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Microbiological Quality and Safety of Fresh Fruits and Vegetables at Retail Levels in Korea
Tango, Charles Nkufi,Wei, Shuai,Khan, Imran,Hussain, Mohammad Shakhawat,Kounkeu, Paul-Franç,ois Ngnitcho,Park, Joong-hyun,Kim, Se-hun,Oh, Deog Hwan Wiley (Blackwell Publishing) 2018 Journal of Food Science Vol.83 No.2
Tango, Charles Nkufi,Akkermans, Simen,Hussain, Mohammad Shakhawat,Khan, Imran,Van Impe, Jan,Jin, Yong-Guo,Oh, Deog Hwan Elsevier 2018 Food microbiology Vol.76 No.-
<P><B>Abstract</B></P> <P>In this work, the effect of environmental factors on <I>Staphylococcus aureus</I> (ATCC 13150) biofilm formation in tryptic soy broth was investigated under different ranges of pH (3.0–9.5), ethanol concentration (EtOH 0.0–20.0%), and a<SUB>w</SUB> (NaCl, 0.866–0.992). Biofilm formation was quantified using the crystal violet staining method and optical density (OD: 590 nm) measurements. Biofilm formation was significantly stronger at pH and a<SUB>w</SUB> close to <I>S. aureus</I> optimal growth conditions, while it was high at EtOH around 2.5–3.5%. Data sets from the difference between the OD measurements of the test and control (ΔOD) were fitted to the cardinal parameter model (CPM) and cardinal parameter model with inflection (CPMI) to describe the effect of the environmental factors. The models showed good quality of fit for the experimental data in terms of calculated RMSE, with the latter ranging from 0.276 to 0.455. CPM gave a good quality of fit compared to CPMI for the environmental factors tested. Optimal pH was close to neutral (6.76–6.81) and biofilm formation was possible till pH = 3.81–3.78 for CPM and CPMI, respectively. Optimum EtOH and a<SUB>w</SUB> conditions for biofilm formation were in the range of 1.99–2.75 and 0.98–0.97, respectively. Predicted OD values observed using strain 13150 were very closely correlated to the OD values predicted with strain 12600 with R<SUP>2</SUP> of 0.978, 0.991, and 0.947 for pH, EtOH, and a<SUB>w</SUB>, respectively. The cultivable bacterial cells within the biofilm were enumerated using standard plate counting and a linear model was applied to correlate the attached biofilm cells to ΔOD of biofilm formation. It was found that the biofilm formation correlated with <I>S. aureus</I> population growth. At 2.5–3.5% of EtOH the maximum population density was lower than that observed at 0.0% of EtOH. As 2.5–3.5% of EtOH initiated a stronger biofilm formation, biofilm formation seems to be induced by ethanol stress. The development of cardinal parameter models to describe the effect environmental factors of importance to biofilm formation, offers a promising predictive microbiology approach to decrypting the <I>S. aureus</I> population growth and survival ability on food processing surfaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biofilm formation was significantly stronger at pH and aw close <I>S. aureus</I> growth optimal conditions. </LI> <LI> Biofilm formation was significantly high at ethanol concentration around 2.5–3.5%. </LI> <LI> CPM showed a better quality of fit compare to CPMI whatever the environmental factors. </LI> <LI> High extracellular matrix production depend on stress induced by ethanol at non-lethal concentrations. </LI> </UL> </P>
Tango, C.N.,Khan, I.,Ngnitcho Kounkeu, P.F.,Momna, R.,Hussain, M.S.,Oh, D.H. ACADEMIC PRESS LTD 2017 FOOD MICROBIOLOGY Vol.67 No.-
<P>Effect of sequential combination of slightly acidic electrolyzed water (SAEW) with chemical and physical treatments on bacterial decontamination on fruits was investigated in this study. Effect of treatments on microbial and sensory quality was also analyzed after subsequent storage at 4 degrees C and room temperature (RT, 23 +/- 0.15 degrees C). Whole apple and tomato fruits were inoculated with cocktail strains of Escherichia coli O157:H7 and Listeria monocytogenes. Uninoculated and inoculated fruits were washed first with distilled water (DW), calcium oxide (CaO), fumaric acid (FA), and SAEW at RT for 3 min. Combinations were performed by adding treatment one at a time to SAEW as following FA + SAEW, CaO + FA + SAEW, and CaO + FA + SAEW + ultrasonication (US) or microbubbles (MB). All the sanitizer treatments resulted in significant (p < 0.05) bacterial reduction compared to DW used as control. Increasing the treatments in combination from FA + SAEW to CaO + FA + SAEW + US resulted in an increased bacterial decontamination. The cavitation induced by ultrasonication in FA + SAEW solution resulted in a higher additive effect in decontamination of Escherichia coil O157:H7 and Listeria monocytogenes compare to the agitation generated by microbubble generator in FA + SAEW solution. CaO + FA + SAEW and CaO + FA + SAEW + US were effective in improving the microbial safety and quality of apple fruits. However, additional treatment of US impacted on the quality of tomato fruits during storage at RT. Therefore, a combination of SAEW with sanitizers (CaO and FA) and mechanical force (Ultrasonication) has the potential to be used in postharvest sanitation processing in the fresh fruit industry. Published by Elsevier Ltd.</P>
TANGO, CHARLES NKUFI,CHOI, NA-JUNG,CHUNG, MYUNG-SUB,OH, DEOG HWAN ational Association for Food Protection 2014 Journal of food protection Vol.77 No.8
<P>Foods grown in organic production systems have been described as representing an increased risk to public health compared with foods from conventional production. Leafy vegetables (spinach, romaine lettuce, and green sesame leaves) grown in organic and conventional systems were collected from various areas in Korea and examined using standard culture methods to compare the microbiological quality of the produce grown in the two agricultural systems. The 354 samples of these leafy vegetables were analyzed for levels of indicator bacteria (aerobic bacteria, coliforms, and Escherichia coli) and the prevalence of the pathogens Staphylococcus aureus, E. coli O157:H7, Listeria monocytogenes, Bacillus cereus, and Salmonella. Aerobic bacteria and coliforms were detected in all vegetable types, but nonpathogenic E. coli was below the limit of detection in all samples. B. cereus was the most prevalent pathogen, found on 7 (11.1%) of the 63 organic spinach samples. The prevalence of S. aureus was highest in organic sesame leaves; it was found on 5 (8.0%) of the 63 samples. The prevalence of L. monocytogenes was highest on organic romaine lettuce and spinach; it was found in 4 (6.4%) of 63 samples of each type of vegetable. E. coli O157:H7 found on only 1 (1.58%) of 55 conventional spinach samples. These results suggest that farming type at most only slightly affects the hygienic quality of leafy vegetables, and no effect was found for sample collection area. Salmonella was not isolated from any of the conventional or organic leafy vegetables. These results do not support the hypothesis that organic produce poses a substantially greater risk of pathogen contamination than does conventional produce.</P>