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In agreement with the recent trend of consumers’ demand for natural antimicrobial products, the importance of using natural compounds in food is increasing. Among numerous natural compounds, grapefruit seed extract (GSE) is widely known for its extremely effective antimicrobial activity. The direct use of GSE in food is the most common method of application. Other GSE applications exist using it with coating materials and incorporating it into edible films. Previously done studies identified benzalkonium chloride, benzethonium chloride, and other synthetic agents from GSE. Unfortunately, the presence of these antibacterial contents does not exactly coincide with the natural aspects of GSE. Even though GSE is identified as a natural antimicrobial, this observation suggests that the GSE antibacterial activity is derived from these synthetic substances such as benzalkonium chloride. Therefore, further research is needed about these controversial issues. This review analyzed the application of GSE as a natural antimicrobial in the food industry and suggested further research directions.

Integration of plasma and pulsed light or ultraviolet has been investigated for microbial decontamination of foods. However, no studies have reported the microbial disinfection of particulate food using a large-scale system integrating the treatments. In the present study, a large-scale plasma jet-pulsed light-ultraviolet (UV)-C (PPU) system has been developed for the microbial decontamination of particulate foods. The effects of PPU treatment on the inactivation of natural mesophilic aerobic bacteria and yeast and molds of rice germ and the quality properties of rice germ were evaluated at various operation times (3, 5, 7, and 10 min) and sample amount (200, 500, 1,000, and 3,000 g). The efficacy of microbial inactivation of PPU treatment was enhanced with increasing treatment time and decreasing sample amount, and the maximum reduction was observed at 7 min with 200 g samples. The number of the natural bacteria and yeast and mold was reduced to 1.0 and 2.0 log CFU/g from an initial number of 5.7 and 3.7 log CFU/g, respectively. Compared to the individual treatments by atmospheric pressure plasma jet (APPJ) and intense pulsed light (IPL), PPU treatment synergistically inactivated microorganisms while not altering the color, antioxidant activity, or sensory properties of rice germ. The results of this study suggest the potential use of the large-scale PPU treatment system for the microbial decontamination of rice germ while minimizing alterations in quality.

Foodborne bacteria are typically present at very low concentrations in food. This study describes a quick and simple method for concentrating E. coli O157:H7 present in lettuce and cabbage, without microbial enrichment culture. This method involved reducing the extraction buffer and DNA elution volumes. The extraction buffer volume was adjusted to 225, 100, 50, 25, and 12.5 mL to isolate E. coli O157:H7 from 25 g of lettuce or cabbage. DNA was concentrated and compared using real-time PCR. When using 12.5 mL of buffer

The demand for rapid, consistent and easy-to-use techniques for detecting and identifying pathogens in various areas, such as clinical diagnosis, the pharmaceutical industry, environmental science and food inspection, is very important. In this study, the reference strains of six food-borne pathogens, namely, Escherichia coli 0157: H7 ATCC 43890, Cronobacter sakazakii ATCC 29004, Salmonella Typhimurium ATCC 43971, Staphylococcus aureus KCCM 40050, Bacillus subtilis ATCC 14579, and Listeria monocytogenes ATCC 19115, were chosen for scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. In our study, the time-consuming sample preparation step for the microbial analysis under SEM was avoided, which makes this detection process notably rapid. Samples were loaded onto a 0.01-µm-thick silver (Ag) foil surface to avoid any charging effect. Two different excitation voltages, 10 kV and 5 kV, were used to determine the elemental information. Information obtained from SEM-EDX can distinguish individual single cells and detect viable and nonviable microorganisms. This work demonstrates that the combination of morphological and elemental information obtained from SEM-EDX analysis with the help of principal component analysis (PCA) enables the rapid identification of single microbial cells without following time-consuming microbiological cultivation methods.

Escherichia coli O157:H7 is an important foodborne pathogen and has been implicated in numerous food poisoning outbreaks worldwide. Although several microbiological and molecular methods have been developed to detect E. coli O157:H7, the difficulty to rapidly detect low levels of the foodborne bacteria persists. Here, the optimization of a filtration technique to concentrate and rapidly detect E. coli O157:H7 was conducted. Using homogenates prepared from freshly cut lettuce and cabbage samples, the E. coli O157:H7 concentration efficiencies of seven membrane filters were compared. Mixed cellulose ester (MCE) and polyvinylidene difluoride (PVDF) filters demonstrated the highest bacterial recoveries. In addition, the optimal E. coli O157:H7 detachment method from MCE filters after filtration was investigated. Tapping for 80 s was demonstrated to be the most effective method for detaching bacteria from the filters. Further, the possibility of the rapid detection of low levels of E. coli O157:H7 in lettuce and cabbage was evaluated using real-time polymerase chain reaction after bacterial concentration using MCE and PVDF filters. The use of MCE filters enabled the detection of 10° CFU/g (5 CFU/g) of E. coli O157:H7 within 2 hr without microbial enrichment culture. Therefore, concentration by filtration can be used for the rapid detection of low levels of foodborne pathogens. PRACTICAL APPLICATION: The modified method, which has been verified in this study, has been optimized to reduce the analysis time and to detect very low concentrations of E. coli O157:H7 within 2 hr. All these detection systems have a direct economic impact on the food analysis of producers, health authorities, or third-party laboratories.

This study was conducted to measure the inactivation characteristics of UVs and TiO2 against Salmonella. Typhimurium and Escherichia coli O157:H7 on black pepper powder. The sample was irradiated by UV-A and UV-C combined with TiO2 coating. After treatment, microbial and physicochemical analysis was carried out. Among various sterilization conditions, the largest number of pathogen in black pepper powder was inactivated by UV-A and UV-C combined with TiO2 coating. The microbial count of black pepper powder treated simultaneously with UV-A and UV-C was less than that of black pepper powder treated with alone. The inactivation effect of UV-A and UV-C was increased when TiO2 coating was combined. Moisture content was decreased with increasing treatment time, but color did not change. In this study, it was indicated that the combined treatment of UV-C, UV-A and TiO2 coating was effective for reducing S. Typhimurium and E. coli O157:H7 on black pepper powder.

Rapid detection of low number of pathogenic bacteria in food is difficult. This study tested the filter-based loop-mediated isothermal amplification-lateral flow immunoassay (LAMP–LFA) method for rapid detection of pathogens in real food. Escherichia coli O157:H7 was inoculated on 25 g of beef and the homogenized sample was filtered with 0.45 μm cellulose nitrate filter, and concentrated E. coli was recovered and DNA was extracted and analyzed by LAMP. LFA reaction was performed by hybridization of digoxygenin-labeled LAMP amplicon and biotinylated probe. The sensitivity of the filtered sample was 100 times more sensitive than that of the unfiltered sample. The total reaction time used for detection from sample preparation to confirmation of E. coli was within 3 h. These results suggest that the LAMP–LFA method can be used in real food systems as point-of-care testing for E. coli O157:H7 in beef.

The effect of a layer-by-layer (LbL) electrostatic deposition coating of alginate and chitosan with grapefruit seed extract was investigated on the shelf life of shrimp (Litopenaeus vannamei) stored for 15 days under refrigeration (4 °C). The shrimp were periodically analyzed for changes in microbiological parameters (total aerobic mesophilic bacteria and total aerobic psychrotrophic bacteria counts), chemical parameters, melanosis, and sensory characteristics. The chitosan–alginate coating had the advantage of reducing the bacterial count by 2 log CFU in combination with the antimicrobial activity of the grapefruit seed extract. The bilayer coating reduced the off-flavor of shrimp during the storage period by preventing the odor of acetic acid that was used to dissolve chitosan. In conclusion, chitosan and chitosan–alginate treatments could prolong the shelf life of shrimp.

In this study, UV-C and mild heat treatments were used alone or in combination for the inactivation of Salmonella Typhimurium and Escherichia coli O157:H7 on the black pepper powder. The treated pepper powder was analyzed microbiologically, and the physicochemical properties of the pepper powder were examined. UV-C combined with heat treatment at 60 °C most effectively inactivated the pathogens. However, heat treatment at 60 °C produced many injured cells and greatly reduced moisture content of the pepper powder. UV-C combined with heat treatment at 45 °C showed significantly (p

Foodborne pathogens are a food safety problem, and there is demand for rapid and sensitive diagnostic methods. Therefore, multiplex PCR-lateral flow assay (mPCR-LFA) with concentration methods was studied for detecting Escherichia coli O157:H7 and Salmonella Typhimurium. To sensitively detect only viable bacteria in cabbage and reduce time required for results, propidium monoazide was used to selectively inhibit DNA amplification and was subjected to filtration and DNA concentration. This increased the sensitivity by 10‒100-fold. E. coli O157:H7 and S. Typhimurium were then simultaneously amplified using mPCR and detected using dual LFA. Our results showed that mPCR-LFA detected 102 CFU/25 g and 101 CFU/25 g of E. coli O157:H7 and S. Typhimurium in 100 min, respectively. This demonstrated that mPCR-LFA and concentration can potentially be performed without cultural enrichment to detect foodborne pathogens.

Thiamine dilauryl sulfate (TDS) is a food additive that is used as a bactericidal agent. This study examines the antimicrobial effect of TDS on tofu inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Bacillus cereus. Tofu was inoculated with 100 μL of each microorganism and TDS solution (0.1, 0.5, 1, and 2%) was added to all bags, which were stored at 5 and 25 °C for 5 days. Sensory evaluations were conducted with tofu stored at 5 °C. At 5 °C, with a 2% TDS, E. coli O157:H7, S. Typhimurium, L. monocytogenes, and B. cereus were reduced by 0.29, 0.36, 0.70, and 1.47 log CFU/g, respectively. None of the sensory characteristics of tofu treated with TDS were significantly different from those of the control. Consequently, this study shows the potential of TDS as an antimicrobial agent with a practical application in tofu to ensure food safety.

This study evaluated the antimicrobial activities [diffusion inhibition zone, minimum inhibitory concentration (MIC), and minimum bactericidal concentration], of heated ginseng extracts (ethanol and methanol). The extract yields, ginsenoside compositions, growth inhibitory effects against Bacillus cereus and Staphylococcus aureus and bacterial cell membrane potential changes, were also investigated. Methanol extracts of heated ginseng, showed higher antimicrobial activity than ethanol extracts. B. cereus was more easily inhibited than S. aureus. Ginseng heated at 100 °C for 2 and 16 h, showed maximum antimicrobial activity against B. cereus and S. aureus, respectively. In the growth inhibitory test, S. aureus and B. cereus were completely inhibited after 2 and 8 h culture at the MIC. The cell membrane potential decreased with increasing concentration of extract, indicating cell metabolism disruption. Ginsenosides Rg3, a potent antibacterial substance, which were absent in non-heated ginseng, were produced by heating ginseng at 100 °C for 4 and 8 h, respectively.

Shelf-life charts of beef according to bacterial contamination and storage temperature were developed via mathematical regressions of the growth curves of spoilage bacteria in beef. Additionally, bacterial contamination in retail beef specimens was investigated using culture-based bacteriological tests, PCR assays, and pyrosequencing analysis. Pathogenic bacteria were infrequently detected in the 100 retail beef specimens, but spoilage bacteria were found in all of the specimens. The populations of spoilage bacteria in retail beef specimens varied from 2.27 to 6.15 log CFU·g −1 . Pyrosequencing analysis of retail beef specimens suggested contamination from multiple sources, since both Lactobacillales and Pseudomonadales, which are prevalent in bovine intestine and feces and in bovine hides and beef-processing facilities, respectively, were detected. Growth of spoilage bacteria in beef at 5–25 °C was predicted via mathematical characterization of experimentally determined growth curves at 5, 10, 15, 20, and 25 °C using a modified-Gompertz function and subsequent nonlinear regressions of the growth characteristics, and then transformed to shelf-life charts according to the level of bacterial contamination and storage temperature. The bacterial contamination and bacteriological standards used to generate the shelf-life charts were 0, 1, 2, 3, 4, and 5 log CFU·g −1 and 5, 6, 7, and 8 log CFU·g −1 , respectively.

This study investigated the microbial contamination of commercial tofu from local supermarkets in Seoul, Korea. Growth modeling of Bacillus cereus isolated from spoiled tofu was used to determine the appropriate and temperature for safe storage of tofu. During the monitoring of 100 commercial tofu products, pathogenic bacteria (B. cereus, Staphylococcus aureus, Listeria monocytogenes, Salmonella spp., and enterohemorrhagic Escherichia coli O157:H7 [EHEC]) were not detected. Aerobic bacteria were isolated from 32 of 100 tofu samples because of different sterilization and packaging methods. To isolate the dominant microorganism involved in tofu putrefaction, tofu was intentionally spoiled by storage at 30 °C for 24 h. After spoilage, the most abundant colonies were harvested and confirmed as B. cereus by analyzing their 16 S ribosomal RNA (rRNA) sequences and fatty acid compositions. To investigate growth properties on tofu, isolated B. cereus was cultured and inoculated on tofu. The growth of B. cereus at different storage temperatures (15 °C, 20 °C, 25 °C, and 30 °C) was analyzed. As a result, the appropriate storage time of tofu stored at 5 °C, 10 °C, and 15 °C was determined to be 9.99, 4.17, and 2.08 days, respectively.

The outbreaks due to the low number of foodborne pathogens present in ready-to-eat products can be prevented by rapid and sensitive detection method. However, as a conventional detection method, it is impossible to monitor foodborne bacteria existing which is less than 50 cfu/25 g in a food. This study was designed to investigate the possibility of detecting 1 cfu in the short-term through filtration, DNA concentration, and qPCR. As a result of the filtration + DNA concentration method, the recovery concentrations of Escherichia coli O157:H7 and Salmonella Typhimurium was not significantly different from initial inoculation (>7 cfu/25 g). In iceberg lettuce and cabbage, this method was able to detect 7 and 7 cfu/25 g of E. coli and 68 and 5 cfu/25 g of S. Typhimurium. We demonstrated the potential of the filtration + DNA concentration method as a shorter time alternative to conventional enrichment-based rapid detection in vegetables.

Methods focused on conventional foodborne pathogen detection by selective media are cumbersome and require long time for culture enrichment. Several rapid tests have been developed for the detection of Escherichia coli O157:H7 in the food industry. However, the E. coli O157:H7 method takes very long and requires more than one day to achieve the detection threshold using PCR based enrichment in food. We reported a combination of filtration-based accelerated sample concentration methods to detect

This study investigated the antimicrobial activity of malic acid (MA), grapefruit seed extract (GSE), and combined (MA+GSE) treatment against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on fresh-cut lettuce. The antimicrobial effects of 1% MA and 0.5% GSE alone and in combination (1% MA+0.5% GSE) were tested on artificially inoculated lettuce during storage at 5°C for 14 days. The maximum reductions of E. coli O157:H7, S. Typhimurium, and L. monocytogenes were 4.96, 4.80, and 3.95 log CFU/g observed with MA+GSE during storage for 14 days, respectively. MA+GSE showed the greatest reduction against in E. coli O157:H7 and L. monocytogenes. These results indicate that the combined treatment was more effective than MA and GSE alone treatment. Therefore, it suggests that MA + GSE could be used as an effective intervention method for improving microbiological safety of fresh-cut lettuce.

It is difficult to detect a small amount of pathogens present in ready-to-eat foods without enriching it. Although enrichment is needed to increase the bacterial population, the time required for this impedes the rapid detection of pathogens. This study was designed to detect Escherichia coli O157:H7 and Salmonella Typhimurium more quickly and sensitively by concentrating bacteria and DNA. Short-term enrichment was used to increase bacterial number and to recovery injured bacteria. Filtration was used to concentrate pathogens and to lower the detection limit. DNA concentration was performed to improve sensitivity by reducing elution volume. Samples were analyzed using real-time PCR. The results showed filtration after enrichment for 2 h allowed the effective detection of E. coli O157:H7 and S. Typhimurium. S. Typhimurium was detected following enrichment for 1 h when DNA concentration was performed. After validation, enrichment for 3 h was shown to be required for detecting E. coli O157:H7 and S. Typhimurium. With DNA concentration, enrichment for 3 h was necessary for the complete detection of E. coli O157:H7, but that for 2 h was needed for S. Typhimurium. The results of this study indicate that this combined method is a rapid and efficient way of detecting pathogens.

Conventional PCR (cPCR) with 38 thermal cycles (cPCR38cycles) failed to amplify 3 copies of Escherichia coli O157:H7 DNA at the presence of 3.28×106 copies of Salmonella Typhimurium DNA, but emulsion PCR (ePCR) with 20 thermal cycles and a subsequent conventional PCR with 38 thermal cycles (ePCR20cycles-sPCR38cycles) amplified them. Partitioning individual E. coli O157:H7 DNA with emulsion droplet improved the specificity of PCR and let 3 copies of E. coli O157:H7 DNA to be amplified specifically at the presence of 3.28×106 copies of S. Typhimurium DNA. Application of ePCR improved the sensitivity of PCR-based pathogen detection and enabled the detection of 3 copies of E. coli O157:H7 DNA.

In this study, we examined the effects of an e-polylysine (PL) and chitosan (CH) coating on the quality of shrimp under refrigeration. Pacific white shrimp (Litopenaeus vannamei) were coated with PL, CH, or CH + PL and stored at 4 °C for 15 days. The quality of shrimp was measured by observing changes in microbiota, pH, total volatile basic nitrogen (TVB-N), and sensory characteristics. Among the coating films, the CH + PL coating most effectively inhibited the growth of mesophilic and psychrotrophic bacteria, Pseudomonas spp., and H2S-producing bacteria. This coating increased the shelf life of shrimp by decreasing the amount of mesophilic and psychrotrophic bacteria, with inhibition greater than three log cycles on the ninth day of storage. In addition, the CH and CH + PL coatings effectively suppressed the formation of TVB-N compared with that in the control by 43% and 30%, respectively. The pH of all treated samples increased slowly compared with that of the control, but no significant difference was observed. Sensory quality was similar to microbial and physicochemical properties, and the acceptability of all treated samples gradually decreased.

This study was conducted to compare the growth parameters of Listeria monocytogenes between beef isolates and Type strains in raw beef. Beef was artificially inoculated with 3 Log CFU/g levels and growth was measured during storage at various temperatures (5–25 °C) using conventional plating methods. The R2 value for lag time (λ) and specific growth rate (μ) were determined using modified-Gompertz model, which were greater than 0.98 at all storage temperature except at 5 °C. B f , A f , and RMSE showed acceptable ranges, showed that the models are suitable for the modeling the growth of L. monocytogenes. At all temperatures, the λ of L. monocytogenes beef isolates was shorter than that of the L. monocytogenes Type strains, and the μ of beef isolates was higher than that of Type strains. These results showed that growth pattern prediction of beef inoculated with L. monocytogenes beef isolates gives more actual results than with Type strains.

The impedimetric characteristics of an immunosensor depend on the electrical properties of an immunosensor substrate. The impedimetric characteristics of an immunosensor compared with adsorption of Listeria monocytogenes were investigated on an aluminum surface insulated with an electrically resistive aluminum oxide layer. Antibody for L. monocytogenes (anti-L. monocytogenes) was immobilized on an aluminum surface that was insulated with a native air-formed aluminum oxide layer. The resistance of impedance (R) value of an aluminum-based immunosensor decreased, especially at 104 to 106 Hz, where the effect of the reactance of impedance (X) was minimal when L. monocytogenes was adsorbed on the immunosensor surface. The R value of the immunosensor at 81 kHz decreased proportionally to the concentration of L. monocytogenes from 1.3 to 4.3 log CFU mL−1. The adsorption of L. monocytogenes produced local protrusions on the immunosensor surface, causing physicochemical changes in the ionic layer formed on the immunosensor surface by a sinusoidal electrical signal input, which might help electrical current to flow and cause the R value to decrease. Practical Application Impedimetric characterization of adsorption of Listeria monocytogenes on the surface of an aluminum-based immunosensor is crucially informative for development of a new rapid pathogen detection method.

This study investigated the antimicrobial activities of Oriental medicinal plant extracts against four Shigella species, i.e., Shigella sonnei, Shigella flexneri, Shigella boydii and Shigella dysenteriae. Twelve Oriental medicinal plants were extracted with 80% ethanol. When the Rhus javanica extract was used at 0.01% concentration, 98.09% of the S. sonnei cells were injured. And S. boydii showed significantly different percentages of injured cells at 0.01% and 0.5% of R. javanica extracts, and S. dysenteriae at 0.01%, 0.1% and 0.5% concentrations of the extracts (P 48 h). However, the T. chebula extract used at the same concentration did not completely inhibit the growth and caused an increased lag time corresponding to 227.0% and 174.4% for S. flexneri and S. dysenteriae, respectively. Practical Applications Shigellosis results in at least 600,000 deaths worldwide each year. And in the U.S.A., it is a major bacteria involved in food poisoning, reported in 10,000–20,000 patients (Centers for Disease Control and Prevention). In the present study, ethanol extracts of oriental medicinal plants were used as basic materials for controlling Shigella species, and there are potentials for medicinal plants, as a natural antimicrobial agent, to be used in the development of eco-friendly reduction technology on Shigella species.

Microbial community analysis was performed on Tarak, a traditional Korean fermented milk product, by 16S rDNA cloning and pyrosequencing to obtain basic data for the standardization and systematization of the Tarak manufacturing process. Microbial analysis of the prokaryotic community revealed a slight difference in microbial abundance between Bontarak (n) and Tarak (n+1), but Firmicute was dominant at the phylum level. At the genus level, the Lactobacillus and Leuconostoc genera constituted over 90% of the population in Bontarak, but Lactococcus was the dominant genus in Tarak. Bontarak and Tarak showed further differences at the species level. Leuconostoc citreum was the dominant species in Bontarak, constituting 40% of the population. In eukaryotic community analysis, all samples were composed of Ascomycota at the phylum level. At the genus level, Saccharomyces was dominant in Bontarak (85% of the population), while Issatchenkia was dominant in Tarak (95% of the population). At the species level, Saccharomyces cerevisiae was detected at a relative abundance in Bontarak (82%), and Pichia kudriavzevii was the dominant species in Tarak, with a relative abundance of 95%. Sensory evaluation indicated that Tarak had a better appearance and texture than Bontarak. As sweetness was not significantly different between the two samples just slightly higher in Tarak, this was likely due to a significant decrease in sourness in Tarak. These results suggest that the microbial community used affects the quality of Tarak produced. Thus, a stable microbial community must be maintained for the production of Tarak with consistent quality.

The objectives of the study were to determine the diversity of organic acid resistance as well as the toxin gene profiles of Bacillus cereus isolated from red pepper powder and to analyze the inhibition kinetics of unstressed type culture and resistant food isolates against organic acids. Among 68 B. cereus isolated from red pepper and processing environmental samples (n = 180), 1.4–16.7% of the cells could survive at 0.5% of acetic, malic and tartaric acid. Parameter α of the Weibull model for type strain were up to threefold lower than for resistant food isolate at 0.2% or lower concentration of organic acid treatment. All the B. cereus isolates were positive for three genes in the nonhemolytic enterotoxin complex (nheA, nheB and nheC), entFM and bceT genes. The ces gene-encoding emetic toxin was detected in nine (13.2%) of the 68 isolates tested. Practical Applications Bacillus cereus is an etiological agent of foodborne illness in Korea. The food products under risk for B. cereus food poisoning are pasteurized (dairy foods or cooked chilled foods) and dry foods. When B. cereus has been exposed to sublethal acid treatment conditions, adapted or resistant strains have developed. Acid resistance of the strain cause a food safety problem because it may result in enhanced protection for cells which are subsequently exposed to lethal heat or hydrogen peroxide stress. The rate of acid resistance and the kinetic parameters of wild type food isolates against organic acid treatment can be used to develop intervention strategies and in risk assessment to assure food safety. A diversity of toxin gene profiles which include diarrheal and emetic toxins also provide useful information in risk assessment of food poisoning caused by B. cereus.

This study determined the antimicrobial activities of acetic acid, citric acid and lactic acid against four Shigella species: S. sonnei, S. flexneri, S. boydii and S. dysenteriae. Minimal inhibitory concentrations of acetic acid and citric acid against Shigella were 200 and 300 ppm, respectively. But S. sonnei was 400 ppm. Lactic acid (0.5%) in tryptic soya broth inhibited the growth of all Shigella species. Citric acid weakly inhibited the growth of S. flexneri, but it strongly inhibited the growth of S. dysenteriae, resulting in a 5-log reduction. Acetic acid exhibited the weakest antimicrobial activity among the tested organic acids but produced the highest ratios of injured cells. When artificially inoculated lettuce was dipped in 1% organic acid solutions, the growth of S. flexneri, S. dysenteriae and S. boydii were reduced by 2 logs. And the growth was further reduced by lactic acid as the dipping time increased. The antimicrobial activities of organic acids against Shigella species differed. Acetic acid exhibited the greatest antimicrobial activity in the paper disk diffusion experiment, but lactic acid was the most effective antimicrobial agent against Shigella species artificially inoculated on lettuce. Practical Applications Shigellosis induced by Shigella species results in at least 600,000 deaths worldwide each year. And in the U.S.A., it is a major bacteria involved in food poisoning, reported in 10,000–20,000 patients. In the present study, organic acids were used as basic materials for controlling Shigella species, and there are potential for organic acids, which are natural antimicrobials, to be used in the development of eco-friendly reduction technology on Shigella species.

The aim of this study was to investigate the antimicrobial characteristics of citral against Salmonella Typhimurium and Staphylococcus aureus. Antimicrobial activities were determined according to the citral concentration and initial pH. The tested citral concentrations were 0-1,000 ppm in tryptic soy broth (TSB) and 0-5,000 ppm in Angelica keiskei juice (NokJeup). The initial pHs tested were 4-7. Antimicrobial activities increased as citral concentration increased. S. aureus was more susceptible than S. Typhimurium during culture in TSB. But S. aureus was less susceptible to pH changes. Citral caused about 1-2 log reduction of S. aureus and 2-5 log reduction of S. Typhimurium after 10 min exposure at different pHs. As the citral concentration in the Algelica keiskei juice increased, S. aureus was easily inactivated but S. Typhimurium was not inactivated.

The object of this study was to compare the performance of commercial enrichment media used for Shigella spp. A total of four enrichment media, Gram negative (GN) broth, Shigella broth (SB), selenite-F (SF) broth, and selenite cystine (SC) broth, were tested. When S. sonnei was inoculated into each enrichment broth at 10 cfu/mL of concentration, the highest growth was observed in Shigella broth. Morganella spp., which was not differentiated in selective agar of Shigella spp. thus can be counted as false positive, did not grow in Shigella broth in enrichment step. When S. sonnei was artificially inoculated into pork, it was mostly recovered through an enrichment process with GN broth and SF broth. However, in the case of beef, S. sonnei was mostly recovered with GN broth but largely failed with Shigella broth. Therefore, enrichment media for Shigella spp. should be selected by considering the food matrix in order to increase the chance of isolating it from foods.

To investigate the distribution of staphylococcal enterotoxin-like (SEl) genes in Staphylococcus aureus from food, a total of 154 S. aureus isolates from ready-to-eat (RTE) foods in Korea were analyzed by mutiplex PCR for the detection of the following 9 staphylococcal enterotoxin-like genes; sek, sel, sem, sen, seo, sep, seq, ser, and seu. Seventy-nine isolates (51.3%) were found to have at least one of SEl genes. The major SEl genes were sek, sem, sen, and seq. Other SEl genes found in the isolates were seo (21 isolates, 13.6%), seu (12 isolates, 7.8%), sep (8 isolates, 5.2%), sel (7 isolates, 4.5%), and ser (2 isolates, 1.3%). Most (95%) of the isolates with staphylococcal enterotoxin (SE) genes were also carried SEl genes. The genes seg, sei, sem, and sen were all detected in the same isolates. Ninety-seven % of isolates with seg+sei+sem+sen also contained seo or seu. Ninety-four % of isolates with sea+seh were found to coexist with sek+seq. The toxic shock syndrome toxin gene, tst-1, was found in all isolates with egc-2, including seg, sei, sem, sen, and seu. The coexistence of SE and SEl genes in S. aureus isolates from RTE foods can be explained by the mobile genetic elements. Because of the mobile genetic element, SE and SEl genes of S. aureus in foods may be transferable to nontoxigenic S. aureus and other food pathogens. Additional studies must be conducted to prevent spread of pathogenic genes such as enterotoxin gene.

In this study, three different selective media, modified cefoperazone charcoal deoxycholate agar (mCCDA), Karmali agar, and Preston agar, were compared for isolating Campylobacter jejuni from artificially contaminated ground beef and fresh-cut vegetables that have different levels of background microflora. Concurrently, an automated enzyme-linked immunosorbent assay method for detecting Campylobacter spp. (VIDAS Campylobacter) was evaluated by comparing it with the culture methods. Food samples inoculated with C. jejuni were enriched in Bolton broth at 42°C for 44 h and then streaked onto the three different selective media, followed by incubation under microaerobic conditions at 42°C for 48 h. The enriched Bolton broth (1 ml) was used in the VIDAS Campylobacter assay. No statistical differences in sensitivities were observed between the three selective media for ground beef and fresh-cut vegetables, but the selectivity of Preston agar was better (P0.05) than those of mCCDA and Karmali agar. The VIDAS Campylobacter assay showed a recovery rate similar (P0.05) to those of all of the medium combinations in ground beef. However, more positive samples (P0.05) were detected with the VIDAS Campylobacter than with the selective agars, except for the combinations of mCCDA plus Preston agar or mCCDA plus Karmali agar plus Preston agar in fresh-cut vegetables.

The aim of this study was to determine microbiological contamination of fresh-red pepper and packaged-red pepper powder commercially available in South Korea. Thirty-seven fresh-red peppers were collected from 5 farms and 31 packaged-red pepper powders were purchased from retail markets in South Korea. Foodborne pathogens (Escherichia coli, Salmonella spp., Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus), total viable counts, Enterobacteriaceae, coliforms, yeast and mold, and Aspergillus flavus were determined. Detection percentage of contamination of Bacillus cereus in fresh-red pepper was 8.1%, which was lower than the 39% of detection rate in packaged-red pepper powder. The contamination level of Bacillus cereus was 1～3 log CFU/g in packaged-red pepper powder. Escherichia coli was detected in 5.4% of fresh-red pepper samples and was not detected in packaged-red pepper powder. Enterobacteriaceae and coliforms were detected in both of fresh-red pepper and packaged-red pepper powders. Foodborne pathogens, except Bacillus cereus and Escherichia coli, were not detected.

Performance comparison tests were carried out on Staphylococcus aureus selective media recommended by food safety agencies or approved by international standardization bodies. The performance of mannitol salt agar (MSA), Baird parker agar, Vogel johnson agar, RAPID’ Staph, and CHROMagar staph aureus are compared. Four out of the 5 media showed 100% sensitivity, with MSA showing 96.5%. MSA also showed only 66.6% specificity, while 4 out of 5 media showed 100% specificity. In recovery tests S. aureus was more easily recovered from instant cooked rice than fish fillet. The tested media did not have a significant difference on recovery activity.

We investigated biofilm formation in various media, growth in low pH, and the hemolytic activity of 14 strains of Cronobacter spp. (Enterobacter sakazakii) isolated from a variety of foods including powdered infant formula (n=75), infant cereal (n=100), honey (n=30), and other infant foods (n=100) in Korea. The Cronobacter spp. adhered and formed biofilms on polyethylene, and a greater extent of biofilm was observed in nutrient-rich media. No clear difference in biofilm-forming ability was noted among the media constituents and the pattern of biofilm formation was strain-dependent. Seven strains out of 14 strains (50%) grew at pH 4.1, indicating that the acid resistance of these Cronobacter spp. isolated in Korea was relatively low. Hemolytic activity was not observed in any of the strains. This study provides basic information for the physiological and biochemical characteristics of Cronobacter spp. isolated from a variety of infant foods in Korea.

Smoke flavors based on the thermal decomposition of wood have been applied to a variety of food products as an alternative for traditional smoking. Despite its increasing use, the available genotoxicity data on wood smoke flavors (WSF) are still controversial. Thus, potential genotoxic effects of WSF in four short-term in vitro genotoxicity assays were investigated, which included the Ames assay, chromosomal aberration assay, micronucleus test and the alkaline comet assay. WSF did not cause any mutation in the Ames assay using five tester strains at six concentrations of 0.16, 0.31, 0.63, 1.25, 2.5 and 5 µl/plate. To assess clastogenic effect, the in vitro chromosomal aberration assay was performed using Chinese hamster lung cells. No statistically significant increase in the number of metaphases with structural aberrations was observed at the concentrations of 1.25, 2.5, and 5 µl/ml. The in vitro comet assay and micronucleus test results obtained on L5178Y cells also revealed that WSF has no genotoxicity potential, although there was a marginal increase in micronuclei frequencies and DNA damage in the respective micronucleus and comet assays. Taken together, based on the results obtained from these four in vitro studies, it is concluded that WSF is not a mutagenic agent in bacterial cells and causes no chromosomal and DNA damage in mammalian cells in vitro.

Enterobacter sakazakii is a member of the Enterobacteriaceae and has physiological characteristics similar to those of Escherichia coli O157:H7 (negative D-sorbitol fermentation, positive glucose and lactose fermentation, and negative H2S production). The purpose of this study was to evaluate the efficiency of enrichment broths recommended for E. sakazakii enrichment. Growth and recovery ratio of E. sakazakii were compared in media including modified tryptone soya broth supplemented with novobiocin (mTSB + N), modified Escherichia coli broth with novobiocin (mEC + N), Enterobacteriaceae enrichment (EE) broth, buffered peptone water supplemented with vancomycin, cefixime and cefsulodin (BPW + VCC), and rehydrated infant milk formula (IMF) with or without antibiotics. The EE broth that was recommended by the FDA showed the most effective enrichment for growth of E. sakazakii, followed by rehydrated IMF. Other media such as mTSB + N, mEC + N and BPW + VCC did not support growth of E. sakazakii compared to EE and rehydrated IMF. They were not considered suitable for the enrichment of E. sakazakii. When evaluated for recovery of E. sakazakii among other Enterobacteriaceae, strains of E. sakazakii were all recovered in EE broth after 6 and 18 h; thus, the EE broth was considered the most effective enrichment broth in this study. Rehydrated IMF also showed higher recovery ratios (3/4, 4/4) after 6 and 18 h than the other recommended enrichment broths.

The ability of tricyclic antidepressants (TCAs) to inhibit phenytoin p-hydroxylation was evaluated in vitro by incubation studies of human liver microsomes and cDNA-expressed cytochrome p450s (p450s). The TCAs tested were amitriptyline, imipramine, nortriptyline, and desipramine. Amitriptyline and imipramine strongly and competitively inhibited phenytoin p-hydroxylation in microsomal incubations (estimated K(i) values of 5.2 and 15.5 micro M, respectively). In contrast, nortriptyline and desipramine produced only weak inhibition. In the incubation study using cDNA-expressed P450s, both CYP2C9 and CYP2C19 catalyzed phenytoin p-hydroxylation, whereas TCAs inhibited only the CYP2C19 pathway. All of the TCAs tested inhibited CYP2D6-catalyzed dextromethorphan-O-demethylation competitively, with estimated K(i) values of 31.0, 28.6, 7.9, and 12.5 micro M, respectively. The tertiary amine TCAs, amitriptyline and imipramine, also inhibited CYP2C19-catalyzed S-mephenytoin 4'-hydroxylation (estimated K(i) of 37.7 and 56.8 micro M, respectively). The secondary amine TCAs, nortriptyline and desipramine, however, showed minimal inhibition of CYP2C19 (estimated IC(50) of 600 and 685 micro M, respectively). None of the TCAs tested produced remarkable inhibition of any other p450 isoforms. These results suggest that TCAs inhibit both CYP2D6 and CYP2C19 and that the interaction between TCAs and phenytoin involves inhibition of CYP2C19-catalyzed phenytoin p-hydroxylation.

This study was conducted to investigate the effects of aerosolized malic acid and ultraviolet light (UV-C) for inhibiting the growth of foodborne pathogens, Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes, on fresh-cut lettuce. The antimicrobial effects of aerosolized 2% malic acid and UV-C, alone or in combination, were tested. Ten grams of lettuce were inoculated with three strains of each pathogens and treated with aerosolized malic acid for 20 min and UV-C for 30 min. After each treatment, lettuce was stored at 5 °C for 15 days. Sequential treatment (aerosolized malic acid after UV-C) was the most effective for reducing E. coli O157:H7, S. Typhimurium, and L. monocytogenes and resulted in reduction of 2.89, 1.38, and 2.95 log10 CFU/g after treatment and 3.15, 3.00, and 4.58 log10 CFU/g after 15 days, respectively. These results suggested that combined treatment with aerosolized malic acid after UV-C can be a useful intervention method for improving the microbial safety of fresh-cut produce. Practical applications The experiment suggested new method on the inactivation of foodborne pathogens on lettuce. Treatment with aerosolized 2% malic acid after UV-C was the most effective method to inhibit the growth of foodborne pathogens in this study. This method will be helpful for fresh-cut lettuce producers to manage the safety and quality of lettuce.

Clostridium difficile exists within the intestines of animals and in meat products. Enrichment of C. difficile in an appropriate medium is necessary for the detection of C. difficile in meat products. Non-selective media (brain heart infusion medium [TBHI] and cooked meat medium containing sodium taurocholate [TCM]) and selective media (cycloserine-cefoxitin-fructose medium [TCCFB] and C. difficile moxalactam-norfloxacin medium containing antibiotics and sodium taurocholate [TCDMN]) can be used to enrich C. difficile. This study aimed to evaluate non-selective and selective enrichment media for the recovery of C. difficile from beef specimens. The efficiency of the enrichment media was investigated on the basis of the recovery frequency of C. difficile from beef specimens inoculated with C. difficile. The beef specimens were inherently contaminated with bacteria (around 10(4)CFUg(-1)), and further inoculated with C. difficile (around 10(0)CFUg(-1)). The antibiotics in TCCFB and TCDMN adversely affected C. difficile growth. The bacteria inherent to these specimens exhibited resistance to antibiotics and grew during the enrichment of C. difficile-inoculated chopped beef in TCCFB and TCDMN, which hindered the recovery of C. difficile. The frequency of recovery of C. difficile from beef specimens in TCM was higher than that from any other enrichment medium.

Minimum time and detection limit required to detect Escherchia coli O157:H7 in fresh-cut cabbage examined by real-time polymerase chain reaction (PCR). The detection limit of E. coli O157:H7 in modified E. coli (mEC) broth by real-time PCR was 1.53 log CFU mL-1. A growth curve was produced by counting the cell number of E. coli O157:H7 in mEC broth during cultivation at 37°C. The growth curve was well fitted by the equation, y=0.0148x2+0.4244x+1.0472 (R2=0.9945), where y is the cell growth concentration (log CFU mL-1) and x is time (h). Assuming that E. coli O157:H7 is present in produce at low concentrations (1 cell in 25 g sample), detection by real-time PCR would be possible only when the cell number increased over the detection limit. The growth curve indicated that culture in mEC broth required at least 6 h and 20 min of enrichment to exceed the detection limit; therefore, the total time required for detection time was less than nine hours, which included the DNA isolation time (30 min) and the real-time PCR operating time (2 h). This method could be used for presumptive screening of E. coli O157:H7 in fresh-cut produce, which demands a rapid detection time for safety management.

Aerosolized sanitizer was investigated as a potential alternative to aqueous and gaseous sanitizers for produce. Peroxyacetic acid was aerosolized (5.42 to 11.42 microm particle diameter) by a commercially available nebulizer into a model cabinet. Iceberg lettuce leaves were inoculated with three strains each of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium and then treated with aerosolized peroxyacetic acid for 10, 30, or 60 min in a model aerosol cabinet at room temperature (22 +/- 2 degrees C). After treatment, surviving healthy and injured bacterial cells were enumerated on appropriate selective agars or using the overlay agar method. Inoculated iceberg lettuce leaves exposed to aerosolized peroxyacetic acid for 10 min exhibited a 0.8-log reduction in E. coli O157:H7, a 0.3-log reduction in Salmonella Typhimurium, and a 2.5-log reduction in L. monocytogenes when compared with the control. After 30 min of treatment, the three pathogens were reduced by 2.2, 3.3, and 2.7 log, and after 60 min, the reductions were 3.4, 4.5, and 3.8 log, respectively. Aerosolization may be a new and convenient method for sanitizing produce for storage or shipping.

Rhus verniciflua Stokes (RVS), one of traditional medicinal plants in Asia, was found to have pharmacological activities such as antioxidative and antiapoptotic effects, raising the possibility for the development of a novel class of anti-cancer drugs. Thus, potential genotoxic effects of RVS in three short-term mutagenicity assays were investigated, which included the Ames assay, in vitro Chromosomal aberration test, and the in vivo Micronucleus assay. In Ames test, the addition of RVS water extracts at doses from 313 up to 5000 mg/plate induced an increase more than 2-fold over vehicle control in the number of revertant colonies in TA98 and TA1537 strains for detecting the frame-shift mutagens. The similar increase in reversion frequency was observed after the addition of RVS ethanol extracts. To assess clastogenic effect, in vitro chromosomal aberration test and in vivo micronucleus assay were performed using Chinese hamster lung cells and male ICR mice, respectively. Both water and ethanol extracts from RVS induced significant increases in the number of metaphases with structural aberrations mostly at concentrations showing the cell survival less than 60% as assessed by in vitro CA test. Also, there was a weak but statistically significant increase in number of micronucleated polychromatic erythrocytes (MNPCEs) in mice treated with water extract at 2000 mg/kg while ethanol extracts of RVS at doses of up to 2000 mg/kg did not induce any statistically significant changes in the incidence of MNPCEs. Therefore, our results lead to conclusion that RVS acts as a genotoxic material based on the available in vitro and in vivo results.

This study was conducted to investigate the effect of steam treatment on the reduction of Salmonella enterica serovar Enteritidis on the surface of raw almonds. Two cultivars, 'Nonpareil' and 'Mission', were studied. Salmonella Enteritidis was inoculated on the surface of raw almonds, which were then treated with steam (93 degrees C +/- 1 degrees C) for 5, 15, 25, 35, 45, 55, and 65 s. After steam treatment, samples were plated on xylose lysine desoxycholate (XLD) and overlay (OV) XLD as a selective and nonselective agar for Salmonella, respectively, to investigate the extent of sublethal injury in Salmonella. Steam treatment of raw almonds effectively reduced Salmonella Enteritidis, and the effect was pronounced with increasing treatment time. After 65 s of steam treatment, reductions in Salmonella Enteritidis populations were 5.7 log and 5.8 log for 'Nonpareil' and 4.0 log and 4.1 log for 'Mission' when enumerated on XLD and OV XLD, respectively. There was no significant difference in population estimates determined with XLD and OV XLD over time (P > 0.05). The effect of the steam treatment was significantly different between two almond cultivars. Salmonella inoculated onto 'Mission' was more resistant to the steam treatment than that on 'Nonpareil', indicating that varietal differences must be considered in the application of steam for the disinfection of raw almonds. The present investigation revealed the potential usefulness of steam treatments for the control of pathogens in raw almonds.