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Frank Devlieghere - One of the best experts on this subject based on the ideXlab platform.
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Characterization of spoilage markers in modified atmosphere packaged Iceberg Lettuce
International journal of food microbiology, 2018Co-Authors: Angelos-gerasimos Ioannidis, Peter Ragaert, Frederiek-maarten Kerckhof, Yasmine Riahi Drif, Mike Vanderroost, Nico Boon, Bruno De Meulenaer, Frank DevlieghereAbstract:Abstract Fresh cut Iceberg Lettuce spoilage was studied considering the microbial and biochemical activity, the formation of volatile organic compounds (VOC) and consumer acceptability. Lettuce was packaged under three different packaging conditions and stored at 4 °C for 10 days: anaerobic packaging (ANAER), equilibrium modified atmosphere packaging with 3% O2 (EMAP) and perforated packages (AIR). Results indicated a clear distinction between packaging conditions. EMAP and AIR resulted in a short shelf life (≤5.6 days) which was limited due to browning, leading to consumer rejection as assessed via the Weibull hazard analysis method, while no off-odors were detected. Culture- independent 16 s rRNA gene amplicon sequencing revealed Pseudomonas spp. as the dominating species. In contrast, under ANAER conditions, lactic acid bacteria dominated with genera of Leuconostoc spp. and Lactococcus spp. proliferating, while also oligotypes of Pseudomonas spp. were found. Spoilage under ANAER occurred after 6.6 days and it was related to strong fermentative-like off-odors that were present by the end of storage. As revealed by selective ion flow tube mass spectrometry (SIFT-MS), these odors were associated with several VOCs such as: ethanol, 3-methyl-1-butanol, 2,3-butanediol, (Z)-3-hexen-1-ol, hexanal, acetic acid, ethyl acetate and dimethyl sulfide. Panelists rejected the Iceberg Lettuce due to the formation of off-odors while the overall appearance remained good throughout the study. Hence a sensor based technology incorporated in the packaging, detecting VOCs and in particular ethanol as dominant compound, could serve as a spoilage indicator for ANAER packed Lettuce, which proved to have the longest shelf life.
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Is There a Relation between the Microscopic Leaf Morphology and the Association of Salmonella and Escherichia coli O157:H7 with Iceberg Lettuce Leaves?
Journal of food protection, 2016Co-Authors: Inge Van Der Linden, Markus Eriksson, Mieke Uyttendaele, Frank DevlieghereAbstract:ABSTRACT To prevent contamination of fresh produce with enteric pathogens, more insight into mechanisms that may influence the association of these pathogens with fresh produce is needed. In this study, Escherichia coli O157:H7 and Salmonella were chosen as model pathogens, and fresh cut Iceberg Lettuce was chosen as a model fresh produce type. The morphological structure of Iceberg Lettuce leaves (stomatal density and length of cell margins per leaf area) was quantified by means of leaf peels and light microscopy of leaves at different stages of development (outer, middle, and inner leaves of the crop) on both leaf sides (abaxial and adxial) and in three leaf regions (top, center, and bottom). The morphology of the top region of the leaves was distinctly different from that of the center and base, with a significantly higher stomatal density (up to five times more stomata), different cell shape, and longer cell margins (two to three times longer). Morphological differences between the same regions of the...
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High oxygen atmospheres can induce russet spotting development in minimally processed Iceberg Lettuce.
Postharvest Biology and Technology, 2015Co-Authors: Francisco López-gálvez, Peter Ragaert, Markus Eriksson, Azizul Haque, Marie-christine Van Labeke, Frank DevlieghereAbstract:Abstract High oxygen modified atmospheres have been suggested as an alternative preservation technique to classical low O2 modified atmosphere packaging (MAP) for fresh-cut Lettuce. The advantages of high O2 storage would be a strong reduction of browning, avoidance of low O2 levels linked to off-odors, and the inhibition of microbial growth. However, storage under high O2 potentially could increase both production of ethylene and sensitivity to this hormone in Lettuce tissue, leading to the development of quality problems linked to ethylene. In this study, different quality parameters (sensory quality, microbiological load, electrolyte leakage, volatile metabolites) were studied on fresh-cut Iceberg Lettuce stored under different gas conditions at 7 °C: (low O2 MAP (3% O2 compensated with N2), atmospheric conditions, high O2 MAP (50 or 90% O2 compensated with N2)). Furthermore, additional experiments using ethylene absorbers were performed in order to assess the link between high O2 storage, ethylene accumulation, and russet spotting. There was no significant difference between storage conditions regarding growth of mesophilic bacteria and yeasts, electrolyte leakage, or ethanol production. On the other hand, high O2 atmospheres reduced browning but promoted russet spotting development compared with low O2 and atmospheric conditions. In further specific experiments the relationship between high O2 storage, ethylene production, and russet spotting in fresh-cut Iceberg Lettuce were made evident.
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Effect of new sanitizing formulations on quality of fresh-cut Iceberg Lettuce
Postharvest Biology and Technology, 2013Co-Authors: Francisco López-gálvez, Peter Ragaert, Ladie Anne Palermo, Markus Eriksson, Frank DevlieghereAbstract:Abstract In the present study, three recently patented decontamination agents: peroxyacetic acid combined with lactic acid, and two different combinations of hydrogen peroxide with citric acid (with and without propylene glycol), were compared with sodium hypochlorite and tap water washing regarding their effect on equilibrium modified atmosphere packaged (EMAP) fresh-cut Iceberg Lettuce. Effects of these sanitizers on respiration rate, electrolyte leakage, microbial levels, and sensory quality of the product after decontamination and during storage (3 d at 4 °C followed by 4 d at 7 °C) were elucidated. Hydrogen peroxide based sanitizers provoked a significant increase in the respiration rate and the electrolyte leakage of fresh-cut Iceberg Lettuce compared with tap water washing. Peroxyacetic acid combined with lactic acid resulted in similar results to those of tap water washing for all the parameters analyzed. However, other aspects of the combination of peroxyacetic and lactic acids (e.g. efficacy for cross-contamination avoidance) should be assessed in the future in order to determine its suitability for fresh-cut Iceberg Lettuce processing.
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efficacy of sodium hypochlorite and peroxyacetic acid to reduce murine norovirus 1 b40 8 listeria monocytogenes and escherichia coli o157 h7 on shredded Iceberg Lettuce and in residual wash water
Journal of Food Protection, 2009Co-Authors: Leen Baert, Frank Devlieghere, Isabelle Vandekinderen, Els Van Coillie, Johan Debevere, Mieke UyttendaeleAbstract:The efficiency of sodium hypochlorite (NaOCl) and peroxyacetic acid (PAA) to reduce murine norovirus 1 (MNV-1), a surrogate for human norovirus, and Bacteroides fragilis HSP40-infecting phage B40-8 on shredded Iceberg Lettuce was investigated. The levels of removal of viruses MNV-1 and B40-8 were compared with the reductions observed for bacterial pathogens Listeria monocytogenes and Escherichia coli O157:H7. Two inoculation levels, one with a high organic load and the other containing a 10-fold lower number of pathogens and organic matter, showed that the effectiveness of NaOCl was greatly influenced by the presence of organic material, which was not observed for PAA. Moreover, the present study showed that 200 mg/liter NaOCl or 250 mg/liter PAA is needed to obtain an additional reduction of 1 log (compared with tap water) of MNV-1 on shredded Iceberg Lettuce, whereas only 250 mg/liter PAA achieved this for bacterial pathogens. None of the treatments resulted in a supplementary 1-log PFU/g reduction of B40-8 compared with tap water. B40-8 could therefore be useful as an indicator of decontamination processes of shredded Iceberg Lettuce based on NaOCl or PAA. Neither MNV-1, B40-8, nor bacterial pathogens could be detected in residual wash water after shredded Iceberg Lettuce was treated with NaOCl and PAA, whereas considerable numbers of all these microorganisms were found in residual wash water consisting solely of tap water. This study illustrates the usefulness of PAA and NaOCl in preventing cross-contamination during the washing process rather than in causing a reduction of the number of pathogens present on Lettuce.
Yong-biao Liu - One of the best experts on this subject based on the ideXlab platform.
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Semi-commercial ultralow oxygen treatment for control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on harvested Iceberg Lettuce
Postharvest Biology and Technology, 2011Co-Authors: Yong-biao LiuAbstract:Pallet-scale ultralow oxygen (ULO) treatment was applied to Iceberg Lettuce after various lengths of postharvest storage to determine the effects of pre-treatment storage on Lettuce tolerance to ULO treatment for control of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Lettuce from seven cultivars was vacuum cooled and stored at 2 ◦ C after harvest for 0, 2, 3, and 5 d before being subjected to 2-d ULO treatment with 0.003% oxygen at 10 ◦C ambient temperature. Complete control of thrips was achieved in all three tests. Temperature of Lettuce increased from about 5 ◦ C at the
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Ultralow Oxygen Treatment for Postharvest Control of Nasonovia ribisnigri (Homoptera: Aphididae) on Iceberg Lettuce
Journal of economic entomology, 2005Co-Authors: Yong-biao LiuAbstract:Abstract The aphid Nasonovia ribisnigri (Mosley) is a common pest of Lettuce in the United States. It hinders export of U.S. Lettuce to the overseas market such as Japan where it is a quarantined pest. Ultralow oxygen treatments were studied for control of the insect on Iceberg Lettuce. Small-scale ultralow oxygen treatments in plastic jars were conducted at 1, 5, and 10°C for different durations to determine effective treatment against nymphs and alates of N. ribisnigri. At oxygen levels of 0.015–0.025%, N. ribisnigri can be controlled in 3 d at 1°C, 2 d at 5°C, and 1 d at 10°C. Large-scale ultralow oxygen treatments were conducted in bulk container treatment chambers with commercial Iceberg Lettuce heads for 2 d at 6°C with oxygen levels of 0.015 and 0.025% and for 3 d at 3°C with oxygen level of 0.015%. All treatments achieved complete control of N. ribisnigri. No negative impact on Lettuce quality was detected after 2 wk of posttreatment storage. Therefore, the selected treatments have potential to be...
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Distribution and population development of Nasonovia ribisnigri (Homoptera: Aphididae) in Iceberg Lettuce.
Journal of economic entomology, 2004Co-Authors: Yong-biao LiuAbstract:A field study was conducted to determine the distribution and development of aphid Nasonovia ribisnigri (Mosley) (Homoptera: Aphididae) populations in Iceberg Lettuce, Lactuca sativa L. ‘Salinas’. Lettuce plants were transplanted and caged individually in the field and inoculated with apterous N. ribisnigri at 0, 1, 2, 3, and 4 wk after transplanting in spring and fall 2002. Plants were harvested 15–50 d after inoculations; numbers of alates and apterous N. ribisnigri were counted or estimated on each leaf for each plant. Inoculations during all 5 wk of plant development resulted in successful colonization of Lettuce heads. Results indicated that head formation did not reduce the risk of colonization by N. ribisnigri to Iceberg Lettuce; plants were susceptible to colonization by N. ribisnigri throughout their development. For later inoculations, N. ribisnigri populations were relatively smaller, and aphids were found mostly within the heads. For earlier inoculations, N. ribisnigri populations were larger, and within-plant distributions shifted toward frame leaves. The shift of population distributions toward frame leaves correlated significantly with increases in N. ribisnigri population density. For most inoculations, more aphids were present on wrapper leaves than on other leaves. The proportion of alates did not vary significantly with population density. Population development of N. ribisnigri also correlated significantly with heat unit accumulation. Yellow sticky cards were used to monitor alates in each cage. Catches of N. ribisnigri alates on yellow sticky cards were significantly correlated with total numbers of alates as well as with total population sizes on individual Lettuce plants.
Hannu Korkeala - One of the best experts on this subject based on the ideXlab platform.
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A Widespread Outbreak of Yersinia pseudotuberculosis O:3 Infection from Iceberg Lettuce
The Journal of infectious diseases, 2004Co-Authors: J. Pekka Nuorti, Taina Niskanen, Saija Hallanvuo, Janne Mikkola, Eija Kela, Maija Hatakka, Maria Fredriksson Ahomaa, Outi Lyytikäinen, Anja Siitonen, Hannu KorkealaAbstract:Background. The vehicles and sources of Yersinia pseudotuberculosis infection are unknown. In Finland, clinical microbiology laboratories routinely report Y. pseudotuberculosis isolations and submit isolates for serotype analysis. In October 1998, the number of serotype 0:3 infections increased markedly. Methods. Case patients with culture-confirmed Y pseudotuberculosis 0:3 infection were identified by use of laboratory-based surveillance. We conducted a population-based case-control study. Healthy community control subjects were matched by age, sex, and postal code. Isolates were subtyped by pulsed-field gel electrophoresis (PFGE). Results. Nationwide, 47 case patients were identified (age range, 2-77 years; median, 19 years). One patient with bacteremia died; 5 underwent appendectomies. We enrolled 38 case patients and 76 control subjects in the case-control study. Seventy-one percent of case patients and 42% of control subjects reported having eaten Iceberg Lettuce (matched odds ratio, 3.8; 95% confidence interval, 1.3-9.4); a dose-response relationship was found for increasing frequency of consumption. Of the 27 isolates obtained from case patients and tested in the analysis, all had indistinguishable PFGE patterns. Four lunch cafeterias that had served Iceberg Lettuce were associated with clusters of case patients. The Lettuce was traced back to originating farms. Conclusions. Iceberg Lettuce was implicated as the vehicle of a widespread foodborne Y. pseudotuberculosis outbreak. Ongoing laboratory-based surveillance and serotype analysis were essential in the rapid detection of infection. Cases of yersiniosis, which appear to be sporadic, may be part of unrecognized outbreaks caused by contaminated fresh produce.
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Occurence of Yersinia pseudotuberculosis in Iceberg Lettuce and Environment
Advances in experimental medicine and biology, 2003Co-Authors: Taina Niskanen, Maria Fredriksson-ahomaa, Hannu KorkealaAbstract:The virF-positive Y. pseudotuberculosis serotype O:2 strain was isolated from food in Finland for the first time. Y. pseudotuberculosis is considered to be a food-borne pathogen, but it has rarely been isolated from foods. Iceberg Lettuce are grown on open fields and irrigated with water from lakes, rivers, and ponds on Ahvenanmaa Island. Y. pseudotuberculosis is frequently isolated from many domestic and wild animals (Fukushima and Gomyoda, 1991; Sanford et al., 1995; Niskanen et al., 2001). There is a large population of deers and hares on Ahvenanmaa Island. These animals can be asymptomatic carriers and reservoirs of Y. pseudotuberculosis (Griffin et al., 1992). Wildlife had access to Lettuce fields and the ponds used to collect irrigation water. It is possible, that wild animals contaminate water, soil, and Lettuce on the fields with their feces containing Y. pseudotuberculosis (Inoue et al., 1991; Fukushima et al., 1995). Contamination of Iceberg Lettuce was likely resulted from use of irrigation water contaminated with animal feces. Also nontypable Y. pseudotuberculosis strains without the virulence plasmid were recovered from environmental samples and a Lettuce sample. Non-pathogenic Y. pseudotuberculosis serotypes O:7-O:14 have been previously recovered in environment (Nagano et al., 1996). Lettuce produced on open fields irrigated with water from natural water systems may contain pathogenic microbes, and should be concern as a possible source of Y. pseudotuberculosis infections.
Elliot T. Ryser - One of the best experts on this subject based on the ideXlab platform.
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Persistence of Escherichia coli O157: H7 during pilot-scale processing of Iceberg Lettuce using flume water containing peroxyacetic acid-based sanitizers and various organic loads
International journal of food microbiology, 2017Co-Authors: Gordon R. Davidson, Chelsea N. Kaminski-davidson, Elliot T. RyserAbstract:In order to minimize cross-contamination during leafy green processing, chemical sanitizers are routinely added to the wash water. This study assessed the efficacy of peroxyacetic acid and mixed peracid against E. coli O157:H7 on Iceberg Lettuce, in wash water, and on equipment during simulated commercial production in a pilot-scale processing line using flume water containing various organic loads. Iceberg Lettuce (5.4kg) inoculated to contain 106CFU/g of a 4-strain cocktail of non-toxigenic, GFP-labeled, ampicillin-resistant E. coli O157:H7, was shredded using a commercial shredder, step-conveyed to a flume tank, washed for 90s using water alone or two different sanitizing treatments (50ppm peroxyacetic acid or mixed peracid) in water containing organic loads of 0, 2.5, 5 or 10% (w/v) blended Iceberg Lettuce, and then dried using a shaker table and centrifugal dryer. Thereafter, three 5.4-kg batches of uninoculated Iceberg Lettuce were identically processed. Various product (25g) and water (50ml) samples collected during processing along with equipment surface samples (100cm2) from the flume tank, shaker table and centrifugal dryer were then assessed for numbers of E. coli O157:H7. Organic load rarely impacted (P>0.05) the efficacy of either peroxyacetic acid or mixed peracid, with typical reductions of >5logCFU/ml in wash water throughout processing for all organic loads. Increases in organic load in the wash water corresponded to changes in total solids, chemical oxygen demand, turbidity, maximum filterable volume, and oxidation/reduction potential. After 90s of exposure to flume water, E. coli O157:H7 reductions on inoculated Lettuce ranged from 0.97 to 1.74logCFU/g using peroxyacetic acid, with an average reduction of 1.35logCFU/g for mixed peracid. E. coli O157:H7 persisted on all previously uninoculated Lettuce following the inoculated batch, emphasizing the need for improved intervention strategies that can better ensure end-product safety.
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Impact of Organic Load on Escherichia coli O157:H7 Survival during Pilot-Scale Processing of Iceberg Lettuce with Acidified Sodium Hypochlorite
Journal of food protection, 2014Co-Authors: Gordon R. Davidson, Chelsea N. Kaminski, Elliot T. RyserAbstract: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 three chlorine treatments against Escherichia coli O157:H7 on Iceberg Lettuce, in wash water, and on surfaces of a pilot-scale processing line using flume water containing various organic loads. Iceberg Lettuce (5.4 kg) was inoculated to contain 106 CFU/g of a 4-strain cocktail of nontoxigenic, green fluorescent protein–labeled, ampicillin-resistant E. coli O157:H7 and held for 24 h at 4°C before processing. Lettuce was shredded using a Urschel TransSlicer, step conveyed to a flume tank, washed for 90 s using water alone or one of three different sanitizing treatments (50 ppm of total chlorine either alone or acidified to pH 6.5 with citric acid or T-128) in water containing organic loads of 0, 2.5, 5, or 10% (wt/vol) blended Iceberg Lettuce, and then dried using a shaker table and centrifugal dryer. Next, three 5.4-kg batches ...
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Efficacy of commercial produce sanitizers against nontoxigenic Escherichia coli O157:H7 during processing of Iceberg Lettuce in a pilot-scale leafy green processing line.
Journal of food protection, 2013Co-Authors: Gordon R. Davidson, Annemarie L. Buchholz, Elliot T. RyserAbstract: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 pr...
Francisco López-gálvez - One of the best experts on this subject based on the ideXlab platform.
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High oxygen atmospheres can induce russet spotting development in minimally processed Iceberg Lettuce.
Postharvest Biology and Technology, 2015Co-Authors: Francisco López-gálvez, Peter Ragaert, Markus Eriksson, Azizul Haque, Marie-christine Van Labeke, Frank DevlieghereAbstract:Abstract High oxygen modified atmospheres have been suggested as an alternative preservation technique to classical low O2 modified atmosphere packaging (MAP) for fresh-cut Lettuce. The advantages of high O2 storage would be a strong reduction of browning, avoidance of low O2 levels linked to off-odors, and the inhibition of microbial growth. However, storage under high O2 potentially could increase both production of ethylene and sensitivity to this hormone in Lettuce tissue, leading to the development of quality problems linked to ethylene. In this study, different quality parameters (sensory quality, microbiological load, electrolyte leakage, volatile metabolites) were studied on fresh-cut Iceberg Lettuce stored under different gas conditions at 7 °C: (low O2 MAP (3% O2 compensated with N2), atmospheric conditions, high O2 MAP (50 or 90% O2 compensated with N2)). Furthermore, additional experiments using ethylene absorbers were performed in order to assess the link between high O2 storage, ethylene accumulation, and russet spotting. There was no significant difference between storage conditions regarding growth of mesophilic bacteria and yeasts, electrolyte leakage, or ethanol production. On the other hand, high O2 atmospheres reduced browning but promoted russet spotting development compared with low O2 and atmospheric conditions. In further specific experiments the relationship between high O2 storage, ethylene production, and russet spotting in fresh-cut Iceberg Lettuce were made evident.
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Effect of new sanitizing formulations on quality of fresh-cut Iceberg Lettuce
Postharvest Biology and Technology, 2013Co-Authors: Francisco López-gálvez, Peter Ragaert, Ladie Anne Palermo, Markus Eriksson, Frank DevlieghereAbstract:Abstract In the present study, three recently patented decontamination agents: peroxyacetic acid combined with lactic acid, and two different combinations of hydrogen peroxide with citric acid (with and without propylene glycol), were compared with sodium hypochlorite and tap water washing regarding their effect on equilibrium modified atmosphere packaged (EMAP) fresh-cut Iceberg Lettuce. Effects of these sanitizers on respiration rate, electrolyte leakage, microbial levels, and sensory quality of the product after decontamination and during storage (3 d at 4 °C followed by 4 d at 7 °C) were elucidated. Hydrogen peroxide based sanitizers provoked a significant increase in the respiration rate and the electrolyte leakage of fresh-cut Iceberg Lettuce compared with tap water washing. Peroxyacetic acid combined with lactic acid resulted in similar results to those of tap water washing for all the parameters analyzed. However, other aspects of the combination of peroxyacetic and lactic acids (e.g. efficacy for cross-contamination avoidance) should be assessed in the future in order to determine its suitability for fresh-cut Iceberg Lettuce processing.