The effect of pulsed UV light on Escherichia coli O157:H7, Listeria monocytogenes,Salmonella Typhimurium,Staphylococcus aureus and staphylococcal enterotoxin A on sliced fermented salami and its chemical quality

Pulsed UV light (PL) applied at a fluence of 3 J/cm² was effective to reduce Listeria monocytogenes, Escherichia coli 0157:H7, Salmonella Typhimurium and Staphylococcus aureus for 2.24, 2.29, 2.25 and 2.12 log CFU/g on the surface of dry fermented salami. Further increase in the fluence of PL treatment did not increase levels of microbial inactivation. However, the time interval between the contamination and PL treatment was found to have a significant impact on the efficacy of PL treatment and should be kept as short as possible. After initial PL treatment slices of fermented salami were packed in vacuum or in 80%CO₂/20%N₂ modified atmosphere and stored at 4 °C to investigate the effect of PL treatment on protein and lipid oxidation as the shelf life of fermented salami is not usually limited by microbial deterioration, but by chemical and sensory alterations. In this study observed lipid oxidation values for PL treated vacuum and modified atmosphere packed fermented salami slices fall within the acceptable threshold for the rancid odor, except for the sample treated with the highest fluence tested (15 J/cm²), packed in modified atmosphere and kept in cold storage for 9 weeks (1.23 mg MDA/kg). All values were below the threshold for rancid flavor, too. The significant rise in protein oxidation of PL treated fermented salami slices, perceived as 28% increase of carbonyl content compared to untreated samples, was observed only after 9 weeks of cold storage in both vacuum and modified atmosphere packed samples. The results of chemical analysis are in agreement with previously published results of sensory analysis. Current results show the applicability of PL to improve microbial safety of sliced fermented salami that are prone to cross-contamination without affecting quality attributes by lipid and protein oxidation.     

Effect of hydrogen peroxide vapor treatment for inactivating Salmonella Typhimurium,Escherichia coli O157:H7 and Listeria monocytogenes on organic fresh lettuce

In this study, the efficacy of hydrogen peroxide vapor (HPV) for reducing Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes on lettuce was investigated as well as its effect on lettuce quality. Lettuce was inoculated with a cocktail containing three strains of each pathogen then treated with vaporized hydrogen peroxide for 0, 2, 4, 6, 8 and 10 min. The concentrations of hydrogen peroxide used were 0, 1, 3, 5 and 10%. With increasing treatment time and hydrogen peroxide concentration, HPV treatment showed significant (P < 0.05) reduction compared to the control (0%, treated with vaporized distilled water). In particular, vaporized 10% hydrogen peroxide treatment for 10 min was the most effective combination for reducing the three pathogens on lettuce. The reduction levels of S. Typhimurium, E. coli O157:H7 and L. monocytogenes on lettuce were 3.12, 3.15 and 2.95 log₁₀ CFU/g, respectively. Furthermore, there were no significant (P > 0.05) quality changes (color and texture) of lettuce among all tested samples, and hydrogen peroxide residues were not detected after 36 h storage time in any of the treated samples. These results suggest that HPV treatment could be an alternative method for reducing S. Typhimurium, E. coli O157:H7 and L. monocytogenes on fresh produce.     

High-pressure processing and boiling water treatments for reducing Listeria monocytogenes,Escherichia coli O157:H7, Salmonella spp., and Staphylococcus aureus during beef jerky processing

Beef jerky is a convenient, ready-to-eat meat product, but requires processing lethality steps to ensure the safety of the product. Previous outbreaks involving various jerky products have highlighted the risks associated with jerky and the importance of utilizing pathogen interventions during processing. In this study, two alternative interventions were evaluated for reducing pathogen populations during jerky processing. Results demonstrated that high pressure processing (HPP; two treatments of 550 MPa, 60 s) could produce significant (p < 0.05), but variable reductions (6.83 and 4.45 log₁₀ CFU/strip) of Salmonella spp. and Escherichia coli O157:H7, respectively, on resulting beef jerky. HPP treatments, however, produced minor reductions (p < 0.05) of Gram-positive pathogens, resulting in reductions of 1.28 and 1.32 log₁₀ CFU/strip of Listeria monocytogenes and Staphylococcus aureus, respectively. Alternatively, boiling water (100 ± 2 °C) treatments (20–30 s) used after marination and prior to dehydration, reduced Salmonella spp., E. coli O157:H7, L. monocytogenes, and S. aureus populations >5.0 log₁₀ CFU/strip in resulting beef jerky. Thus, 20 or 30 s boiling water (100 ± 2 °C) treatments could be effective interventions for commercial jerky processors or home food preservers. Future validation of these processes in-plant could provide processors and regulators with alternative strategies for safe and shelf-stable jerky products.     

Survival of E. coli O157:H7 Staphylococcus aureus,Shigella flexneri and Salmonella spp. in fermenting `Borde', a traditional Ethiopian beverage

The survival and inhibition of food-borne pathogens during the fermentation of different foods and beverages is documented. This prompted the study to evaluate survival of Staphylococcus aureus, Shigella flexneri, Salmonella spp. and Escherichia coli O157:H7 during the fermentation of `Borde', a traditional Ethiopian fermented low-alcohol beverages. The pH of mixtures of `Borde' ingredients at the start of fermentation was between 4.28 and 4.31. At ambient temperatures all test strains grew well in the control and reached counts as high as log 6.6 cfu/ml for E. coli O157:H7 and >log 7 cfu/ml for S. aureus, S. flexneri, and Salmonella spp. When co-inoculated with lactic acid bacteria (LAB), counts of E. coli O157:H7, S. aureus and S. flexneri were >log 2 cfu/ml and >log 1.5 cfu/ml at 12 h and at 16 h, respectively. At 24 h, these counts were <log 1.3 cfu/ml. The count of Salmonella spp., however, was <log 2 at 16 h and they were eliminated at 24 h. LAB-fermented `Borde' had final pH of 3.85 and titratable acidity of 0.41%. At refrigeration temperature, there was no marked growth of test strains in the control. In the presence of LAB, counts of S. aureus were reduced by 2 log units whereas the counts of the other test strains were reduced only by <1 log unit. LAB increased by 1 log unit between 12 and 16 h. The survival of test strains at levels of >2 log cfu/ml between 12 and 16 h indicated health hazard as fermentation of `Borde' is completed within 12 h and consumed within 4 h thereafter.     

Efficacy of sanitizers in reducing Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes populations on fresh-cut carrots

Shredded carrots were inoculated with Escherichia coli O157:H7, Salmonella or Listeria monocytogenes and washed for 1 or 2 min with chlorine (Cl; 200 ppm), peroxyacetic acid (PA; 40 ppm) or acidified sodium chlorite (ASC; 100, 200, 500 ppm) under simulated commercial processing conditions. After washed, the carrots were spin dried, packaged and stored at 5 °C for up to 10 days. Bacterial enumeration was significantly (P ⩽ 0.05) reduced by 1, 1.5 and 2.5 log CFU/g after washing with ASC 100, 250 and 500 ppm, respectively. All sanitizers reduced pathogen load below that of tap water wash and unwashed controls. During storage at 5 °C the bacterial load of all treatments increased gradually, but to different extent in different treatments. ASC inhibited bacterial growth more effectively than the other sanitizers and also maintained the lowest pathogen counts (<1 log CFU/g) during storage. Organic matter in the process water significantly (P ⩽ 0.05) reduced the antibacterial efficacy of Cl, but not that of PA or ASC. Therefore, ASC shows the potential to be used as a commercial sanitizer for washing shredded carrots.     

Evaluation of a novel antimicrobial solution and its potential for control Escherichia coli O157:H7, non-O157:H7 shiga toxin-producing E. coli,Salmonella spp., and Listeria monocytogenes on beef

The goal of this study was to evaluate the efficacy of a novel antimicrobial solution made with chitosan, lauric arginate ester, and organic acids on Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, and non-O157 shiga toxin-producing E. coli cocktails and to test its potential to be used as a marinade for raw beef. Fresh beef top round steaks were surface-inoculated with the pathogen cocktails at approximately 2.5 or 4.5 Log CFU/cm², marinated with the antimicrobial solution (AMS), and then stored at 4 °C for 6, 24, and 48 h. Three commercially available marinades were used for comparison. Results revealed that AMS had the most antimicrobial effect regardless of the type or inoculation level of pathogens (P < 0.05). After 6 h, the AMS marination reduced all pathogens to levels below the limit of detection (<1 Log CFU/cm²), resulting in a 3.5 Log CFU/cm² reduction. When AMS was diluted with autoclaved distilled water by 5 times (AMS 1:5) or 10 times (AMS 1:10), its antimicrobial efficacy was impacted by marination time, the inoculated pathogens, and the inoculation levels. This study demonstrates that the developed antimicrobial solution has a great potential to be used during marination by consumers to ensure better food safety.     

The bactericidal activity of acidic electrolyzed oxidizing water against Escherichia coli O157:H7, Salmonella Typhimurium,and Listeria monocytogenes on raw fish,chicken and beef surfaces

The bactericidal efficacy of acidic electrolyzed oxidizing water (AC-EW) (pH = 2.30, free chlorine = 38 ppm) and sterile distilled water (DW) on three pathogens (Escherichia coli O157:H7 Salmonella Typhimurium, and Listeria monocytogenes) inoculated on raw trout skin, chicken legs and beef meat surfaces was evaluated. The decontaminating effect of AC-EW and DW was tested for 0 (control), 1, 3, 5 and 10 min at 22 °C. AC-EW significantly (P < 0.05) reduced the three pathogens in the inoculated samples compared to the control and DW. The level of reduction ranged between ca.1.5–1.6 logs for E. coli O157:H7 and S. Typhimurium in the inoculated foods. However, AC-EW exhibited less bactericidal effect against L. monocytogenes (1.1–1.3 logs reduction). AC-EW elicited about 1.6–2.0 log reduction in the total mesophilic count. Similar treatment with DW reduced pathogens load by ca. 0.2–1.0 log reduction and total mesophiles by ca. 0.5–0.7 logs. No complete elimination of the three pathogens was obtained using AC-EW possibly because of the level of organic matter and blood moving from food samples to the AC-EW solution. This study demonstrates that AC-EW could considerably reduce common foodborne pathogens in fish, chicken and beef products.     

Evaluation of Zataria multiflora Boiss. essential oil activity against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes by propidium monoazide quantitative PCR in vegetables

Essential oils (EOs) have long been applied as flavoring agents in foods, and due to their content in antimicrobial compounds, they have potential as natural agents for food preservation. Recently, real-time PCR in combination with PMA has successfully been applied to discriminate between live Escherichia coli O157:H7 and dead bacteria killed by cumin, clove, oregano and cinnamon EOs. In this study, initial experiments were performed in order to elucidate the minimum bactericidal concentration of Zataria multiflora EOs on E. coli O157:H7, Salmonella enterica and Listeria monocytogenes. Thereafter PMA-qPCR was applied in order to selectively quantify life cells within a bacterial population treated with Z. multiflora EO. Inactivation was obtained at EO concentrations of 0.02, 0.035, 0.045 for L. monocytogenes, E. coli O157:H7 and S. enterica, respectively. L. monocytogenes were totally killed in 30 min while it took 1 h 30 min for the gram negative pathogens. As a conclusion Z. multiflora EO has potential as natural food additive or biopreservative since it was able to irreversibly inactivate the three pathogens tested, at lower concentrations than other EOs and short exposition times. In addition, the PMA-qPCR approach proved efficient to selectively detect live pathogenic bacteria in vegetables following inactivation with Z. multiflora EO.     

Reduction of Escherichia coli O157, Listeria monocytogenes and Salmonella enterica sv. Typhimurium populations on fresh-cut bell pepper using gaseous ozone

Bacterial contamination is the main cause of food poisoning which can lead to diarrhoea, abdominal cramp, vomiting as well as death. Bacterial contamination can potentially be controlled by application of gaseous ozone due to its antibacterial activity. Therefore, the objective of this study was to investigate the efficacy of gaseous ozone for reducing food-borne pathogens such as Escherichia coli O157, Listeria monocytogenes and Salmonella enterica sv. Typhimurium on fresh-cut bell pepper. Efficacy of gaseous ozone to reduce bacterial populations was investigated in vitro and in vivo. Results showed that optimum effect of ozone on reducing bacterial populations was achieved with short term exposures of less than 6 h. Ozone reduced the bacterial population by disrupting bacterial cell structure, which lead to cellular death. Results also showed that bacterial cells have different resistance to ozone where ozone was more effective against L. monocytogenes, followed by E. coli O157 and Salmonella Typhimurium. Optimal reduction of the bacterial population on fresh-cut bell pepper was achieved with exposure to 9 ppm ozone for 6 h. This treatment reduced 2.89, 2.56 and 3.06 log of E. coli O157, Salmonella Typhimurium and L. monocytogenes populations, respectively. In conclusion, exposure to 9 ppm ozone for 6 h helps in reducing food-borne pathogen on fresh-cut bell pepper and has high potential to be an alternative sanitization treatment to reduce pathogen population on fruit.     

A comparison of saturated steam and superheated steam for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium,and Listeria monocytogenes biofilms on polyvinyl chloride and stainless steel

This study was performed to compare the effectiveness of saturated steam (SS) and superheated steam (SHS) in the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes biofilms on polyvinyl chloride (PVC) and stainless steel. Biofilms were formed on PVC and stainless steel coupons by using a mixture of three strains each of three foodborne pathogens at 25 °C. After biofilm development, PVC and stainless steel coupons were treated with SS at 100 °C and SHS at 125, 150, 175, and 200 °C for 5, 10, 20, and 30 s on both sides. The viable cell numbers of biofilms were significantly (p < 0.05) reduced as SHS temperature and exposure time increased. For all biofilm cells, SHS treatment resulted in an additional log reduction compared to SS treatments. After exposure to 200 °C steam for 30 s or 10 s on PVC or stainless steel, respectively, the numbers of biofilm cells were reduced to below the detection limit (1.48 log). This study demonstrated that SHS treatment effectively reduced populations of biofilm cells and reduced disinfection time compared to SS treatments and further evaluated its potential as an excellent intervention for controlling microbial biofilms and enhancing safety in the food processing industry.     

Antimicrobial activity of essential oils against Escherichia coli O157:H7 in organic soil

Soil can be a significant source of preharvest contamination of produce by pathogens. Demand for natural pesticides such as essential oils for organic farming continues to increase. We examined the antimicrobial activity of several essential oils against Escherichia coli O157:H7 in soil. Two essential oils (cinnamaldehyde and eugenol), two bio-pesticides (Ecotrol and Sporan) containing essential oils, and an organic acid (acetic acid) at 0.5%, 1.0%, 1.5% and 2.0%, were mixed with organic sandy soil and inoculated with five different strains of E. coli O157:H7. Soils were incubated at room temperature (22 °C) and samples obtained at 1, 7 and 28 days were enumerated to determine survival. E. coli O157:H7 populations in soil were reduced by up to 5 log cfu/g after 24 h incubation at room temperature with 2% cinnamanaldehyde, Ecotrol, Sporan or vinegar. Reduction in E. coli O157:H7 by eugenol was not significantly different from control. Overall, E. coli O157:H7 strain 4406 was the most sensitive of all the five strains tested and cinnamaldehyde was superior to other treatments in reducing E. coli O157:H7 in soil. In general, increases in essential oil concentrations corresponded to reduced survival of E. coli O157:H7 with all oils used in this study. The results suggest that oils can reduce potential contamination of fresh organic produce inadvertently contaminated by soil.     

Antimicrobial effects of modified chitosan based coating containing nanoemulsion of essential oils,modified atmosphere packaging and gamma irradiation against Escherichia coli O157:H7 and Salmonella Typhimurium on green beans

The antibacterial activity of modified chitosan-based coatings containing nanoemulsion of essential oils (EOs), gamma irradiation, modified atmosphere packaging (MAP), alone or in combinations, against Escherichia coli O157:H7 and Salmonella Typhimurium was evaluated on inoculated green bean samples. Firstly, four different nanoemulsions, made of carvacrol, mandarin, bergamot and lemon Eos, respectively, were compared in terms of minimum inhibitory concentration (MIC) against the two bacteria evaluated in vitro using the micro-broth dilution method. Carvacrol nanoemulsion resulted to be the most effective antibacterial agent and was therefore selected to be incorporated into modified chitosan (MC) to form a bioactive coating. Secondly, the radiosensitivity of E. coli and S. Typhimurium to gamma irradiation was evaluated on inoculated green beans after coating deposition and MAP. Results showed that, without MAP, MC-based coating containing carvacrol nanoemulsion significantly increased the radiosensitization of E. coli and S. Typhimurium by 1.32-fold and 1.30-fold, respectively. Remarkably, the use of bioactive coating under MAP caused a synergistic effect with an increase in radiosensitivity by 1.80-fold and 1.89-fold for E. coli and S. Typhimurium, respectively. Thirdly, the antibacterial effects of the antimicrobial coating, gamma irradiation, MAP alone and their combinations were evaluated against these two bacteria during a 13-days storage of green beans at 4 °C. Bioactive coating deposition or gamma irradiation treatment resulted effective in controlling the growth of the two bacteria during the entire shelf-life. Moreover, it was also found that the combined treatment of antimicrobial coating, gamma irradiation and MAP caused the reduction of microbial population to undetectable levels during the whole storage period for E. coli and from day 7 to the end of storage for S. Typhimurium. The obtained results can be interested to food companies aiming to ensure the food safety with a prolonged shelf life.     

Incidence of Listeria monocytogenes and Escherichia coli O157:H7 in two Kasar Cheese processing environments

This study was designed to determine the presences of two environmental pathogens in two dairy factories in Sakarya, Turkey. A total of 264 environmental samples, raw milk and cheese samples were taken at four different seasons. According to the results, Listeria monocytogenes or Escherichia coli O157:H7 was isolated from 26 or 2.7% of the samples collected from both factories, respectively. None of the cheese or curd samples were found to be positive for Listeria or E. coli O157:H7. However, 50% of raw milk samples contained Listeria innocua. Listeria was mostly isolated from the swap samples taken from the drains or the floors in processing or packaging areas. However, E. coli was also isolated from the swap samples taken from the workers’ hands and gloves as well as the drains and the floor. Only one raw milk sample contained E. coli O157:H7. A higher prevalence of both pathogens was observed in the summer months than in the other months.     

Antimicrobial activity of malic acid against Listeria monocytogenes,Salmonella Enteritidis and Escherichia coli O157:H7 in apple,pear and melon juices

Minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations of malic acid against Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7 inoculated in apple, pear and melon juices stored at 5, 20 and 35 °C were evaluated. MICs and MBCs against L. monocytogenes, S. Enteritidis and E. coli O157:H7 were significantly affected by storage temperature, juice characteristics and type of microorganism. Malic acid was more effective at 35 and 20 °C than at 5 °C in all studied fruit juices. E. coli O157:H7 was more resistant to malic acid than S. Enteritidis and L. monocytogenes. Apple, pear and melon juices without malic acid were inhibitory to E. coli O157:H7, S. Enteritidis and L. monocytogenes at 5 °C, whereas, MBCs of 1.5% (v/v) of malic acid in apple and pear juices, and 2% (v/v) in melon juice at 5 °C were needed to reduce E. coli O157:H7, those concentrations being higher than those required to reduce S. Enteritidis and L. monocytogenes in those fruit juices. In addition, concentrations of 2%, 2.5% and 2.5% (v/v) of malic acid added to apple, pear and melon juices, respectively, were required to inactivate the three pathogens by more than 5 log cycles after 24 h of storage at 5 °C. Transmission electron microscopy showed that malic acid produced damage in the cell cytoplasm of pathogens without apparent changes in the cell membrane.     

The influence of acid stress on the growth of Listeria monocytogenes and Escherichia coli O157:H7 on cooked ham

Acid solutions are increasingly being used for decontaminating meat surfaces. On the surfaces of acid-treated meat, the population of microorganism is reduced due to the low pH of acids, and the subsequent growth of the microorganism is reduced due to the residual acids on meat surfaces. Microbial cells on meat surfaces subjected to acid treatments may cross-contaminate untreated meat surfaces, e.g., microorganisms on the surfaces of acid-treated cooked ham cross contaminate the untreated surfaces during slicing. The objective of this study was to examine this scenario in determining the subsequent growth of acid-treated Listeria monocytogenes and Escherichia coli O157:H7 on the surfaces of untreated meat. Cells of multiple-strain L. monocytogenes or E. coli O157:H7 were exposed to HCl solutions of pH 3, 4, or 5 and deionized water at room temperature for 24 h. The acid or deionized water-treated cells were inoculated separately onto cooked ham. Samples inoculated with L. monocytogenes were stored at 4 and 8 °C and samples inoculated with E. coli O157:H7 were stored at 10 and 12 °C. Populations of the pathogens on ham were enumerated during storage, and the lag phase durations (LPD, h) and growth rates (GR, log CFU/h) of the pathogens were determined. The populations of L. monocytogenes and E. coli O157:H7 in pH 5, 4, and 3 solutions were 1.2–3.1 and 0.6–2.4 log CFU/ml, respectively, lower than those in deionized water, indicating an increased acid stress on both microorganisms at lower pHs. L. monocytogenes subjected to pH 3 and pH 4 stresses and E. coli O157:H7 subjected to pH 3 stress exhibited significantly (p < 0.05) extended LPDs and reduced GRs on cooked ham. The growth of L. monocytogenes on ham was more readily reduced by acid stress than that of E. coli O157:H7. This study showed that acid treatments reduced the viability of L. monocytogenes and E. coli O157:H7and the acid stress reduced their subsequent growth ability on untreated ham. Therefore, cross-contamination of L. monocytogenes or E. coli O157:H7 cells from acid-treated meat surfaces onto untreated meat surfaces may not impose increased risk to the product.     

Antimicrobial activity of mustard essential oil against Escherichia coli O157:H7 and Salmonella typhi

The aim of this study was to investigate how mustard essential oil (EO) affected the cell membrane of Escherichia coli O157:H7 and Salmonella typhi. Intracellular pH and ATP concentration and the release of cell constituents were measured when mustard EO was in contact with E. coli and S. typhi at its minimal inhibitory concentration (MIC) and maximal tolerated concentration (MTC). The treatment with mustard EO affected the membrane integrity of bacteria and induced a decrease of the intracellular ATP concentration. Also, the extracellular ATP concentration increased and a reduction of the intracellular pH was observed in both bacteria. A significantly (P ? 0.05) higher release of cell constituent was observed when both bacteria cells were treated with mustard EO. Electronic microscopy observations showed that the cell membranes of both bacteria were apparently damaged by mustard EO. In conclusion, mustard EO affects the concentration of intracellular component, such as ATP in both bacteria and affects the pH suggesting that cytoplasmic membrane is involved in the antimicrobial action of mustard EO. Mustard EO can be used as an effective antimicrobial agent. We have demonstrated that mustard EO affected the cell membrane integrity, resulting in a loss of cell homeostasis.     

Simultaneous detection of Escherichia coli O175:H7, Salmonella spp., and Listeria monocytogenes by multiplex PCR

The wide application of nucleic acid amplification techniques and the increasing industrial interest toward rapid methods has led to the development and application of PCR based methods for the detection of microbial pathogens in food. In the present paper we describe the development of a multiplex PCR method for simultaneous detection of Salmonella enterica serovar Typhimurium, Listeria monocytogenes and Escherichia coli O157:H7 in a complex food matrix (liquid whole egg).Four different DNA extraction procedures were evaluated for their application on food and, among these, Chelex resin combined with a DNA purification step were found to better perform on the food system considered.A multiplex PCR system was developed, based on the evaluation and combination of published primer sets, and applied to the simultaneous detection of the target pathogens plus an internal amplification control, both in culture media and in a model food system.The overall system proposed, based on an overnight enrichment step followed by DNA isolation and multiplex PCR, was satisfactorily tested for its specificity and sensitivity and allowed the detection of the presence of bacterial DNA and the identification of the target pathogens down to 10 cells/25 g liquid whole egg.     

Responses of E. coli O157:H7, L. monocytogenes 1/2 c and Salmonella enteritidis to pH,aw and temperature stress combinations

This study compared the responses of Escherichia coli O157:H7, Listeria monocytogenes 1/2 c and Salmonella enteritidis toward different combinations of physicochemical stresses (pH: 3–8; a_w: 0.93–0.99; temperature: 3–62 °C). Results showed that L. monocytogenes generally had lower inactivation rates and was able to exhibit growth in most number of tested combinations, including those with very high and very low factor settings. Temperature introduced the greatest variation in the measured growth and death parameters but the contributions of both pH and a_w in all temperature ranges were also noted. The results of this study may be applied in the selection of appropriate pathogens in the evaluation of safety of foods that are preserved using individual or combined physicochemical factor control.     

Simulation of decontamination and transmission of Escherichia coli O157:H7, Salmonella Enteritidis,and Listeria monocytogenes during handling of raw vegetables in domestic kitchens

Epidemiological data indicates that a large number of foodborne illnesses are attributed to cross-contamination during food preparation in the domestic kitchen. The objectives of this study were to evaluate the efficiency of household washing practices in removing Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Enteritidis on artificially contaminated lettuce and to determine the transfer rate of these three foodborne pathogens from contaminated lettuce to wash water, tomato, cabbage, and cutting boards during washing and cutting processes. Washing under the running tap water with scrubbing for 60 s was the most effective method in reducing pathogen populations by 1.86–2.60 log₁₀ CFU/g. Also, final rinsing and scrubbing practices were found to enhance the efficiency of washing treatment. In this study, the transfer rates of S. Enteritidis, E. coli O157:H7, and L. monocytogenes from cutting board to cabbage and tomato via cutting process (17.5–31.7%) were higher (P < 0.05) than from wash water to cabbage and tomato (0.8–23.0%) during washing treatment. Overall, our findings suggest that wash water and cutting board can be potential vehicles in the dissemination of foodborne pathogens. Therefore, there is a need to promote consumer awareness for proper handling practices in the kitchen to minimise the risk of foodborne infection.     

Decimal reduction times of acid-adapted and non-adapted Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes in young Cocos nucifera Linn. liquid endosperm

The study established the decimal reduction times at 55 °C (D_55 °C values) of acid-adapted and non-adapted Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in young coconut liquid endosperm. Acid adaptation of the test pathogens was conducted by cultivating cells in a gradually acidifying nutrient broth supplemented with 1% glucose. Results showed that acid adaptation had varying influence on the subsequent thermal resistances of the pathogens. The non-adapted E. coli O157:H7 exhibited the greatest resistance among the tested pathogens with a D_55 °C of 23.20 min. Prior adaptation to acidity decreased the D_55 °C to 16.16 min. On the other hand, acid adaptation increased the D_55 °C values of S. enterica and L. monocytogenes from 8.76 to 10.55 min, and from 7.47 to 18.09 min, respectively. The D_55 °C of the non-adapted E. coli O157:H7 was used to establish a pasteurization process schedule with an order of lethality equal to 5-logarithmic (99.999%) reduction. Sensory evaluation revealed that the overall acceptability, color, aroma, coconut flavor, and freshness characteristics of non-pasteurized and pasteurized liquid endosperms were not significantly different (p > 0.05). Moreover, the sensory quality attributes of coconut beverages (80:20 vol/vol endosperm-to-water ratio, soluble solids adjusted to 10 °Brix with sucrose) prepared from both non-pasteurized and pasteurized liquid endosperm samples did not significantly vary. The results obtained from the study may be used in the establishment and validation of thermal process schedules for young coconut liquid endosperm beverages.