the cell suspensions was evaluated by enumeration on nonselective and selective agars. Cell morphology was evaluated by scanning electron microscopy and transmission electron microscopy. A260 increased dramatically with pH and temperature for both E. coli and S. enteritidis; however, with L. monocytogenes material with A260 was not detected at any of the pHs tested. At pH 12, numbers of E. coli and S. enteritidis decreased at least 8 logs within 15 s, whereas L. monocytogenes decreased by only 1 log in 10 min. There was a very strong correlation between the initial rate of release of material with A260 and death rate of the gram-negative pathogens (r = 0.997). At pH 12, gram-negative test cells appeared collapsed and showed evidence of lysis while gram-positive L. monocytogenes did not, when observed by scanning and transmission electron microscopy. It was concluded that destruction of gram-negative food-borne pathogens by high pH involves disruption of the cytoplasmic membrane.

Glycine betaine confers enhanced osmotolerance and cryotolerance on Listeria monocytogenes

Listeria monocytogenes is a gram-positive food-borne pathogen that is notably resistant to osmotic stress and can grow at refrigerator temperatures. These two characteristics make it an insidious threat to public health. Like several other organisms, L. monocytogenes accumulates glycine betaine, a ubiquitous and effective osmolyte, intracellularly when grown under osmotic stress. However, it also accumulates glycine betaine when grown under chill stress at refrigerator temperatures. Exogenously added glycine betaine enhances the growth rate of stressed but not unstressed cells, i.e., it confers both osmotolerance and cryotolerance. Both salt-stimulated and cold-stimulated accumulation of glycine betaine occur by transport from the medium rather than by biosynthesis. Direct measurement of glycine betaine uptake shows that cells transport betaine 200-fold faster at high salt concentration (4% NaCl) than without added salt and 15-fold faster at 7 than at 30 degrees C. The kinetics of glycine betaine transport suggest that the two transport systems are indistinguishable in terms of affinity for betaine and may be the same. Hyperosmotic shock and cold shock experiments suggest the transport system(s) to be constitutive; activation was not blocked by chloramphenicol. A cold-activated transport system is a novel observation and has intriguing implications concerning the physical state of the cell membrane at low temperature.

An in-vitro meat model for the immediate bactericidal effect of lactic acid decontamination on meat surfaces

An in-vitro model of the lactic acid decontamination (LAD) of meat is described. As LAD is a disinfection rather than a preservation process the model is based on the inactivation kinetics of bacteria in a suspension of pork skin. The model takes account of interfering factors present in nature, such as microbial interactions, leaching of organic material from the meat surfaces and buffering activity.

Decontamination with lactic acid/sodium lactate buffer in combination with modified atmosphere packaging effects on the shelf life of fresh poultry

The effect of the treatment with various concentrations (2%, 5%, 7.5% and 10% w/v) of lactic acid/sodium lactate buffer (pH 3.0) combined with modified atmosphere packaging (MAP) (90% CO2/10% O2) on the shelf life and organoleptic quality of fresh chicken legs stored at 6 degrees C was investigated. The CO2 concentration of all samples packed in modified atmosphere (MA) decreased during the first 3 days of storage, followed by a gradual increase after the third day, while O2 showed a corresponding decrease. The buffering capacity of the buffer systems seem to be sufficient to maintain a low pH of the skin during storage. Legs treated with 2, 5, 7.5, and 10% (w/v) lactic acid/sodium lactate buffer (pH 3.0) combined with MAP have a shelf life at 6 degrees C of 14, 15, 16 and 17 days, respectively. The shelf life when the product was not treated with lactic acid was 1, 2.3 and 4 days shorter, respectively.

Inhibition, survival and growth of Listeria monocytogenes on poultry as influenced by buffered lactic acid treatment and modified atmosphere packaging

The effect of the treatment with various concentrations (2%, 5% and 10% w/v) of lactic acid/sodium lactate buffer (pH 3.0), modified atmosphere (MAP) packaging (90% CO2 and 10% O2) and 10% (w/v) lactic acid/sodium lactate buffer (pH 3.0) combined with MAP on Listeria monocytogenes Z7 serotype 1 and on the shelf life of chicken legs stored at 6 degrees C was investigated. The initial contamination level of L. monocytogenes on the chicken legs surface was 8.3 x 10(2) cfu/cm2 of skin. After 2 days of storage at 6 degrees C the number of L. monocytogenes on legs treated with 2%, 5%, 10% lactic acid/sodium lactate buffer (pH 3.0) and 10% lactic acid/sodium lactate buffer (pH 3.0) combined with MAP was significantly lower than the initial number of L. monocytogenes. Later, growth of L. monocytogenes was observed. After 13 days of storage at 6 degrees C the number of L. monocytogenes on legs treated with 10% lactic acid/sodium lactate buffer (pH 3.0) combined with MAP was still similar to the initial number. Legs treated with 2%, 5%, 10% lactic acid/sodium lactate buffer (pH 3.0), MAP and 10% lactic acid/sodium lactate buffer (pH 3.0) combined with MAP, have a shelf life at 6 degrees C of respectively 8, 9, 10, 13 and 17 days. This means a prolongation of 2, 3, 4, 7 and 11 days, respectively for storage at 6 degrees C. The antimicrobial effect of lactic acid buffer systems (pH 3.0) increased with increasing concentrations of lactic acid in the buffered system. The best results were obtained by the combined use of 10% acid/sodium lactate buffer (pH 3.0) and MAP.

The effect of treatment with buffered lactic acid on microbial decontamination and on shelf life of poultry

The use of buffered lactic acid systems compared with unbuffered lactic acid solutions enhances the decontaminating effect and increases shelf life of chicken legs. A reduction of about 2 pH units of the chicken skin is obtained by treatment with 10% lactic acid buffer. The buffer keeps the pH of the skin lower than that of untreated legs. Legs treated with 10% lactic acid buffer have a shelf life of 12 days at 6 degrees C, which means an increase of 6 days compared with the shelf life of untreated legs.