Determination of Free Chlorine Concentrations Needed To Prevent Escherichia coli O157:H7 Cross-Contamination during Fresh-Cut Produce Wash†

2011 ◽  
Vol 74 (3) ◽  
pp. 352-358 ◽  
Author(s):  
YAGUANG LUO ◽  
XIANGWU NOU ◽  
YANG YANG ◽  
ISABEL ALEGRE ◽  
ELLEN TURNER ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Free Chlorine ◽  
Chlorine Concentration ◽  
Wash Water ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
E Coli ◽  
Wash Solution ◽  
Fresh Cut ◽  
Experimental Trials

This study was conducted to investigate the effect of free chlorine concentrations in wash water on Escherichia coli O157:H7 reduction, survival, and transference during washing of fresh-cut lettuce. The effectiveness of rewashing for inactivation of E. coli O157:H7 on newly cross-contaminated produce previously washed with solutions containing an insufficient amount of chlorine also was assessed. Results indicate that solutions containing a minimum of 0.5 mg/liter free chlorine were effective for inactivating E. coli O157:H7 in suspension to below the detection level. However, the presence of 1 mg/liter free chlorine in the wash solution before washing was insufficient to prevent E. coli O157:H7 survival and transfer during washing because the introduction of cut lettuce to the wash system quickly depleted the free chlorine. Although no E. coli O157:H7 was detected in the wash solution containing 5 mg/liter free chlorine before washing a mix of inoculated and uninoculated lettuce, low numbers of E. coli O157:H7 cells were detected on uninoculated lettuce in four of the seven experimental trials. When the prewash free chlorine concentration was increased to 10 mg/liter or greater, no E. coli O157:H7 transfer was detected. Furthermore, although rewashing newly cross-contaminated lettuce in 50 mg/liter free chlorine for 30 s significantly reduced (P = 0.002) the E. coli O157:H7 populations, it failed to eliminate E. coli O157:H7 on lettuce. This finding suggests that rewashing is not an effective way to correct for process failure, and maintaining a sufficient free chlorine concentration in the wash solution is critical for preventing pathogen cross-contamination.

Development of an Algorithm for Feed-Forward Chlorine Dosing of Lettuce Wash Operations and Correlation of Chlorine Profile with Escherichia coli O157:H7 Inactivation

2014 ◽  
Vol 77 (4) ◽  
pp. 558-566 ◽  
Author(s):  
BIN ZHOU ◽  
YAGUANG LUO ◽  
XIANGWU NOU ◽  
PATRICIA MILLNER
Keyword(s):  
Escherichia Coli ◽  
Reduction Potential ◽  
Free Chlorine ◽  
Organic Load ◽  
Escherichia Coli O157 ◽  
Feed Forward ◽  
E Coli ◽  
Wash Solution ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

The dynamic interactions of chlorine and organic matter during a simulated fresh-cut produce wash process and the consequences for Escherichia coli O157:H7 inactivation were investigated. An algorithm for a chlorine feed-forward dosing scheme to maintain a stable chlorine level was further developed and validated. Organic loads with chemical oxygen demand of 300 to 800 mg/liter were modeled using iceberg lettuce. Sodium hypochlorite (NaOCl) was added to the simulated wash solution incrementally. The solution pH, free and total chlorine, and oxidation-reduction potential were monitored, and chlorination breakpoint and chloramine humps determined. The results indicated that the E. coli O157:H7 inactivation curve mirrored that of the free chlorine during the chlorine replenishment process: a slight reduction in E. coli O157:H7 was observed as the combined chlorine hump was approached, while the E. coli O157:H7 cell populations declined sharply after chlorination passed the chlorine hump and decreased to below the detection limit (<0.75 most probable number per ml) after the chlorination breakpoint was reached. While the amounts of NaOCl required for reaching the chloramine humps and chlorination breakpoints depended on the organic loads, there was a linear correlation between NaOCl input and free chlorine in the wash solution once NaOCl dosing passed the chlorination breakpoint, regardless of organic load. The data obtained were further exploited to develop a NaOCl dosing algorithm for maintaining a stable chlorine concentration in the presence of an increasing organic load. The validation tests results indicated that free chlorine could be maintained at target levels using such an algorithm, while the pH and oxidation-reduction potential were also stably maintained using this system.

scholarly journals Modeling of Free Chlorine Consumption and Escherichia coli O157:H7 Cross‐Contamination During Fresh‐Cut Produce Wash Cycles

2019 ◽  
Vol 84 (10) ◽  
pp. 2736-2744 ◽  
Author(s):  
Mohammadreza Dehghan Abnavi ◽  
Ali Alradaan ◽  
Daniel Munther ◽  
Chandrasekhar R. Kothapalli ◽  
Parthasarathy Srinivasan
Keyword(s):  
Escherichia Coli ◽  
Free Chlorine ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
Fresh Cut

Efficacy of Commercial Produce Sanitizers against Nontoxigenic Escherichia coli O157:H7 during Processing of Iceberg Lettuce in a Pilot-Scale Leafy Green Processing Line

2013 ◽  
Vol 76 (11) ◽  
pp. 1838-1845 ◽  
Author(s):  
GORDON R. DAVIDSON ◽  
ANNEMARIE L. BUCHHOLZ ◽  
ELLIOT T. RYSER
Keyword(s):  
Escherichia Coli ◽  
Fluorescent Protein ◽  
Pilot Scale ◽  
Wash Water ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
E Coli ◽  
Iceberg Lettuce ◽  
Processing Line ◽  
Green Fluorescent

Chemical sanitizers are routinely used during commercial flume washing of fresh-cut leafy greens to minimize cross-contamination from the water. This study assessed the efficacy of five commercial sanitizer treatments against Escherichia coli O157:H7 on iceberg lettuce, in wash water, and on equipment during simulated commercial production in a pilot-scale processing line. Iceberg lettuce (5.4 kg) was inoculated to contain 106 CFU/g of a four-strain cocktail of nontoxigenic, green fluorescent protein–labeled, ampicillin-resistant E. coli O157:H7 and processed after 1 h of draining at ~22°C. Lettuce was shredded using a commercial slicer, step-conveyed to a flume tank, washed for 90 s using six different treatments (water alone, 50 ppm of peroxyacetic acid, 50 ppm of mixed peracid, or 50 ppm of available chlorine either alone or acidified to pH 6.5 with citric acid [CA] or T-128), and then dried using a shaker table and centrifugal dryer. Various product (25-g) and water (50-ml) samples collected during processing along with equipment surface samples (100 cm2) from the flume tank, shaker table, and centrifugal dryer were homogenized in neutralizing buffer and plated on tryptic soy agar. During and after iceberg lettuce processing, none of the sanitizers were significantly more effective (P ≤ 0.05) than water alone at reducing E. coli O157:H7 populations on lettuce, with reductions ranging from 0.75 to 1.4 log CFU/g. Regardless of the sanitizer treatment used, the centrifugal dryer surfaces yielded E. coli O157:H7 populations of 3.49 to 4.98 log CFU/100 cm2. Chlorine, chlorine plus CA, and chlorine plus T-128 were generally more effective (P ≤ 0.05) than the other treatments, with reductions of 3.79, 5.47, and 5.37 log CFU/ml after 90 s of processing, respectively. This indicates that chlorine-based sanitizers will likely prevent wash water containing low organic loads from becoming a vehicle for cross-contamination.

scholarly journals Evaluation of Potential Impacts of Free Chlorine during Washing of Fresh‐Cut Leafy Greens on Escherichia coli O157:H7 Cross‐Contamination and Risk of Illness

Risk Analysis ◽  
2021 ◽  
Author(s):  
Amir Mokhtari ◽  
Hao Pang ◽  
Sofia Santillana Farakos ◽  
Gordon R. Davidson ◽  
Elizabeth Noelia Williams ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Free Chlorine ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
Leafy Greens ◽  
Fresh Cut

Impact of Wash Water Quality on Sensory and Microbial Quality, Including Escherichia coli Cross-Contamination, of Fresh-Cut Escarole

2008 ◽  
Vol 71 (12) ◽  
pp. 2514-2518 ◽  
Author(s):  
ANA ALLENDE ◽  
MARIA V. SELMA ◽  
FRANCISCO LÓPEZ-GÁLVEZ ◽  
RAQUEL VILLAESCUSA ◽  
MARÍA I. GIL
Keyword(s):  
Escherichia Coli ◽  
Water Quality ◽  
Sensory Quality ◽  
Wash Water ◽  
Microbial Load ◽  
Contamination Level ◽  
Cross Contamination ◽  
Inoculum Level ◽  
E Coli ◽  
Fresh Cut

The influence of wash water quality on the microbial load and sensory quality of fresh-cut escarole was evaluated. Additionally, the degree of Escherichia coli cross-contamination between inoculated and uninoculated products after washing was also studied. Three types of wash water, i.e., potable water, diluted recirculated water, and recirculated water, containing different microbial counts and organic loads, were used. Results showed that microbial load (P > 0.02) and sensory quality (P > 0.625) of the product were not influenced by the water quality after washing and storage. Cross-contamination between inoculated and uninoculated products was observed after washing, as there was significant transmission of E. coli cells from the product to the wash water (P < 0.001). When fresh-cut escarole was contaminated at a high inoculum level (5.1 log CFU/g), wash water quality influenced the level of cross-contamination, as the highest E. coli load (P < 0.001) was shown in uninoculated fresh-cut escarole washed with recirculated water. However, when fresh-cut escarole was contaminated at a low inoculum level (3.2 log CFU/g), the wash water quality did not influence the level of cross-contamination, as E. coli slightly increased, although not at a statistically significant level, after the uninoculated product was washed with recirculated water (P > 0.035). Therefore, the contamination level may impact the effectiveness of water quality to reduce pathogen concentrations. It was clearly observed that cross-contamination of fresh-cut escarole with E. coli occurs, thereby suggesting that small amounts of contamination could impact the overall product and indicating the necessity of using wash water sanitizers to eliminate pathogens.

Tracking an Escherichia coli O157:H7–Contaminated Batch of Leafy Greens through a Pilot-Scale Fresh-Cut Processing Line

2014 ◽  
Vol 77 (9) ◽  
pp. 1487-1494 ◽  
Author(s):  
ANNEMARIE L. BUCHHOLZ ◽  
GORDON R. DAVIDSON ◽  
BRADLEY P. MARKS ◽  
EWEN C. D. TODD ◽  
ELLIOT T. RYSER
Keyword(s):  
Escherichia Coli ◽  
Membrane Filtration ◽  
Fluorescent Protein ◽  
Pilot Scale ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Leafy Greens ◽  
Iceberg Lettuce ◽  
Processing Line ◽  
Fresh Cut

Cross-contamination of fresh-cut leafy greens with residual Escherichia coli O157:H7–contaminated product during commercial processing was likely a contributing factor in several recent multistate outbreaks. Consequently, radicchio was used as a visual marker to track the spread of the contaminated product to iceberg lettuce in a pilot-scale processing line that included a commercial shredder, step conveyor, flume tank, shaker table, and centrifugal dryer. Uninoculated iceberg lettuce (45 kg) was processed, followed by 9.1 kg of radicchio (dip inoculated to contain a four-strain, green fluorescent protein–labeled nontoxigenic E. coli O157:H7 cocktail at 106 CFU/g) and 907 kg (2,000 lb) of uninoculated iceberg lettuce. After collecting the lettuce and radicchio in about 40 bags (~22.7 kg per bag) along with water and equipment surface samples, all visible shreds of radicchio were retrieved from the bags of shredded product, the equipment, and the floor. E. coli O157:H7 populations were quantified in the lettuce, water, and equipment samples by direct plating with or without prior membrane filtration on Trypticase soy agar containing 0.6% yeast extract and 100 ppm of ampicillin. Based on triplicate experiments, the weight of radicchio in the shredded lettuce averaged 614.9 g (93.6%), 6.9 g (1.3%), 5.0 g (0.8%), and 2.8 g (0.5%) for bags 1 to 10, 11 to 20, 21 to 30, and 31 to 40, respectively, with mean E. coli O157:H7 populations of 1.7, 1.2, 1.1, and 1.1 log CFU/g in radicchio-free lettuce. After processing, more radicchio remained on the conveyor (9.8 g; P < 0.05), compared with the shredder (8.3 g), flume tank (3.5 g), and shaker table (0.1 g), with similar E. coli O157:H7 populations (P > 0.05) recovered from all equipment surfaces after processing. These findings clearly demonstrate both the potential for the continuous spread of contaminated lettuce to multiple batches of product during processing and the need for improved equipment designs that minimize the buildup of residual product during processing.

scholarly journals The Effect Ultrasound and Surfactants on Nanobubbles Efficacy against Listeria innocua and Escherichia coli O157:H7, in Cell Suspension and on Fresh Produce Surfaces

Foods ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2154
Author(s):  
Shamil Rafeeq ◽  
Reza Ovissipour
Keyword(s):  
Escherichia Coli ◽  
Cell Suspension ◽  
Sodium Dodecyl ◽  
Listeria Innocua ◽  
Wash Water ◽  
Tween 20 ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Bacterial Removal ◽  
The Impact

Removing foodborne pathogens from food surfaces and inactivating them in wash water are critical steps for reducing the number of foodborne illnesses. In this study we evaluated the impact of surfactants on enhancing nanobubbles’ efficacy on Escherichia coli O157:H7, and Listeria innocua removal from spinach leaves. We evaluated the synergistic impact of nanobubbles and ultrasound on these two pathogens inactivation in the cell suspension. The results indicated that nanobubbles or ultrasound alone could not significantly reduce bacteria in cell suspension after 15 min. However, a combination of nanobubbles and ultrasonication caused more than 6 log cfu/mL reduction after 15 min, and 7 log cfu/mL reduction after 10 min of L. innocua and E. coli, respectively. Nanobubbles also enhanced bacterial removal from spinach surface in combination with ultrasonication. Nanobubbles with ultrasound removed more than 2 and 4 log cfu/cm2 of L. innocua and E. coli, respectively, while ultrasound alone caused 0.5 and 1 log cfu/cm2 of L. innocua and E. coli reduction, respectively. No reduction was observed in the solutions with PBS and nanobubbles. Adding food-grade surfactants (0.1% Sodium dodecyl sulfate-SDS, and 0.1% Tween 20), did not significantly enhance nanobubbles efficacy on bacterial removal from spinach surface.

Effect of Modified Atmosphere Packaging on the Persistence and Expression of Virulence Factors of Escherichia coli O157:H7 on Shredded Iceberg Lettuce†

2011 ◽  
Vol 74 (5) ◽  
pp. 718-726 ◽  
Author(s):  
MANAN SHARMA ◽  
SUDESNA LAKSHMAN ◽  
SEAN FERGUSON ◽  
DAVID T. INGRAM ◽  
YAGUANG LUO ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Virulence Factors ◽  
Modified Atmosphere Packaging ◽  
Ambient Air ◽  
Modified Atmosphere ◽  
Escherichia Coli O157 ◽  
Atmospheric Conditions ◽  
E Coli ◽  
Leafy Greens ◽  
Fresh Cut

Fresh-cut leafy greens contaminated with Escherichia coli O157:H7 have caused foodborne outbreaks. Packaging conditions, coupled with abusive storage temperatures of contaminated lettuce, were evaluated for their effect on the potential virulence of E. coli O157:H7. Shredded lettuce was inoculated with 5.58 and 3.98 log CFU E. coli O157:H7 per g and stored at 4 and 15°C, respectively, for up to 10 days. Lettuce was packaged under treatment A (modified atmosphere packaging conditions used for commercial fresh-cut produce, in gas-permeable film with N2), treatment B (near–ambient air atmospheric conditions in a gas-permeable film with microperforations), and treatment C (high-CO2 and low-O2 conditions in a gas-impermeable film). E. coli O157:H7 populations from each treatment were determined by enumeration of numbers on MacConkey agar containing nalidixic acid. RNA was extracted from packaged lettuce for analysis of expression of virulence factor genes stx2, eae, ehxA, iha, and rfbE. E. coli O157:H7 populations on lettuce at 4°C under all treatments decreased, but most considerably so under treatment B over 10 days. At 15°C, E. coli O157:H7 populations increased by at least 2.76 log CFU/g under all treatments. At 15°C, expression of eae and iha was significantly greater under treatment B than it was under treatments A and C on day 3. Similarly, treatment B promoted significantly higher expression of stx2, eae, ehxA, and rfbE genes on day 10, compared with treatments A and C at 15°C. Results indicate that storage under near–ambient air atmospheric conditions can promote higher expression levels of O157 virulence factors on lettuce, and could affect the severity of E. coli O157:H7 infections associated with leafy greens.

Two Generally Recognized as Safe Surfactants plus Acidulants Inactivate Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in Suspension or on Dip-Inoculated Grape Tomatoes

2020 ◽  
Vol 83 (4) ◽  
pp. 637-643
Author(s):  
JOSHUA B. GURTLER
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Bovine Serum ◽  
Fresh Produce ◽  
Free Chlorine ◽  
Sodium Dodecylbenzene Sulfonate ◽  
Escherichia Coli O157 ◽  
E Coli

ABSTRACT Contamination of fresh produce with the foodborne pathogens Salmonella enterica, Listeria monocytogenes, and Escherichia coli O157:H7 continues to be problematic, resulting in outbreaks of foodborne illness and costly corporate recalls. Various individual concentrations of citric or lactic acids (0.35 to 0.61%) or isopropyl citrate (0.16 to 0.54%) combined with two generally recognized as safe surfactants, 0.025% sodium-2-ethyl-hexyl sulfate and 0.025% sodium dodecylbenzene-sulfonate, were tested against these three pathogens in suspension and when inoculated and dried on the surface of grape tomatoes. The efficacy of sodium hypochlorite (NaClO; at 46 ppm) was also evaluated under dirty and clean conditions in suspension after addition of 0.3 or 0.03% bovine serum albumin, respectively, as an organic load. NaClO (46 ppm) inactivated the three pathogens in suspension by <0.76 log CFU/mL after 5 min in the presence of 0.3% bovine serum albumin, whereas 9 and 15 ppm of free chlorine inactivated the pathogens by 0.64 and 2.77 log CFU/mL, respectively, after 5 min under clean conditions. Isopropyl citrate (0.16% acidulant) plus 0.05% total concentration of the two surfactants inactivated the pathogens in suspension by up to 7.0 log CFU/mL within 2 min. When applied to grape tomatoes for 2 min, 0.54% isopropyl citrate plus 0.025% concentrations of each of the two surfactants reduced Salmonella, E. coli O157:H7, and L. monocytogenes by as much as ca. 5.47, 4.89, and 4.19 log CFU/g, respectively. These reductions were significantly greater than those achieved with 49 ppm of free chlorine. Citric acid and lactic acid plus surfactant washes achieved greater inactivation than water-only washes, reducing Salmonella, E. coli O157:H7, and L. monocytogenes on tomatoes by up to 4.90, 4.37, and 3.98 log CFU/g, respectively. These results suggest that these combinations of acidulants and surfactants may be an effective tool for preventing cross-contamination during the washing of grape tomatoes, for reducing pathogens on the fruit itself, and as an alternative to chlorine for washing fresh produce. HIGHLIGHTS

Approaches toward Identification of Surrogates To Validate Antimicrobial Washes as Preventive Controls for Fresh-Cut Leafy Greens

2017 ◽  
Vol 80 (10) ◽  
pp. 1600-1604
Author(s):  
A. Shazer ◽  
D. Stewart ◽  
K. Deng ◽  
M. Tortorello
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
Process Variables ◽  
Leafy Greens ◽  
Microbial Characteristics ◽  
Leaf Surfaces ◽  
Fresh Cut ◽  
Contamination Events

ABSTRACT In fresh-cut produce production, antimicrobials may be used during washing to control the risk of cross-contamination by microbial hazards. Surrogate microorganisms have long been used to validate processes, but none have been identified for validating the efficacy of antimicrobial washing of fresh-cut produce. The objective of this study was to develop procedures by which surrogates may be identified for use in validating the control of cross-contamination for fresh-cut lettuce operations. Four microbial characteristics, which may be important factors in cross-contamination events, were quantitatively evaluated in potential surrogate microorganisms for comparison to a reasonably foreseeable hazard, Escherichia coli O157:H7: sensitivity to chlorine in solution, sensitivity to chlorine on lettuce leaf surfaces, shedding from contaminated lettuce leaves into the water during washing, and cross-contamination from inoculated to uninoculated lettuce leaves during chorine washing. A procedure of practical quantitative experiments for comparing the characteristics reduced the original pool of 80 potential strains, which consisted of lactic acid bacteria, probiotics, and isolates obtained from lettuce enrichment cultures, to five strains: Lactobacillus plantarum, Pediococcus pentosaceus, probiotic 22C, and two lettuce enrichment isolates. These strains may be evaluated in additional studies involving comparisons to other reasonably foreseeable hazards and including other potential process variables that should be understood and controlled to prevent cross-contamination in fresh-cut lettuce operations.

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