Category Archives: Food Technology

Research – Antifungal Activity of Selected Natural Preservatives against Aspergillus westerdijkiae and Penicillium verrucosum and the Interactions of These Preservatives with Food Components

Posted on October 3, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

The present study examined the influence of primary food components on the antifungal activity of the essential oil of Origanum vulgare, carvacrol, thymol, eugenol, and trans-cinnamaldehyde against Penicillium verrucosum and Aspergillus westerdijkiae. The MIC was determined in food model media enriched with proteins (1, 5, or 10%), carbohydrates (1, 4, or 6%), or oil (1, 5, or 10%). Proteins increased the antifungal activity of O. vulgare essential oil, carvacrol, thymol, and eugenol, whereas the effect of trans-cinnamaldehyde decreased with increasing protein content. The presence of carbohydrates diminished the inhibitory effect of the natural preservatives on A. westerdijkiae; for P. verrucosum, their inhibitory effect increased with carbohydrates. Only the antifungal activity of trans-cinnamaldehyde did not depend on the carbohydrate content. The presence of oil had the strongest influence. At a concentration of 1% oil, the antifungal activity decreased significantly, and at 10% oil, almost no inhibition was observed. To investigate the effect of the antifungal agents on the morphology of the target molds, they were grown on malt extract agar containing carvacrol and trans-cinnamaldehyde and were examined by scanning electron microscopy. The hyphae, conidiophores, vesicles, and phialides were severely altered and deformed, and spore formation was clearly suppressed.

HIGHLIGHTS

  • The antifungal activity of natural preservatives is influenced by the food matrix.

  • Proteins increase the impact of O. vulgare EO, carvacrol, thymol, and eugenol.

  • Carbohydrates diminish the inhibition of natural preservatives on A. westerdijkiae.

  • In the presence of oil, natural inhibitors lose their antifungal effect.

  • Carvacrol and trans-cinnamaldehyde lead to distorted hyphae and loss of sporulation.

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

Research – Inactivation of Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica under High Hydrostatic Pressure: A Quantitative Analysis of Existing Literature Data

Posted on October 3, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

High hydrostatic pressure processing (HPP) is a mild preservation technique, and its use for processing foods has been widely documented in the literature. However, very few quantitative synthesis studies have been conducted to gather and analyze bacterial inactivation data to identify the mechanisms of HPP-induced bacterial inactivation. The purpose of this study was to conduct a quantitative analysis of three-decimal reduction times (t3δ) from a large set of existing studies to determine the main influencing factors of HPP-induced inactivation of three foodborne pathogens (Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica) in various foods. Inactivation kinetics data sets from 1995 to 2017 were selected, and t3δ values were first estimated by using the nonlinear Weibull model. Bayesian inference was then used within a metaregression analysis to build and test several models and submodels. The best model (lowest error and most parsimonious) was a hierarchical mixed-effects model including pressure intensity, temperature, study, pH, species, and strain as explicative variables and significant factors. Values for t3δ and ZP associated with inactivation under HPP were estimated for each bacterial pathogen, with their associated variability. Interstudy variability explained most of the variability in t3δ values. Strain variability was also important and exceeded interstudy variability for S. aureus, which prevented the development of an overall model for this pathogen. Meta-analysis is not often used in food microbiology but was a valuable quantitative tool for modeling inactivation of L. monocytogenes and Salmonella in response to HPP treatment. Results of this study could be useful for refining quantitative assessment of the effects of HPP on vegetative foodborne pathogens or for more precisely designing costly and labor-intensive experiments with foodborne pathogens.

HIGHLIGHTS

  • A meta-analysis was performed to identify factors influencing HPP inactivation of pathogens.

  • Three-decimal reduction times following HPP were estimated from existing data.

  • Staphylococcus aureus is the most piezoresistant of the three pathogens studied.

  • These three foodborne pathogens are less HPP resistant in acidic products.

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

Research – Culture-Independent Evaluation of Bacterial Contamination Patterns on Pig Carcasses at a Commercial Slaughter Facility

Posted on October 3, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Traditionally, the microbiological status of meat is determined by culture-based techniques, although many bacteria are not able to grow on conventional media. The aim of this study was to obtain quantitative data on total bacterial cell equivalents, as well as taxa-specific abundances, on carcass surfaces during pig slaughter using quantitative real-time PCR. We evaluated microbial contamination patterns of total bacteria, Campylobacter, Escherichia coli, Lactobacillus group, Listeria monocytogenes, Salmonella, and Pseudomonas species throughout slaughtering and on different carcass areas. In addition, we compared contamination levels of breeding sow carcasses with fattening pig carcasses, and we assessed the efficacy of carcass polishing machines under two water amount conditions. Our results demonstrate that relevant meat-spoilage organisms show similar contamination patterns to total bacteria. The highest bacterial load was detected in the stunning chute (4.08 × 105 bacterial cell equivalents per cm2) but was reduced by 3 log levels after singeing and polishing (P < 0.001). It increased again significantly by a 4.73-fold change until the classification step. Levels of Campylobacter, Lactobacillus, and Pseudomonas species and of E. coli followed a similar trend but varied between 0 and 2.49 × 104 bacterial cell equivalents per cm2. Microbial levels did not vary significantly between sampled carcass areas for any analyzed taxa. Running the polishing machine with a low water amount proved to be less prone to microbial recontamination compared with a high water amount (17.07-fold change, P = 0.024). In the studied slaughterhouse, slaughter of breeding sows did not produce microbiologically safe meat products (>104 cells per cm2) and the implementation of specific hazard analysis critical control point systems for the slaughter of breeding sows should be considered. A larger cohort from different abattoirs is needed to confirm our results and determine whether this is universally valid.

HIGHLIGHTS

  • Spoilage bacteria maintain consistent populations throughout slaughtering.

  • Greater water volume during polishing creates higher bacterial populations on carcasses.

  • Microbial populations on breeding sows are higher compared with fattening pigs.

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Posted in Campylobacter, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Technology, lactic acid bacteria, Listeria monocytogenes, microbial contamination, Microbiology, Pseudomonas, Research, Salmonella, Technology, Uncategorized

Research – Your energy-efficient washing machine could be harbouring pathogens

Posted on September 30, 2019 by | Leave a comment

Science Daily 

For the first time ever, investigators have identified a washing machine as a reservoir of multidrug-resistant pathogens. The pathogens, a single clone of Klebsiella oxytoca, were transmitted repeatedly to newborns in a neonatal intensive care unit at a German children’s hospital. The transmission was stopped only when the washing machine was removed from the hospital. The research is published this week in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.

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

Research -Interaction of Gaseous Chlorine Dioxide and Mild Heat on the Inactivation of Salmonella on Almonds

Posted on September 29, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

The interactive effects of mild heat and gaseous chlorine dioxide (ClO2) on populations of Salmonella on almonds were studied. Almonds, dip inoculated with a two-strain cocktail of attenuated Salmonella Typhimurium, were treated with three concentrations of ClO2 at ambient temperature (ca. 22°C), and at 45, 50, 55, and 60°C for 4 h and with more than 90% relative humidity. Concentrations of ClO2 during treatments were measured, and populations of Salmonella were determined following treatments. Results demonstrated that ClO2 at concentrations of more than 4 mg/L and ambient temperature only reduced populations of Salmonella by 1.46 log CFU/g. With increasing treatment temperature, the efficacy of gaseous ClO2 increased. At 55 and 60°C, >1 mg/L ClO2, and a 4-h treatment time, >4 log CFU/g Salmonella was inactivated. Reductions greater than 4 log of the bacterium by gaseous ClO2 at 55°C were confirmed using a three-strain cocktail of pathogenic Salmonella. Overall, results demonstrated that mild heating is necessary for gaseous ClO2 to achieve more than 4 log CFU/g inactivation of Salmonella on almonds.

HIGHLIGHTS

  • ClO2 applied at ambient temperature achieves less than 2-log reductions of Salmonella.

  • Mild heat and ClO2 have a synergistic effect on the reduction of Salmonella.

  • Surrogate Salmonella Typhimurium and pathogenic Salmonella behave similarly to ClO2 and heat.

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

Research – Effect of Tartary Buckwheat Peptides on Shelf Life of Tilapia (Oreochromis niloticus) Fillets

Posted on September 28, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Tartary buckwheat peptides (TBPs), produced from tartary buckwheat through solid-state fermentation, were used as a dip treatment solution to preserve tilapia fillets. Fillets were dip treated with different concentrations of TBPs (0.5, 1, and 2% [v/v]) and stored at 4°C for 12 days. The effect of TBPs on thiobarbituric acid, total volatile base nitrogen, surface color, texture profile analysis, total viable counts, and changes in sensory properties of tilapia fillets during storage was investigated. Compared with the control group, the groups treated with TBPs displayed reduced rates of quality deterioration in physicochemical, bacteriological, and sensory characteristics. Based on total volatile base nitrogen content, total viable counts, and sensory scores, the shelf life of control tilapia fillets was 4 days and that for TBP-treated fillets was 8 days, twice as long as that of the control group. Thus, TBPs can be used as preservatives to maintain the quality and extend the shelf life of tilapia fillets stored at 4°C.

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

Research – Comparison of pH effects on ohmic heating and conventional heating for inactivation of Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium and Listeria monocytogenes in orange juice

Posted on September 16, 2019 by | Leave a comment

Science Direct

Highlights

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Effect of pH on ohmic heating compared to conventional heating was investigated.

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Adjusting pH has significant effect on the heating rate of ohmic heating.

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Unusual tendency of pathogen inactivation was identified in ohmic heating.

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Quality aspects of samples were not severely degraded regardless of pH.

Abstract

The objective of the current study is to identify the influence of acidity on ohmic heating compared to conventional heating for inactivation of food-borne pathogensin orange juice. For conventional heating, the heating rate was not significantly different (P > 0.05) regardless of pH and pathogens were inactivated more effectively at lower pH. However, different patterns were observed for ohmic heating. Although temperature and electrical conductivity were not greatly affected by lowering pH, temperature increased more rapidly with increasing pH due to higher electrical conductivity. Also, the inactivation patterns were significantly different (P < 0.05) from conventional heating. While Salmonella Typhimurium was inactivated most rapidly at pH 2.5, Escherichia coli O157:H7 and Listeria monocytogenes were inactivated most rapidly at pH 4.5. When pathogens were exposed to each heating method at a fixed temperature, additional effects of ohmic heating were not observed. Also, the overall quality of orange juice subjected to ohmic heating was not greatly affected at any pH level. Therefore, increasing as well as lowering pH can also be considered effective ways to optimize pasteurization of orange juice when using ohmic heating. The different characteristics of ohmic heating compared to conventional heating indicate the necessity of a new approach.

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

Research – Antimicrobial resistance profile of Escherichia coli isolates recovered from diarrheic patients at Selam Health Center, Addis Ababa, Ethiopia

Posted on September 14, 2019 by | Leave a comment

Academic Journals

Abstract

Antimicrobials have been playing an important role in preventing illness and death associated with infections due to bacteria. However, the emergence and spread of resistance by pathogens have decreased the effectiveness of the commonly prescribed antimicrobials. Intestinal Escherichia coli are among bacterial pathogens that are endowed with such resistance traits because they are important source and reservoir of genes that encode antimicrobial resistance. To determine the antimicrobial resistance profile of fecal isolates of E. coli from diarrheic patients. Stool samples were collected consecutively from 100 individuals who visited Selam Health Center during the study period, April to June 2018. Samples were collected and transported under sterile condition to the National Clinical Bacteriology and Mycology reference Laboratory, Ethiopian Public Health Institute. The samples were streaked on MacConkey agar and incubated overnight at 37°C. E. coli isolates were further confirmed using conventional biochemical tests. Antimicrobial susceptibility status was determined using the disk diffusion method on Mueller Hinton agar as recommended by the Clinical Laboratory Standard Institute. The raw data was compiled and entered to spreadsheet and analysis was done using SPSS Version 20 with p-value ≤0.05 considered statistically significant. Out of the 100 patients, 43 were female and the rest were male. Confirmed E. coli were isolated from 73 individuals. Antimicrobial susceptibility testing showed that E. coli isolated in this study were highly resistant to trimethoprim-sulfamethoxazole 49 (67.1%) and amoxicillin-clavulanic acid 47(64.4 %). No isolates showed resistance to gentamicin and tobramicin.  Of all the isolates, 11(15.1%) were multidrug resistant. No association was observed between antimicrobial resistance status and sex of individuals included in this study. However, there was an association between age and resistance patterns. Resistance to commonly prescribed antibiotics among E. coli isolated in this study was high and a considerable proportions of the strains were multidrug resistant. This is an indication for an alarming rate of resistance of intestinal E. coli to first line antimicrobials. To reduce the problem, regular monitoring and education for the community are very important.

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

Research – Identification and genotyping of Listeria monocytogenes in the chicken shredding line

Posted on September 12, 2019 by | Leave a comment

Wiley Online

Abstract

The present research was carried out to determine the presence of Listeria monocytogenes in the equipment, staff, and products in the chicken shredding facilities operating in Samsun, and to serotype and genotype the isolates by PCR and PFGE analysis, respectively. Of the total of 192 samples tested, 25 were found to be L. monocytogenes positive from which 51 isolates were acquired. In serotyping of the 51 isolates; 47 (92.2%) and four isolates (7.8%) were identified as 1/2a (3a) and 1/2c (3c), respectively. Twenty‐six of the 51 isolates (51%) were resistant to at least one antibiotic, and 13 (25.5%) were resistant to more than one antibiotic. In the PFGE evaluation, at least 80% similarity was taken as a basis, and in the dendrogram, it was determined as a result of restricting with the Apal enzyme that the isolates were distributed to 25 different clusters and 45 subsets, and as a result of restricting with the AscI enzyme, they were distributed to 29 different clusters and 36 subsets.

Practical Application

Listeria monocytogenes constitutes a major problem for the food industry due to its widespread availability in nature and its role as an environmental contaminant in food processing plants.

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Posted in Food Micro Blog, Food Microbiology Blog, Food Technology, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Technology, Uncategorized

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

Posted on September 10, 2019 by | Leave a comment

Wiley Online

campy2

Image CDC

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 Campylobacter, food contamination, Food Hygiene, Food Micro Blog, Food Microbiology Blog, Food Safety, Food Technology, Food Testing, microbial contamination, Microbiology, Technology, Uncategorized