Recognition of Low-water Activity Foods and Food Ingredients as Sources of Foodborne Pathogens

Larry R. Beuchat 한국식품영양과학회 2013 한국식품영양과학회 학술대회발표집 Vol.2013 No.11

Inactivation of Salmonella enterica in chicken feces on the surface of eggshells by simultaneous treatments with gaseous chlorine dioxide and mild wet heat

Park, S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Academic Press 2017 Food microbiology Vol.62 No.-

<P>The aim of this study was to investigate the lethal effects of simultaneous treatments with gaseous chlorine dioxide (ClO2) and mild wet heat (55 degrees 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 degrees 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 degrees 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 degrees 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. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Identification of <i>Yersinia enterocolitica</i> using a random genomic DNA microarray chip

Bang, J.,Beuchat, L.R.,Gu, M.B.,Chang, H.-I.,Ryu, J.-H. Blackwell Publishing Ltd 2010 Letters in applied microbiology Vol.51 No.6

<P>Abstract</P><P>Aims: </P><P>To fabricate a DNA chip containing random fragments of genomic DNA of <I>Yersinia enterocolitica</I> and to verify its diagnostic ability.</P><P>Methods and Results: </P><P>A DNA microarray chip was fabricated using randomly fragmented DNA of <I>Y. enterocolitica</I>. Chips were hybridized with genomic DNA extracted from other <I>Y. enterocolitica</I> strains, other <I>Yersinia</I> spp. and bacteria in different genera. Genomic DNA extracted from <I>Y. enterocolitica</I> showed a significantly higher hybridization rate compared with DNA of other <I>Yersinia</I> spp. or bacterial genera, thereby distinguishing it from other bacteria.</P><P>Conclusions: </P><P>A DNA chip containing randomly fragmented genomic DNA from <I>Y. enterocolitica</I> can detect <I>Y. enterocolitica</I> and clearly distinguish it from other <I>Yersinia</I> spp. and bacteria in different genera.</P><P>Significance and Impact of the Study: </P><P>A microarray chip containing randomly fragmented genomic DNA of <I>Y. enterocolitica</I> was fabricated without sequence information, and its diagnostic ability to identify <I>Y. enterocolitica</I> was verified.</P>

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

Choi, S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Academic Press 2016 FOOD MICROBIOLOGY Vol.54 No.-

<P>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 ClO2 (200 mg/ml, 5 min) or dry-heat (80 degrees C/23% relative humidity [RH], 24 h) were determined. Pak choi, red radish, and tatsoi seeds showed highest tolerance to both ClO2 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 ClO2 (200 mg/ml, 5 min), drying (45 degrees C/23% RH, 24 h), and dry heat (80 degrees 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 ClO2, 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 (<1.0 log CFU/g) increased to >5.3 and >8.4 log CFU/g of sprouts, respectively. This study shows that sequential treatments of pak choi seeds with ClO2, drying, and dry heat are effective in reducing large numbers of E. coli O157:H7 and S. enterica without loss of seed viability. (C) 2015 Elsevier Ltd. All rights reserved.</P>

Inactivation of <i>Salmonella</i> Typhimurium on red chili peppers by treatment with gaseous chlorine dioxide followed by drying

Lee, Huyong,Beuchat, Larry R.,Ryu, Jee-Hoon,Kim, Hoikyung Elsevier 2018 FOOD MICROBIOLOGY Vol.76 No.-

<P><B>Abstract</B></P> <P>Chili pepper (<I>Capsicum annuum</I> L.) powder and other powdered spices containing chili peppers are occasionally contaminated with foodborne pathogens. We applied chlorine dioxide (ClO<SUB>2</SUB>) gas treatment to chili peppers prior to drying to inactivate <I>Salmonella</I> Typhimurium. Chili peppers inoculated with <I>S</I>. Typhimurium were exposed to ClO<SUB>2</SUB> gas generated from 0.77 mL of aqueous ClO<SUB>2</SUB> for 6 h at 25 °C and 100% relative humidity, followed by air drying at 55 °C for up to 24 h. Populations of <I>S</I>. Typhimurium and total aerobic bacteria (TAB) on peppers, chromaticity values, and moisture content were determined after various treatment times. <I>S</I>. Typhimurium (ca. 5.6 log cfu/g) was reduced to <0.7 log cfu/g of peppers treated with ClO<SUB>2</SUB> gas for 0.5 h at 25 °C, but was detected by enrichment (>1 cfu/10.8 g) after treatment for 4 h. The pathogen was not detected after treatment with ClO<SUB>2</SUB> gas for 6 h. <I>S.</I> Typhimurium did not decrease significantly (<I>P</I> > 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 ClO<SUB>2</SUB> 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 <0.7 log cfu/g after subsequent drying for 24 h at 55 °C. The lightness (<I>L</I> value) of treated and untreated chili peppers did not change during drying, but redness (<I>a</I> value) and yellowness (<I>b</I> value) decreased. Results showed that treatment of chili peppers containing <I>S</I>. Typhimurium (5.6 log cfu/g) with ClO<SUB>2</SUB> gas for 6 h prior to drying at 55 °C reduced the population to < 1 cfu/10.8 g.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Salmonella</I> Typhimurium was completely inactivatedon red chili peppers by gaseous ClO<SUB>2</SUB> and drying. </LI> <LI> Concentration of ClO<SUB>2</SUB> gas released from ClO<SUB>2</SUB> solution was peaked within 0.25 h. </LI> <LI> Moisture content and color values of the peppers were not affected by treatment with ClO<SUB>2</SUB> gas. </LI> <LI> Numbers of TAB on the peppers exposed to ClO<SUB>2</SUB>gas decreased to < 0.7 log cfu/g. </LI> </UL> </P>

Production and stability of chlorine dioxide in organic acid solutions as affected by pH, type of acid, and concentration of sodium chlorite, and its effectiveness in inactivating Bacillus cereus spores

Kim, H.,Kang, Y.,Beuchat, L.R.,Ryu, J.-H. Academic Press 2008 Food microbiology Vol.25 No.8

We studied the production and stability of chlorine dioxide (ClO<SUB>2</SUB>) in organic acid solutions and its effectiveness in killing Bacillus cereus spores. Sodium chlorite (5000, 10,000, or 50,000μg/ml) was added to 5% acetic, citric, or lactic acid solution, adjusted to pH 3.0, 4.0, 5.0, or 6.0, and held at 21<SUP>o</SUP>C for up to 14 days. The amount of ClO<SUB>2</SUB> produced was higher as the concentration of sodium chlorite was increased and as the pH of the acid solutions was decreased. However, the stability in production of ClO<SUB>2</SUB> was enhanced by increasing the pH of the organic acid solutions. To evaluate the lethal activity of ClO<SUB>2</SUB> produced in various acid solutions as affected by acidulant and pH, suspensions of B. cereus spores were treated at 21<SUP>o</SUP>C for 1, 3, 5, or 10min in hydrochloric acid or organic acid solutions (pH 3.0, 4.0, 5.0, or 6.0) containing ClO<SUB>2</SUB> at concentrations of 100, 50, or 25μg/ml. Populations of viable spores treated with ClO<SUB>2</SUB> at concentrations of 100 or 50μg/ml in organic acid solutions decreased more rapidly than populations treated with the same concentrations of ClO<SUB>2</SUB> in HCl. Rates of inactivation tended to increase with higher pH of ClO<SUB>2</SUB> solutions. Results show that ClO<SUB>2</SUB> formed in organic acid solutions has higher stability and is more lethal to B. cereus spores than ClO<SUB>2</SUB> formed at the same concentration in HCl solution. This finding emphasizes the benefits of using organic acid solutions to prepare ClO<SUB>2</SUB> intended for use as an antimicrobial.

Development of an experimental apparatus and protocol for determining antimicrobial activities of gaseous plant essential oils

Seo, H.S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Elsevier Science Publishers 2015 International journal of food microbiology Vol.215 No.-

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 (0.0391μl/ml), followed by thyme-thymol EO gas (0.0781μl/ml), oregano EO gas (0.3125μl/ml), peppermint EO gas (0.6250μl/ml), and thyme-linalool EO gas (0.6250μl/ml). The order of the MLC values of the EO gases against the E. coli O157:H7 was thyme-thymol (0.0781μl/ml)<cinnamon bark (0.1563μl/ml)<oregano (0.3125μl/ml)<peppermint (0.6250μl/ml)=thyme-linalool (0.6250μl/ml). The experimental apparatus and protocol enable rapid and accurate determination of the MIC and MLC values of EO gases and perhaps other types of gaseous antimicrobial agents.

Inhibition of Staphylococcus aureus by antimicrobial biofilms formed by competitive exclusion microorganisms on stainless steel

Son, H.,Park, S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Elsevier Science Publishers 2016 International journal of food microbiology Vol.238 No.-

<P>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 24 h on stainless steel coupons (SSCs) immersed in Bennet's broth and tryptic soy broth at 25 degrees 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 degrees 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. (C) 2016 Published by Elsevier B.V.</P>

Development of non-pathogenic bacterial biofilms on the surface of stainless steel which are inhibitory to Salmonella enterica

Kim, Y.,Kim, H.,Beuchat, L.R.,Ryu, J.H. Academic Press 2018 FOOD MICROBIOLOGY Vol.69 No.-

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 <SUP>o</SUP>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 <SUP>o</SUP>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.

Synergistic antimicrobial activities of essential oil vapours against <i>Penicillium corylophilum</i> on a laboratory medium and beef jerky

Ji, Hyegeun,Kim, Hoikyung,Beuchat, Larry R.,Ryu, Jee-Hoon Elsevier 2019 International journal of food microbiology Vol.291 No.-

<P><B>Abstract</B></P> <P>This study was done to determine the antifungal activities of essential oil (EO) vapours of 97 plants against <I>Penicillium corylophilum</I> 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 <I>P. corylophilum</I> on a laboratory medium. A combination of cinnamon bark, citronella, and may chang EO vapours had synergistic activity in inhibiting growth of <I>P. corylophilium</I> on beef jerky. Observations reported here provide basic information valuable when developing strategies to inhibit the growth of <I>P. corylophilum</I> and possibly other moderately xerophilic molds on intermediate-moisture foods.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Antifungal effect of 97 essential oil (EO) vapours against <I>P. corylophilum</I> was tested. </LI> <LI> Eight EO vapours showed strong antifungal activities against <I>P. corylophilum</I>. </LI> <LI> The MICs of these EO vapours were 0.0390–0.6250 μL/mL. </LI> <LI> Combinations of EO vapours showed synergistic inhibition to <I>P. corylophilum</I>. </LI> </UL> </P>