The growth and survival of Escherichia coli O157:H7 on minced bison and pieces of bison meat stored at 5 and 10 °C

This study investigated the growth and survival of Escherichia coli O157:H7 on minced and whole pieces of bison meat. Growth curves of native microflora, including Pseudomonas spp. and Enterobacteriaceae were also generated. A marked E. coli O157:H7 strain was inoculated onto minced and whole pieces of bison meat at an initial level of 1.5 log₁₀ cfu g⁻¹. The inoculated meat was stored at either 5 °C for 28 days or 10 °C for 21 days. Survival, but no growth, of E. coli O157:H7 was observed on both forms of bison meat stored at 5 °C, while significant growth of the organism was observed at 10 °C. E. coli O157:H7 counts on whole pieces were generally higher than counts observed on minced bison meat, and reached their highest population by 14 days, with a total increase of 3.36 log₁₀ cfu g⁻¹ on whole pieces and 2.12 log₁₀ cfu g⁻¹on minced bison meat stored at 10 °C. Under the same storage temperature, Pseudomonas spp. and total counts displayed similar growth patterns on both pieces and minced bison meat, while the Enterobacteriaceae showed a slower growth rate. This study showed that the growth of E. coli O157:H7 on bison meat is similar to that observed in studies of beef.     

Microbiological conditions of moisture-enhanced pork before and after cooking

Substantial numbers of aerobic bacteria but few coliforms or Listeria spp. and no Escherichia coli were recovered from both swab samples and brines circulated in cleaned equipment used for injecting pork loins. After meat was processed for 30 or 60 min, the numbers of aerobic bacteria in brines had increased by >1 log unit, to about 4.5 log cfu ml⁻¹, but coliforms were <2 and E. coli and Listeria spp. were <1 log cfu ml⁻¹. The numbers of bacteria on the surfaces of pork loins before and after injection of the meat were similar. No bacteria were recovered from the deep tissues of the uninjected meat, but aerobic bacteria were recovered at log-mean numbers of 2.1 log cfu g⁻¹ and coliforms at log-total numbers of 1.2 log cfu 25 g⁻¹ from 25 samples of deep tissues of injected meat. Aerobic bacteria were recovered at log total numbers of 1.0 log cfu 25 g⁻¹ from 25 samples of injected pork cooked to a central temperature of 61 °C, but no bacteria were recovered from the deep tissues of meat cooked to 70 °C. The findings suggest that moisture-enhanced pork cooked to a medium rare condition can be microbiologically safe.     

Sensory and Microbiological Parameters of Stored Wild Boar Meat

The influence of temperature on microbiological and sensory parameters of wild boar meat kept for 21 days was studied. Total viable count was higher in meat stored at 15 °C than at lower temperatures on day 21. Colour saturation and hue did not differ at any temperature, but odor differences occurred in meat at 15 °C. Redness (a*) in meat at 0 °C was higher than at 15 °C. Meat stored at 0 or 15 °C differed in b* after 21 days, and in L* after 7 days. Observance of National and European legislation concerning handling of wild game is important in providing health-friendly meat.     

Survival of Listeria monocytogenes in Galotyri,a traditional Greek soft acid-curd cheese,stored aerobically at 4°C and 12°C

Galotyri is a traditional Greek soft acid-curd cheese, which is made from ewes’ or goats’ milk and is consumed fresh. Because cheese processing may allow Listeria monocytogenes post-process contamination, this study evaluated survival of the pathogen in fresh cheese during storage. Portions (0.5 kg) of two commercial types (<2% salt) of Galotyri, one artisan (pH 4.0±0.1) and the other industrial (pH 3.8±0.1), were inoculated with ca. 3 or 7 log cfu g⁻¹ of a five-strain cocktail of L. monocytogenes and stored aerobically at 4°C and 12°C. After 3 days, average declines of pathogen's populations (PALCAM agar) were 1.3–1.6 and 3.7–4.6 log cfu g⁻¹ in cheese samples for the low and high inocula, respectively. These declines were independent (P>0.05) of the cheese type or the storage temperature. From day 3, however, declines shifted to small or minimal to result in 1.4–1.8 log cfu g⁻¹ of survivors at 28 days of storage of all cheeses at 4°C, indicating a strong “tailing” independent of initial level of contamination. Low (1.2–1.7 log cfu g⁻¹) survival of L. monocytogenes also occurred in cheeses at 12°C for 14 days, which were prone to surface yeast spoilage. When ca. 3 log cfu g⁻¹ of L. monocytogenes were inoculated in laboratory scale prepared Galotyri of pH ≅4.4 and ≅3% salt, the pathogen died off at 14 and 21 days at 12°C and 4°C, respectively, in artisan type cheeses fermented with the natural starter. In contrast, the pathogen survived for 28 days in cheeses fermented with the industrial starter. These results indicate that L. monocytogenes cannot grow but may survive during retail storage of Galotyri despite its low pH of or slightly below 4.0. Although contamination of Galotyri with L. monocytogenes may be expected low (<100 cfu g⁻¹) in practice, that long-term survival of the pathogen in commercial cheeses was shown to be unaffected by the artificial contamination level (3 or 7 logs) and the storage temperature (4°C or 12°C), which should be a concern.     

Protective role of Lactobacillus fermentum R6 against Clostridium perfringens in vitro and in chicken breast meat under temperature abuse conditions

Six bacterial species were evaluated to determine their inhibitory effects on Clostridium perfringens in vitro (brain heart infusion broth) and in situ (chicken breast meat) under temperature abuse conditions (4 ± 1 °C for 12 h, followed by 7 h at 28 ± 1 °C and then 4 ± 1 °C for 53 h). During abusive storage, rapid growth of C. perfringens from vegetative cell and spore inocula was observed, exhibiting a 2.68–3.37 log CFU/mL (or g) increase in bacterial counts. In the presence of Pediococcus pentosaceus P1 or Lactobacillus fermentum R6, the counts of C. perfringens remained unchanged in the samples containing vegetative cells at the end of storage (P < 0.05); for those containing spores, the germination and outgrowth were also effectively inhibited, decreasing in bacterial counts of > 1.9 log CFU/mL (or g) compared to those of the control (P < 0.05). The pH of chicken meat was slightly declined by 0.09 in the presence of L. fermentum (P > 0.05), and the inhibitory effect against C. perfringens was ascribed to non-acid antimicrobial substances. These results indicate a potential solution for bio-protecting chicken meat from C. perfringens growth.Industrial relevanceClostridium perfringens is a common pathogen that contaminates meat and meat products, but the organism cannot multiply under cold chain conditions at 4 °C. However, it was reported that temperature abuses commonly occurred during the transportation, storage or retail display of the food chill chain. During the abusive storage, C. perfringens could grow rapidly, which may lead to food poisoning. It is a serious problem for food safety.In this study, Lactobacillus fermentum R6 was found to show effective inhibition on both the growth of C. perfringens vegetative cells and the germination and outgrowth of its spores in chicken meat (P < 0.05) under temperature abuse conditions, and also it had a minimal effect on the pH of the meat (P > 0.05). The results reveal a potential technology for bio-protecting chicken meat from C. perfringens growth.     

The control of Listeria innocua and Lactobacillus sakei in broth and meat slurry with the bacteriocinogenic strain Lactobacillus casei CRL705

The effect of the bacteriocin-producing strain, Lactobacillus casei CRL705, in the control of Listeria innocua 7 and Lactobacillus sakei CRL1424 in MRS medium and meat slurry during the storage under vacuum at chill temperatures was evaluated. L. sakei CRL 1424 isolated from vacuum-packaged contaminated raw meat was identified as the predominant indigenous lactic acid bacterial flora. Co-inoculation of MRS broth at 8°C with L. casei CRL705 caused growth inhibition of L. sakei CRL1424 and L. innocua 7 after 10 and 4 days of storage, respectively. At 4°C the complete inhibition of both strains occurred within 14 and 8 days for L. sakei CRL1424 and L. innocua 7, respectively. Bacteriocin activity in broth was observed to be maximal at 8°C reaching 2130 AU ml⁻¹ after10 days and 400 AU m1⁻¹ after 8 days of storage, while at 4°C maximal activities, 690 and 30 AU ml⁻¹ were obtained at 14 and 10 days, respectively. Addition of bacteriocinogenic strain to the meat slurry did not allow the growth of L. sakei and L. innocua, showing a bacteriostatic effect during 21 days of storage at 4°C. In addition, L. casei CRL705, as a protective culture did not change significantly the pH of the meat slurry in the assayed storage conditions. The results presented here confirm that the bacteriocinogenic strain L. casei CRL705 can be used as a useful tool to improve the microbial stability and safety in the commercial meat preservation.     

Effect of pre-incubation conditions on growth and survival of Staphylococcus aureus in sliced cooked chicken breast

In this work, the effect of pre-incubation conditions (temperature: 10, 15, 37 °C; pH 5.5, 6.5 and water activity, a_w: 0.997, 0.960) was evaluated on the subsequent growth, survival and enterotoxin production (SE) of Staphylococcus aureus in cooked chicken breast incubated at 10 and 20 °C. Results showed the ability of S. aureus to survive at 10 °C when pre-incubated at low a_w (0.960) what could constitute a food risk if osmotic stressed cells of S. aureus which form biofilms survive on dried surfaces, and they are transferred to cooked meat products by cross-contamination. Regarding growth at 20 °C, cells pre-incubated at pH 5.5 and a_w 0.960 had a longer lag phase and a slower maximum growth rate. On the contrary, it was highlighted that pre-incubation at optimal conditions (37 °C/pH 6.5/a_w 0.997) produced a better adaptation and a faster growth in meat products what would lead to a higher SE production. These findings can support the adoption of management strategies and preventive measures in food industries leading to avoid growth and SE production in meat products.     

Efficacy of plant extracts in inhibitingAeromonas hydrophilaandListeria monocytogenesin refrigerated,cooked poultry

Alcohol extracts of angelica root, banana purée, bay, caraway seed, carrot root, clove (eugenol), marjoram, pimento leaf and thyme were applied to cooked chicken to determine their antimicrobial activities against Aeromonas hydrophilaand Listeria monocytogenes.Skinless chicken breast meat was cooked to an internal temperature of 85°C, allowed to cool to c. 5°C, then treated by surface application with plant extracts. Low (10 cfu g⁻¹)or high (10⁵ cfu g⁻¹)populations of A. hydrophilaand L. monocytogeneswere applied and samples were stored at either 5 or 15°C for up to 14 or 7 days, respectively. Eugenol and pimento extracts were most effective in inhibiting growth of both bacteria. A. hydrophilawas the more sensitive to the two treatments, with 4 log₁₀ cfu g⁻¹less growth occurring at 14 days at 5°C on eugenol-treated breast meat than on control samples. These results suggested that plant extracts might be useful as antimicrobials in cooked, ready-to-eat chicken meat.     

Viability of Listeria monocytogenes on commercially-prepared hams surface treated with acidic calcium sulfate and lauric arginate and stored at 4°C

We demonstrated the effectiveness of delivering an antimicrobial purge/fluid into shrink-wrap bags immediately prior to introducing the product and vacuum sealing, namely the “Sprayed Lethality In Container” (SLIC™) intervention delivery method. The pathogen was Listeria monocytogenes, the antimicrobials were acidic calcium sulfate (ACS; calcium sulfate plus lactic acid; 1:1 or 1:2 in dH₂O) and lauric arginate (LAE; Ethyl-N-dodecanoyl-l-arginate hydrochloride; 5% or 10% in dH₂O), and the product was commercially prepared “table brown” ham (ca. 3 pounds each). Hams were surface inoculated with a five-strain cocktail of L. monocytogenes (ca. 7.0 log₁₀ CFU per ham), added to shrink-wrap bags that already contained ACS or LAE, vacuum-sealed, and stored at 4 °C for 24 h. Pathogen levels decreased by 1.2, 1.6, 2.4, and 3.1 log₁₀ CFU/ham and 0.7, 1.6, 2.2, and 2.6 log₁₀ CFU/ham in samples treated with 2, 4, 6, and 8 mL of a 1:1 and 1:2 solution of ACS, respectively. In samples treated with 2, 4, 6, and 8 mL of a 5% solution of LAE, pathogen levels decreased by 3.3, 6.5, 5.6, and 6.5 log₁₀ CFU/ham, whereas when treated with a 10% solution of LAE pathogen levels decreased ca. 6.5 log₁₀ CFU/ham for all application volumes tested. The efficacy of ACS and LAE were further evaluated in shelf-life studies wherein hams were surface inoculated with either ca. 3.0 or 7.0 log₁₀ CFU of L. monocytogenes, added to shrink-wrap bags that contained 0, 4, 6, or 8 mL of either a 1:2 solution of ACS or a 5% solution of LAE, vacuum-sealed, and stored at 4 °C for 60 days. For hams inoculated with 7.0 log₁₀ CFU, L. monocytogenes levels decreased by ca.1.2, 1.5, and 2.0 log₁₀ CFU/ham and 5.1, 5.4, and 5.5 log₁₀ CFU/ham within 24 h at 4 °C in samples treated with 4, 6, and 8 mL of a 1:2 solution of ACS and a 5% solution of LAE, respectively, compared to control hams that were not treated with either antimicrobial. Thereafter, pathogen levels remained relatively unchanged (±1.0 log₁₀ CFU/ham ) after 60 days at 4 °C in hams treated with 4, 6, and 8 mL of a 1:2 solution of ACS and increased by ca. 2.0–5.0 log₁₀ CFU/ham in samples treated with 4, 6, and 8 mL of a 5% solution of LAE. For hams inoculated with 3.0 log₁₀ CFU, L. monocytogenes levels decreased by 1.3, 1.9, and 1.8 log₁₀ CFU/ham within 24 h at 4 °C in samples treated with 4, 6, and 8 mL of a 1:2 solution of ACS, respectively, compared to control hams that were not treated. Likewise, levels of the pathogen were reduced to below the limit of detection (i.e., 1.48 log₁₀ CFU/ham) in the presence of 4, 6, and 8 mL of a 5% solution of LAE within 24 h at 4 °C. After 60 days at 4 °C, pathogen levels remained relatively unchanged (±0.3 log₁₀ CFU/ham) in hams treated with 4, 6, and 8 mL of a 1:2 solution of ACS. However, levels of L. monocytogenes increased by ca. 2.0 log₁₀ CFU/ham in samples treated with 4 and 6 mL of a 5% LAE solution within 60 days but remained below the detection limit on samples treated with 8 mL of this antimicrobial. These data confirmed that application via SLIC™ of both ACS and LAE, at the concentrations and volumes used in this study, appreciably reduced levels of L. monocytogenes on the surface of hams within 24 h at 4 °C and showed potential for controlling outgrowth of the pathogen over 60 days of refrigerated storage.     

Effect of modified atmosphere packaging,storage period,and storage temperature on the residual nitrate of sliced-pastırma,dry meat product,produced from fresh meat and frozen/thawed meat

The amount of nitrite in sliced-pastirma made, from fresh or frozen (which was stored at −18 °C for 240 days and then thawed at 10 °C for 24 h) M. Longissimus dorsi muscle was determined. Sliced-pastirma samples were stored in modified atmosphere packages (50% N₂ + 50% CO₂) at 4 and 10 °C for 150 days, and the amount of residual nitrite was measured after 0, 30, 60, 90, and 150 days of storage. The residual nitrite of pastirma samples made with frozen/thawed meat was higher than that of the pastirma made from fresh meat at both 0 day and at the end of the storage (150 days). The storage temperature (p < 0.01), storage period (p < 0.01) and the storage period × the storage temperature interaction (p < 0.01) had significant effects on the amount of the residual nitrite.     

Kinetic parameters of Escherichia coli O157:H7 survival during fermentation of milk and refrigeration of home-made yoghurt

The survival parameters of Escherichia coli O157:H7 during milk fermentation (carried out by the LIM or “longer incubation method” at 30 °C, or by the SIM or “short incubation method” at 43 °C) and storage of home-made yoghurt at refrigeration temperatures (2, 4, or 8 °C) were studied. The E. coli O157:H7 counts increased slightly during fermentation by the LIM, from 5.1 to 5.4 log cfu mL⁻¹, and it was not found after 21 d of storage at 2 or 4 °C, and after 10 d at 8 °C. The microorganism counts increased from 4.8 to 5.4 log cfu mL⁻¹ during the SIM, and it was not detected after 7 d stored at 8 °C. The microorganism grew faster at 43 °C (generation time=0.93 h) than at 30 °C (4.12 h) during the fermentation period. The death time decreased with the increase of the storage temperature (from 38.1 h at 2 °C to 30.1 h at 8 °C) in the yoghurt produced by fermentation at 30 °C; however, a clear relationship between death time and storage temperature was not evident at 43 °C. The pH values of the yoghurt ranged from 4.0 to 4.7.     

Comparison of the murine norovirus-1 inactivation in cabbage Kimchi with two different salinities during storage

Enteric noroviruses are occasionally detected in Kimchi, which is a traditional dish made of fermented vegetables. This study was aimed at examining the effects of two levels of salt concentrations on the survival of murine norovirus-1 (MNV-1), a human norovirus surrogate, in experimentally contaminated cabbage Kimchi stored at 5 °C for 10 weeks. The number of total aerobic bacteria (TAB) and lactic acid bacteria (LAB), MNV-1 titer pH, and acidity were measured every week. The titers of MNV-1 in both low (1.17%) and normal (2.22%) salinity cabbage Kimchi were significantly (P < 0.05) decreased with increase in storage time. The overall reduction was 1.75 log₁₀ plaque-forming unit (PFU)/mL in normal salinity cabbage Kimchi and 1.24 log₁₀ PFU/mL in low salinity cabbage Kimchi. The time required to reduce the titer by > 1 log₁₀ PFU/mL in normal and low salinity cabbage Kimchi were 4 and 8 weeks, respectively. The pH value under both salinities significantly (P < 0.05) decreased until 4 weeks. The maximum acidity was 0.83% and 0.79% in normal and low salinity cabbage Kimchi, respectively, during the 10 weeks. The population of TAB and LAB reached up to 7.33 log₁₀ colony-forming unit (CFU)/g as a maximum population during the storage period of 3 weeks in normal salinity cabbage Kimchi. However, the population of TAB and LAB in low salinity cabbage Kimchi reached to 6.99 and 7.04 log₁₀ CFU/g at 5 and 4 weeks, respectively. Through these findings, fermentation factors such as TAB, LAB, pH, and acidity of cabbage Kimchi were influenced by salt concentration. The inactivation of MNV-1 in normal salinity cabbage Kimchi was much faster than that in low salinity cabbage Kimchi because the fermentation in normal salinity cabbage Kimchi progressed more quickly than that in low salinity cabbage Kimchi. However, both salinity cabbage Kimchi were able to infect cells for 70 days even though the MNV-1 was reduced over 1 log₁₀ during fermentation. Therefore, the way to protect cabbage Kimchi from norovirus must be considered.     

Destruction of Salmonella Enteriditis inoculated onto raw almonds by high hydrostatic pressure

The effects of continuous (50,000, 60,000 and 70,000 psi with holding times of 5 and 10 min) and discontinuous (oscillatory) (six cycles at 60,000 psi with a holding time of 20 s) high hydrostatic pressure (HHP) treatments on the viability of two Salmonella Enteriditis strains (FDA and PT30) inoculated onto raw almonds were evaluated at 25, 50, and 55 °C. Complete inactivation of the S. Enteriditis was achieved in 0.1% peptone water after continuous pressurization at 60,000 psi and 25 °C for 5 min. Continuous pressurization of raw almonds inoculated with S. Enteriditis at 60,000 psi and 50 °C for 5 min resulted in less than a log reduction (log₁₀ 0.83) of vegetative cells. The decimal reduction time using the continuous pressurization parameters was determined to be 9.78 min. A discontinuous process consisting of six cycles of pressurization at 60,000 psi and 50 °C for 20 s provided greater than a one log reduction (log₁₀ 1.27 for FDA and log₁₀ 1.16 for PT30) of the S. Enteriditis concentration. The low water activity (a_w) of the almonds was found to impart baroprotective attributes on the S. Enteriditis cells. When the almonds were directly suspended in water and then pressurized, a log₁₀ reduction of 3.37 was achieved. HHP of certain dry foods appears to be feasible if the food is directly suspended in the pressurizing medium (water).     

Resistance of Enterobacter sakazakii to pulsed electric fields

The influence of various environmental factors on Enterobacter sakazakii inactivation by pulsed electric fields was studied and the mechanisms underlying the changes in resistance were also explored. E. sakazakii PEF resistance was higher upon entering the stationary growth phase, but it did not significantly change with growth temperature. E. sakazakii cells were also more resistant to PEF in both acidified and low water activity media. Thus, for stationary-phase cells grown at 30 °C a treatment of 50 pulses at 31 kV/cm led to 5.1 log₁₀ cycles of inactivation in media of pH 7.0 (a_w > 0.99), 1.4 log₁₀ cycles in media of pH 4.0 (a_w > 0.99) and 0.3 log₁₀ cycles in media of a_w = 0.98 (pH 7.0). However, whereas the higher PEF tolerance in acid media was coincident with an increased number of cells capable of repairing their sublethally-injured cytoplasmic membranes, the higher resistance in media of lower water activity was not. To the best of our knowledge, this is the first time that sublethal injuries in outer membrane after PEF treatments have been found.Industrial relevanceThis work provides data about PEF inactivation kinetics and PEF resistance of E. sakazakii under several conditions that might be useful for designing food pasteurization processes by PEF technology. The occurrence of sublethal injuries in cytoplasmic and outer membranes under the most protective treatment conditions, gives the chance to develop combined processes that might increase the effectiveness of the PEF process.     

The influence of lactoperoxidase,heat and low pH on survival of acid-adapted and non-adapted Escherichia coli O157:H7 in goat milk

In hot climates where quality of milk is difficult to control, a lactoperoxidase (LP) system can be applied in combination with conventional preservation treatments at sub-lethal levels to inhibit pathogenic microbes. This study investigated the effect of combined heat treatments (55 °C, 60 °C and 72 °C) and milk acidification (pH 5.0) on survival of acid-adapted and non-adapted Escherichia coli O157:H7 strains UP10 and 1062 in activated LP goat milk. Heat treatment at 72 °C eliminated E. coli O157:H7. Acid-adapted strains UP10 and 1062 cells showed resistance to combined LP and heat at 60 °C in fresh milk. The inhibition of acid-adapted and non-adapted E. coli O157:H7 in milk following combined LP-activation, heat (60 °C) and milk acidification (pH 5.0) suggests that these treatments can be applied to reduce E. coli O157:H7 cells in milk when they occur at low numbers (<5 log₁₀ cfu mL^?1) but does not eliminate E. coli O157:H7 to produce a safe product.     

Production of cured meat color in nitrite-free Harbin red sausage by Lactobacillus fermentum fermentation

Lactobacillus fermentum was substituted for nitrite to produce cured pink color in a Chinese-style sausage. Treatments included inoculations (10⁴, 10⁶, and 10⁸ CFU/g meat) followed by fermentation at 30 °C for 8 h and then at 4 °C for 16 h. Control sausage (with sodium nitrite, 60 mg/kg meat) was cured at 4 °C for 24 h without L. fermentum. The UV–Vis spectra of pigment extract from L. fermentum-treated sausage were identical to that of nitrosylmyoglobin (NO-Mb) formed in nitrite-treated control. The NO-Mb concentration and the colorimetric a¹ value of sausage treated with 10⁸ CFU/g meat of L. fermentum essentially replicated those in nitrite-cured meat. Free amino acid content in sausage treated with L. fermentum was greater and the pH slightly lower compared with the nitrite-cured control sample. This study showed that L. fermentum has the potential to substitute for nitrite in the sausage production.     

Effect of mild heat pre-treatment with alkaline electrolyzed water on the efficacy of acidic electrolyzed water against Escherichia coli O157:H7 and Salmonella on Lettuce

Cut lettuce dip-inoculated with Escherichia coli O157:H7 and Salmonella was treated with alkaline electrolyzed water (AlEW) at 20°C for 5 min, and subsequently washed with acidic electrolyzed water (AcEW) at 20°C for 5 min. Pre-treatment with AlEW resulted in an approximate 1.8 log₁₀ cfu/g reduction of microbial populations, which was significantly (p⩽0.05) greater than microbial reductions resulting from other pre-treatment solutions, including distilled water and AcEW. Repeated AcEW treatment did not show a significant bacterial reduction. Mildly heated (50°C) sanitizers were compared with normal (20°C) or chilled (4°C) sanitizers for their bactericidal effect. Mildly heated AcEW and chlorinated water (200 ppm free available chlorine) with a treatment period of 1 or 5 min produced equal reductions of pathogenic bacteria of 3 log₁₀ and 4 log₁₀ cfu/g, respectively. The procedure of treating with mildly heated AlEW for 5 min, and subsequent washing with chilled (4°C) AcEW for period of 1 or 5 min resulted in 3–4 log₁₀ cfu/g reductions of both the pathogenic bacterial counts on lettuce. Extending the mild heat pre-treatment time increased the bactericidal effect more than that observed from the subsequent washing time with chilled AcEW. The appearance of the mildly heated lettuce was not deteriorated after the treatment. In this study, we have illustrated the efficacious application of AlEW as a pre-wash agent, and the effective combined use of AlEW and AcEW.     

Application of statistical process control,sampling, and validation for producing Listeria monocytogenes-free chicken leg quarters processed in steam followed by impingement cooking

Chicken leg quarters (180–230 g) were processed for 4 min in steam at 99°C and then in an air impingement oven for 24 min at an oven temperature of 232°C, an air velocity of 2 m/s, and a humidity of 60%. The cooked chicken leg quarters were sampled to measure for the end-point internal temperatures. Sampling size in each subgroup for the internal temperature measurements was determined based on a normal distribution at a confidence level of 95%. The process mean, range, and standard deviation at 95% confidence level were 73.9°C, 1.8°C, and 0.9°C, respectively, for the internal temperatures of the cooked chicken leg quarters. The process lethality was validated for up to 7  log₁₀ cfu/g reductions of Listeria monocytogenes in the cooked chicken leg quarters and verified by an inoculation study in which the chicken leg quarters were injected with 0.1 ml of the culture per cm² of the product surface area to contain 7–8 log₁₀ cfu/g of L. monocytogenes. This paper provided an approach for process control, sampling, and validation to reduce pathogens in fully cooked poultry products.     

High pressure carbon dioxide combined with high power ultrasound processing of dry cured ham spiked with Listeria monocytogenes

Traditionally, thermal treatments for the inactivation of Listeria monocytogenes in meat products involve undesirable changes of the product quality. In recent years, efforts have been carried out to develop alternative methods to inactivate L. monocytogenes without affecting the product quality attributes. In this context, the feasibility of combined high pressure carbon dioxide and high power ultrasound (HPCO₂ + HPU) treatment to inactivate L. monocytogenes inoculated on the surface of dry cured ham was investigated. Inactivation data were determined at 6, 8 and 12 MPa, as a function of temperature (22, 35, 45 °C) and treatment time (0.5 to 30 min), and compared to those obtained after thermal and HPCO₂ treatments.Color, pH and acidity changes of the samples after both thermal and HPCO₂ + HPU treatments were measured and compared, sensorial profile of the treated samples was evaluated by a sensory panel and shelf-life was determined by a storage study for 4 weeks at 4 °C.The results clearly revealed that HPU alone was not able to induce any microbial inactivation while HPCO₂ + HPU treatment always assured a certain level of inactivation, variable with the process temperature used: the inactivation efficiency was demonstrated higher at 35 °C rather than 22 °C and no enhancement was observed at 45 °C compared to 35 °C. Process conditions of 12 MPa, 35 °C, at 10 W for 5 min assured inactivation to undetectable level of L. monocytogenes spiked on the surface of the product with an initial concentration of about 10⁹ CFU/g. No differences were detected between acidity, pH, color and sensory attributes of the untreated and HPCO₂ + HPU treated dry cured ham surface, while slight differences were measured between the values obtained for the untreated and thermally treated samples. Additionally, the storage study demonstrated that a full microbial and quality shelf-life was assured for 4 weeks at 4 °C. The results obtained may open the doors to the application of such an innovative process at industrial level, in particular to treat ham-type or meat products.     

“Blown pack” Probabilistic Modeling for C. Algidicarnis and C. Estertheticum under the Effects of Storage Temperature,Vacuum Level and Package Shrink Temperature

A model for ‘blown pack’ probability (BPP) caused by spores of C.estertheticum DSM8809 and C.algidicarnis, was developed as a function of vacuum packaging variables: storage temperature(ST:-2, 2, 4 and 15 °C), vacuum level(VL:6 and 9mBar) and heat shrink temperature(HST:83 and 87 °C). Beef meat pieces, were inoculated with spore suspensions individually at 10²spores/cm², packed and daily monitored up to 90 days. The lower BPP, estimated by the log-logistic model, for C.algidicarnis was 0.8% at:-1.5 °C/6mBar/87 °C while for C.estertheticum was 99.13% at the same conditions. For both organisms, tested variables were unable to eliminate the risk of blown packaged spoilage, at 10²spores/cm² contamination level.