115 results on '"Jee Hoon Ryu"'
Search Results
2. Inactivation of Salmonella Newport on blueberries by treatment with chlorine dioxide gas and its effect on blueberry qualities
- Author
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Eungyeong Kim, Jee-Hoon Ryu, and Hoikyung Kim
- Subjects
Biochemistry ,Food Science - Published
- 2023
3. Antimicrobial effects of essential oil vapors on Bacillus cereus on nutrient agar and iceberg lettuce
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Hyewon Yang, Woorim Yeom, Jiwon Oh, Hoikyung Kim, Larry R. Beuchat, and Jee-Hoon Ryu
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Biochemistry ,Food Science - Published
- 2023
4. Effects of temperature, pH and sodium chloride on antimicrobial activity of magnesium oxide nanoparticles against E. coli O157:H7
- Author
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Joon Young Yoon, Woorim Yeom, Hoikyung Kim, Larry R. Beuchat, and Jee-Hoon Ryu
- Subjects
Anti-Infective Agents ,Colony Count, Microbial ,Food Microbiology ,Temperature ,Nanoparticles ,General Medicine ,Hydrogen-Ion Concentration ,Sodium Chloride ,Escherichia coli O157 ,Magnesium Oxide ,Applied Microbiology and Biotechnology ,Biotechnology - Abstract
Aim This study was done to determine the effects of temperature, pH and sodium chloride (NaCl) on antimicrobial activity of magnesium oxide (MgO) nanoparticles (NPs) against E. coli O157:H7. Methods and results Culture conditions were established by varying the pH (5.0, 7.2 and 9.0), NaCl concentration (0.5, 2.0, 3.5 and 5.0%, w/v), and incubation temperatures (4, 12, 22 and 37°C). At each condition, the antimicrobial activities of MgO-NPs (0, 1, 2 and 4 mg/ml) against E. coli O157:H7 were measured. Four-way analysis of variance indicated interactions among all factors had a significant effect (p ≤ 0.05) on the antimicrobial activity of MgO-NPs. The concentration of MgO-NPs necessary to cause a 5-log reduction of E. coli O157:H7 under the most inhibitory conditions (37°C, pH 9.0, and 5.0% NaCl) was 0.50 mg/ml of MgO-NPs. Conclusion The antimicrobial activity of the MgO-NPs increased significantly (p ≤ 0.05) with increased temperature, pH and NaCl concentration in TSB. Significance and impact of the study The influence of intrinsic and extrinsic factors on antimicrobial activity of MgO-NPs we found will contribute to the development of microbial decontamination strategies using MgO in the food industry.
- Published
- 2022
5. Antimicrobial activities of plant essential oil vapours against Acidovorax citrulli and Xanthomonas campestris on Cucurbitaceae, Brassicaceae and Solanaceae seeds
- Author
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Min Young Chung, Hoikyung Kim, Larry R. Beuchat, and Jee Hoon Ryu
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Population ,Xanthomonas campestris ,Applied Microbiology and Biotechnology ,law.invention ,Comamonadaceae ,Anti-Infective Agents ,law ,medicine ,Oils, Volatile ,Plant Oils ,education ,Essential oil ,Solanaceae ,education.field_of_study ,biology ,Chemistry ,food and beverages ,General Medicine ,biology.organism_classification ,medicine.disease ,Antimicrobial ,Horticulture ,Cucurbitaceae ,Germination ,Brassicaceae ,Seeds ,Vapours ,Biotechnology - Abstract
Aim This study was done to develop a seed decontamination treatment for organic seeds against plant pathogens (Acidovorax citrulli and Xanthomonas campestris) using essential oil (EO) vapours without affecting the seeds' germination rate. Methods and Results By using a diffusion assay and determining minimum inhibitory and lethal concentrations, we screened two EO vapours which were most inhibitory to A. citrulli (cinnamon bark and garlic EO vapours) and X. campestris (onion and garlic EO vapours). After 48 h of exposure to EO vapours at 25°C and 43% or 85% relative humidity (RH), no significant decrease (p > 0.05) in germination rates was observed compared with those of control seeds. It was observed that EO vapour treatment at 25°C and 43% or 85% RH for 48 h caused significant population reductions (p ≤ 0.05) (ca. 0.3–2.6 log colony forming unit/g) compared to those of untreated seeds. Conclusion Applications of EO vapours showed significant (p ≤ 0.05) antimicrobial effects against A. citrulli and X. campestris on both laboratory mediums and plant seeds without decreasing the germination rate of seeds. Significance and Impact of the Study This study provides useful information for the development of natural seed sterilization treatments using EO vapours.
- Published
- 2021
6. Antimicrobial activities of a combination of chlorine dioxide gas and heat against Xanthomonas campestris and Salmonella enterica on cabbage, chili pepper, and radish seeds
- Author
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Xi Li, Woorim Yeom, Hoikyung Kim, Larry R. Beuchat, and Jee-Hoon Ryu
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Food Science ,Biotechnology - Published
- 2022
7. Synergistic antimicrobial activities of essential oil vapours against Penicillium corylophilum on a laboratory medium and beef jerky
- Author
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Hyegeun Ji, Larry R. Beuchat, Hoikyung Kim, and Jee Hoon Ryu
- Subjects
Antifungal ,Antifungal Agents ,medicine.drug_class ,Acyclic Monoterpenes ,Penicillium corylophilum ,Food Contamination ,Microbial Sensitivity Tests ,Mentha spicata ,Microbiology ,law.invention ,Thymus Plant ,03 medical and health sciences ,chemistry.chemical_compound ,Linalool ,law ,Origanum ,Pepper ,Oils, Volatile ,medicine ,Food science ,Cymbopogon ,Thymol ,Essential oil ,030304 developmental biology ,0303 health sciences ,030306 microbiology ,Chemistry ,Penicillium ,food and beverages ,Drug Synergism ,General Medicine ,medicine.disease ,Antimicrobial ,Meat Products ,Food Microbiology ,Monoterpenes ,Vapours ,Food Science - Abstract
This study was done to determine the antifungal activities of essential oil (EO) vapours of 97 plants against Penicillium corylophilum and to test combinations of EO vapours for synergistic antifungal effects. Among 97 commercially available EOs extracted from plant parts, garlic, cinnamon bark, may chang (mountain pepper), citronella, thyme thymol, oregano, spearmint, and thyme linalool EO vapours exhibited relatively strong antifungal activities. The minimal inhibitory concentrations of these EO vapours were 0.0390–0.6250 μL/mL. A combination of cinnamon bark, citronella, and may chang EO vapours, as well as a combination of cinnamon bark and citronella EO vapours, showed synergistic inhibitory activities to P. corylophilum on a laboratory medium. A combination of cinnamon bark, citronella, and may chang EO vapours had synergistic activity in inhibiting growth of P. corylophilium on beef jerky. Observations reported here provide basic information valuable when developing strategies to inhibit the growth of P. corylophilum and possibly other moderately xerophilic molds on intermediate-moisture foods.
- Published
- 2019
8. Antimicrobial activity of ClO
- Author
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Jihwan, Lim, Eungyung, Kim, Yeseul, Shin, Jee-Hoon, Ryu, and Hoikyung, Kim
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Microbial Viability ,Food Storage ,Salmonella enteritidis ,Food Preservation ,Food Preservatives ,Nuts ,Oxides ,Gases ,Chlorine Compounds ,Prunus dulcis - Abstract
Nuts, including almonds, are occasionally contaminated with Salmonella spp. In this study, we used chlorine dioxide (ClO
- Published
- 2021
9. Inhibition of Staphylococcus aureus on a laboratory medium and black peppercorns by individual and combinations of essential oil vapors
- Author
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Jiwon Oh, Larry R. Beuchat, Jee Hoon Ryu, and Hoikyung Kim
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Piper ,education.field_of_study ,biology ,Chemistry ,Population ,food and beverages ,Caraway seed ,medicine.disease_cause ,biology.organism_classification ,law.invention ,chemistry.chemical_compound ,Minimum inhibitory concentration ,Staphylococcus aureus ,law ,medicine ,Cinnamon Bark ,Food science ,education ,Thymol ,Essential oil ,Food Science ,Biotechnology - Abstract
The objectives of this study were to screen essential oil (EO) vapors for inhibitory activities against Staphylococcus aureus on a laboratory medium and to validate their antibacterial effects on dried black peppercorns (Piper nigrum). Among 84 commercially available EOs, using a vapor disc assay, vapors from caraway seed, carrot seed, cinnamon bark, citronella, kanuka, lemongrass, may chang, oregano, and thyme thymol EOs were found to be more inhibitory to S. aureus. The minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) of nine EO vapors from these plant materials were measured on a laboratory medium. Citronella, lemongrass, and oregano EO vapors had the lowest MIC and MLC values, at 0.0781 and 0.1563 μL/mL, respectively. Using a checkerboard assay, partial synergism in inhibitory activity of a combination of citronella and lemongrass EO vapors was observed (fractional inhibitory concentration index = 0.6250). When tested against S. aureus on black peppercorns, citronella, lemongrass, and oregano EO vapors, both individually and in combination, showed a significant antibacterial effect (P ≤ 0.05). Notably, a combination of citronella and lemongrass EO vapors (1:4 vol ratio) showed significant synergistic activity, reducing the S. aureus population by ca. ≥ 1.3–1.8 log CFU/g more than treatment with single EOs (P ≤ 0.05). The results of this study provide important basic information for developing technologies to control S. aureus on the surfaces of dried foods using EO vapors.
- Published
- 2022
10. Produce Handling and Processing Practices
- Author
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Larry R. Beuchat and Jee-Hoon Ryu
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United States ,Medicine ,Infectious and parasitic diseases ,RC109-216 - Abstract
In the past decade, outbreaks of human illness associated with the consumption of raw vegetables and fruits (or unpasteurized products produced from them) have increased in the United States. Changes in agronomic, harvesting, distribution, processing, and consumption patterns and practices have undoubtedly contributed to this increase. Pathogens such as Listeria monocytogenes, Clostridium botulinum, and Bacillus cereus are naturally present in some soil, and their presence on fresh produce is not rare. Salmonella, Escherichia coli O157:H7, Campylobacter jejuni, Vibrio cholerae, parasites, and viruses are more likely to contaminate fresh produce through vehicles such as raw or improperly composted manure, irrigation water containing untreated sewage, or contaminated wash water. Contact with mammals, reptiles, fowl, insects, and unpasteurized products of animal origin offers another avenue through which pathogens can access produce. Surfaces, including human hands, which come in contact with whole or cut produce represent potential points of contamination throughout the total system of growing, harvesting, packing, processing, shipping, and preparing produce for consumption. Treatment of produce with chlorinated water reduces populations of pathogenic and other microorganisms on fresh produce but cannot eliminate them. Reduction of risk for human illness associated with raw produce can be better achieved through controlling points of potential contamination in the field; during harvesting; during processing or distribution; or in retail markets, food-service facilities, or the home.
- Published
- 1997
- Full Text
- View/download PDF
11. Antimicrobial activities of organic acid vapors against Acidovorax citrulli, Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes on Cucurbitaceae seeds
- Author
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Hye Jung Shin, Jee Hoon Ryu, Larry R. Beuchat, and Hoikyung Kim
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Formates ,Formic acid ,Germination ,medicine.disease_cause ,Escherichia coli O157 ,Microbiology ,Comamonadaceae ,03 medical and health sciences ,Acetic acid ,chemistry.chemical_compound ,food ,Listeria monocytogenes ,medicine ,Food science ,030304 developmental biology ,Acetic Acid ,chemistry.chemical_classification ,0303 health sciences ,biology ,030306 microbiology ,food and beverages ,Salmonella enterica ,biology.organism_classification ,Antimicrobial ,food.food ,Anti-Bacterial Agents ,Cucurbitaceae ,chemistry ,Honeydew melon ,Seeds ,Propionates ,Acids ,Food Science ,Organic acid - Abstract
This study investigated the antimicrobial activities of organic acid vapors against a phytopathogen (Acidovorax citrulli) and foodborne pathogens (Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes) on the surface of Cucurbitaceae seeds. Germination percentages of cucumber, honeydew melon and watermelon seeds treated with acetic and propionic acid vapors (100 mg/L) at 50 °C and 43% or 85% relative humidity (RH) for up to 2 h did not significantly (P > 0.05) decrease. Treatment with formic acid significantly (P ≤ 0.05) decreased the germination percentage. The antimicrobial activities of acetic and propionic acid vapors (100 mg/L; 50 °C; 43% or 85% RH) were determined. A. citrulli was inactivated within 1 h on cucumber and watermelon seeds, regardless of type of organic acid or RH. The phytopathogen was reduced to levels below the detection limit (−0.5 log CFU/g) for enrichment on honeydew melon seeds treated with acetic acid vapor. S. enterica and L. monocytogenes were inactivated within 2 h at 85% RH on honeydew melon and watermelon seeds treated with acetic acid and propionic acid vapors. E. coli O157: H7 was inactivated by treatment with acetic acid vapor at 85% RH. This study provides useful information for developing a method to decontaminate Curcurbitaceae seeds using organic acid vapors as lethal agents.
- Published
- 2020
12. Antimicrobial activities of gaseous essential oils against Listeria monocytogenes on a laboratory medium and radish sprouts
- Author
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Gyeongmin Lee, Larry R. Beuchat, Jee Hoon Ryu, Hoikyung Kim, and Yoonbin Kim
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0301 basic medicine ,Cinnamomum zeylanicum ,Acyclic Monoterpenes ,030106 microbiology ,Microbial Sensitivity Tests ,Biology ,medicine.disease_cause ,Microbiology ,Raphanus ,Foodborne Diseases ,Thymus Plant ,03 medical and health sciences ,chemistry.chemical_compound ,Minimum inhibitory concentration ,0404 agricultural biotechnology ,Linalool ,Listeria monocytogenes ,Origanum ,Botany ,Oils, Volatile ,medicine ,Food microbiology ,Food science ,Thymol ,04 agricultural and veterinary sciences ,General Medicine ,Antimicrobial ,040401 food science ,Anti-Bacterial Agents ,chemistry ,visual_art ,Food Microbiology ,Monoterpenes ,visual_art.visual_art_medium ,Bark ,Gases ,Plant Preparations ,Nutrient agar ,Food Science - Abstract
The aim of this study was to evaluate the antimicrobial activities of gaseous essential oils (EO gases) against Listeria monocytogenes on the surfaces of a laboratory medium and radish sprouts. We determined the minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) values of EO gases from eight EOs extracted from basil leaves, carrot seed, cinnamon bark, cinnamon leaves, clove flower buds, oregano leaves, thyme flowers (linalool), and thyme leaves (thymol) against L. monocytogenes on a nutrient agar supplemented with 1% glucose and 0.025% bromocresol purple (NGBA). Oregano, thyme thymol, and cinnamon bark EO gases showed the strongest antilisterial activities (MIC and MLC, 78.1 μL/L). We also investigated the inhibitory and lethal activities of these gases against L. monocytogenes on the surface of radish sprouts. The number of L. monocytogenes after exposure to EO gases at ≥ 156 μL/L was significantly (P ≤ 0.05) lower than that of untreated L. monocytogenes. For example, the initial number of L. monocytogenes on the surface of radish sprouts (ca. 6.3 log CFU/g) decreased by 1.4 log CFU/g within 24 h at 30 °C and 43% relative humidity (RH) without EO gas treatment, whereas the number of L. monocytogenes after exposure to oregano, thyme thymol, and cinnamon bark EO gases at 156 μL/L decreased by 2.1, 2.1, and 1.8 log CFU/g, respectively, after 24 h. Although EO gases exerted greater lethal activities at higher concentrations (312 and 625 μL/L), L. monocytogenes on the surface of radish sprouts was not completely inactivated. The number of L. monocytogenes on sprouts treated with oregano, thyme thymol, and cinnamon bark EO gases at 625 μL/L decreased by 2.7–3.0 log CFU/g after 24 h at 30 °C and 43% RH. Results indicate that EO gases that showed antilisterial activities on a laboratory medium also exhibited reduced lethal activity on the surface of radish sprouts. These findings will be useful when developing strategies to inactivate L. monocytogenes and possibly other foodborne pathogens on sprouts and perhaps other foods using EO gases.
- Published
- 2018
13. Inactivation of Escherichia coli O157:H7 on radish and cabbage seeds by combined treatments with gaseous chlorine dioxide and heat at high relative humidity
- Author
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Larry R. Beuchat, Woorim Yeom, Hoikyung Kim, and Jee Hoon Ryu
- Subjects
Hot Temperature ,Sodium chlorite ,Germination ,Hydrochloric acid ,Brassica ,Escherichia coli O157 ,medicine.disease_cause ,Microbiology ,Raphanus ,03 medical and health sciences ,chemistry.chemical_compound ,medicine ,Relative humidity ,Food science ,Escherichia coli ,Decontamination ,030304 developmental biology ,Detection limit ,0303 health sciences ,Chlorine dioxide ,Microbial Viability ,030306 microbiology ,food and beverages ,Humidity ,Oxides ,Human decontamination ,chemistry ,Seeds ,Chlorine ,Chlorine Compounds ,Disinfectants ,Food Science - Abstract
This study was done to develop a method to inactivate Escherichia coli O157:H7 on radish and cabbage seeds using simultaneous treatments with gaseous chlorine dioxide (ClO2) and heat at high relative humidity (RH) without decreasing seeds’ viability. Gaseous ClO2 was spontaneously vaporized from a solution containing hydrochloric acid (HCl, 1 N) and sodium chlorite (NaClO2, 100,000 ppm). Using a sealed container (1.8 L), an equation (y = 5687×, R2 = 0.9948) based on the amount of gaseous ClO2 generated from HCl–NaClO2 solution at 60 °C and 85% RH was developed. When radish or cabbage seeds were exposed to gaseous ClO2 at concentrations up to 3,000 ppm for 120 min, germination rates did not significantly decrease (P > 0.05). When seeds inoculated with E. coli O157:H7 were treated with 2,000 or 3,000 ppm of gaseous ClO2 in an atmosphere with 85% RH at 60 °C, populations (6.8–6.9 log CFU/g) on both types of seeds were decreased to below the detection limit for enrichment (−0.5 log CFU/g) within 90 min. This study provides useful information for developing a decontamination method to control E. coli O157:H7 and perhaps other foodborne pathogens on plant seeds by simultaneous treatment with gaseous ClO2 and heat at high RH.
- Published
- 2021
14. Antimicrobial activity of ClO2 gas against Salmonella Enteritidis on almonds
- Author
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Yeseul Shin, Eungyung Kim, Jee Hoon Ryu, Hoikyung Kim, and Jihwan Lim
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Detection limit ,0303 health sciences ,Salmonella ,education.field_of_study ,Chlorine dioxide ,030306 microbiology ,Inoculation ,Chemistry ,Salmonella enteritidis ,Population ,food and beverages ,medicine.disease_cause ,Antimicrobial ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,Volume (thermodynamics) ,medicine ,Food science ,education ,030304 developmental biology ,Food Science - Abstract
Nuts, including almonds, are occasionally contaminated with Salmonella spp. In this study, we used chlorine dioxide (ClO2) gas to inactivate S. enterica subsp. Enterica serovar Enteritidis on almonds. Almonds inoculated with a single strain of S. Enteritidis (8.95 log cfu/mL) were exposed to ClO2 gas generated from 1.0 or 1.5 mL ClO2 solution in a sealed container at 50 or 60 °C (43% relative humidity) for up to 10 h. The concentration of ClO2 gas peaked at 354–510 and 750–786 ppm within 0.5 h upon deposition of 1.0 and 1.5 mL of aqueous ClO2, respectively, and gradually decreased thereafter. Population of S. Enteritidis on almonds treated at 50 °C decreased to 1.70–2.32 log cfu/sample within 1 h of exposure to ClO2 gas and decreased to below the detection limit (1.7 log cfu/sample) at all ClO2 concentrations after 8 h. At 60 °C, the microbial population fell below the detection limit within 1 h, regardless of the volume of ClO2 solution supplied. Microbial survival on almonds treated with ClO2 gas and stored at 12 or 25 °C was observed for up to 8 weeks and the organism was not recovered from the almonds treated for 10 h and stored at 12 °C for 2–8 weeks. The lightness (L value) and redness (a value) of almonds treated for 10 h were not changed by ClO2 gas treatment, but yellowness (b value) increased. Results showed that Salmonella on almonds was successfully inactivated by ClO2 gas treatment and the microbial survival did not occur during storage.
- Published
- 2021
15. Synergistic antimicrobial activities of plant essential oils against Listeria monocytogenes in organic tomato juice
- Author
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Jee Hoon Ryu, Hoikyung Kim, Jiwon Kim, and Larry R. Beuchat
- Subjects
chemistry.chemical_compound ,chemistry ,Listeria monocytogenes ,medicine ,Cinnamon Bark ,Food service ,Food science ,Diffusion assay ,Antimicrobial ,medicine.disease_cause ,Thymol ,Food Science ,Biotechnology - Abstract
The objective of this study was to identify combinations of plant essential oils (EOs) that have synergistic antilisterial effects in raw organic tomato juice. Among the EOs approved for addition to organic foods in the Republic of Korea, twenty-four EOs were screened for antilisterial activity using a well diffusion assay. Six EOs (cinnamon bark, lemon, lemongrass, oregano, peppermint, and thyme thymol) showed relatively strong inhibitory activities (diameter of zone of inhibition ≥ 35.0 mm) against Listeria monocytogenes. The minimal inhibitory concentrations (MICs) and minimal lethal concentrations (MLCs) of these EOs against L. monocytogenes in a laboratory medium were determined. Oregano and thyme thymol EOs had the lowest MIC (0.3125 μL/mL), and cinnamon bark, oregano, and thyme thymol EOs had the lowest MLC (0.6250 μL/mL). The synergistic antilisterial activities of combinations of EOs in a laboratory medium were determined using a modified checkerboard assay. Combinations of cinnamon bark and lemongrass EOs, cinnamon bark and thyme thymol EOs, and lemongrass and thyme thymol EOs showed synergistic antilisterial activities (fractional inhibitory concentration index = 0.5). A combination of cinnamon bark and thyme thymol EOs was tested for synergistic antilisterial activity in tomato juice incubated at 10 °C and 25 °C for up to 48 h. The number of L. monocytogenes in juice treated with combined EOs at a total concentration of 0.3125 μL/mL decreased significantly (P ≤ 0.05) compared to numbers in juice treated with 0.3125 μL/mL of either cinnamon bark EO or thyme thymol EO alone. These observations show the potential for using combinations of EOs for controlling L. monocytogenes in juice released from cut or bruised raw organic tomatoes intended for consumption in food service or home settings.
- Published
- 2021
16. Halloysite Nanocapsules Containing Thyme Essential Oil: Preparation, Characterization, and Application in Packaging Materials
- Author
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Gyeong Min Lee, Su Il Park, Si Hoon Jang, Jee Hoon Ryu, No Hyung Park, and So Ri Jang
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Thermogravimetric analysis ,Materials science ,Scanning electron microscope ,Nanotechnology ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Halloysite ,Controlled release ,Nanocapsules ,0104 chemical sciences ,Nanomaterials ,Surface coating ,Chemical engineering ,engineering ,Fourier transform infrared spectroscopy ,0210 nano-technology ,Food Science - Abstract
Halloysite nanotubes (HNTs), which are natural nanomaterials, have a hollow tubular structure with about 15 nm inner and 50 nm outer diameters. Because of their tubular shape, HNTs loaded with various materials have been investigated as functional nanocapsules. In this study, thyme essential oil (TO) was encapsulated successfully in HNTs using vacuum pulling methods, followed by end-capping or a layer-by-layer surface coating process for complete encapsulation. Nanocapsules loaded with TO were mixed with flexographic ink and coated on a paper for applications as food packaging materials. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the nanocapsules and to confirm the TO loading of the nanocapsules. Fourier transform infrared spectroscopy and thermogravimetric analyses analysis were used to complement the structural information. In addition, the controlled release of TO from the nanocapsules showed sustained release properties over a period of many days. The results reveal that the release properties of TO in these nanocapsules could be controlled by surface modifications such as end-capping and/or surface coating of bare nanocapsules. The packaging paper with TO-loaded HNT capsules was effective in eliminating against Escherichia coli during the first 5 d and showed strong antibacterial activity for about 10 d.
- Published
- 2017
17. Teriyaki sauce with carvacrol or thymol effectively controls Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and indigenous flora in marinated beef and marinade
- Author
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Hyeree Moon, Min Suk Rhee, Soon Han Kim, Jee Hoon Ryu, Younghoon Kim, and Nam Hee Kim
- Subjects
Salmonella typhimurium ,0301 basic medicine ,Salmonella ,Food Handling ,030106 microbiology ,Population ,Color ,Biology ,Escherichia coli O157 ,medicine.disease_cause ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,Listeria monocytogenes ,Lipid oxidation ,medicine ,Animals ,Carvacrol ,Food science ,education ,Escherichia coli ,Thymol ,education.field_of_study ,Hydrogen-Ion Concentration ,Anti-Bacterial Agents ,Red Meat ,chemistry ,Food Microbiology ,Monoterpenes ,Cymenes ,Cattle ,Antibacterial activity ,Food Science - Abstract
An effective bactericidal cold-marinating method for beef products is described, exploiting the synergism between soy sauce and natural compounds (carvacrol, CV or thymol, TM) to reduce microbiological risks. Beef slices inoculated with Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium (3.1-3.5logCFU/g) were marinated in a teriyaki sauce with or without CV and TM (0.3 and 0.5%). After 1, 3, and 7days at 4°C, indigenous microflora population, color, lipid oxidation, marinade uptake, and pH of marinated beef and leftover marinade samples were examined. Teriyaki sauce alone did not reduce or inhibit any of the target pathogens or indigenous bacteria, while 0.5% CV- or TM-containing teriyaki sauce inactivated all inocula without recovery within 7days (p0.05). The pathogens relocated from the beef into the leftover marinade (3.0-3.4logCFU/mL) were also completely inactivated. The treatment inhibited growth of indigenous aerobic bacteria (p0.05) and inactivated coliform bacteria. Physicochemical parameters were not significantly affected (p0.05).
- Published
- 2017
18. Inactivation ofBacillus cereusSpores on Red Chili Peppers Using a Combined Treatment of Aqueous Chlorine Dioxide and Hot-Air Drying
- Author
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Songyi Kim, Huyong Lee, Jee Hoon Ryu, and Hoikyung Kim
- Subjects
0301 basic medicine ,Chlorine dioxide ,Aqueous solution ,biology ,Chemistry ,fungi ,030106 microbiology ,Bacillus cereus ,food and beverages ,biology.organism_classification ,Spore ,03 medical and health sciences ,chemistry.chemical_compound ,Cereus ,Sodium hypochlorite ,Botany ,Pepper ,Relative humidity ,Food science ,Food Science - Abstract
The effect of a combined treatment using aqueous chlorine dioxide (ClO2 ) and hot-air drying to inactivate Bacillus cereus spores on red chili peppers was evaluated. Ten washed and dried pepper samples, each comprising half of a single pepper (Capsicum annuum L.), were inoculated with B. cereus spore suspension. The inoculated samples were washed with sodium hypochlorite (NaOCl; 50, 100, or 200 μg/mL) or ClO2 (50, 100, or 200 μg/mL) solution for 1 min and then air-dried (25 ± 1 °C, 47 ± 1% relative humidity), which was followed by drying with hot air at 55 °C for up to 48 h. The spore populations on the samples were enumerated and their aw and chromaticity values were measured. The spore numbers immediately after treatment with NaOCl and ClO2 were not significantly different. A more rapid reduction in spore numbers was observed in the samples treated with ClO2 than those treated with NaOCl during drying. A combined treatment of ClO2 and hot-air drying significantly reduced the spore populations to below the detection limit (1.7 log CFU/sample). B. cereus spores on chili peppers were successfully inactivated by washing with ClO2 solution followed by hot-air drying whereas the pepper color was maintained.
- Published
- 2017
19. Sanitizing radish seeds by simultaneous treatments with gaseous chlorine dioxide, high relative humidity, and mild heat
- Author
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Moonhak Choi, Jihyun Bang, Yoonsook Kim, Larry R. Beuchat, Hyeri Son, Jee Hoon Ryu, and Hoikyung Kim
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inorganic chemicals ,0301 basic medicine ,Hot Temperature ,Aerobic bacteria ,030106 microbiology ,Sodium chlorite ,Population ,Colony Count, Microbial ,Food Contamination ,Germination ,Escherichia coli O157 ,complex mixtures ,Microbiology ,Raphanus ,03 medical and health sciences ,chemistry.chemical_compound ,Hand sanitizer ,Botany ,Relative humidity ,Food science ,education ,Decontamination ,Chlorine dioxide ,education.field_of_study ,Aqueous solution ,food and beverages ,Humidity ,Oxides ,Sulfuric acid ,General Medicine ,respiratory tract diseases ,030104 developmental biology ,chemistry ,Seeds ,Food Microbiology ,Gases ,Chlorine ,Chlorine Compounds ,Disinfectants ,Food Science - Abstract
Sanitizing radish seeds intended for edible sprout production was achieved by applying simultaneous treatments with gaseous chlorine dioxide (ClO2), high relative humidity (RH, 100%), and mild heat (55°C). Gaseous ClO2 was produced from aqueous ClO2 (0.66ml) by mixing sulfuric acid (5% w/v) with sodium chlorite (10 mg/mL) in a sealed container (1.8L). Greater amounts of gaseous ClO2 were measured at 23% RH (144ppm after 6h) than at 100% RH (66ppm after 6h); however, the lethal activity of gaseous ClO2 against naturally occurring mesophilic aerobic bacteria (MAB) on radish seeds was significantly enhanced at 100% RH. For example, when exposed to gaseous ClO2 at 23% RH, the number of MAB on radish seeds decreased from 3.7logCFU/g to 2.6logCFU/g after 6h. However, when exposed to gaseous ClO2 at 100% RH for 6h, the MAB population decreased to 0.7logCFU/g after 6h. Gaseous ClO2 was produced in higher amounts at 55°C than at 25°C, but decreased more rapidly over time at 55°C than at 25°C. The lethal activity of gaseous ClO2 against MAB on radish seeds was greater at 55°C than at 25°C. When radish seeds were treated with gaseous ClO2 (peak concentration: 195ppm) at 100% RH and 55°C, MAB were reduced to populations below the detectable level ( 0.05) decreased after treatment for 6h. The information reported here will be useful when developing decontamination strategies for producing microbiologically safe radish seed sprouts.
- Published
- 2016
20. Survival and growth ofListeria monocytogenesandStaphylococcus aureuson conventional and low‐sodium bacon—A short communication
- Author
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Yeseul Shin, Eungyung Kim, Jee Hoon Ryu, Hoikyung Kim, Huyong Lee, and Larry R. Beuchat
- Subjects
business.industry ,Sodium ,chemistry.chemical_element ,medicine.disease_cause ,Food safety ,Microbiology ,Listeria monocytogenes ,chemistry ,Staphylococcus aureus ,medicine ,Parasitology ,Food science ,business ,Food Science ,Low sodium - Published
- 2019
21. Viability of sprout seeds as affected by treatment with aqueous chlorine dioxide and dry heat, and reduction of Escherichia coli O157:H7 and Salmonella enterica on pak choi seeds by sequential treatment with chlorine dioxide, drying, and dry heat
- Author
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Larry R. Beuchat, Hoikyung Kim, Jee Hoon Ryu, and Seonyeong Choi
- Subjects
0301 basic medicine ,Chlorine dioxide ,Aqueous solution ,biology ,Inoculation ,Chemistry ,030106 microbiology ,food and beverages ,biology.organism_classification ,medicine.disease_cause ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,Horticulture ,030104 developmental biology ,Salmonella enterica ,Germination ,Botany ,medicine ,Relative humidity ,Tatsoi ,Escherichia coli ,Food Science - Abstract
Germination rates of 11 types of sprout seeds (alfalfa, broccoli, kohlrabi, kyona, mustard, pak choi, red kohlrabi, red radish, red young radish, tatsoi, and violet radish) treated with ClO 2 (200 μg/ml, 5 min) or dry-heat (80 °C/23% relative humidity [RH], 24 h) were determined. Pak choi, red radish, and tatsoi seeds showed highest tolerance to both ClO 2 and dry-heat treatments. Next, pak choi seeds were inoculated with Escherichia coli O157:H7 (5.4 log CFU/g) or Salmonella enterica (4.8 log CFU/g) and sequentially treated with ClO 2 (200 μg/ml, 5 min), drying (45 °C/23% RH, 24 h), and dry heat (80 °C/23% RH, 48 h). E. coli O157:H7 was inactivated, but S. enterica was not eliminated (>3.8 log CFU/g reduction). Pak choi seeds inoculated with the pathogens were treated with ClO 2 , drying, and dry heat and subsequently sprouted for 5 days. When seeds were not completely decontaminated, initial populations of E. coli O157:H7 and S. enterica on seeds ( 5.3 and > 8.4 log CFU/g of sprouts, respectively. This study shows that sequential treatments of pak choi seeds with ClO 2 , drying, and dry heat are effective in reducing large numbers of E. coli O157:H7 and S. enterica without loss of seed viability.
- Published
- 2016
22. Development of an experimental apparatus and protocol for determining antimicrobial activities of gaseous plant essential oils
- Author
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Larry R. Beuchat, Hyun Sun Seo, Hoikyung Kim, and Jee Hoon Ryu
- Subjects
Food industry ,Food Handling ,Acyclic Monoterpenes ,Microbial Sensitivity Tests ,Escherichia coli O157 ,Microbiology ,Thymus Plant ,chemistry.chemical_compound ,Minimum inhibitory concentration ,Anti-Infective Agents ,Origanum ,Oils, Volatile ,Plant Oils ,Food microbiology ,Thymol ,Chromatography ,biology ,business.industry ,Food Packaging ,Mentha piperita ,General Medicine ,biology.organism_classification ,Antimicrobial ,Food packaging ,chemistry ,Food Microbiology ,Monoterpenes ,business ,Concentration gradient ,Food Science - Abstract
There is a growing interest in the use of naturally-occurring antimicrobial agents such as plant essential oils (EOs) to inhibit the growth of hazardous and spoilage microorganisms in foods. Gaseous EOs (EO gases) have many potential applications in the food industry, including use as antimicrobial agents in food packaging materials and sanitizing agents for foods and food-contact surfaces, and in food processing environments. Despite the potentially beneficial applications of EO gases, there is no standard method to evaluate their antimicrobial activities. Thus, the present study was aimed at developing an experimental apparatus and protocol to determine the minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) of EO gases against microorganisms. A sealed experimental apparatus was constructed for simultaneous evaluation of antimicrobial activities of EO gases at different concentrations without creating concentration gradients. A differential medium was then evaluated in which a color change allowed for the determination of growth of glucose-fermenting microorganisms. Lastly, an experimental protocol for the assessment of MIC and MLC values of EO gases was developed, and these values were determined for 31 EO gases against Escherichia coli O157:H7 as a model bacterium. Results showed that cinnamon bark EO gas had the lowest MIC (0.0391 μl/ml), followed by thyme-thymol EO gas (0.0781 μl/ml), oregano EO gas (0.3125 μl/ml), peppermint EO gas (0.6250 μl/ml), and thyme-linalool EO gas (0.6250 μl/ml). The order of the MLC values of the EO gases against the E. coli O157:H7 was thyme-thymol (0.0781 μl/ml)
- Published
- 2015
23. Application of yuba films for preserving beef patties
- Author
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Woojeong Kim, Yookyung Kim, and Jee Hoon Ryu
- Subjects
0106 biological sciences ,Chemistry ,04 agricultural and veterinary sciences ,Grapefruit seed extract ,Shelf life ,040401 food science ,01 natural sciences ,Antioxidant capacity ,0404 agricultural biotechnology ,Lipid oxidation ,010608 biotechnology ,Water barrier ,Food science ,Food Science - Abstract
This study focused on yuba films coated with active agents to improve microbiological and oxidative stability and the feasibility of preserving beef patties. Yuba films (YC) coated with oregano essential oil (YO), grapefruit seed extract (YG), and their mixture (YOG) were characterized and applied to beef patties. YO (2.56 × 10 − 10 g m/Pa·sec· m 2 ) displayed exceptional water barrier properties compared to YC (4.27 × 10 − 10 g m/Pa·sec· m 2 ) . All coated yuba films showed increased antioxidant capacity, particularly YG. In disc diffusion, all coated yuba films (inhibition zones ≥ 20.0 mm) were strongly effective against L. monocytogenes, whereas YO (27.17 mm) and YOG (29.00 mm) were effective against E. coli O157:H7. In the application to beef patties, YG beef patties (1.69 MDA mg/kg) showed the highest oxidative stability as a result of lipid oxidation inhibition (YC 1.88 MDA mg/kg). Furthermore, YG beef patties maintained the highest quality of meat color, which was dark purplish-red, during storage. While E. coli O157:H7 in beef patties was significantly inhibited by YO and YOG, the growth of L. monocytogenes in beef patties was impeded by all coated yuba films throughout the storage period. Overall, YOG can be potentially used to increase microbiological safety and extend the shelf life of beef patties.
- Published
- 2020
24. Antimicrobial activity of gaseous chlorine dioxide against Aspergillus flavus on green coffee beans
- Author
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Jee Hoon Ryu, Huyong Lee, and Hoikyung Kim
- Subjects
Population ,Colony Count, Microbial ,Coffea ,Aspergillus flavus ,Shelf life ,medicine.disease_cause ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,Food Preservation ,Mold ,medicine ,Relative humidity ,Food science ,education ,030304 developmental biology ,Detection limit ,0303 health sciences ,Chlorine dioxide ,education.field_of_study ,biology ,030306 microbiology ,Oxides ,biology.organism_classification ,Antimicrobial ,chemistry ,Seeds ,Chlorine ,Chlorine Compounds ,Food Science - Abstract
The aim of this study was to use chlorine dioxide (ClO2) gas to inactivate Aspergillus flavus on green coffee beans. Green coffee beans inoculated with A. flavus were exposed to ClO2 gas generated from 0.75, 1, 1.25, or 1.5 mL of ClO2 solution in a sealed container at 25 or 50 °C (100% relative humidity [RH]) for up to 10 h. Numbers of A. flavus on beans treated at 25 °C decreased by 1.1–2.2 log cfu/bean within 1 h of exposure to ClO2 and decreased to below the detection limit (≤1.0 log cfu/bean) at all ClO2 concentrations after 10 h. At 50 °C, the microbial population reached the detection limit within 0.5 h regardless of the ClO2 solution concentration. Beans exposed to gas for 10 h at 25 °C were stored for 14 days under conditions of 43, 75, or 100% RH and 4, 12, or 25 °C. At 4 °C, visible mold growth was not established regardless of RH. After 12 days, mold was observed only at 25 °C. At 100% RH, beans stored under the same conditions without ClO2 gas treatment showed mold formation at 13 and 4 days at 12 and 25 °C, respectively.
- Published
- 2020
25. Synergistic activities of gaseous oregano and thyme thymol essential oils against Listeria monocytogenes on surfaces of a laboratory medium and radish sprouts
- Author
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Hoikyung Kim, Yurim Cho, Jee Hoon Ryu, and Larry R. Beuchat
- Subjects
Cinnamomum zeylanicum ,Microbial Sensitivity Tests ,medicine.disease_cause ,Microbiology ,Raphanus ,Thymus Plant ,03 medical and health sciences ,chemistry.chemical_compound ,Listeria monocytogenes ,Origanum ,Oils, Volatile ,medicine ,Plant Oils ,Food science ,Thymol ,030304 developmental biology ,0303 health sciences ,030306 microbiology ,Drug Synergism ,Antimicrobial ,Anti-Bacterial Agents ,Culture Media ,chemistry ,Cinnamon Bark ,Gases ,Bromocresol purple ,Nutrient agar ,Food Science - Abstract
We investigated combinations of gaseous essential oils (EO gases) for their synergistic inhibitory activities against Listeria monocytogenes on a laboratory medium and radish sprouts. The minimum inhibitory concentrations and minimum lethal concentrations of oregano, thyme thymol, and cinnamon bark EO gases against L. monocytogenes were 0.0781 μL/mL on nutrient agar supplemented with glucose and bromocresol purple (NGBA). A checkerboard assay showed that combinations of oregano and thyme thymol EO gases and of oregano and cinnamon bark EO gases exert the strongest synergistic antilisterial activity (fractional inhibitory concentration index [FICI] = 0.3750). A combination of thyme thymol and cinnamon bark EO gases also had a synergistic effect (FICI = 0.5000) on L. monocytogenes on NGBA. Combinations of oregano and thyme thymol EO gases were tested for synergistic antimicrobial activity against L. monocytogenes on radish sprouts. A combination of these gases, each at 0.313 μL/mL, caused a significant (P ≤0.05) reduction in the number of L. monocytogenes on radish sprouts compared with reductions caused by treatment with oregano or thyme thymol EO gas alone at the same concentration. Our findings provide information that will be useful when developing antimicrobial applications using EO gases to control L. monocytogenes in the food industry.
- Published
- 2020
26. Inactivation of Salmonella Typhimurium on red chili peppers by treatment with gaseous chlorine dioxide followed by drying
- Author
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Huyong Lee, Hoikyung Kim, Jee Hoon Ryu, and Larry R. Beuchat
- Subjects
0301 basic medicine ,Salmonella typhimurium ,Salmonella ,Aerobic bacteria ,030106 microbiology ,Colony Count, Microbial ,Color ,medicine.disease_cause ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,0404 agricultural biotechnology ,medicine ,Relative humidity ,Food science ,Desiccation ,Water content ,Detection limit ,Chlorine dioxide ,Microbial Viability ,Chemistry ,Inoculation ,food and beverages ,Oxides ,04 agricultural and veterinary sciences ,Contamination ,040401 food science ,Food Microbiology ,Gases ,Capsicum ,Chlorine Compounds ,Food Science - Abstract
Chili pepper (Capsicum annuum L.) powder and other powdered spices containing chili peppers are occasionally contaminated with foodborne pathogens. We applied chlorine dioxide (ClO2) gas treatment to chili peppers prior to drying to inactivate Salmonella Typhimurium. Chili peppers inoculated with S. Typhimurium were exposed to ClO2 gas generated from 0.77 mL of aqueous ClO2 for 6 h at 25 °C and 100% relative humidity, followed by air drying at 55 °C for up to 24 h. Populations of S. Typhimurium and total aerobic bacteria (TAB) on peppers, chromaticity values, and moisture content were determined after various treatment times. S. Typhimurium (ca. 5.6 log cfu/g) was reduced to 1 cfu/10.8 g) after treatment for 4 h. The pathogen was not detected after treatment with ClO2 gas for 6 h. S. Typhimurium did not decrease significantly (P > 0.05) on peppers exposed to air at 25 °C for 6 h, but rapidly decreased to 1.6 log cfu/g after subsequent drying for 6 h at 55 °C. The initial number of TAB (ca. 6.5 log cfu/g) decreased to 1.4 log cfu/g after treatment with ClO2 gas for 0.5 h and was less than the detection limit (0.7 log cfu/g) after 2 h. TAB counts were not reduced by treating peppers with air for 6 h, but decreased to
- Published
- 2018
27. Inhibition of Listeria monocytogenes using biofilms of non-pathogenic soil bacteria (Streptomyces spp.) on stainless steel under desiccated condition
- Author
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Jee Hoon Ryu, Hoikyung Kim, Larry R. Beuchat, and Yoonbin Kim
- Subjects
Food Handling ,Population ,Colony Count, Microbial ,medicine.disease_cause ,Microbiology ,Streptomyces ,03 medical and health sciences ,Listeria monocytogenes ,Antibiosis ,Republic of Korea ,medicine ,Food science ,Desiccation ,education ,Soil Microbiology ,030304 developmental biology ,0303 health sciences ,education.field_of_study ,biology ,Strain (chemistry) ,030306 microbiology ,Chemistry ,Inoculation ,Biofilm ,biology.organism_classification ,Stainless Steel ,Biofilms ,Food Microbiology ,Streptomyces purpureus ,Food Science - Abstract
Of the 1648 microbial isolates from 133 soil samples collected from 30 diverse locations in the Republic of Korea, two isolates exhibited strong antilisterial activity and ability to grow to high populations (>8.0 log CFU/ml) in Bennett's broth. Isolates were identified as Streptomyces lactacystinicus (strain Samnamu 5–15) and Streptomyces purpureus (strain Chamnamu-sup 4–15). Both isolates formed biofilms on the surface of stainless steel coupons (SSCs) immersed in Bennett's broth within 24 h at 25 °C. Cells retained antilisterial activity after biofilm formation and showed significantly (P ≤ 0.05) enhanced resistance against dry conditions (43% relative humidity [RH]) compared to the cells not in biofilm. An initial population (ca. 3.2 log CFU/cm2) of Listeria monocytogenes inoculated on SSCs lacking Streptomyces biofilm decreased to 1.4 log CFU/cm2 within 48 h at 25 °C and 43% RH. In contrast, L. monocytogenes (3.3 log CFU/cm2) inoculated on SSCs containing Streptomyces biofilm decreased to populations below the theoretical detection limit (0.5 log CFU/cm2) within 24 h. The results indicate that biofilms formed by the Streptomyces spp. inhibitory to L. monocytogenes showed enhanced resistance to desiccation condition (43% RH) and effectively inhibited the growth of L. monocytogenes on the surfaces of SSCs. Antilisterial biofilms developed in this study may be applicable on desiccated environmental surfaces in food related environments such as food storage, handling, and processing facilities to enhance the microbiological safety of foods.
- Published
- 2017
28. Inhibition of Escherichia coli O157:H7 on stainless steel using Pseudomonas veronii biofilms
- Author
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Young-Gyun Kim, Larry R. Beuchat, Hoikyung Kim, and Jee Hoon Ryu
- Subjects
0301 basic medicine ,Food Handling ,030106 microbiology ,Population ,Colony Count, Microbial ,Pseudomonas veronii ,medicine.disease_cause ,Escherichia coli O157 ,Applied Microbiology and Biotechnology ,Tryptic soy broth ,Foodborne Diseases ,03 medical and health sciences ,chemistry.chemical_compound ,Pseudomonas ,Antibiosis ,medicine ,Food science ,Desiccation ,education ,Escherichia coli ,education.field_of_study ,biology ,Strain (chemistry) ,Biofilm ,Lettuce ,Antimicrobial ,biology.organism_classification ,Stainless Steel ,chemistry ,Biofilms ,Food Microbiology - Abstract
We produced a Pseudomonas veronii biofilm on the surface of a stainless steel that is inhibitory to Escherichia coli O157:H7. Pseudomonas veronii strain KACC 81051BP, isolated from lettuce, readily formed biofilm on the surface of stainless steel coupons (SSCs) immersed in tryptic soy broth at 25°C. Cells showed significantly (P ≤ 0·05) enhanced tolerance to desiccation stress (43% relative humidity (RH)) and retained antimicrobial activity against E. coli O157:H7. The number of E. coli O157:H7 (control; 4·1 ± 0·1 log CFU per coupon) on sterile SSCs decreased to 2·7 ± 0·2 log CFU per coupon after exposure to 43% RH at 25°C for 48 h, while the population of E. coli O157:H7 (4·1 ± 0·0 log CFU per coupon) on SSCs containing P. veronii biofilm decreased to below the theoretical detection limit (1·5 log CFU per coupon) within 24 h. The antimicrobial biofilm produced on stainless steel may have application in preventing cross-contamination by E. coli O157:H7 on other abiotic surfaces in food-contact environments. Significance and impact of the study The presence of Escherichia coli O157:H7 on environmental surfaces of food manufacturing, transportation and storage facilities is a significant food safety concern because it can result in cross-contamination of food products. In this study, we developed a Pseudomonas veronii biofilm on the surface of a stainless steel that inhibits the growth of E. coli O157:H7. Since P. veronii in biofilm resists desiccation, it provides persistent antimicrobial activity. Information presented here provides novel and practical insights to developing biological strategies to inactivate E. coli O157:H7 on diverse surfaces in food processing and handling environments.
- Published
- 2017
29. Fate of mesophilic aerobic bacteria and Salmonella enterica on the surface of eggs as affected by chicken feces, storage temperature, and relative humidity
- Author
-
Yoonsook Kim, Hoikyung Kim, Seonyeong Choi, Jee Hoon Ryu, Sunhyung Park, Byeong Sam Kim, and Larry R. Beuchat
- Subjects
Aerobic bacteria ,Eggs ,Microorganism ,Population ,Colony Count, Microbial ,Food Contamination ,Microbiology ,Egg Shell ,Feces ,Animals ,Food science ,Eggshell ,education ,education.field_of_study ,biology ,Inoculation ,Salmonella enterica ,Humidity ,biology.organism_classification ,Bacteria, Aerobic ,Cold Temperature ,Food Storage ,Consumer Product Safety ,Chickens ,Food Science ,Mesophile - Abstract
We compared the microbiological quality of chicken eggshells obtained from a traditional wholesale market and a modern supermarket. We also determined the survival and growth characteristics of naturally occurring mesophilic aerobic bacteria (MAB) and artificially inoculated Salmonella enterica on eggshells under various environmental conditions (presence of chicken feces, temperature [4, 12, or 25 °C], and relative humidity [RH; 43 or 85%]). The populations of MAB, coliforms, and molds and yeasts on eggshells purchased from a traditional wholesale market were significantly (P ≤ 0.05) higher than those from a modern supermarket. In the second study, when we stored uninoculated eggs under various storage conditions, the population of MAB on eggshells (4.7-4.9 log CFU/egg) remained constant for 21 days, regardless of storage conditions. However, when eggshells were inoculated with S. enterica and stored under the same conditions, populations of the pathogen decreased significantly (P ≤ 0.05) under all tested conditions. Survival of S. enterica increased significantly (P ≤ 0.05) in the presence of feces, at low temperatures, and at low RH. These observations will be of value when predicting the behavior of microorganisms on eggshells and selecting storage conditions that reduce the populations of S. enterica on eggshells during distribution.
- Published
- 2015
30. Efficacy of gaseous chlorine dioxide in inactivating Bacillus cereus spores attached to and in a biofilm on stainless steel
- Author
-
Jihyun Bang, Hyun Sun Seo, Hyegyeong Nam, Larry R. Beuchat, Hoikyung Kim, and Jee Hoon Ryu
- Subjects
inorganic chemicals ,Sodium chlorite ,Colony Count, Microbial ,Bacillus cereus ,Microbiology ,chemistry.chemical_compound ,Spores, Bacterial ,Chlorine dioxide ,Microbial Viability ,Aqueous solution ,biology ,fungi ,Biofilm ,Oxides ,Sulfuric acid ,General Medicine ,Stainless Steel ,biology.organism_classification ,Spore ,chemistry ,Cereus ,Biofilms ,Gases ,Chlorine Compounds ,Disinfectants ,Food Science ,Nuclear chemistry - Abstract
We evaluated the lethal activity of gaseous chlorine dioxide (ClO2) against Bacillus cereus spores attached to and in biofilm formed on a stainless steel surface. Aqueous ClO2 was prepared by mixing sulfuric acid (5% w/v) with sodium chlorite (10mg/mL), and gaseous ClO2 was produced by vaporization of aqueous ClO2 in an air-tight container. The concentration of gaseous ClO2 in the air within the container increased rapidly at first but gradually decreased over time. The lethality of gaseous ClO2 against B. cereus spores attached to stainless steel coupons (SSCs) and in biofilm formed by the pathogen on SSCs was determined. The B. cereus spores attached to SSCs (5.3±0.1logCFU/coupon) were completely inactivated within 1h at 25°C when treated with gaseous ClO2 (peak concentration: 115.3±5.0 parts per million [ppm]). The total number of vegetative cells and spores in biofilm formed by B. cereus on SSCs was 5.9±0.3logCFU/coupon; the spore count was 5.3±0.1logCFU/coupon. The vegetative cells and spores in biofilm were completely inactivated within 6h (peak concentration: 115.3±5.0ppm). Results show that B. cereus spores in biofilms are more resistant to gaseous ClO2 than are attached spores not in biofilms. Gaseous ClO2 was, nevertheless, very effective in killing B. cereus spores in biofilm on the surface of stainless steel. Results show promise for application of gaseous ClO2 to enhance the microbiological safety of foods that may come in contact with stainless steel and possibly other hard surfaces on which B. cereus biofilms have formed.
- Published
- 2014
31. Heat Tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici Inoculated into Galactooligosaccharide
- Author
-
Hoikyung Kim, Moonkak Choi, Jee Hoon Ryu, Jihyun Bang, Haeseok Jeong, Sangseob Lee, and Yoonbin Kim
- Subjects
0301 basic medicine ,Thermotolerance ,Salmonella ,Hot Temperature ,Water activity ,Food Handling ,030106 microbiology ,Population ,Colony Count, Microbial ,medicine.disease_cause ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,0404 agricultural biotechnology ,Cronobacter sakazakii ,medicine ,Food science ,education ,D-value ,Pediococcus acidilactici ,education.field_of_study ,biology ,Galactooligosaccharide ,food and beverages ,04 agricultural and veterinary sciences ,biology.organism_classification ,040401 food science ,chemistry ,Food Microbiology ,Z-value ,Food Science - Abstract
Food-grade galactooligosaccharide (GOS) with low water activity (aw of ca. 0.7) is used as an ingredient in various foods. We evaluated heat tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici at temperatures (70 to 85°C) used during the saturation process of GOS by comparing decimal reduction time (D-values) and thermal resistance constants (z-values). To determine the D- and z-values, GOS containing Salmonella (5.1 to 5.8 log CFU/g) or C. sakazakii (5.3 to 5.9 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 40, 25, or 15 s, respectively, and GOS containing P. acidilactici (6.1 to 6.5 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 150, 75, or 40 s, respectively. The D-values were calculated using a linear model for heating time versus microbial population for each bacterium. When the D-values for Salmonella, C. sakazakii, and P. acidilactici in GOS were compared, the thermal resistance of all bacteria decreased as the temperature increased. Among the three bacteria, P. acidilactici had higher D-values than did Salmonella and C. sakazakii. The z-values of Salmonella, C. sakazakii, and P. acidilactici were 30.10, 33.18, and 13.04°C, respectively. Overall order of thermal resistance was P. acidilactici > Salmonella ≈ C. sakazakii. These results will be useful for selecting appropriate heat treatment conditions for the decontamination of pathogenic microorganisms during GOS manufacturing.
- Published
- 2017
32. Halloysite Nanocapsules Containing Thyme Essential Oil: Preparation, Characterization, and Application in Packaging Materials
- Author
-
Si-Hoon, Jang, So-Ri, Jang, Gyeong-Min, Lee, Jee-Hoon, Ryu, Su-Il, Park, and No-Hyung, Park
- Subjects
Thymus Plant ,Microscopy, Electron, Transmission ,Nanocapsules ,Plant Extracts ,Spectroscopy, Fourier Transform Infrared ,Thermogravimetry ,Food Packaging ,Microscopy, Electron, Scanning ,Oils, Volatile ,Clay ,Aluminum Silicates ,Anti-Bacterial Agents - Abstract
Halloysite nanotubes (HNTs), which are natural nanomaterials, have a hollow tubular structure with about 15 nm inner and 50 nm outer diameters. Because of their tubular shape, HNTs loaded with various materials have been investigated as functional nanocapsules. In this study, thyme essential oil (TO) was encapsulated successfully in HNTs using vacuum pulling methods, followed by end-capping or a layer-by-layer surface coating process for complete encapsulation. Nanocapsules loaded with TO were mixed with flexographic ink and coated on a paper for applications as food packaging materials. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the nanocapsules and to confirm the TO loading of the nanocapsules. Fourier transform infrared spectroscopy and thermogravimetric analyses analysis were used to complement the structural information. In addition, the controlled release of TO from the nanocapsules showed sustained release properties over a period of many days. The results reveal that the release properties of TO in these nanocapsules could be controlled by surface modifications such as end-capping and/or surface coating of bare nanocapsules. The packaging paper with TO-loaded HNT capsules was effective in eliminating against Escherichia coli during the first 5 d and showed strong antibacterial activity for about 10 d.
- Published
- 2017
33. Development of non-pathogenic bacterial biofilms on the surface of stainless steel which are inhibitory to Salmonella enterica
- Author
-
Yoonbin Kim, Larry R. Beuchat, Jee Hoon Ryu, and Hoikyung Kim
- Subjects
0301 basic medicine ,Salmonella ,030106 microbiology ,Biology ,medicine.disease_cause ,Microbiology ,Tryptic soy broth ,Desiccation tolerance ,03 medical and health sciences ,chemistry.chemical_compound ,Pseudomonas ,Antibiosis ,medicine ,Soil Microbiology ,Biofilm ,Salmonella enterica ,biology.organism_classification ,Antimicrobial ,Stainless Steel ,030104 developmental biology ,chemistry ,Biofilms ,Food Microbiology ,Desiccation ,Bacteria ,Food Science - Abstract
Non-pathogenic bacterial biofilms were developed on the surface of stainless steel possessing desiccation tolerance and antimicrobial activity against Salmonella enterica. Three bacteria exhibiting strong antimicrobial activities against S. enterica were isolated from various soils, foods, and food-contact surfaces. Isolates were identified as Pseudomonas extremorientalis (strain Lettuce-28), Paenibacillus peoriae (strain Lettuce-7), and Streptomyces cirratus (strain Geumsan-207). These bacteria grew rapidly and formed biofilms within 24 h on the surface of stainless steel coupons (SSCs) immersed in laboratory media (tryptic soy broth or Bennet's broth) at 25 °C. Cells in biofilms had enhanced tolerance to desiccation (exposure to 43% atmospheric relative humidity [RH]) and retained antimicrobial activity against S. enterica. Populations of S. enterica deposited on SSCs containing biofilm formed by Ps. extremorientalis strain Lettuce-28, for example, decreased by > 2.5 log CFU/coupon within 24 h at 25 °C and 43% RH, while the number of cells inoculated on SSCs lacking biofilm decreased by 1.5 log CFU/coupon. Antimicrobial activities of the three antagonistic bacteria against S. enterica persisted in desiccated biofilms. This study provides insights to developing strategies to inactivate Salmonella and perhaps other foodborne pathogens on abiotic surfaces using non-pathogenic antagonistic bacteria.
- Published
- 2017
34. Comparison of the Microbiological Quality of Environmentally Friendly and Conventionally Grown Vegetables Sold at Retail Markets in Korea
- Author
-
Larry R. Beuchat, Jee Hoon Ryu, Hoikyung Kim, Eun Gyeong Kim, and Minju Kim
- Subjects
Microbial safety ,Harvest season ,Chili pepper ,food and beverages ,Raw vegetables ,Microbiological quality ,Food science ,Biology ,Crown daisy ,Environmentally friendly ,Iceberg lettuce ,Food Science - Abstract
Fresh produce is usually eaten raw without cooking or heating, which may increase the probability of foodborne infection. The microbiological quality of 11 types of fresh, raw vegetables (romaine lettuce, sesame leaves, crown daisy, garlic chives, iceberg lettuce, cabbage, broccoli, leek, chili pepper, capsicum, and zucchini) purchased at retail markets in Iksan, Korea as affected by cultivation method (environmentally friendly vegetables [organic, pesticide-free, and low-pesticide vegetables] and conventionally grown vegetables) and harvest season was determined. Escherichia coli O157:H7 and Salmonella were not detected in all samples of vegetables tested. Aerobic mesophiles (>6 log cfu/g) were detected in environmentally friendly romaine lettuce and crown daisy and environmentally friendly and conventionally grown garlic chives, which also contained coliforms (>3 log cfu/g). Sesame leaf and crown daisy (regardless of cultivation method), as well as conventionally grown romaine lettuce and leek, contained >1 log cfu/g of E. coli. The overall microbiological quality of environmentally friendly and conventionally grown vegetables was not significantly different (P > 0.05). However, there were seasonal effects on populations of coliforms and generic E. coli on vegetables. The greatest numbers of microorganisms were isolated from environmentally friendly or conventionally grown vegetables purchased in winter. The vegetables, regardless of cultivation method or season, should be subjected to appropriate antimicrobial treatment to enhance their microbial safety.
- Published
- 2014
35. Fate of Bacillus cereus and naturally occurring microbiota on milled rice as affected by temperature and relative humidity
- Author
-
Jee Hoon Ryu, Yoonsook Kim, Seonyeong Choi, Larry R. Beuchat, Hoikyung Kim, and Byeong Sam Kim
- Subjects
Oryza sativa ,Bacteria ,biology ,Aerobic bacteria ,Microbiota ,Fungi ,Temperature ,Food storage ,Bacillus cereus ,food and beverages ,Humidity ,Oryza ,biology.organism_classification ,Microbiology ,Food Storage ,Agronomy ,Relative humidity ,Brown rice ,Food science ,Food Science ,Mesophile - Abstract
We studied the survival and growth patterns of Bacillus cereus, mesophilic aerobic bacteria (MAB), and molds and yeasts (MY) on rough and milled brown and white Korean rice stored at 12 and 21 °C and 43, 68, and 85% relative humidity (RH) for up to 24 wk. The initial populations of MAB present on rough rice, brown rice, and white rice were 7.7, 5.7, and 3.3 log CFU/g, respectively, and remained constant or decreased (P ≤ 0.05) by 0.7-1.8 log CFU/g during storage. The initial populations of B. cereus on the three types of laboratory-inoculated rice were 3.1-3.8 log CFU/g and remained constant (P > 0.05) during storage, regardless of degree of milling, storage temperature, and RH. The initial populations of MY on rough rice, brown rice, and white rice were 6.2, 4.2, and 2.1 log CFU/g, respectively. At 12 °C and 85% RH, the MY increased significantly (P ≤ 0.05) only on brown rice; however, at 21 °C and 85% RH, MY increased (P ≤ 0.05) on all types of rice during storage. These observations will be useful when assessing conditions affecting survival of B. cereus and determining environmental conditions necessary to prevent growth of potentially mycotoxigenic molds on various types of milled rice during storage.
- Published
- 2014
36. Survival of Microorganisms in Galactooligosaccharide Stored at Various Temperatures
- Author
-
Hoikyung Kim, Jihyun Bang, Jee Hoon Ryu, and Seonyeong Choi
- Subjects
Salmonella ,biology ,Water activity ,Galactooligosaccharide ,Inoculation ,Microorganism ,Aspergillus flavus ,biology.organism_classification ,medicine.disease_cause ,Microbiology ,chemistry.chemical_compound ,chemistry ,Listeria monocytogenes ,medicine ,Parasitology ,Food science ,Bacteria ,Food Science - Abstract
Food-grade galactooligosaccharide (GOS) has a low water activity (aw). We investigated the survival of Escherichia coli, Salmonella spp., Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, Aspergillus flavus and Saccharomyces cerevisiae in GOS as affected by inoculum levels and storage temperatures. The five bacteria (inoculated at 3 or 6 log cfu/g), and the fungus A. flavus (3 log cfu/g) and S. cerevisiae (3 log cfu/g), were inoculated into GOS and the material stored at 4, 22 or 50C for 28 days. When ca. 6 log cfu/g of microorganisms were inoculated into GOS, the final numbers of L. monocytogenes and S. aureus (thus after 28 days of storage) were higher than those of E. coli, Salmonella spp. and P. aeruginosa, at all storage temperatures tested. In GOS inoculated with ca. 3 log cfu/g of microorganisms, A. flavus numbers were the highest after 28 days. S. cerevisiae levels were lower than those of gram-positive but higher than those of gram-negative bacteria. The overall level of survival by temperature was 4C > 22C > 50C, regardless of inoculum level. Thus, microbial survival in low-aw GOS was affected by temperature and inoculum level but the microorganisms did not grow during the storage. Practical Applications This study showed that survival of microorganisms in GOS was affected by storage temperature and inoculum level. Microorganisms did not grow in GOS at all temperatures tested, but they still survived in GOS for up to 28 days upon storage temperature. This information will be useful in development of effective microbiological safety strategies to be incorporated in preparation or storage of low-aw food and food ingredients.
- Published
- 2014
37. Inactivation of Bacillus cereus Spores on Red Chili Peppers Using a Combined Treatment of Aqueous Chlorine Dioxide and Hot-Air Drying
- Author
-
Songyi, Kim, Huyong, Lee, Jee-Hoon, Ryu, and Hoikyung, Kim
- Subjects
Spores, Bacterial ,Bacillus cereus ,Sodium Hypochlorite ,Food Preservation ,Colony Count, Microbial ,Oxides ,Desiccation ,Capsicum ,Chlorine Compounds - Abstract
The effect of a combined treatment using aqueous chlorine dioxide (ClO
- Published
- 2016
38. Control of Kimchi Fermentation by the Addition of Natural Antimicrobial Agents Originated from Plants
- Author
-
Jinsol Kim, Jee Hoon Ryu, Seonhwa Kim, Jaejoon Han, and Hyun Sun Seo
- Subjects
biology ,Caesalpinia sappan ,food and beverages ,biology.organism_classification ,Antimicrobial ,Applied Microbiology and Biotechnology ,law.invention ,Microbiology ,Lactic acid ,chemistry.chemical_compound ,chemistry ,law ,Fermentation ,Food science ,Agar well diffusion ,Essential oil ,Lactobacillus plantarum ,Bacteria ,Food Science ,Biotechnology - Abstract
Hyun-Sun Seo, Seonhwa Kim, Jinsol Kim, Jaejoon Han, and Jee-Hoon Ryu*Department of Food Bioscience and Technology, College of Life Sciences and Biotechnology, Korea UniversityAbstract We investigated the delay of kimchi fermentation by the addition of plant extracts. Fifteen plant extracts werescreened for inhibitory activity aginst Lactobacillus plantarum by using an agar well diffusion assay, and determined theminimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) were determined. The lowest MIC forgrapefruit seed extract (GFSE; 0.0313 mg/mL) was determined, followed by Caesalpinia sappan L. extract (CSLE; 0.25 mg/mL), and oregano essential oil (OREO; 1.0 mg/mL). GFSE, CSLE, and OREO were individually added to kimchi, andincubated the samples at 10 for up to 20 days. Results showed that the addition of GFSE (0.3 and 0.5%), CSLE (0.1, 0.3,and 0.5%), or OREO (0.5 and 1.0%) led to a significant increase in the pH of kimchi, and also a significant reduction in thenumbers of lactic acid bacteria. Taken together, the addition of natural antimicrobial agents can delay kimchi fermentation.Keywords: kimchi, fermentation, plant extract
- Published
- 2013
39. Inhibitory Activity ofPaenibacillus polymyxaon the Biofilm Formation ofCronobacterspp. on Stainless Steel Surfaces
- Author
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Soonwook Yang, Seonhwa Kim, Jee Hoon Ryu, and Hoikyung Kim
- Subjects
education.field_of_study ,biology ,Microorganism ,Population ,Biofilm ,biology.organism_classification ,Competitive exclusion ,Incubation period ,Microbiology ,Cronobacter ,Paenibacillus polymyxa ,education ,Antibacterial activity ,Food Science - Abstract
The objective of this study was to control the survival or biofilm formation of Cronobacter spp. on stainless steel surfaces using Paenibacillus polymyxa. The antibacterial activity of a cell-free culture supernatant (CFCS) of P. polymyxa against Cronobacter spp. was found to vary with P. polymyxa incubation time. Maximum activity occurred when P. polymyxa was incubated at 25 or 30 °C for 96 h. When the CFCS was introduced to Cronobacter spp. adhered to stainless steel strips at 25 °C for up to 72 h, the CFCS successfully inhibited Cronobacter biofilm formation. Additionally, stainless steel surfaces with a preformed P. polymyxa biofilm were exposed to Cronobacter spp. suspensions in PBS or 0.1% peptone water at 3, 5, or 7 log CFU/mL to facilitate its attachment. The Cronobacter population significantly decreased on this surface, regardless of inoculum level or carrier, when the P. polymyxa biofilm was present. However, the microbial population decreased within 6 h and remained unchanged thereafter when the surface was immersed in an inoculum suspended in 0.1% peptone water at 5 or 7 log CFU/mL. These results indicate that P. polymyxa is able to use a promising candidate competitive-exclusion microorganism to control Cronobacter spp.
- Published
- 2013
40. Effect of Chlorine Dioxide Treatment and Storage in a Modified Atmosphere on the Inactivation of Cronobacter spp. on Radish Seeds
- Author
-
Eun Gyeong Kim, Hoikyung Kim, and Jee Hoon Ryu
- Subjects
Chlorine dioxide ,biology ,Nalidixic acid ,Inoculation ,food and beverages ,biology.organism_classification ,Antimicrobial ,Microbiology ,chemistry.chemical_compound ,Hand sanitizer ,chemistry ,Germination ,Modified atmosphere ,Botany ,medicine ,Parasitology ,Food science ,Cronobacter ,Food Science ,medicine.drug - Abstract
This study evaluated the inactivation of Cronobacter spp. on radish seeds using ClO2 treatment followed by storage in modified atmosphere (MA) for up to 4 days. Radish seeds were inoculated with Cronobacter spp. (6 log cfu/g), adapted to nalidixic acid and treated with a ClO2 aqueous solution (0, 50 or 100 μL/mL). The seeds were then stored in an ambient air or MA (10% O2, 10% CO2 and 80% N2; 5% O2, 10% CO2 and 85% N2; or 10% O2, 0% CO2 and 90% N2) for up to 4 days. The Cronobacter spp. (6.2 log cfu/g) populations on the radish seeds were reduced to 3.9, 3.8 or 2.6 log cfu/g after treatment with 0, 50 or 100 μL/mL ClO2, respectively, and then to 3.7, 3.1 or ≤ 1.6 log cfu/g after 2 h of drying. After 2–3 days of storage under MA (5 or 10% O2 with 10% CO2), no Cronobacter spp. were detected on the seeds treated with 100 μL/mL aqueous ClO2. More than 94.3% of the radish seeds germinated after ClO2 treatment followed by exposure to an MA, regardless of the ClO2 concentration. Practical Applications These results indicate that sprout seeds should be treated with sanitizers at an appropriate concentration. Sanitizer treatment of the seeds is more critical than following storage conditions for enhancing microbial safety. In addition, sprout seeds should be dried or stored after ClO2 treatment to increase its antimicrobial activity because a greater reduction in microbial populations occurred when the seeds treated with ClO2 were dried or stored than immediately after the treatment.
- Published
- 2013
41. Development of a random genomic DNA microarray for the detection and identification of Listeria monocytogenes in milk
- Author
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Heenam Stanley Kim, Man Bock Gu, Han Song, Hyo Ihl Chang, Larry R. Beuchat, Jee Hoon Ryu, and Jihyun Bang
- Subjects
Population ,Biology ,medicine.disease_cause ,Sensitivity and Specificity ,Microbiology ,Listeria monocytogenes ,medicine ,Animals ,education ,Oligonucleotide Array Sequence Analysis ,education.field_of_study ,Bacteria ,Reproducibility of Results ,General Medicine ,biology.organism_classification ,Molecular biology ,Restriction enzyme ,genomic DNA ,Milk ,Agarose gel electrophoresis ,Food Microbiology ,Listeria ,DNA microarray ,Food Science - Abstract
We developed a DNA microarray that contains random genomic DNA fragments of Listeria monocytogenes, validated its diagnostic abilities using cells grown in laboratory media and milk, and established enrichment conditions for detection of a low population of L. monocytogenes in milk. Genomic DNA of L. monocytogenes strain ATCC 19111 was fractionated by agarose gel electrophoresis after being cleaved using several different pairs of restriction enzymes. Sixty DNA fragments of different sizes were randomly selected and spotted onto an amine-coated glass slide. To validate diagnostic ability, probes on the DNA microarray were hybridized with genomic DNA extracted from L. monocytogenes, other Listeria spp., and foodborne pathogenic bacteria belonging to other genera grown in laboratory media. The DNA microarray showed 98-100% positive hybridization signals for the 16 strains of L. monocytogenes tested, 7-85% positive signals for 9 strains of other Listeria spp., and 0-32% positive signals for 13 strains of other types of foodborne pathogens. In milk, the detection limit of the DNA microarray was approximately 8 log CFU/mL. When milk contained L. monocytogenes (3-4 log CFU/mL) with other types of bacteria (Bacillus spp., B. cereus, Salmonella Montevideo, Peudomonas aeruginosa, and Yersinia enterocolitica; ca. 3 log CFU/mL each), L. monocytogenes enriched in UVM modified Listeria enrichment broth at 37°C for 24h was successfully detected by the DNA microarray. Results indicate that the DNA microarray can detect L. monocytogenes and distinguish it from other Listeria spp. and other foodborne pathogens in laboratory media and milk. This platform will be useful when developing a DNA microarray to rapidly and simultaneously detect and identify various foodborne pathogens in foods.
- Published
- 2013
42. Development of an antimicrobial sachet containing encapsulated allyl isothiocyanate to inactivate Escherichia coli O157:H7 on spinach leaves
- Author
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Seung Yong Cho, Jee Hoon Ryu, Hoikyung Kim, Jihyun Bang, Larry R. Beuchat, and Hyun Sun Seo
- Subjects
Calcium alginate ,Alginates ,Colony Count, Microbial ,Food Contamination ,Escherichia coli O157 ,medicine.disease_cause ,Shelf life ,Microbiology ,chemistry.chemical_compound ,Anti-Infective Agents ,Glucuronic Acid ,Isothiocyanates ,Spinacia oleracea ,Food Preservation ,Botany ,Escherichia coli ,medicine ,Food science ,biology ,Hexuronic Acids ,Temperature ,Food preservation ,food and beverages ,Humidity ,General Medicine ,Antimicrobial ,Allyl isothiocyanate ,biology.organism_classification ,Plant Leaves ,Low-density polyethylene ,chemistry ,Spinach ,Food Science - Abstract
A sachet releasing allyl isothiocyanate (AIT) vapor was developed and its effectiveness as an antimicrobial packaging system for fresh spinach was evaluated. AIT was encapsulated in calcium alginate beads (AIT beads) and the release of AIT as affected by temperature and relative humidity (RH) was determined. The release rate of AIT from beads increased with increased temperature, but was not significantly affected by RH. A low-density polyethylene (LDPE) sachet containing AIT beads (AIT sachet) was prepared and the rate of release of AIT as affected by film thickness and temperature was studied. The release of AIT from sachets increased significantly with decreased LDPE thickness and increased temperature. Finally, antimicrobial effects of the AIT sachet against Escherichia coli O157:H7 and molds and yeasts (MY) on fresh spinach leaves were determined. E. coli O157:H7 and MY had similar sensitivities to AIT vapor. The number of E. coli O157:H7 on spinach leaves (5.6logCFU/leaf) decreased by 1.6-2.6logCFU/leaf at 4°C and 2.1-5.7logCFU/leaf at 25°C within 5days. The reduction of E. coli O157:H7 was significantly greater at 85% RH than at 43% RH. Reductions on control leaves (no AIT sachet) did not exceed 1.2logCFU/leaf under any of the test conditions. Results of the study will be useful when developing antimicrobial packaging systems to increase the microbiological safety and extend the shelf life of spinach and possibly other fresh produces.
- Published
- 2012
43. Inhibition of Staphylococcus aureus by antimicrobial biofilms formed by competitive exclusion microorganisms on stainless steel
- Author
-
Hyeri Son, Larry R. Beuchat, Jee Hoon Ryu, Sunhyung Park, and Hoikyung Kim
- Subjects
0301 basic medicine ,Bacillus safensis ,Staphylococcus aureus ,030106 microbiology ,medicine.disease_cause ,Bacterial Physiological Phenomena ,Microbiology ,Tryptic soy broth ,03 medical and health sciences ,chemistry.chemical_compound ,Antibiosis ,medicine ,Soil Microbiology ,biology ,Bacteria ,Biofilm ,General Medicine ,biology.organism_classification ,Antimicrobial ,Stainless Steel ,chemistry ,Biofilms ,Antimicrobial surface ,Antibacterial activity ,Food Science - Abstract
The goal of this study was to develop a desiccation resistant antimicrobial surface using biofilm of competitive exclusion (CE) microorganism inhibitory to Staphylococcus aureus. We isolated 161 microorganisms from soils, foods, and food-contact surfaces that are inhibitory to S. aureus. Among them, three CE microorganisms (Streptomyces spororaveus strain Gaeunsan-18, Bacillus safensis strain Chamnamu-sup 5-25, and Pseudomonas azotoformans strain Lettuce-9) exhibiting strong antibacterial activity and high growth rates were selected for evaluation. These isolates formed biofilms within 24h on stainless steel coupons (SSCs) immersed in Bennet's broth and tryptic soy broth at 25°C. Cells in these biofilms showed significantly (P≤0.05) enhanced resistance to a desiccation (43% relative humidity [RH]) compared to those attached to SSCs but not in biofilms. The antimicrobial activities of biofilms formed by these isolates on SSCs against S. aureus at 25°C and 43% RH were determined. Compared to SSCs lacking biofilms formed by CE microorganisms, populations of S. aureus on SSCs harboring CE biofilms were significantly lower (P≤0.05). Results indicate that persistent antimicrobial activity against S. aureus on stainless steel surfaces can be achieved by the presence of biofilms of CE microorganisms. This information will be useful when developing strategies to improve the microbiological safety of foods during storage, processing, and distribution by facilitating the development of effective antimicrobial food-contact surfaces.
- Published
- 2016
44. Inactivation of Salmonella enterica in chicken feces on the surface of eggshells by simultaneous treatments with gaseous chlorine dioxide and mild wet heat
- Author
-
Jee Hoon Ryu, Larry R. Beuchat, Hoikyung Kim, and Sunhyung Park
- Subjects
0106 biological sciences ,0301 basic medicine ,Hot Temperature ,030106 microbiology ,Colony Count, Microbial ,01 natural sciences ,Microbiology ,Peak concentration ,03 medical and health sciences ,chemistry.chemical_compound ,Egg Shell ,Feces ,Hand sanitizer ,010608 biotechnology ,Animals ,Relative humidity ,Food science ,Eggshell ,Chlorine dioxide ,biology ,Chemistry ,Salmonella enterica ,Humidity ,Oxides ,biology.organism_classification ,Food Microbiology ,Gases ,Chlorine Compounds ,Chickens ,Food Science ,Disinfectants - Abstract
The aim of this study was to investigate the lethal effects of simultaneous treatments with gaseous chlorine dioxide (ClO2) and mild wet heat (55 °C at 100% relative humidity [RH]) on Salmonella enterica in chicken feces on the surface of eggshells. Gaseous ClO2 production decreased significantly (P ≤ 0.05) as the RH (23, 43, 68, 85, and 100%) at 25 °C was increased. The lethality of gaseous ClO2 against S. enterica in feces on eggshells increased significantly (P ≤ 0.05) as RH increased. For example, when treated with gaseous ClO2 at 85 and 100% RH at 25 °C, S. enterica (5.9 log CFU/egg) was inactivated within 4 h. In contrast, at 23, 43, and 68% RH, the pathogen remained at 5.1, 5.0, and 2.8 log CFU/egg, respectively, after 6 h. Finally, when eggshells surface-contaminated with S. enterica (5.8 log CFU/egg) were treated with gaseous ClO2 (peak concentration of ClO2: 185.6 ppm) at 100% RH and 55 °C, inactivation occurred within 1 h. These results indicate that treatment of surface-contaminated shell eggs with gaseous ClO2 at elevated RH and temperature is effective in inactivating S. enterica. These observations will be useful when developing an effective sanitation program to enhance the microbiological safety of shell eggs.
- Published
- 2016
45. Survival and colonization of Escherichia coli O157:H7 on spinach leaves as affected by inoculum level and carrier, temperature and relative humidity
- Author
-
Hoikyung Kim, Seonyeong Choi, Larry R. Beuchat, Jee Hoon Ryu, and Jihyun Bang
- Subjects
chemistry.chemical_classification ,Inoculation ,food and beverages ,General Medicine ,Biology ,biology.organism_classification ,Applied Microbiology and Biotechnology ,Horticulture ,Nutrient ,chemistry ,Distilled water ,Botany ,Postharvest ,Spinach ,Organic matter ,Colonization ,Relative humidity ,Biotechnology - Abstract
Aims: To determine survival and colonization of Escherichia coli O157:H7 on spinach leaves as affected by inoculum level and carrier, temperature and relative humidity (r.h.). Methods and Results: Spinach leaves were inoculated with suspensions of E. coli O157:H7 in distilled water (DW) and 0·1% peptone water (PW) and incubated at 4, 12 and 25°C and 43, 85 and 100% r.h. The number of E. coli O157:H7 on leaves (5·6 or 1·9 log CFU per leaf) inoculated using DW as a carrier medium increased significantly at 25°C and 100% r.h. within 120 h but remained constant or decreased significantly under other test conditions. E. coli O157:H7 on leaves (5·4 log CFU per leaf) inoculated using PW as a carrier increased significantly within 72 and 24 h, respectively, at 12 or 25°C and 100% r.h.; counts using a low inoculum (2·2 log CFU per leaf) increased significantly within 24 h at 25°C. Conclusions: Escherichia coli O157:H7 can colonize on spinach leaves at 12 or 25°C in a 100% r.h. environment. Organic matter in the inoculum carrier may provide protection and nutrients which enhance survival and colonization. Significance and Impact of the Study: Colonization of E. coli O157:H7 on spinach leaves as affected by organic matter in the inoculum, temperature and r.h. was determined. These observations will be useful when developing strategies to prevent growth of E. coli O157:H7 on pre- and postharvest spinach.
- Published
- 2011
46. Production of high γ-aminobutyric acid (GABA) sour kimchi using lactic acid bacteria isolated from mukeunjee kimchi
- Author
-
Hyun Jin Park, Seung Yong Cho, Ki Myong Kim, Jee Hoon Ryu, and Min Jung Park
- Subjects
biology ,biology.organism_classification ,Applied Microbiology and Biotechnology ,Aminobutyric acid ,Lactic acid ,chemistry.chemical_compound ,Starter ,chemistry ,Biochemistry ,Fermentation ,Food science ,Bacteria ,Food Science ,Biotechnology ,Lactobacillus buchneri - Abstract
A sour kimchi product with an elevated amount of γ-aminobutyric acid (GABA) was produced using starter lactic acid bacteria (LAB) for mukeunjee kimchi fermentation. The starter LAB were screened and isolated from the commercial mukeunjee kimchi product that showed the highest GABA content and was identified as Lactobacillus buchneri. The maximum GABA production of L. buchneri in MRS media was 5.83 mg/mL at pH 4.2 and the addition of 3% NaCl did not significantly (p>0.05) changed GABA production of L. buchneri. The amount of GABA in L. buchneri-inoculated sour kimchi was 61.65 mg/100 g, which represented about 8 times higher than the L. buchneri uninoculated kimchi (control kimchi). A sensory evaluation test of L. buchneri-inoculated sour kimchi and control kimchi showed that the L. buchneri inoculation may produce more sour kimchi than control kimchi, but there was no difference in the general acceptance between the 2 kimchi products (p>0.05).
- Published
- 2011
47. Combined effects of chlorine dioxide, drying, and dry heat treatments in inactivating microorganisms on radish seeds
- Author
-
Jihyun Bang, Hae Young Kim, Jee Hoon Ryu, Hoikyung Kim, and Larry R. Beuchat
- Subjects
Hot Temperature ,Aerobic bacteria ,Population ,Colony Count, Microbial ,Raphanus ,Escherichia coli O157 ,Microbiology ,chemistry.chemical_compound ,Food Preservation ,Botany ,Food microbiology ,Relative humidity ,Food science ,Desiccation ,education ,Legume ,education.field_of_study ,Chlorine dioxide ,biology ,Food preservation ,food and beverages ,Oxides ,biology.organism_classification ,chemistry ,Consumer Product Safety ,Seeds ,Food Microbiology ,Chlorine Compounds ,Disinfectants ,Food Science - Abstract
We determined the combined effectiveness of ClO(2) (200 and 500 μg/ml, 5 min), air drying [25 °C, 40% relative humidity (RH), 2 h], and mild dry heat (55 °C, 23% RH, up to 48 h) treatments in killing total aerobic bacteria (TAB), Escherichia coli O157:H7, and molds and yeasts (MY) on radish seeds. A 5.1-log reduction in the number of TAB was achieved on radish seeds treated with 200 or 500 μg/ml ClO(2) followed by air drying for 2 h and dry heat treatment for 48 h or 24 h, respectively. When radish seeds were treated with 200 and 500 μg/ml ClO(2), air dried, and heat treated for 12 h and 6 h, respectively, the initial population of E. coli O157:H7 (5.6 log CFU/g) on seeds was reduced to an undetectable level (0.8 log CFU/g). However, the pathogen was detected in 5-day-old sprouts. The reduction of MY (1.2-1.0 log CFU/g) on radish seeds under similar experimental conditions was not changed significantly during subsequent heat treatment up to 48 h. Results show that treating radish seeds with 500 μg/ml ClO(2), followed by air dried at 25 °C for 2 h and heat treatment at 55 °C for 36 h achieved a5-log CFU/g reduction of TAB and E. coli O157:H7. These observations will be useful when developing effective strategies and practices to enhance the microbiological safety of radish sprouts.
- Published
- 2011
48. A Subtractively Optimized DNA Microarray Using Non-sequenced Genomic Probes for the Detection of Food-Borne Pathogens
- Author
-
Man Bock Gu, Jin Yong Lee, Joo Myung Ahn, Hyo Ihl Chang, Byoung Chan Kim, Jee Hoon Ryu, and Kwan Jong Chang
- Subjects
Salmonella typhimurium ,Staphylococcus aureus ,DNA nanoball sequencing ,Bacteria ,DNA Microarray Chip ,Hybridization probe ,Bioengineering ,Sequence Analysis, DNA ,General Medicine ,Biology ,Applied Microbiology and Biotechnology ,Biochemistry ,Genome ,Molecular biology ,genomic DNA ,Restriction enzyme ,Bacillus cereus ,Food Microbiology ,Genomic library ,DNA microarray ,DNA Probes ,Molecular Biology ,Genome, Bacterial ,Oligonucleotide Array Sequence Analysis ,Biotechnology - Abstract
In this study, we present the successful detection of food-borne pathogens using randomly selected non-sequenced genomic DNA probes-based DNA microarray chips. Three food-borne pathogens, Staphylococcus aureus, Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium), and Bacillus cereus, were subjected for the preparation of the DNA microarray probes. Initially, about 50 DNA probes selected randomly from non-sequenced genomic DNA of each pathogen were prepared by using a set of restriction enzyme pairs. The proto-type of DNA microarray chip for detecting three different pathogens simultaneously was fabricated by using those DNA probes prepared for each pathogen. This proto-type DNA microarray has been tested with three target pathogens and additional seven bacteria, and successfully verified with a few cross-hybridized probes. After this primary verification of the DNA microarray hybridization, this proto-type DNA microarray chip was redesigned and successfully optimized by eliminating a few cross-hybridized probes. The specificity of this redesigned DNA microarray chip to each pathogen was confirmed without any serious cross-hybridizations, and its multiplexing capability in its pathogen detection was found to be possible. This randomly selected non-sequenced genomic DNA probes-based DNA microarray was successfully proved to be the high-throughput simultaneous detection chip for the detection of food-borne pathogens, without knowing the exact sequence information of the target bacteria. This could be the first fabrication of DNA microarray chip for the simultaneous detection of different kinds of food-borne pathogens.
- Published
- 2010
49. Identification of Yersinia enterocolitica using a random genomic DNA microarray chip
- Author
-
J. Bang, Larry R. Beuchat, Hyo Ihl Chang, Man Bock Gu, and Jee Hoon Ryu
- Subjects
Genetics ,biology ,Genomics ,Yersinia ,biology.organism_classification ,Applied Microbiology and Biotechnology ,Molecular biology ,Genome ,chemistry.chemical_compound ,genomic DNA ,chemistry ,bacteria ,Genomic library ,DNA microarray ,Yersinia enterocolitica ,DNA - Abstract
Aims: To fabricate a DNA chip containing random fragments of genomic DNA of Yersinia enterocolitica and to verify its diagnostic ability. Methods and Results: A DNA microarray chip was fabricated using randomly fragmented DNA of Y. enterocolitica. Chips were hybridized with genomic DNA extracted from other Y. enterocolitica strains, other Yersinia spp. and bacteria in different genera. Genomic DNA extracted from Y. enterocolitica showed a significantly higher hybridization rate compared with DNA of other Yersinia spp. or bacterial genera, thereby distinguishing it from other bacteria. Conclusions: A DNA chip containing randomly fragmented genomic DNA from Y. enterocolitica can detect Y. enterocolitica and clearly distinguish it from other Yersinia spp. and bacteria in different genera. Significance and Impact of the Study: A microarray chip containing randomly fragmented genomic DNA of Y. enterocolitica was fabricated without sequence information, and its diagnostic ability to identify Y. enterocolitica was verified.
- Published
- 2010
50. Attachment of and biofilm formation by Enterobacter sakazakii on stainless steel and enteral feeding tubes
- Author
-
Hoikyung Kim, Jee-Hoon, Ryu, and Beuchat, Larry R.
- Subjects
Microbial mats -- Research ,Bacterial cell walls -- Research ,Enterobacter -- Physiological aspects ,Enterobacter -- Growth ,Enterobacter -- Environmental aspects ,Enterobacteriaceae -- Physiological aspects ,Enterobacteriaceae -- Growth ,Enterobacteriaceae -- Environmental aspects ,Company growth ,Biological sciences - Abstract
A study to determine the influence of temperature and availability of nutrients on attachment to and biofilm formation on stainless steel and enteral feeding tubes by Enterobacter sakazakii is presented. The significance of temperature control in reconstituted infant formula preparation and storage areas in restricting the attachment and biofilm formation by E. sakazakii and the role of nutrient availability in processes resulting in biofilm formation are confirmed.
- Published
- 2006
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