Category Archives: Technology

Research – Salmonella sensitivity to sodium hypochlorite and citric acid in washing water of lettuce residues

Posted on December 24, 2019 by | Leave a comment

Wiley Online Salmonella kswfoodworld

Salmonella spp. is one of the main lettuce pathogens and should be inactivated during the disinfection of these vegetables before consumption. In minimally processed vegetable industries, residues of organic matter can prevent the inactivation of this pathogen by disinfectants. The objective of the present work was to evaluate the inactivation of Salmonella isolated from organic lettuce to sodium hypochlorite (25 and 50 ppm) and citric acid (0.5 and 1%) in washing water added with lettuce residues. To do so, a washing water with lettuce residues was elaborated, and Salmonella was added in the order of 106 CFU/ml. Thereafter, each sanitizer was added separately to evaluate its effect on reducing Salmonella counts. After 1, 2, 3, 4, 5, 10, and 15 min of contact with the sanitizers, serial dilutions using neutralizer (0.5% sodium thiosulfate) were performed and each dilution was sown in Xylose‐Lysine‐Desoxycholate medium. Total aerobic mesophilic counts of wash water with lettuce residues before testing (without Salmonella) and after 15 min of exposure to each sanitizer (with Salmonella) were also performed. In addition, the free chlorine still present in the samples after the contact of sodium hypochlorite with lettuce residues for 15 min. The results demonstrated that 50 and 25 ppm sodium hypochlorite could reduce 6 log CFU/ml of Salmonella in 1 and 3 min of contact, respectively, while 0.5 and 1% citric acid was able to reduce 1.26 and 1.74 log CFU/ml respectively from the same microorganism within 15 min of contact. The total aerobic mesophilic counts of the wash water before being tested were, on average, 1.5 log CFU/ml. After addition of Salmonella, with 15 min of contact with the sanitizer, the results of total counts showed the same magnitude as the Salmonella counts. Organic matter may have reacted with the free chlorine present, reducing chlorine concentrations, since values of 30.4 ppm were observed when the initial concentration should be 50 and 17.1 ppm when the initial concentration should be 25 ppm. Based on the results, sodium hypochlorite demonstrated a greater microbial reduction capacity in wash water with lettuce residues, indicating that it is more appropriate to avoid cross‐contamination between batches during sanitation of lettuce in washing tanks.

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Posted in Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, Microbiology, Research, Salmonella, Technology, Uncategorized, water microbiology

Research – Effect of high hydrostatic pressure on Salmonella spp inactivation and meat-quality of frozen chicken breast

Posted on December 24, 2019 by | Leave a comment

Science Direct

The aim of this study was to evaluate the effect of the pressure level and holding time on the Salmonella spp inactivation during HHP processing in frozen chicken breast fillets. Once identified the most effective process, meat quality (color and texture) was evaluated. Results showed that the treatments at 500 MPa for 1 min and 400 MPa for 5 min were enough to guarantee Salmonella spp inactivation in frozen chicken breast fillets. With respect to quality parameters, an extension of shelf life is expected with both treatments, as counts of indigenous microbiota were below the detectable level (<2 logs CFU/g). However, chromatic parameters and texture profile of the fillets treated with HHP suffered significant changes. Even so, the treatment of 500 MPa for 1 min was more effective at preserving chromatic parameters than treatment of 400 MPa for 5 min. The texture profile between fillets treated was not significantly different.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized

Research – Environmental persistence and virulence of Salmonella spp. isolated from a poultry slaughterhouse

Posted on December 23, 2019 by | Leave a comment

Science Direct

Salmonella spp. is responsible for severe foodborne disease, and is one of the main agents involved in foodborne outbreaks worldwide. Contamination occurs mainly as a result of poultry and egg consumption since they can carry some serotypes pathogenic to humans. The aim of the study was to evaluate the persistence and pathogenic potential of Salmonella spp. (n = 40) isolated from poultry slaughterhouse mats, using adhesion and invasion assays, antimicrobial susceptibility by disc diffusion, and biofilm production as phenotypic tests and genotypic analyses. Polystyrene mats presented 3.2 times greater chance of isolating Salmonella than canvas mats. Besides, we observed resistance to tetracycline (17.5%), ampicillin (10%), cefotaxime (7.5%), trimethoprim-sulfamethoxazole (5%), and chloramphenicol (2.5%). All strains possessed the invA, sipB, sipD, ssaR, sifA, sitC, iroN, tolC, flgK, fljB, and flgL genes. The genes sopB and sipA were both present in 92.5% of the isolates, while sopD and spvB were observed in 90% and 32.5% of strains, respectively. All strains adhered to and invaded HeLa cells. Regarding biofilm production, 31 (77.5%) strains were able to produce biofilm on polystyrene microplates. Using PFGE, we detected the persistence of clones in the environment for up to 18 fromthe 20 weeks. The ability of these strains to produce a biofilm and thus persist in the environment and disperse through contact surfaces in the processing plant favors the contamination of food, aggravated by the pathogenic potential of these isolates demonstrated by their adhesion capacity, invasion and resistance to various antibiotic agents.

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Posted in Biofilm, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized

Research – Inactivating foodborne pathogens in apple juice by combined treatment with fumaric acid and ultraviolet-A light, and mechanisms of their synergistic bactericidal action

Posted on December 19, 2019 by | Leave a comment

Science Direct

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.

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Posted in E.coli, E.coli O157, E.coli O157:H7, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Pathogen, Food Technology, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Pathogen, pathogenic, Research, Salmonella, Technology, Uncategorized

Research – Eugenol as an antimicrobial wash treatment reduces Campylobacter jejuni in postharvest poultry

Posted on December 18, 2019 by | Leave a comment

Wiley Online

Abstract

The efficacy of the natural plant‐derived compound, eugenol (EG), as an antimicrobial wash treatment to reduce Campylobacter jejuni in postharvest poultry was investigated. The antimicrobial efficacy of EG was studied as a suspension, emulsion, or nanoemulsion treatment (two trials each). In each trial, chicken skin samples were inoculated with C. jejuni (∼7.2 Log CFU/sample), washed with treatments (0, 0.125, 0.25, 0.5, 1, or 2% EG corresponds to 0, 7.61, 15.22, 30.45, 60.90, or 121.8 mM, respectively) for 1 min, drip dried for 2 min, and then processed at 0, 8, and 24 hr of refrigerated storage (n = 5 samples/treatment/time point). All doses of the EG suspension consistently reduced C. jejuni counts with the greatest reduction (>2.0 Log CFU/sample) for the 2% dose when compared with controls (p < .05). EG emulsions or nanoemulsions did not provide any additional reduction in C. jejuni when compared to EG suspension. Our results suggest that EG could be an effective postharvest intervention strategy for reducing C. jejuni contamination on poultry products.

Practical Applications

Campylobacter jejuni, a leading cause of foodborne illness in humans, is strongly associated with the consumption of contaminated poultry products. Interventions reducing C. jejuni contamination in poultry would reduce the risk of subsequent human infections. In this study, the antimicrobial efficacy of eugenol was studied in three different delivery systems; suspension, emulsion, or nanoemulsion. Our results demonstrated that eugenol was effective in reducing C. jejuni counts on chicken skin and can be used as a potential strategy to reduce Campylobacter on poultry products.

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Posted in Antimicrobials, Campylobacter, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research – Antibacterial mechanism of Tetrapleura tetraptera extract against Escherichia coli and Staphylococcus aureus and its application in pork

Posted on December 18, 2019 by | Leave a comment

Wiley Online

Abstract

The antibacterial activity and the mechanism of Tetrapleura tetraptera root extract against Escherichia coli and Staphylococcus aureus were investigated. The mechanism of action of T. tetraptera on tested bacterial species was predominantly characterized by the study of transmission electron microscopy, which revealed severe damage on the primary target which affected the cell integrity and cell membrane permeability. The loss of soluble proteins studied by bacterial protein sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis and the decreased adenosine triphosphate and DNA contents confirmed the leakage of cell wall. In addition, the studies revealed that the root extract of T. tetraptera could also disrupt the respiratory metabolism by inhibiting the bacteria through the Embden–Meyerhof–Parnas and the hexose monophosphate pathways. T. tetraptera extract possessed a high level of antimicrobial activity in pork, which significantly reduced total viable bacterial population. This study clearly indicates that the T. tetraptera could be a potential source of new antimicrobial agent which has proven effective activity against antibiotic‐resistant strains of pathogens.

Practical Applications

Tetrapleura tetraptera is a flowering plant native to Africa with a wide range of applicability in local cuisines and traditional medicine. The T. tetraptera root extract possesses high antimicrobial activity against both gram‐positive and gram‐negative bacteria. This study could contribute to the better understanding of antibacterial mechanism of T. tetraptera. As a natural food preservative, it has broad prospect to be utilized in the meat industry.

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Posted in Antibiotic Resistance, Antimicrobials, E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Staphylococcus aureus, Technology, Uncategorized

Research – Chemical composition and antimicrobial activity against food‐related microorganisms of different essential oils from Lebanon

Posted on December 17, 2019 by | Leave a comment

Wiley Online

Abstract

Essential oils (EOs) have long been recognized for their medicinal properties. Application of EOs in food preservation has gained recent interest as natural alternatives to conventional chemicals. Even though the properties of EOs are extensively documented, their effect on several food‐related microorganisms is yet to be explored. In this study, six EOs were extracted by hydrodistillation and analyzed using GC/MS techniques, and then antimicrobial activity was tested against microorganisms of food interests through minimal inhibitory concentration (MIC) techniques. Both Coridothymus capitatus and Origanum syriacum EOs showed an antifungal activity (MIC ≤ 0.625 μL/mL). Interestingly all foodborne pathogens tested were sensitive to C. capitatus EO and two of them, Staphylococcus aureus and Listeria monocytogenes, to O. syriacum EO (MIC ≤ 1.25 μL/mL) while the beneficial food‐related bacteria (Lactobacillus sp.) were not affected (MIC ± 10 μL/mL). Finally, Cinnamomum zeylanicum EO showed a broader antimicrobial activity on all microorganisms analyzed.

Practical Applications

Essential oils from Lebanese plants could be used to selectively control foodborne pathogens, including fungi and bacteria. These essential oils could represents an alternative to conventional anti microbials as they did not affect benefiacial food‐related bacteria.

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Posted in Antimicrobials, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, Staphylococcus aureus, Technology, Uncategorized

Research – Simultaneous Effects of UV-A and UV-B Irradiation on the Survival of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in Buffer Solution and Apple Juice

Posted on December 15, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

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.

HIGHLIGHTS

  • Antimicrobial effect of UV-A+B irradiation in PBS and apple juice was investigated.

  • UV-A+B irradiation was antagonistic for inactivating pathogens in the PBS and juice.

  • The degree of antagonistic effect in apple juice was greater than that in PBS.

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Posted in E.coli, E.coli O157, E.coli O157:H7, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized, UV Microbiology

Research – Evaluation of Inactivation of Murine Norovirus in Inoculated Shell Oysters by High Hydrostatic Pressure Treatment

Posted on December 14, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

One of the major foods causing norovirus gastroenteritis is bivalve shellfish, such as oysters. Depuration and relaying methods have been used to control norovirus. However, these methods may be inadequate to control norovirus gastroenteritis. The present study aimed to investigate the effectiveness of high hydrostatic pressure (HHP) treatment in controlling norovirus in shelled oysters, by evaluating the inactivating effect of HHP on murine norovirus strain 1 (MNV-1) inoculated into a buffer, oyster homogenate, and shelled oysters. First, MNV-1 was inoculated (infectivity of 4.5 log PFU/mL) into the buffer and oyster homogenate, with a pH of 6.3 and salinity (NaCl) of 1.5%, mimicking the habitats of the Pacific oyster (Crassostrea gigas). HHP treatment at 100, 200, 275, and 300 MPa for 2 and 5 min was conducted at an initial temperature of 0 or 5°C. The infectivity of MNV-1 in both the buffer and the oyster homogenate was lower when the initial temperature was 0°C. In the buffer, the infectivity of MNV-1 decreased to 1.8 log PFU/mL after HHP treatment (200 MPa for 5 min at 0°C), and the inactivating effect was higher in the buffer than in the oyster homogenate. MNV-1 was inoculated into shelled oysters (4.8 log PFU per oyster), and HHP treatment was done at 275, 300, and 350 MPa for 5 min at the initial temperature of 0°C. The infectivity of MNV-1 decreased to 2.8 log PFU per oyster after HHP treatment at 275 MPa for 5 min. The results indicate that the inactivating effect of HHP treatment varies, depending on the medium surrounding the viral particles. Inactivation was best in buffer, followed by oyster homogenate and shelled oysters. The data could inform the development of methods to control norovirus in oysters.

HIGHLIGHTS

  • HHP inactivation of MNV-1 was more pronounced at 0°C than at 5°C.

  • Inactivation differed, depending on the medium surrounding the virus.

  • HHP at 275 MPa for 5 min at 0°C inactivated MNV-1 inoculated in shucked oysters.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, Food Virus, microbial contamination, Microbiology, Norovirus, Research, Technology, Uncategorized, Virus

Research – Evaluating the Antimicrobial Efficacy of White Mustard Essential Oil Alone and in Combination with Thymol and Carvacrol against Salmonella

Posted on December 11, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

It is estimated that nontyphoidal Salmonella causes approximately 1 million illnesses and 378 deaths per year in the United States. Reduction of Salmonella-related foodborne infections can be achieved through application of food antimicrobials. Essential oils in combination with other antimicrobials can be added to food products to reduce the levels of the organism below the infectious dose for healthy individuals. The purpose of this study was to investigate the antimicrobial efficacy of white mustard essential oil (WMEO) against serovars of Salmonella and its potential to be used with carvacrol or thymol to control Salmonella. Results showed that WMEO at the highest concentration of 0.84% (v/v) compared with the positive control had approximately a 6- to 7-log reduction for all serovars. It was found that no difference in susceptibility existed among the serovars tested (P > 0.05). In addition, the MICs were determined to be 0.5, 0.02, and 0.02% for WMEO, carvacrol, and thymol, respectively, against Salmonella Typhimurium. The fractional inhibitory concentration index was calculated. A score of 1 indicated an additive effect occurred when WMEO was combined with thymol or carvacrol. Combining WMEO with carvacrol or thymol indicated that the concentration of individual essential oils needed to inhibit Salmonella can be reduced using these combinations and warrants further study to determine potential use in controlling Salmonella in commercial food products.

HIGHLIGHTS

  • WMEO showed no significant difference in antimicrobial activity between Salmonella serovars.

  • The MIC of WMEO against Salmonella Typhimurium was 0.5%.

  • Combination with thymol or carvacrol had an additive effect on the antimicrobial activity of WMEO.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized