Category Archives: Technology

Research – Prevalence of Salmonella in cucumbers, antibiotic and acid resistances and description of the kinetic behavior with dynamic model during storage

Posted on January 14, 2020 by | Leave a comment

Wiley Online

This study isolated Salmonella from cucumbers, analyzed the antibiotic resistance and acid resistance for the isolates and developed a dynamic model. Salmonella prevalence in cucumbers and their resistances were determined. To describe the kinetic behavior of Salmonella isolates, the isolates were inoculated into cucumbers, and Salmonella cell counts were enumerated during storage at 10–30°C. The Baranyi model was fitted to the cell count data to calculate kinetic parameters (lag phase duration [LPD] and maximum specific growth rate (μmax)], and a polynomial model was fitted to the kinetic parameters as a function of temperature. The model performance was evaluated with root mean square error (RMSE). Using these models, a dynamic model was developed. Salmonella were detected in 3 of 24 cucumbers, all of which were multidrug‐resistant and one was acid‐resistant. As storage temperature increased, LPD decreased and μmax increased. These models were appropriate with 0.367 of RMSE. These results suggest that cross‐contaminated Salmonella could increase during transportation, and it may lead to human infection.

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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 – Treatment of fresh produce with a Salmonella‐targeted bacteriophage cocktail is compatible with chlorine or peracetic acid and more consistently preserves the microbial community on produce

Posted on January 14, 2020 by | Leave a comment

Wiley Online

Diets rich in minimally processed foods are associated with numerous health benefits, in part, due to their diverse, natural microbiota. However, antimicrobials, such as chlorine and peracetic acid (PAA), that are used to address food safety concerns may damage the natural microflora of fresh produce. One promising approach for targeting pathogenic bacteria in foods without impacting the normal food microbiota are bacteriophages. In this study, we observed that combinational treatment of conventional antimicrobials (PAA and chlorine) and bacteriophages, specifically the Salmonella‐targeted preparation SalmoFresh, retained the bactericidal effectiveness of individual interventions, and in some cases, achieved substantially increased efficacy. Additionally, the bacterial microbiomes of farm fresh and organic produce were less affected after phage treatment compared to PAA and chlorine. Finally, our study revealed that resistance rates against SalmoFresh were relatively minor and unaffected by the stresses introduced after chemical washes and/or bacteriophage treatment.

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

Research-Nisin-Based Organic Acid Inactivation of Salmonella on Grape Tomatoes: Efficacy of Treatment with Bioluminescence ATP Assay

Posted on January 12, 2020 by | Leave a comment

Journal of Food Protection

ABSTRACT

The antimicrobial activity of a new nisin-based organic acid sanitizer (NOAS), developed in our laboratory, was tested against viable aerobic mesophilic bacteria and Salmonella populations inoculated on produce surfaces. The activity of NOAS was compared with 200 ppm of chlorinated wash water and a bioluminescence ATP technique to determine the efficacy of treatments compared with plate count methods. The activity of the 10% final concentration of NOAS against viable populations of 109 CFU/mL Salmonella in phosphate-buffered saline (PBS), sterile deionized distilled water, and buffered peptone water was tested in vitro and on grape tomatoes inoculated with Salmonella at 2.5 log CFU/g. A similar batch of inoculated tomatoes were treated with 200 ppm of total available chlorinated water. All treatments for inactivation of viable Salmonella in vitro was tested up to 30 min and 5 min for the attached populations on tomatoes. Inactivation of viable Salmonella at 109 log CFU/mL by 10% the NOAS solution averaged >107 log CFU/mL in PBS, sterile deionized distilled water, and buffered peptone water. Similarly, Salmonella bacteria inactivated on tomato surfaces by the NOAS solution was significantly (P < 0.05) greater than numbers on chlorinated washed tomatoes, and surviving bacterial populations on NOAS and chlorine-treated tomatoes were <1 and 4 CFU/g, respectively. A significant linear correlation coefficient (r2 = 0.99) between the bioluminescence ATP assay and aerobic plate counts of inoculated and untreated grape tomatoes were recorded but not with NOAS and chlorine-treated tomatoes, as bacterial populations were less than the minimum baseline for determination. Also, the results indicated that the NOAS solution is a better alternative antimicrobial wash solution than 200 ppm of chlorinated water.

HIGHLIGHTS

  • The antimicrobial activity of NOAS was compared with chlorinated water.

  • Salmonella bacteria were more susceptible to NOAS than chlorinated water.

  • Assay correlated with aerobic plate count of inoculated and untreated tomatoes, not treated ones.

  • NOAS is an excellent alternative antimicrobial wash solution compared with chlorinated wash water.

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

Research – Inactivation of Murine Norovirus on Fruit and Vegetable Surfaces by Vapor Phase Hydrogen Peroxide

Posted on January 12, 2020 by | Leave a comment

Journal of Food Protection

ABSTRACT

Vapor phase hydrogen peroxide (H2O2) can be utilized to inactivate murine norovirus (MNV), a surrogate of human norovirus, on surface areas. However, vapor phase H2O2 inactivation of virus on fruits and vegetables has not been characterized. In this study, MNV was used to determine whether vaporized H2O2 inactivates virus on surfaces of various fruits and vegetables (apples, blueberries, cucumbers, and strawberries). The effect of vapor phase H2O2 decontamination was investigated with two application systems. Plaque assays were performed after virus recovery from untreated and treated fresh produce to compare the quantity of infective MNV. The Mann-Whitney U test was applied to the test results to evaluate the virus titer reductions of treated food samples, with significance set at P ≤ 0.05. The infective MNV populations were significantly reduced on smooth surfaces by 4.3 log PFU (apples, P < 0.00001) and 4 log PFU or below the detection limit (blueberries, P = 0.0074) by treatment with vapor phase H2O2 (60 min, maximum of 214 ppm of H2O2). Similar treatments of artificially contaminated cucumbers resulted in a virus titer reduction of 1.9 log PFU. Treatment of inoculated strawberries resulted in 0.1- and 2.8-log reductions of MNV. However, MNV reduction rates on cucumbers (P = 0.3809) and strawberries (P = 0,7414) were not significant. Triangle tests and color measurements of untreated and treated apples, cucumbers, blueberries, and strawberries revealed no differences in color and consistency after H2O2 treatment. No increase of the H2O2 concentration in treated fruits and vegetables compared with untreated produce was observed. This study reveals for the first time the conditions under which vapor phase H2O2 inactivates MNV on selected fresh fruit and vegetable surfaces.

HIGHLIGHTS

  • Produce was treated with vapor phase H2O2 for 60 min (maximum of 260 ppm of H2O2).

  • A 4-log reduction in MNV was achieved by H2O2 treatment on apples and blueberries.

  • Reductions of MNV on treated strawberries and cucumbers were not significant.

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

Research- Survival Evaluation of Salmonella and Listeria monocytogenes on Selective and Nonselective Media in Ground Chicken Meat Subjected to High Hydrostatic Pressure and Carvacrol

Posted on January 11, 2020 by | Leave a comment

Journal of Food Protection

ABSTRACT

High pressure processing (HPP) and treatment with the essential oil extract carvacrol had synergistic inactivation effects on Salmonella and Listeria monocytogenes in fresh ground chicken meat. Seven days after HPP treatment at 350 MPa for 10 min, Salmonella treated with 0.75% carvacrol was reduced to below the detection limit (1 log CFU/g) at 4°C and was reduced by ca. 6 log CFU at 10°C. L. monocytogenes was more sensitive to these imposed stressors, remaining below the detection limit during storage at both 4 and 10°C after HPP treatment at 350 MPa for 10 min following treatment with 0.45% carvacrol. However, pressure-injured bacterial cells may recover and lead to an overestimation of process lethality when a selective medium is used without proper justification. For HPP-stressed Salmonella, a 1- to 2-log difference was found between viable counts on xylose lysine Tergitol 4 agar and aerobic plate counts, but no significant difference was found for HPP-stressed L. monocytogenes between polymyxin–acriflavine–lithium chloride–ceftazidime–esculin–mannitol (PALCAM) agar and aerobic plate counts. HPP-induced bacterial injury and its recovery have been investigated by comparing selective and nonselective agar plate counts; however, few investigations have addressed this issue in the presence of essential oil extracts, taking into account the effect of high pressure and natural antimicrobial compounds (e.g., carvacrol) on bacterial survival in various growth media. Use of selective media may overestimate the efficacy of bacterial inactivation in food processing evaluation and validation studies, and the effects of various media should be systematically investigated.

HIGHLIGHTS

  • HPP and carvacrol had synergistic pathogen inactivation effects in ground chicken meat.

  • HPP at 350 MPa for 10 min with 0.60% carvacrol treatment resulted in a >5-log pathogen reduction.

  • A 1- to 2-log difference was found for counts of HPP-treated Salmonella on two growth media.

  • Counts of HPP-treated L. monocytogenes were similar on selective and nonselective media.

  • Carvacrol suppressed the growth and recovery of the HPP-treated bacterial cells.

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

Research -Inactivation of Bacillus cereus Spores on Stainless Steel by Combined Superheated Steam and UV-C Irradiation Treatment

Posted on January 11, 2020 by | Leave a comment

Journal of Food Protection

ABSTRACT

Bacillus cereus spore contamination on food contact surfaces is of great concern in the food industry. Thus, in the present study, superheated steam (SHS) was used alone or combined with UV-C irradiation for inactivation of B. cereus spores inoculated on stainless steel coupons. Temperatures higher than 250°C were needed to effectively inactivate B. cereus spores by SHS treatment alone, while a synergistic bactericidal effect resulted from the sequential treatment of SHS before or after UV-C irradiation. The increased dipicolinic acid ratio obtained by the combined treatment had a significant role in the synergistic bactericidal effect. Therefore, the combined treatment of SHS and UV-C could be used effectively to inactivate B. cereus on stainless steel. It is recommended to use hurdle technology with reduced energy consumption to ensure microbiological safety on food contact surfaces.

HIGHLIGHTS

  • Inactivation of Bacillus cereus spores on stainless steel was identified in this study.

  • Superheated steam (SHS) was applied solely or combined with UV-C irradiation.

  • A synergistic effect was observed by combination treatment for spore inactivation.

  • The dipicolinic acid (DPA) release level increased significantly by combination treatment.

  • The combination treatment can be applied to sanitize food processing equipment.

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

Research – Edible films containing carvacrol and cinnamaldehyde inactivate Escherichia coli O157:H7 on organic leafy greens in sealed plastic bags

Posted on January 7, 2020 by | Leave a comment

Wiley Online Eurofins Food Testing UK

The antimicrobial effects of apple‐, carrot‐, and hibiscus‐based edible films containing carvacrol and cinnamaldehyde against Escherichia coli O157:H7 on organic leafy greens in sealed plastic bags were investigated. Fresh‐cut Romaine and Iceberg lettuce, and mature and baby spinach leaves were inoculated with E. coli O157:H7 and placed into Ziploc® bags. Edible films were then added to the bags, which were stored at 4°C. The evaluation of samples taken at days 0, 3, and 7 showed that on all leafy greens, 3% carvacrol‐containing films had the greatest effect against E. coli O157:H7, reducing the bacterial population by about 5 log CFU/g on day 0. All three types of 3% carvacrol‐containing films reduced E. coli O157:H7 by about 5 log CFU/g at day 0. The 1.5% carvacrol‐containing films reduced E. coli O157:H7 by 1–4 logs CFU/g at day 7. Films with 3% cinnamaldehyde showed reduction of 0.6–3 logs CFU/g on different leafy greens.

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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 Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, STEC E.coli, Technology, Uncategorized

Research – Removal of Salmonella enterica serovar Typhimurium and Cronobacter sakazakii biofilms from food contact surfaces through enzymatic catalysis

Posted on December 29, 2019 by | Leave a comment

Wiley Online

Bacterial biofilms are highly difficult to control, hence significant economic resources have been allocated to develop strategies to eradicate them. This study evaluated the effect of an enzymatic treatment to be used as a cleaning product to control the presence of biofilms. Two different materials used in the food industry, polystyrene and stainless steel, were tested using Salmonella Typhimuirum and Cronobacter sakazakii. Biofilm formation was carried out by inoculating the surfaces with a standardized concentration of 4 log (CFU cm−2) and incubated for 48 hr with renewal of nutrients. The biofilm formation and subsequent enzymatic treatment were quantified using fluorescence microscopy and the conventional culture method. The enzymatic treatment showed significant reductions of 2–3 log (CFU cm−2) in biofilm cells, which was attributed to the degradation of the extracellular matrix and the further detachment of both microorganisms. The maximum biofilm detachment obtained with the preventive formula was 46.67%; however, this percentage could be increased by applying an aggressive treatment or by adding a subsequent disinfection step that would eliminate adhered microbial cells. Further, the enzymatic cleaning treatment could be exploited as a potent technology to control bacterial adherence and biofilm formation in the food industry.

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Posted in Biofilm, Food Hygiene, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Safety, Food Technology, Food Testing, Technology, Uncategorized

Research – Effects of edible coating containing Williopsis saturnus var. saturnus on fungal growth and aflatoxin production by Aspergillus flavus in peanuts

Posted on December 28, 2019 by | Leave a comment

Wiley Online

Abstract

Production of aflatoxin by Aspergillus flavus in peanuts is both a health hazard and major problem. This study investigated the ability of a whey protein concentrate (WPC)‐based edible coating containing Williopsis saturnus var. saturnus to prevent growth of A. flavus and aflatoxin production in peanuts. WPC with/without W. saturnus (7 log colony‐forming unit [CFU]/g) or W. saturnus alone was sprayed on peanuts inoculated with A. flavus (3 log CFU/g) and stored for 84 days at 25°C. Application of coating with W. saturnus reduced both growth of A. flavus and aflatoxin level by 82 and 69.5% compared with the control, respectively. Thiobarbituric acid values were around 60% lower in peanuts coated with WPC compared with the control. Sensory and chemical properties of peanuts were not significantly affected by coating treatment (p < .05). Based on results, coating with W. saturnus appears useful in preventing both growth of A. flavus and aflatoxin production in peanuts.

Practical Applications

Improved WPC based coating containing W. saturnus can be applied on surface of roasted peanuts to prevent growth of A. flavus and aflatoxin production.

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Posted in Aflatoxin, Aspergillus, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, Food Toxin, microbial contamination, Microbiology, Mould Toxin, Mycotoxin, Research, Technology, Uncategorized

Research – Cold plasma enhances the efficacy of aerosolized hydrogen peroxide in reducing populations of Salmonella Typhimurium and Listeria innocua on grape tomatoes, apples, cantaloupe and romaine lettuce

Posted on December 26, 2019 by | Leave a comment

Science Direct

In the present study, we investigated whether cold plasma activation affected the efficacy of aerosolized hydrogen peroxide against S. Typhimurium and L. innocua. Stem scars and smooth surfaces of grape tomatoes, surfaces of Granny Smith apples and Romaine lettuce (both midrib and upper leaves) and cantaloupe rinds were inoculated with two-strain cocktails of S. Typhimurium and 3-strain cocktails of L. innocua. The inoculated samples were treated with 7.8% aerosolized H2O2 with and without cold plasma for various times. For all fresh produce items and surfaces, cold plasma significantly (P < 0.05) improved the efficacy of aerosolized H2O2 against Salmonella and L. innocua. Without cold plasma activation, H2O2 aerosols only reduced populations of Salmonella by 1.54–3.17 log CFU/piece while H2O2 with cold plasma achieved 2.35–5.50 log CFU/piece reductions of Salmonella. L. innocua was more sensitive to the cold plasma-activated H2O2 than Salmonella. Cold plasma activated H2O2 aerosols reduced Listeria populations by more than 5 log CFU/piece on all types and surfaces of fresh produce except for the tomato stem scar area. Without cold plasma, the reductions by H2O2 were only 1.35–3.77 log CFU/piece. Overall, our results demonstrated that cold plasma activation significantly enhanced the efficacy of H2O2 mist against bacteria on fresh produce.

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