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1.
Int J Food Microbiol ; 421: 110800, 2024 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-38878705

RESUMO

To our knowledge, this study is the first to elucidate the bactericidal efficacy of unpeeled carrots (hereafter referred to as carrots) pretreated with Ultra Violet-C (UV-C) against subsequent contamination with Listeria monocytogenes. Carrots pretreated with UV-C (240 mJ/cm2) exhibited a significant antilisterial effect within 2 h. In fact, the population of UV-C-pretreated carrots decreased from 7.94 log CFU/cm2 to levels below the limit of detection (LOD; <1.65 log CFU/cm2) within 24 h. For carrots that were not pretreated with UV-C, 3-4 log reductions were found after 24 h. Carrots pretreated with UV-C exhibited antimicrobial activity against another gram-positive pathogen, Staphylococcus aureus, but not against the gram-negative pathogens, E. coli O157:H7 and Salmonella enterica. Pretreatment with UV-C created a lasting antimicrobial effect as introducing L. monocytogenes on carrots, 72 h post-UV-C treatment, still maintained the antilisterial effect. Notably, all UV-C doses in the range of 48-240 mJ/cm2 induced a lasting antilisterial effect. The bactericidal effects against L. monocytogenes were confirmed in three varieties of washed and unwashed carrots (Danvers, Nantes, and Chantenay). Fluorescence microscopy confirmed the bactericidal effect of UV-C-pretreated carrots on the survival of L. monocytogenes. Conclusively, pretreating carrots with UV-C can reduce the population of L. monocytogenes to levels below the LOD and may further prevent pathogen growth during cold storage. Additional studies are necessary to discern the mechanism underlying the bactericidal efficacy of UV-C-pretreated carrots.


Assuntos
Daucus carota , Listeria monocytogenes , Raios Ultravioleta , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/efeitos da radiação , Daucus carota/microbiologia , Microbiologia de Alimentos , Staphylococcus aureus/efeitos dos fármacos , Contaminação de Alimentos/prevenção & controle , Contaminação de Alimentos/análise , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/efeitos da radiação , Escherichia coli O157/crescimento & desenvolvimento , Salmonella enterica/efeitos dos fármacos , Salmonella enterica/efeitos da radiação , Salmonella enterica/crescimento & desenvolvimento
2.
Int J Food Microbiol ; 400: 110266, 2023 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-37263173

RESUMO

Ultrasound technology has been focused on due to its unique advantages in biofilm removal compared with traditional antibacterial methods. Herein, the anti-biofilm properties of low-frequency ultrasound (LFUS) were studied against Enterohemorrhagic Escherichia coli O157: H7 (E. coli O157:H7). After ultrasonication (20 kHz, 300 W) for 5 min, the removal rate of biofilm from polystyrene sheets reached up to 99.999 %. However, the bacterial cells could not be inactivated completely even extending the duration of ultrasonic irradiation to 30 min. Fortunately, this study indicated that LFUS could efficiently weaken the metabolic capacity and biofilm-forming ability of bacterial cells separated from biofilm. It could be associated with the removal of cell surface appendages and damage to cell membrane induced by mechanical vibration and acoustic cavitation. Besides, the genetic analysis proved that the transcription level of genes involved in curli formation was significantly down-regulated during ultrasonic irradiation, thus impeding the process of irreversible adhesion and cells aggregation. Finally, the actual application effect of LFUS was also evaluated in different fresh produces model. The results of this study would provide a theoretical basis for the further application of ultrasound in the food preservation.


Assuntos
Biofilmes , Escherichia coli O157 , Microbiologia de Alimentos , Ondas Ultrassônicas , Escherichia coli O157/citologia , Escherichia coli O157/efeitos da radiação , Biofilmes/efeitos da radiação , Viabilidade Microbiana , Cucumis sativus/microbiologia , Cucumis sativus/efeitos da radiação , Cucumis melo/microbiologia , Cucumis melo/efeitos da radiação , Lactuca/microbiologia , Lactuca/efeitos da radiação , Contaminação de Alimentos
3.
Lett Appl Microbiol ; 76(1)2023 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-36688747

RESUMO

Escherichia coli O157: H7 is a representative foodborne pathogen that causes haemorrhagic colitis, bloody diarrhea, and fatal haemolytic uraemic syndrome. Previously, only conventional heat treatment was used to pasteurised food; however, this method decreases food quality, including colour change, denatures proteins, and causes lipid oxidation. Therefore, emerging technologies to inactivate pathogens in food that affect food quality minimally have been researched and developed. This review aims to compile research since 2018 and briefly describe the inactivation mechanisms of emerging technologies such as microwave, radio frequency, ohmic heating, superheated steam, ionising radiation (gamma irradiation, electron beam, and X-rays), high pressure, ultraviolet light, pulsed light, ultrasound, gas treatment, plasma, and combination treatments. Pulsed electric field and electrolysed water were excluded because few research papers were published after 2018. In addition, the shortcomings of emerging technologies in the control of E. coli O157: H7 and the directions for emerging technology research are presented. Taking advantage of emerging technologies with many benefits will significantly improve food safety.


Assuntos
Escherichia coli O157 , Humanos , Escherichia coli O157/efeitos da radiação , Radiação Ionizante , Inocuidade dos Alimentos , Temperatura Alta , Diarreia , Microbiologia de Alimentos , Contagem de Colônia Microbiana
4.
J Food Prot ; 85(8): 1172-1176, 2022 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-35512126

RESUMO

ABSTRACT: Inshell walnuts can be contaminated with pathogens through direct contact or cross-contamination during harvesting and postharvest hulling, drying, or storage. This study aimed to assess the efficacy of UV-C radiation in inactivating foodborne pathogens on inshell walnut surfaces. Intact inshell walnut surfaces were inoculated separately with Salmonella,Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus and then were subjected to UV-C radiation at doses of 29.4, 147.0, 294.0, 588.0, and 882.0 mJ/cm2. UV-C radiation inactivated the inoculated pathogens in a dose-dependent manner, and a tailing effect was observed for the inactivation of pathogens. UV-C radiation at 29.4 and 882.0 mJ/cm2 reduced the populations of Salmonella Enteritidis PT 30, Salmonella Typhimurium, E. coli O157:H7, L. monocytogenes, and S. aureus on inshell walnut surfaces by 0.82 to 1.25 and 1.76 to 2.41 log CFU per walnut, respectively. Scanning electron photomicrographs showed pathogenic bacterial cells in the cracks and crevices of the inshell walnut surface, and the shielding of microorganisms by the cracks and crevices may have contributed to the tailing effect observed during UV-C inactivation. No significant changes (P > 0.05) were found in walnut lipid oxidation following UV-C radiation at doses up to 882.0 mJ/cm2. Together, the results indicate that UV-C radiation could be a potential technology for reducing the populations of various foodborne pathogens on inshell walnut surfaces while maintaining the quality of walnuts.


Assuntos
Escherichia coli O157 , Juglans , Listeria monocytogenes , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos , Juglans/microbiologia , Listeria monocytogenes/fisiologia , Salmonella typhimurium/efeitos da radiação , Staphylococcus aureus
5.
Food Microbiol ; 99: 103825, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34119110

RESUMO

This study aimed to investigate the effect of different growth temperatures on the resistance of Escherichia coli O157:H7 and Salmonella Typhimurium to low-energy X-ray irradiation. Irradiation of contaminated phosphate-buffered saline with 0.6 kGy X-ray decreased the counts of E. coli O157:H7 cultured at 37 °C to below the detection limit (<1.0 colony-forming unit (CFU)/mL) and those of E. coli O157:H7 cultured at 25 and 15 °C by 4.82 and 4.45 log CFU/mL, respectively. The viable counts of S. Typhimurium cultured at 37, 25, and 15 °C in phosphate-buffered saline decreased by 3.56, 3.08, and 2.75 log CFU/mL, respectively, after irradiation with 0.6 kGy X-ray. Irradiation of contaminated lettuce with 0.4 kGy decreased the counts of E. coli O157:H7 cultured at 37, 25, and 15 °C by 3.97, 3.45, and 3.10 log CFU/cm2, respectively, and those of S. Typhimurium by 4.41, 3.84, and 3.40 log CFU/cm2, respectively. Growth temperature influenced pathogen resistance to X-ray irradiation by modulating cellular membrane and DNA integrity, intracellular enzyme activity, and efflux pump function. The results of this study suggest that the stress resistance status of pathogenic bacteria cultured at different growth temperatures should be considered for the application of X-ray irradiation for fresh produce sterilization.


Assuntos
Escherichia coli O157/crescimento & desenvolvimento , Escherichia coli O157/efeitos da radiação , Lactuca/microbiologia , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/efeitos da radiação , Contagem de Colônia Microbiana , Contaminação de Alimentos/prevenção & controle , Irradiação de Alimentos , Folhas de Planta/microbiologia , Temperatura , Raios X
6.
Appl Environ Microbiol ; 87(15): e0063121, 2021 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-33990307

RESUMO

The aim of this study was to evaluate the antibacterial activity of caffeic acid (CA), which is a natural polyphenol, combined with UV-A light against the representative foodborne bacteria Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes. Data regarding the inactivation of these bacteria and its dependence on CA concentration, light wavelength, and light dose were obtained. E. coli O157:H7 and Salmonella Typhimurium were reduced to the detection limit when treated with 3 mM CA and UV-A for 3 J/cm2 and 4 J/cm2, respectively, and 5 J/cm2 treatment induced 3.10 log reduction in L. monocytogenes. To investigate the mechanism for inactivation of Salmonella Typhimurium and L. monocytogenes, measurement of polyphenol uptake, membrane damage assessment, enzymatic activity assay, and transmission electron microscopy (TEM) were conducted. It was revealed that CA was significantly (P < 0.05) absorbed by bacterial cells, and UV-A light allowed a higher uptake of CA for both pathogens. Additionally, CA plus UV-A treatment induced significant (P < 0.05) cell membrane damage. In the enzymatic activity assay, the activities of both pathogens were reduced by CA, and a greater reduction occurred by use of CA plus UV-A. Moreover, transmission electron microscopy (TEM) images indicated that CA plus UV-A treatment notably destroyed the intercellular structure. In addition, antibacterial activity was also observed in commercial apple juice, which showed results similar to those obtained from phosphate-buffered saline (PBS), resulting in a significant (P < 0.05) reduction for all three pathogens without any changes in color parameters (L*, a*, and b*), total phenolic compounds, and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity. IMPORTANCE Photodynamic inactivation (PDI), which involves photoactivation of a photosensitizer (PS), is an emerging field of study, as it effectively reduces various kinds of microorganisms. Although there are several PSs that have been used for PDI, there is a need to find naturally occurring PSs for safer application in the food industry. Caffeic acid, a natural polyphenol found in most fruits and vegetables, has recently been studied for its potential to act as a novel photosensitizer. However, no studies have been conducted regarding its antibacterial activity depending on treatment conditions and its antibacterial mechanism. In this study, we closely examined the effectiveness of caffeic acid in combination with UV-A light for inactivating representative foodborne bacteria in liquid medium. Therefore, the results of this research are expected to be utilized as basic data for future application of caffeic acid in PDI, especially when controlling pathogens in liquid food processing.


Assuntos
Antibacterianos/farmacologia , Ácidos Cafeicos/farmacologia , Escherichia coli O157 , Conservação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Listeria monocytogenes , Salmonella typhimurium , Raios Ultravioleta , Membrana Celular/efeitos dos fármacos , Membrana Celular/efeitos da radiação , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Escherichia coli O157/metabolismo , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos , Frutas , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/metabolismo , Listeria monocytogenes/efeitos da radiação , Malus , Polifenóis/metabolismo , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/metabolismo , Salmonella typhimurium/efeitos da radiação
7.
Int J Food Microbiol ; 339: 109024, 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33348312

RESUMO

In-house treatment strategy for fresh produce decontamination has not been emphasized as much as industrial washing. The most common treatment for fresh produce decontamination and cleaning at home and other point-of-use places such as cafeteria is rinsing and/or soaking in a sink. In this study, an appliance utilizing UV and agitated water to decontaminate fresh produce was developed and its effectiveness was investigated in an aim to identify optimum processing parameters. Grape tomato and spinach representing two different surface smoothness were dip-inoculated in a four-strain Salmonella cocktail to reach a final population of 5-8 log CFU/g and air-dried. The produce samples were then washed in 1 gallon tap water under varying conditions, water agitation speed (0-190 RPM), sample size (50-400 g), UV intensity (0-30 mW/cm2) and treatment time (2, 5 and 10 min). In general, increasing the agitation speed and UV intensity enhanced Salmonella inactivation for both grape tomato and spinach. Sample size significantly affected the UV inactivation of Salmonella on grape tomato, but not on spinach. The effect of extending treatment time from 2 to 10 min was insignificant for almost all the UV treatments and the controls. The effect of UV intensity and treatment time on inactivation of Salmonella on spot-inoculated grape tomato and spinach was also determined. The most severe treatment used in this study, 30 mW/cm2 UV for 10 min, resulted in >4 log reductions of Salmonella dip- or spot-inoculated on grape tomato (200 g sample size and 190 RPM agitation speed) and 3.5 log reductions of Salmonella dip- or spot-inoculated on spinach (100 g sample size and 110 RPM agitation speed). We foresee that the UV appliance developed and evaluated in this study could be further fine-tuned and optimized to eventually construct a point-of-use UV appliance that can be used at home, cafeteria, restaurants, and hospitals for fresh produce decontamination and cleaning. The UV appliance could be an inexpensive and effective tool to improve fresh produce safety.


Assuntos
Descontaminação/instrumentação , Descontaminação/métodos , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/instrumentação , Microbiologia de Alimentos/métodos , Raios Ultravioleta , Contagem de Colônia Microbiana , Descontaminação/normas , Solanum lycopersicum/microbiologia , Salmonella/efeitos da radiação , Spinacia oleracea/microbiologia , Água
8.
J Photochem Photobiol B ; 214: 112081, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33239223

RESUMO

The objective of this study was to investigate synergistic antibacterial activity based on a combination of UV-A light and three classes of food grade compounds: benzoic acid derivatives, cinnamic acid derivatives, and gallates. By using Escherichia coli O157:H7 as the model strain, it was observed that three cinnamic acid derivatives (ferulic acid, coumaric acid, and caffeic acid) and one benzoic acid derivative (2,5-dihydroxybenzoic acid) presented strong synergistic antibacterial activity with UV-A light radiation, where 1 mM levels of these compounds plus with 15 min of UV-A light (total light dose of 6.1 cm-2) led to more than 7-log CFU mL-1 of bacterial inactivation. In contrast, synergistic antibacterial activity between UV-A light and most benzoic acid derivatives (benzoic acid, gallic acid, vanillic acid, and 2,5-dimethoxybenzoic acid) were only observed after higher concentrations of these compounds were applied (10 mM). Lastly, from the three gallates tested (methyl gallate, ethyl gallate, and propyl gallate), only propyl gallate showed strong antibacterial synergism with UV-A light, where 10 mM of propyl gallate plus 15 min of UV-A light led to approximately 6.5-log of bacterial reduction. Presence of antioxidant compounds mitigated the light-mediated antibacterial activity of gallic acid, 2,5-dihydroxybenzoic acid, and propyl gallate. Similarly, the light-mediated antibacterial activity of these compounds was significantly (P < 0.05) reduced against metabolic-inhibited bacterial cells (sodium azide pretreatment). On the other hand, the antibacterial synergism between ferulic acid and UV-A light was not affected by the presence of antioxidants or the metabolic state of the bacterial cells. Due to the increasing concerns of antimicrobial resistant (AMR) pathogens, the study also investigated the proposed synergistic treatment on AMR Salmonella. Combinations of 1 mM of ferulic acid or 1 mM of 2,5-dihydroxybenzoic acid with UV-A light radiation was able to inactivate more than 6-log of a multi-drug resistant Salmonella Typhimurium strain.


Assuntos
Antibacterianos/química , Hidroxibenzoatos/química , Fármacos Fotossensibilizantes/química , Antibacterianos/farmacologia , Antioxidantes/química , Antioxidantes/farmacologia , Terapia Combinada , Ácidos Cumáricos/farmacologia , Avaliação Pré-Clínica de Medicamentos , Resistência Microbiana a Medicamentos , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/efeitos da radiação , Ácido Gálico/farmacologia , Gentisatos/farmacologia , Hidroxibenzoatos/farmacologia , Fotoquimioterapia , Fármacos Fotossensibilizantes/farmacologia , Relação Estrutura-Atividade , Raios Ultravioleta
9.
Int J Food Microbiol ; 337: 108936, 2021 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-33161345

RESUMO

Development of novel and effective decontamination technologies to ensure the microbiological safety of fresh produce has gained considerable attention, mainly driven by numerous outbreaks. This work presented the first approach regarding to the application of the previously reported hurdle technologies on the sanitization of artificially contaminated cherry tomatoes. Thyme (Thymus daenensis) essential oil nanoemulsion (TEON, 8.28 nm in diameter with a narrow size distribution) was formulated via ultrasonic nanoemulsification, showing remarkably improved antimicrobial activity against Escherichia coli (E. coli) O157:H7, compared to the coarse emulsion. The antimicrobial effect of ultrasound (US), thyme essential oil nanoemulsion (TEON) and the combination of both treatments was assessed against E. coli O157:H7. The remarkable synergistic effects of the combined treatments were achieved, which decontaminated the E. coli populations by 4.49-6.72 log CFU/g on the surface of cherry tomatoes, and led to a reduction of 4.48-6.94 log CFU/sample of the total inactivation. TEON combined with US were effective in reducing the presence of bacteria in wastewater, which averted the potential detrimental effect of cross-contamination resulted from washing wastewater in fresh produce industry. Moreover, the treatments did not noticeably alter the surface color and firmness of cherry tomatoes. Therefore, ultrasound combined with TEON is a promising and feasible alternative for the reduction of microbiological contaminants, as well as retaining the quality characteristics of cherry tomatoes.


Assuntos
Descontaminação/métodos , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Óleos Voláteis/farmacologia , Ondas Ultrassônicas , Contagem de Colônia Microbiana , Solanum lycopersicum/microbiologia
10.
Food Sci Technol Int ; 27(2): 99-111, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32580589

RESUMO

As a result of increasing interest in non-thermal technologies as a possible alternative or complementary to milk pasteurization processing, the objectives of this study were to determine the effects of different ultraviolet-C light doses on the viability of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium and chemical changes to camel milk components. Pasteurized and inoculated camel milk samples were ultraviolet-C treated in a continuous flow system. The viability of E. coli O157:H7 and S. Typhimurium was evaluated with both in vivo imaging system and traditional plate count agar method. Samples subjected to the 4.15, 8.30, and 12.45 mJ/cm2 of ultraviolet-C treatment resulted in 1.9, 3.3, and 3.9-log reductions in E. coli O157:H7 and 0.9, 3, and 3.9-log reductions in S. Typhimurium, respectively. The measurement of secondary lipid peroxidation products (or ThioBarbituric Acid Reactive Substance values) showed no significant (P > 0.05) differences between the raw and ultraviolet-C treated milk samples. Additionally, no changes (P > 0.05) in the protein profiles of αs1-casein, α-lactalbumin, and lactoferrin were observed between both samples. Compared to the untreated raw milk, c9t11 conjugated linoleic acid decreased (P < 0.01) while t10c12 conjugated linoleic acid increased (P < 0.01) in the ultraviolet-C treated milk. Furthermore, three new volatile compounds were identified in the ultraviolet-C treated milk compared to the control. In conclusion, milk treated with the ultraviolet-C light at a dose of 12.45 mJ/cm2 did not meet the Food and Drug Administration (FDA) requirements for the 5-log pathogen reduction. The ultraviolet-C treatment, on the other hand, had minimal effects on camel milk components.


Assuntos
Escherichia coli O157 , Microbiologia de Alimentos , Leite , Salmonella typhimurium , Raios Ultravioleta , Animais , Camelus , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Leite/microbiologia , Salmonella typhimurium/efeitos da radiação
11.
Food Microbiol ; 92: 103584, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32950168

RESUMO

The objectives of this study were to evaluate the bactericidal effects of X-ray irradiation and gallic acid (GA) against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on lettuce leaves and in phosphate-buffered saline (PBS). Inoculated PBS and lettuce were exposed to X-rays (0.05, 0.1, and 0.15; 0.1, 0.2, and 0.3 kGy, respectively), and GA was applied to lettuce leaves as a solution and in PBS at concentrations of 0.5% (w/v). Combined treatment with 0.3 kGy and 0.5% GA reduced E. coli O157:H7, S. Typhimurium, and L. monocytogenes cell counts 5.41, 2.57, and 1.36 log CFU/cm2 on lettuce, respectively. Combined treatment with 0.15 kGy X-ray and 0.5% GA reduced counts for the same species by 6.54, 4.24, and 1.51 log CFU/mL in PBS. The combined treatments exerted a synergistic antibacterial effect against E. coli O157:H7 on lettuce, but not against S. Typhimurium or L. monocytogenes. In PBS, the synergistic effect was confirmed in both E. coli O157:H7 and S. Typhimurium cells. Mechanistic investigations indicated that the synergistic antibacterial effect was associated with intracellular reactive oxygen species (ROS) generation and bacterial cell membrane damage. Additionally, the X-ray and GA combination treatment did not adversely affect the color, total phenol content, and texture of lettuce. These findings demonstrate that treatment with X-ray radiation and GA can enhance the microbiological safety of fresh produce.


Assuntos
Antibacterianos/farmacologia , Conservação de Alimentos/métodos , Ácido Gálico/farmacologia , Lactuca/microbiologia , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Escherichia coli O157/efeitos da radiação , Irradiação de Alimentos/métodos , Conservação de Alimentos/instrumentação , Conservantes de Alimentos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/efeitos da radiação , Viabilidade Microbiana/efeitos dos fármacos , Viabilidade Microbiana/efeitos da radiação , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/efeitos da radiação , Raios X
12.
Food Microbiol ; 91: 103543, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32539944

RESUMO

In this study, we investigated the antimicrobial activity of the X-ray irradiation and citric acid (CA) combination against Escherichia coli O157:H7 and Listeria monocytogenes on the surface of spinach leaves and elucidated the mechanisms underlying their synergistic interaction. Upon treatment with 0.3 kGy X-ray irradiation and 1% CA combination, the cell counts of E. coli O157:H7 and L. monocytogenes reduced by 4.23 and 3.69 log CFU/mL on spinach leaves, respectively. The synergistic reduction in the cell counts of E. coli O157:H7 and L. monocytogenes by the combination treatment was 0.95 and 1.14 log units, respectively. The X-ray and CA combination exerts its antimicrobial effect by damaging the bacterial cell membrane and enhancing the generation of intracellular reactive oxygen species in the pathogens. The enhanced bactericidal effect of the combination treatment may not be due to the loss of intracellular enzyme activity. We also evaluated the effect of the combination treatment on the quality attributes of spinach leaves. The combination treatment did not result in adverse changes in color and texture of spinach leaves. These results demonstrate the potential of citric acid and X-ray irradiation combination for decontaminating foodborne pathogens on fresh produce.


Assuntos
Ácido Cítrico/farmacologia , Desinfetantes/farmacologia , Irradiação de Alimentos/métodos , Spinacia oleracea/microbiologia , Membrana Celular/efeitos dos fármacos , Membrana Celular/efeitos da radiação , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Escherichia coli O157/metabolismo , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/metabolismo , Listeria monocytogenes/efeitos da radiação , Folhas de Planta/microbiologia , Espécies Reativas de Oxigênio/metabolismo , Raios X
13.
Food Microbiol ; 88: 103401, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31997758

RESUMO

This study determined the efficacy of UV-C as a decontamination process against some foodborne bacteria in dried whole black peppercorns. Artificially-inoculated Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus were subjected to UV-C with a surface irradiance of 0.43 mW/cm2 and were all found to exhibit a biphasic inactivation pattern with fast log-linear inactivation followed by a tail. Total log reductions (TLR) ranged from 1.92 (S. aureus) to 3.60 log CFU/g (E. coli O157:H7). Increasing the lamp number from 1 to 5 also linearly (R2 = 0.98) increased the surface irradiance from 0.43 to 1.70 and the TLR of the most resistant S. aureus from 1.92 to 2.62 log CFU/g. Quality evaluation showed very small, variable changes in color coordinates, which were not detected by a same/different test involving a 50-member sensory evaluation panel. Mercury deposition was not detected after a maximum exposure time of 90 min to 0.43 and 1.70 mW/cm2. Finally small, non-significant changes in the innate bacterial microflora of the black peppercorns were determined after 90 min-treatment using 1 lamp and 5 lamps, emphasizing the limitation of utility of UV-C as additional decontamination process for post-process-introduced microorganisms. Good Manufacturing Practices throughout the dried black peppercorn manufacturing process were recommended.


Assuntos
Bactérias/efeitos da radiação , Descontaminação/métodos , Irradiação de Alimentos/métodos , Viabilidade Microbiana/efeitos da radiação , Raios Ultravioleta , Contagem de Colônia Microbiana , Colorimetria , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Listeria monocytogenes/efeitos da radiação , Staphylococcus aureus/efeitos da radiação
14.
Food Microbiol ; 87: 103382, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948623

RESUMO

Although due to their acidity some fruit juices are considered safe, several outbreaks have been reported. For processing fruit juices, microwave heating offers advantages such as shorter come-up time, faster and uniform heating, and energy efficiency. Thus, it could be a beneficial alternative to conventional pasteurization. The objective of this study was to study the inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium under microwave pasteurization at temperatures between 80 and 90 °C, i.e., at conditions that are employed in conventional pasteurization. Inoculated juices were treated at different power levels (600 W, 720 W) and treatment times (5s, 10s, 15s, 20s, 25s). Time-temperature profiles were obtained by fiber-optic sensors in contact with the samples allowing continuous data collection. The log-logistic and Arrhenius equations were used to account for the influence of the temperature history; thus, resulting in two different modeling approaches that were compared in terms of their prediction abilities. Survival kinetics including non-isothermal conditions were described by a non-linear ordinary differential equation that was numerically solved by the Runge-Kutta method (ode45 in MATLAB ®). The lsqcurvefit function (MATLAB®) was employed to estimate the corresponding survival parameters, which were obtained from freshly made apple juice, whereas the prediction ability of these parameters was evaluated on commercial apple juices. Results indicated that inactivation increased with power level, temperature, and treatment time reaching a microbial reduction up to 7 Log10 cycles. The study is relevant to the food industry because it provides a quantitative tool to predict survival characteristics of pathogens at other non-isothermal processing conditions.


Assuntos
Escherichia coli O157/efeitos da radiação , Irradiação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Malus/microbiologia , Salmonella typhimurium/efeitos da radiação , Contagem de Colônia Microbiana , Escherichia coli O157/crescimento & desenvolvimento , Irradiação de Alimentos/instrumentação , Micro-Ondas , Salmonella typhimurium/crescimento & desenvolvimento , Temperatura
15.
Food Microbiol ; 87: 103387, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948628

RESUMO

We evaluated the bactericidal efficacy of the simultaneous application of ultraviolet-A (UV-A) irradiation and fumaric acid (FA) against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in apple juice and as well as investigated the effects of this treatment on product quality. Further, we elucidated the mechanisms underlying their synergistic bactericidal action. Simultaneous UV-A light irradiation and 0.1% FA treatment for 30 min resulted in 6.65-, 6.27-, and 6.49-log CFU/ml reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, which involved 3.15, 2.21, and 3.43 log CFU reductions, respectively, and these were attributed to the synergistic action of the combined treatments. Mechanistic investigations suggested that the combined UVA-FA treatment resulted in significantly greater bacterial cell membrane damage and intracellular reactive oxygen species (ROS) generation. UVA-FA treatment for 30 min did not cause significant changes to the color, nonenzymatic browning index, pH, and total phenolic content of apple juice. These results suggest that combined UVA-FA treatment can be effectively used to control foodborne pathogens in apple juice without affecting its quality.


Assuntos
Antibacterianos/farmacologia , Conservação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Fumaratos/farmacologia , Malus/microbiologia , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Escherichia coli O157/metabolismo , Escherichia coli O157/efeitos da radiação , Conservação de Alimentos/instrumentação , Sucos de Frutas e Vegetais/análise , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/metabolismo , Listeria monocytogenes/efeitos da radiação , Viabilidade Microbiana/efeitos dos fármacos , Viabilidade Microbiana/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/metabolismo , Salmonella typhimurium/efeitos da radiação , Raios Ultravioleta
16.
J Food Prot ; 82(12): 2065-2070, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31714805

RESUMO

The objective of this study was to evaluate the efficacy of simultaneous UV-A and UV-B irradiation (UV-A+B) for inactivating Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in both phosphate-buffered saline (PBS) and apple juice. A cocktail of the three pathogens was inoculated into PBS and apple juice, and then the suspensions were irradiated with UV lamps of 356 nm (UV-A) and 307 nm (UV-B). Significant (P < 0.05) log reductions of the three pathogens in PBS and apple juice were observed after a maximum dose of UV-B alone or the UV-A+B treatment, but few reductions were observed upon UV-A treatment alone. At all irradiation times, antagonistic effects were observed for the application of UV-A+B against in E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes in PBS and apple juice. The degree of antagonistic effect in apple juice was greater than that in PBS. The results of this study suggest that the combined treatment of commercial UV-A and UV-B lamps would be impractical for disinfecting juice products.


Assuntos
Escherichia coli O157 , Microbiologia de Alimentos , Listeria monocytogenes , Viabilidade Microbiana , Salmonella typhimurium , Raios Ultravioleta , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Listeria monocytogenes/efeitos da radiação , Malus , Viabilidade Microbiana/efeitos da radiação , Salmonella typhimurium/efeitos da radiação
17.
J Food Prot ; 82(11): 1879-1889, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31622165

RESUMO

We assessed a fresh produce decontamination system using a combined method of UV and washing (water-assisted UV [WUV]) in different scales. The system used tap water to wash fresh produce while exposing it to UV light. First, the reduction of Salmonella in tap water under UV treatment (1 to 1,740 mJ/cm2) was determined. Increasing the UV dose significantly (P < 0.05) increased the Salmonella reduction in wash water, and UV intensity of more than 2 mW/cm2 could reduce Salmonella in tap water to below 1 CFU/mL given enough processing time (more than 1 min; UV dose of 120 mJ/cm2). Then, the decontamination effectiveness of a small WUV system was tested on blueberries (50 g). Blueberries were spot or dip inoculated with a Salmonella cocktail and treated by the small WUV system (200 mL of water). In general, WUV treatments achieved significantly better Salmonella inactivation than tap water wash; tap water wash (10 min) and 2 mW/cm2 WUV treatment (with a UV dose of 1,200 mJ/cm2) reduced populations of spot-inoculated Salmonella on blueberries by 2.44 and 5.45 log, respectively. Compared with spot-inoculated Salmonella on blueberries, dip-inoculated Salmonella was more difficult to be inactivated by WUV treatments. Then, the decontamination effectiveness of WUV treatments was tested on blueberries (170 g), tomatoes (290 g), strawberries (170 g), baby spinach (60 g), and lettuce (60 g) using a larger WUV system. In general, 10 min of 29 mW/cm2 WUV treatment (a high UV dose of 17,400 mJ/cm2) resulted in significantly better Salmonella inactivation than tap water wash (for 10 min) regardless the inoculation method, agreeing with the results of the small-scale study. For both spot- and dip-inoculated lettuce, no significant difference (P > 0.05) in Salmonella inactivation by WUV treatments was observed when the quantity of lettuce increased from 50 to 100 g.


Assuntos
Escherichia coli O157 , Frutas , Raios Ultravioleta , Mirtilos Azuis (Planta)/microbiologia , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Fragaria/microbiologia , Frutas/microbiologia , Lactuca/microbiologia , Solanum lycopersicum/microbiologia , Spinacia oleracea/microbiologia
18.
Food Microbiol ; 84: 103277, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31421776

RESUMO

The purpose of this study was to evaluate the synergistic bactericidal efficacy of combining ultrasound (US) and fumaric acid (FA) treatment against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in apple juice and to identify the synergistic bactericidal mechanisms. Additionally, the effect of combination treatment on juice quality was determined by measuring the changes in color, pH, non-enzymatic browning index, and total phenolic content. A mixed cocktail of the three pathogens was inoculated into apple juice, followed by treatment with US (40 kHz) alone, FA (0.05, 0.1, and 0.15%) alone, and a combination of US and FA for 1, 2, 3, 4, and 5 min. Combined US and 0.15% FA treatment for 5 min achieved 5.67, 6.35, and 3.47 log reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, with the 1.55, 2.37, and 0.57 log CFU reductions attributed to the synergistic effect. Although the pH value slightly decreased as FA increased, there were no significant (P > 0.05) differences in color values, browning indices, and phenolic content between untreated and treated samples. To identify the mechanism of this synergistic bactericidal action, membrane integrity, malfunctions in the membrane efflux pump, and intracellular enzyme activity were measured. The analyses confirmed that damage to the cell envelope (membrane integrity and efflux pump) was strongly related to the synergistic microbial inactivation. These results suggest that simultaneous application of US treatment and FA is a novel method for ensuring the microbial safety of apple juice.


Assuntos
Antibacterianos/farmacologia , Bactérias/efeitos da radiação , Sucos de Frutas e Vegetais/microbiologia , Fumaratos/farmacologia , Malus/microbiologia , Viabilidade Microbiana/efeitos da radiação , Ondas Ultrassônicas , Bactérias/patogenicidade , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Conservação de Alimentos/métodos , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/efeitos da radiação , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/efeitos da radiação
19.
Food Sci Technol Int ; 25(8): 680-691, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31272222

RESUMO

Pulsed ultraviolet light is a potential postprocessing decontamination method which is able to reduce pathogens on solid food surfaces. Cheese surfaces may become easily contaminated with pathogens due to improper handling or contact with unhygienic surfaces during or after processing. In this study, the effects of pulsed ultraviolet light on Staphylococcus aureus and Escherichia coli O157:H7 on fresh kashar cheese were investigated. Pulsed ultraviolet light was applied to kashar cheese for different times (5, 15, 30, 45, 60 s) at 5, 8, and 13 cm from the quartz window in a pulsed ultraviolet light system. Based on the inactivation level, time, and visual evaluation, the most favorable treatment was determined as the 45 s-13 cm treatment (∼44 J/cm2). This treatment yielded about 1.62 and 3.02 log10 reductions (cfu/cm2) for S. aureus and E. coli O157:H7, respectively, while did not alter (p>0.05) the pH, lipid oxidation, and moisture content of kashar cheese, except the color parameters. When 0.5 cm thick kashar cheese was treated with pulsed ultraviolet light at a distance of 5 cm from the quartz window, the highest energy transmittance was found to be about 9.16%. These findings demonstrate that pulsed ultraviolet light has the potential for postprocessing decontamination of semi-hard cheese surfaces.


Assuntos
Queijo/microbiologia , Descontaminação/métodos , Escherichia coli O157/efeitos da radiação , Manipulação de Alimentos/métodos , Staphylococcus aureus/efeitos da radiação , Raios Ultravioleta , Queijo/análise , Queijo/efeitos da radiação , Contagem de Colônia Microbiana , Cor , Análise de Alimentos , Contaminação de Alimentos/prevenção & controle , Concentração de Íons de Hidrogênio , Viabilidade Microbiana , Staphylococcus aureus/crescimento & desenvolvimento , Fatores de Tempo
20.
Appl Environ Microbiol ; 85(12)2019 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-30952663

RESUMO

In this study, we developed a washing system capable of decontaminating fresh produce by combining the Spindle apparatus, which detaches microorganisms on sample surfaces, and a 222-nm krypton-chlorine excimer lamp (KrCl excilamp) (Sp-Ex) and investigated their decontamination effect against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes on apple (Malus domestica Borkh.) and bell pepper (Capsicum annuum L.) surfaces. Initial levels of the three pathogens were approximately 108 CFU/sample. Both E. coli O157:H7 and S. Typhimurium were reduced to below the detection limit (2.0 log CFU/sample) after 5 and 7 min of treatment on apple and bell pepper surfaces, respectively. The amounts of L. monocytogenes on apple and bell pepper surfaces were reduced by 4.26 and 5.48 logs, respectively, after 7 min of treatment. The decontamination effect of the Sp-Ex was influenced by the hydrophobicity of the sample surface as well as the microbial cell surface, and the decontamination effect decreased as the two hydrophobicity values increased. To improve the decontamination effect of the Sp-Ex, Tween 20, a surfactant that weakens the hydrophobic interaction between the sample surface and pathogenic bacteria, was incorporated into Sp-Ex processing. It was found that its decontamination effect was significantly (P < 0.05) increased by the addition of 0.1% Tween 20. Sp-Ex did not cause significant quality changes in apple or bell pepper surfaces during 7 days storage following treatment (P > 0.05). Our results suggest that Sp-Ex could be applied as a system to control pathogens in place of chemical sanitizer washing by the fresh-produce industry.IMPORTANCE Although most fresh-produce processing currently controls pathogens by means of washing with sanitizers, there are still problems such as the generation of harmful substances and changes in product quality. A combination system composed of the Spindle and a 222-nm KrCl excilamp (Sp-Ex) developed in this study reduced pathogens on apple and bell pepper surfaces using sanitizer-free water without altering produce color and texture. This study demonstrates the potential of the Sp-Ex to replace conventional washing with sanitizers, and it can be used as baseline data for practical application by industry. In addition, implementation of the Sp-Ex developed in this study is expected not only to meet consumer preference for fresh, minimally processed produce but also to reduce human exposure to harmful chemicals while being beneficial to the environment.


Assuntos
Capsicum/microbiologia , Cloro/farmacologia , Descontaminação/métodos , Desinfetantes/farmacologia , Criptônio/farmacologia , Lasers de Excimer , Malus/microbiologia , Descontaminação/instrumentação , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos , Listeria monocytogenes/efeitos da radiação , Salmonella typhimurium/efeitos da radiação
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