Efficacy of alkaline washing for the decontamination of orange fruit surfaces inoculated with Escherichia coli

The effectiveness of washing treatments to decontaminate orange fruit surfaces inoculated with Escherichia coli was evaluated. Washing on roller brushes with fruit cleaners or sanitizers followed by potable water rinse reduced E. coli by 1.9 to 3.5 log cycles. Prewetting fruit for 30 s before washing provided no significant benefit in most cases. Additional sanitizing treatments either with chlorine or acid sanitizers did not enhance the results of alkaline washing. In general, high pH washing solutions (pH 11.8) applied with an adequate spray volume effectively reduced the surface contamination of fruit that lowered the microbial load of fresh juice as well.     

Simultaneous detection by PCR of Escherichia coli, Listeria monocytogenes and Salmonella typhimurium in artificially inoculated wheat grain

A multiplex PCR procedure was established to detect Escherichia coli, Listeria monocytogenes and Salmonella typhimurium in artificially inoculated wheat grain. The PCR protocol with an enrichment step successfully detected all three organisms inoculated together in non-autoclaved wheat grain. After a one day enrichment, E. coli, L. monocytogenes and S. typhimurium were detected at levels of 56, 1800 and <54 CFU/mL, respectively, in the initial sample. For L. monocytogenes, an improved detection limit of <62 CFU/mL was achieved using singleplex PCR. For autoclaved wheat grain inoculated with the three bacterial strains individually, a detection limit of 3 CFU/mL was achieved after an enrichment step. The ability to test for the three bacteria simultaneously will save time and increase the ability to assure grain quality.     

Location of Escherichia coli O157:H7 on and in apples as affected by bruising, washing, and rubbing

Confocal scanning laser microscopy (CSLM) was used to determine the location of Escherichia coli O157:H7 cells on the surface and in tissue of bruised Red Delicious cv. apples. Undamaged and bruised apples were inoculated by immersing in a suspension of E. coli O157:H7 cells transformed with a plasmid that encodes for the production of a green fluorescent protein. Apples were then washed in 0.1% (wt/vol) peptone water and/or rubbed with a polyester cloth and examined to determine if these treatments removed or introduced cells into lenticels, cutin, and cracks on the skin surface. Optical slices of the apples obtained using CSLM were examined to determine the depth at which colonization or attachment of cells occurred. Populations of E. coli O157:H7 on the surface of apples were determined to assess the effectiveness of washing and rubbing in physically removing cells. The location of cells on or in undamaged and bruised areas of apples that were not washed or rubbed did not differ significantly. However, washing apples resulted in an approximate 2-log reduction in CFU of E. coli O157:H7 per cm2 of apple surface. On unwashed apples, cells were detected at depths up to 30 microm below the surface. No E. coli O157:H7 cells were detected at locations more than 6 microm below the surface of washed apples. Cells that remained on the surface of rubbed apples appeared to be sealed within naturally occurring cracks and crevices in waxy cutin platelets. These cells may be protected from disinfection and subsequently released when apples are eaten or pressed for cider production.     

Efficacy of various plant hydrosols as natural food sanitizers in reducing Escherichia coli O157:H7 and Salmonella Typhimurium on fresh cut carrots and apples

In the present study, inhibitory effects of the hydrosols of thyme, black cumin, sage, rosemary and bay leaf were investigated against Salmonella Typhimurium and Escherichia coli O157:H7 inoculated to apple and carrots (at the ratio of 5.81 and 5.81 log cfu/g for S. Typhimurium, and 5.90 and 5.70 log cfu/g for E. coli O157:H7 on to apple and carrot, respectively). After the inoculation of S. Typhimurium or E. coli O157:H7, shredded apple and carrot samples were washed with the hydrosols and sterile tap water (as control) for 0, 20, 40 and 60 min. While the sterile tap water was ineffective in reducing (P > 0.05) S. Typhimurium and E. coli O157:H7, 20 min hydrosol treatment caused a significant (P < 0.05) reduction compared to the control group. On the other hand, thyme and rosemary hydrosol treatments for 20 min produced a reduction of 1.42 and 1.33 log cfu/g respectively in the E. coli O157:H7 population on apples. Additional reductions were not always observed with increasing treatment time. Moreover, thyme hydrosol showed the highest antibacterial effect on both S. Typhimurium and E. coli O157:H7 counts. Inhibitory effect of thyme hydrosol on S. Typhimurium was higher than that for E. coli O157:H7. Bay leaf hydrosol treatments for 60 min reduced significantly (P < 0.05) E. coli O157:H7 population on apple and carrot samples. In conclusion, it was shown that plant hydrosols, especially thyme hydrosol, could be used as a convenient sanitizing agent during the washing of fresh-cut fruits and vegetables.     

Effectiveness of commercial household steam cleaning systems in reducing the populations of Listeria monocytogenes and spoilage bacteria on inoculated pork skin surfaces

In a previous study conducted in our laboratory, a commercial household steam cleaner was found to be effective in reducing the naturally occurring bacterial populations on 72 beef and 72 hog carcasses processed by four small and very small meat processing plants. The goals of this study were to determine the maximum levels of bacterial reduction caused by treatments using the steam cleaner, and to compare the efficacy of this cleaner with the efficacies of two other commercial household steam cleaning systems in reducing bacterial populations on the surface of pork skin artificially inoculated with ca. 7.61 or of Listeria monocytogenes. The contaminated pork skin samples were treated with the three stream cleaners for 30-180 s in 30 s intervals, and assayed for the populations of L. monocytogenes as well as total aerobic and thermoduric bacteria. The application of steam significantly reduced the population of L. monocytogenes (7.61-), as well as total aerobic (5.68-) and thermoduric (6.12-) bacteria on the surface of pork skin (P?0.05). Significant differences in microbial reductions were observed between different inoculation levels, treatment times, and types of cleaning systems used in the study (P?0.05).     

Survival of Escherichia coli O157:H7 and Salmonella Muenchen on apples as affected by application of commercial fruit waxes

Survival of Escherichia coli O157:H7, Salmonella Muenchen, and yeasts and molds on apples as affected by application of five commercial apple waxes was investigated. Red Delicious cv. apples at 21 degrees C were spot inoculated with E. coli O157:H7 and S. Muenchen and spray coated with waxes. Apples sprayed with water served as controls. Apples were dried at either 21 or 55 degrees C for 2 min before subjecting to microbiological analysis after storage for 0, 1, 3, 6, and 12 weeks at 2 or 21 degrees C. Drying temperature did not significantly influence populations of E. coli O157:H7 and S. Muenchen. Waxing reduced populations E. coli O157:H7 and S. Muenchen by up to 1.48 log10 cfu/apple. Compared to untreated apples, treatment of apples with water or waxes resulted in significant (P < or = 0.05) reductions in populations of E. coli O157:H7 and S. Muenchen during storage at 2 degrees C. Reductions on waxed apples stored at 21 degrees C were not as marked compared to reductions on waxed apples stored at 2 degrees C. With the exception of one wax, drying temperature did not significantly influence populations of yeasts and molds. Mold populations were less affected by wax applications than were yeasts, and were detected in higher numbers on apples treated with three of the five waxes compared to populations recovered from untreated control apples. None of the waxes evaluated can be relied upon to kill or remove E. coli O157:H7 and Salmonella on apples.     

Efficacy of acidified sodium chlorite treatments in reducing Escherichia coli O157:H7 on Chinese cabbage

Efficacy of acidified sodium chlorite for reducing the population of Escherichia coli O157:H7 pathogens on Chinese cabbage leaves was evaluated. Washing leaves with distilled water could reduce the population of E. coli O157:H7 by approximately 1.0 log CFU/g, whereas treating with acidified chlorite solution could reduce the population by 3.0 log CFU/g without changing the leaf color. A similar level of reduction was achieved by washing with sodium chlorite solution containing various organic acids. However, acidified sodium chlorite in combination with a mild heat treatment reduced the population by approximately 4.0 log CFU/g without affecting the color, but it softened the leaves. Moreover, the efficacy of the washing treatment was similar at low (4 degrees C) and room (25 degrees C) temperatures, indicating that acidified sodium chloride solution could be useful as a sanitizer for surface washing of fresh produce.     

Efficacy of selected acidulants in pureed green beans inoculated with pathogens (Escherichia coli O157:H7 and Listeria monocytogenes)

Studies were conducted to evaluate the combined effect of selected acidulants (acetic, citric, malic, and phosphoric acid) and heat on foodborne pathogens (Escherichia coli O157:H7 and Listeria monocytogenes) in pureed green beans. To establish a consistent reference point for comparison, the molar concentrations of the acids remained constant while the acid-to-puree ratio, titratable acidity, and undissociated acid were either measured or calculated for a target acidified green beans at a pH of 3.8, 4.2, and 4.6. The D-values at 149 degrees F were used as the criteria for acid efficacy. Generally, acetic acid (puree, pH 3.8 and 4.2) represented the most effective acid with comparatively low D-values irrespective of the target microorganism. A 10-s heating at 149 degrees F inactivated approximately 10(6) CFU/ml of E. coli O157:H7 in pureed beans at pH 3.8. The efficacy of acetic acid is likely related to the elevated percent titratable acidity, undissociated acid, and acid-to-puree ratio. The effectiveness (which in this study represents the combined effect of acid and heat) of the remaining acids (citric, malic, and phosphoric) at puree pH values of 3.8 and 4.2 were statistically insignificant (alpha = 0.05). Surprisingly, acetic acid (puree, pH 4.6) appeared to be the least effective as compared to the other acids tested (citric, malic, and phosphoric) especially on E. coli O157:H7 cells, while L. monocytogenes had a similar resistance to all acids at puree pH 4.6. With the exception of citric acid (pH 3.8), acetic acid (pH 4.6), and malic acid (pH 3.8 and 4.6), which were statistically insignificant (P > 0.05), the D-values for L. monocytogenes were statistically different (P < or = 0.05) and higher than the D-values for E. coli under similar experimental conditions. A conservative process recommendation (referred to as the "safe harbor" process) was found sufficient and applicable to pureed green beans for the pH range studied.     

Influence of treatment time and pulse frequency on Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes populations inoculated in melon and watermelon juices treated by pulsed electric fields

Consumption of unpasteurized melon and watermelon juices has caused several disease outbreaks by pathogenic microorganisms worldwide. Pulsed electric field (PEF) has been recognized as a technology that may inactivate those bacteria present in fluid food products at low temperatures. Hence, PEF treatment at 35 kV/cm, 4 mus pulse duration in bipolar mode and square shape were applied on Salmonella Enteritidis, E. coli and L. monocytogenes populations inoculated in melon and watermelon juices without exceeding 40 degrees C outlet temperatures. Different levels of treatment time and pulse frequency were applied to evaluate their effects on these microorganisms. Treatment time was more influential than pulse frequency (P相似文献   

Comparison of aqueous commercial cleaners for effectiveness in removing Escherichia coli O157:H7 and Salmonella muenchen from the surface of apples

Unpasteurized fruit juice and cider have been implicated in outbreaks of Escherichia coli O157:H7 and Salmonella infections, yet various processes used to clean and sanitize fruits before producing juice have not been thoroughly studied for their effectiveness in removing pathogens. The objective of this study was to evaluate cleaners used in the apple industry for their efficacy in removing E. coli O157:H7 and Salmonella from the surface of apples. E. coli O157:H7 was transformed with green fluorescent protein plasmid (pGFP). In addition to encoding for the production of GFP, the plasmid also encodes for ampicillin resistance. S. muenchen was adapted to grow in media containing 50 microg/ml nalidixic acid. The use of ampicillin and nalidixic acid resistant strains enabled enumeration of the pathogen without interference by microflora naturally present on apples. Unwaxed Red Delicious cv. apples were surface inoculated with 8.58 log10 cfu of E. coli O157:H7 and 8.11 log10 cfu of S. muenchen. Five commercial apple cleaners were applied at concentrations and exposure times recommended by manufacturers. Populations of E. coli O157:H7, S. muenchen, aerobic mesophiles, and yeasts and molds on apples treated with cleaners and water (control) were determined. Compared to washing with water, treatment with cleaners removed or killed up to 2.86, 3.11, 2.48, and 0.73 log10 cfu of E. coli O157:H7, S. muenchen, aerobic mesophiles, and yeasts and molds per apple, respectively. There were differences in the effectiveness of cleaners in removing pathogens, but pH (2.0 and 12.0) and concentration (1% and 5%) of cleaner, and time of exposure (0.5-2 min) were not correlated with magnitude of reduction in population. The use of some types of cleaners commercially formulated for apples may contribute significantly in attaining target 5-log10 reductions of pathogens on the fruit intended for unpasteurized juice production or the fresh produce market.     

Spatial distribution of Salmonella, Escherichia coli O157:H7, and other bacterial populations in commercial and laboratory-scale sprouting mung bean beds

The reliability of testing spent irrigation water to assess the microbiological status of sprouting mung bean beds has been investigated. In commercial trials, the distribution of opportunistic contaminants within 32 bean sprout beds (25 kg of mung beans per bin) was assessed 48 h after germination. The prevalence of generic Escherichia coli, thermotolerant coliforms, and Aeromonas in sprouts (n = 288) was 5, 11, and 39%, respectively, and 57, 70, and 79% in the corresponding spent irrigation water samples (n = 96). Contamination was heterogeneously distributed within the seedbed. In laboratory trials, beans inoculated with a five-strain cocktail of either Salmonella or E. coli O157:H7 (10(3) to 10(4) CFU/g) were introduced (1 g/500 g of noninoculated seeds) at defined locations (top, middle, or base), and the beans were then sprouted for 48 h. When seeds inoculated with pathogens were introduced at the base or top of the seedbed, the pathogens were typically restricted to these sites and resulted in 44% of the spent irrigation water samples returning false-negative results. Introducing inoculated beans into the middle or at the presoak stage enhanced the distribution of both pathogens within the subsequent sprout bed and resulted in comparable levels recovered in spent irrigation water. The study demonstrated that even though screening a single sample of spent irrigation water is more reliable than testing sprouts directly, it does not provide an accurate assessment of the microbiological status of sprouting mung bean beds. Such limitations may be addressed by ensuring that bean batches are mixed prior to use and by taking spent irrigation water samples from multiple sites at the latter stages of the sprouting process.     

Efficacy of washing with hydrogen peroxide followed by aerosolized antimicrobials as a novel sanitizing process to inactivate Escherichia coli O157:H7 on baby spinach

Aerosolization was investigated as a potential way to apply allyl isothiocyanate (AIT), hydrogen peroxide (H₂O₂), acetic acid (AA) and lactic acid (LA) on fresh baby spinach to control Escherichia coli O157:H7 during refrigeration storage. In this study, baby spinach leaves were dip-inoculated with E. coli O157:H7 to a level of 6 log CFU/g and stored at 4 °C for 24 h before treatment. Antimicrobials were atomized into fog-like micro-particles by an ultrasonic nebulizer and routed into a jar and a scale-up model system where samples were treated. Samples were stored at 4 °C for up to 10 days before the survival of the cells was determined. A 2-min treatment with 5% AIT resulted in a > 5-log reduction of E. coli O157:H7 on spinach after 2 days refrigeration regardless if the samples were pre-washed or not; however, this treatment impaired the sensory quality of leaves. Addition of LA to AIT improved the antimicrobial efficacy of AIT. In the jar system, washing with 3% H₂O₂ followed by a 2-min treatment of 2.5% LA + 1% AIT or 2.5% LA + 2% AIT reduced E. coli O157:H7 population by 4.7 and > 5 log CFU/g, respectively, after 10 days refrigeration. In the scale-up system, up to 4-log reduction of bacterial population was achieved for the same treatments without causing noticeable adverse effect on the appearance of leaves. Thus, this study demonstrates the potential of aerosolized AIT + LA as a new post-washing intervention strategy to control E. coli O157:H7 on baby spinach during refrigeration storage.     

Effectiveness of spraying with tween 20 and lactic acid in decontaminating inoculated Escherichia coli O157:H7 and indigenous Escherichia coli biotype I on beef.

Beef carcass quarters and fat-covered subprimal cuts were suspended vertically and inoculated with a bovine manure slurry containing a five-strain mixture of Escherichia coli O157:H7 to deliver about 4 to 5 log10 CFU/cm2. To identify treatments that would improve the effectiveness of spraying with lactic acid (LA), the inoculated quarters and cuts were treated as follows: experiment A, (i) not treated (control), (ii) sprayed with 2% (vol/vol) LA, (iii) tempered at 21 degrees C for 4 h, and (iv) tempered and then sprayed with LA; experiment B, (v) sprayed with water, (vi) sprayed with LA, (vii) sprayed with LA containing 0.5% (vol/vol) sodium benzoate (SB), and (viii) sprayed with LA containing SB and 5% (vol/vol) Tween 20 (TW20); and experiment C, (ix) sprayed with water (no prespray), (x) presprayed with TW20 and then sprayed with LA, and (xi) presprayed with TW20 and then sprayed with LA containing SB. In experiment A, spraying carcasses with LA significantly (P < 0.05) reduced the numbers of E. coli Biotype I and serotype O157:H7 after 1 and 3 days of storage, respectively. The tempering process employed did not affect the effectiveness of the LA spray on either type of E. coli. In experiment B, there was no significant difference in the reduction of E. coli O157:H7 on subprimal cuts sprayed with water and that on cuts sprayed with LA alone or with LA in combination with SB and TW20 after 1 or 3 days of storage (total reductions ranged from about 1.6 to 2.8 log10 CFU/cm2). In experiment C, prespraying subprimal cuts with TW20 significantly (P < 0.05) increased the effectiveness of LA (reductions of 2.8 and 3.2 log10 CFU/cm2, respectively) and that of LA with SB (reductions of 2.6 and 3.3 log10 CFU/cm2, respectively) compared with spraying with water alone (reductions of ca. 1.0 and 2.0 log10 CFU/cm2, respectively) after I and 3 days of storage, respectively. In a separate experiment, the incorporation of TW20 (0.1 or 0.25%) into buffered peptone water prior to the maceration of excised carcass surface samples resulted in the recovery of significantly larger numbers (ca. 5.1 to 5.2 log10 CFU/cm2) of E. coli O157:H7 cells than did the control treatment without added TW20 (ca. 3.8 to 4.6 log10 CFU/cm2). These results demonstrate that the treatment of beef carcasses with LA reduces the number of viable E. coli O157:H7 cells and that this inactivation or removal by LA is enhanced by prespraying of the carcass with a 5% solution of TW20.     

Preharvest evaluation of coliforms, Escherichia coli, Salmonella, and Escherichia coli O157:H7 in organic and conventional produce grown by Minnesota farmers

Microbiological analyses of fresh fruits and vegetables produced by organic and conventional farmers in Minnesota were conducted to determine the coliform count and the prevalence of Escherichia coli, Salmonella, and E. coli O157:H7. A total of 476 and 129 produce samples were collected from 32 organic and 8 conventional farms, respectively. The samples included tomatoes, leafy greens, lettuce, green peppers, cabbage, cucumbers, broccoli, strawberries, apples, and seven other types of produce. The numbers of fruits and vegetables was influenced by their availability at participating farms and varied from 11 strawberry samples to 108 tomato samples. Among the organic farms, eight were certified by accredited agencies and the rest reported the use of organic practices. All organic farms used aged or composted animal manure as fertilizer. The average coliform counts in both organic and conventional produce were 2.9 log most probable number per g. The percentages of E. coli-positive samples in conventional and organic produce were 1.6 and 9.7%, respectively. However, the E. coli prevalence in certified organic produce was 4.3%, a level not statistically different from that in conventional samples. Organic lettuce had the largest prevalence of E. coli (22.4%) compared with other produce types. Organic samples from farms that used manure or compost aged less than 12 months had a prevalence of E. coli 19 times greater than that of farms that used older materials. Serotype O157:H7 was not detected in any produce samples, but Salmonella was isolated from one organic lettuce and one organic green pepper. These results provide the first microbiological assessment of organic fruits and vegetables at the farm level.     

Escherichia coli O157 prevalence and enumeration of aerobic bacteria, Enterobacteriaceae, and Escherichia coli O157 at various steps in commercial beef processing plants

The effectiveness of current antimicrobial interventions used in reducing the prevalence or load of Escherichia coli O157 and indicator organisms on cattle hides and carcasses at two commercial beef processing plants was evaluated. Sponge sampling of beef cattle was performed at five locations from the initial entry of the animals to the slaughter floor to the exit of carcasses from the "hotbox" cooler. For each sample, E. coli O157 prevalence was determined and total aerobic bacteria, Enterobacteriaceae, and E. coli O157 were enumerated. E. coli O157 was found on 76% of animal hides coming into the plants, but no carcasses leaving the cooler were identified as contaminated with E. coli O157. A positive relationship was seen between the incidence of E. coli O157 in hide samples and that in preevisceration samples. Aerobic plate counts and Enterobacteriaceae counts averaged 7.8 and 6.2 log CFU/100 cm2, respectively, on hides, and 1.4 and 0.4 log CFU/100 cm2, respectively, on chilled carcasses. Aerobic plate counts and Enterobacteriaceae counts on preevisceration carcasses were significantly related to the respective levels on the corresponding hides; the carcasses of animals whose hides carried higher numbers of bacteria were more likely to carry higher numbers of bacteria. Implementation of the sampling protocol described here would allow processors to evaluate the efficacy of on-line antimicrobial interventions and allow industrywide benchmarking of hygienic practices.     

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium DT104, and Listeria monocytogenes on inoculated alfalfa seeds with a fatty acid-based sanitizer

Alfalfa seeds were inoculated with a three-strain cocktail of Escherichia coli O157:H7, Salmonella enterica subsp. enterica serovar Typhimurium DT104, or Listeria monocytogenes by immersion to contain approximately 6 to 8 log CFU/g and then treated with a fatty acid-based sanitizer containing 250 ppm of peroxyacid, 1,000 ppm of caprylic and capric acids (Emery 658), 1,000 ppm of lactic acid, and 500 ppm of glycerol monolaurate at a reference concentration of 1X. Inoculated seeds were immersed at sanitizer concentrations of 5X, 10X, and 15X for 1, 3, 5, and 10 min and then assessed for pathogen survivors by direct plating. The lowest concentration that decreased all three pathogens by >5 log was 15. After a 3-min exposure to the 15X concentration, populations of E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes decreased by >5.45, >5.62, and >6.92 log, respectively, with no sublethal injury and no significant loss in seed germination rate or final sprout yield. The components of this 15x concentration (treatment A) were assessed independently and in various combinations to optimize antimicrobial activity. With inoculated seeds, treatment C (15,000 ppm of Emery 658, 15,000 ppm of lactic acid, and 7,500 ppm of glycerol monolaurate) decreased Salmonella Typhimurium, E. coli O157:H7, and L. monocytogenes by 6.23 and 5.57 log, 4.77 and 6.29 log, and 3.86 and 4.21 log after 3 and 5 min of exposure, respectively. Treatment D (15,000 ppm of Emery 658 and 15,000 ppm of lactic acid) reduced Salmonella Typhimurium by >6.90 log regardless of exposure time and E. coli )157:H7 and L. monocytogenes by 4.60 and >5.18 log and 3.55 and 3.14 log after 3 and 5 min, respectively. No significant differences (P > 0.05) were found between treatments A, C, and D. Overall, treatment D, which contained Emery 658 and lactic acid as active ingredients, reduced E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes populations by 3.55 to >6.90 log and may provide a viable alternative to the recommended 20,000 ppm of chlorine for sanitizing alfalfa seeds.     

Inactivation of Escherichia coli O157:H7 on inoculated alfalfa seeds with ozonated water and heat treatment

Alfalfa seeds inoculated with a five-strain mixture of Escherichia coli O157:H7 were immersed in water containing 4, 8, 10, and 21 ppm of ozone for 2, 4, 8, 16, 32, and 64 min at 4 degrees C. Direct ozone sparging of seeds in water was used as an alternative mode of ozone treatment. Ozone-sparged seeds were also subsequently exposed to heat treatment at 40, 50, and 60 degrees C for 3 h. Populations of E. coli O157:H7 on untreated and treated seeds were determined by spread plating diluted samples on tryptic soy agar supplemented with 50 microg/ml of nalidixic acid. Since E. coli O157:H7 was released from inoculated seeds during treatment with ozone, the rate of release of cells from inoculated seeds soaked in 0.1% peptone water for up to 64 min was also determined. The overall reduction of E. coli O157:H7 on seeds treated with ozonated water without continuous sparging ranged from 0.40 to 1.75 log10 CFU/g (59.6 to 98.2%), whereas reductions for control seeds were 0.32 to 1.03 log10 CFU/g (51.7 to 90.5%). Treatment with higher ozone concentrations enhanced inactivation, but contact time longer than 8 min did not result in significantly higher reductions (P > 0.05). For seeds treated by ozone sparging, a 1.12-log10 CFU/g (92.1%) reduction was achieved using a 2-min contact time, and a 2.21-log10 CFU/g (99.4%) reduction was achieved with a 64-min contact time. The corresponding reductions for control seeds were 0.71 log10 CFU/g (79.5%) and 2.21 log10 CFU/g (99.4%), respectively. Treatment of ozone-sparged seeds at 60 degrees C for 3 h reduced the population to an undetectable level by direct plating (4 to 4.8 log10 CFU/g), although survivors were detected by enrichment. Ozone did not have a detrimental effect on seed germination percentage.     

Application of polylactic acid coating with antimicrobials in reduction of Escherichia coli O157:H7 and Salmonella Stanley on apples

Abstract: Survival of Escherichia coli O157:H7 and Salmonella Stanley on apples as affected by application of polylactic acid (PLA) coating with antimicrobials was investigated. Golden Delicious apples were spot inoculated with E. coli O157:H7 or S. Stanley and spray coated with PLA solutions containing lactic acid (LA), disodium ethylenediaminetetraacetic acid (EDTA), sodium benzoate (SB), potassium sorbate (PS), or their combination (LA + EDTA, SB + LA, SB + LA + EDTA). Apples without any coating treatment served as controls. Coating treatments were allowed to dry fully, and the apples were stored at 4 °C for 14 d. Antimicrobial coatings reduced populations of E. coli O157:H7 and S. Stanley by up to 4 log CFU/cm² at 1 d and 4.7 log CFU/cm² at 14 d, compared to controls. SB + LA combination had a similar effectiveness as the SB + LA + EDTA combination against both pathogens and was more effective than other coating treatments. Without antimicrobial treatment, E. coli O157:H7 and S. Stanley were able to survive on apples stored at 4 °C for up to 14 d. The antimicrobial PLA coating provides an alternative intervention to reduce the pathogens on apples. Practical Application: Antimicrobial PLA coatings provide an alternative method to reduce pathogenic contaminations on fruit surface, and therefore, reduce the risk of food‐borne outbreaks.