Publications by authors named "Inmaculada Viñas"

31 Publications

Water UV-C treatment alone or in combination with peracetic acid: A technology to maintain safety and quality of strawberries.

Int J Food Microbiol 2020 Dec 11;335:108887. Epub 2020 Sep 11.

IIRTA, Postharvest Programme, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida, Catalonia, Spain.. Electronic address:

Disinfection of fruits is one of the most important steps since they are going to be eaten fresh-or minimally-processed. This step affects quality, safety, and shelf-life of the product. Despite being a common sanitizer in the fruit industry, chlorine may react with organic matter leading to the formation of toxic by-products. Alternative sustainable disinfection strategies to chlorine are under study to minimize environmental and human health impact. Water-assisted UV-C light (WUV-C) is proposed here as an alternative sanitizing method for strawberries. In this study, strawberries were washed for 1 or 5 min in a tank with 2 or 4 lamps on, each emitting UV-C light at 17.2 W/cm, or in a chlorine solution (200 ppm, pH 6.5). Moreover, trials with 4 lamps on, together with a washing solution consisting on peracetic acid at 40 or 80 ppm, were carried out. Overall, quality and nutritional parameters of strawberries after treatments were maintained. Changes in color were not noticeable and fruits did not lose firmness. No major changes were observed in antioxidant activity, organic acid, anthocyanin, vitamin C, and total phenolic content. Yeasts and molds were not affected by the WUV-C treatment, and 5 min were needed to significantly reduce total aerobic mesophylls population. However, reductions of artificially inoculated Listeria innocua and Salmonella Typhimurium after WUV-C treatments were comparable to those obtained with chlorine-wash, which were 3.0 log CFU / g. Moreover, WUV-C light was effective to minimize microorganisms remaining in washing water, avoiding cross-contamination and thus, allowing water recirculation. This effect was improved when combining the action of UV-C light with peracetic acid, showing the suitability of this combined treatment, understood as an alternative to chlorine sanitation, for sanitizing strawberries and keeping the populations of pathogenic bacteria in washing water lower than 0.6 ± 0.1 log CFU / mL.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2020.108887DOI Listing
December 2020

Formation of patulin-glutathione conjugates induced by pulsed light: A tentative strategy for patulin degradation in apple juices.

Food Chem 2020 Jun 23;315:126283. Epub 2020 Jan 23.

Food Technology Department, UTPV-XaRTA, Agrotecnio Center, University of Lleida, Rovira Roure 191, 25198 Lleida, Spain.

Patulin is a toxic mycotoxin usually associated with apple products. Due to its unhealthy effects for humans, its content is regulated by the food safety authorities. The removal or degradation of this mycotoxin in contaminated apple juices has been studied with different approaches with uneven effectiveness. However, a strategy based on the chemical reaction between patulin and glutathione (GSH), in order to generate the conjugates that are formed during cell detoxification process, is an innovative approach yet to be evaluated. In this work, the formation of patulin-GSH conjugates activated by the application of pulsed light treatments and catalyzed by Fe ions was evaluated. The study of patulin degradation and effect of the GSH/Fe molar ratio showed that a molar ratio of 5 allows an adequate catalytic effect of the metal ions. In addition, mono-substituted patulin-glutathione adducts were identified as the main type of generated conjugates.
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http://dx.doi.org/10.1016/j.foodchem.2020.126283DOI Listing
June 2020

Effects of long-term controlled atmosphere storage, minimal processing, and packaging on quality attributes of ( L.).

Food Sci Technol Int 2020 Jul 23;26(5):403-412. Epub 2019 Dec 23.

IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic Agroalimentari, Parc de Gardeny, Lleida, Spain.

are the immature floral stems of the second-year onion ( L.) resprouts. Modified atmosphere packaging or vacuum packaging are suitable alternatives to preserve fresh-cut vegetables. The objective of this study was to evaluate the effect of postharvest storage time of raw vegetable stored under controlled atmosphere and used packaging system after minimal processing on the quality of fresh-cut . used for minimal processing were stored under 1.0 kPa O + 2.0 kPa CO at 1 ℃ for 30 and 60 days. Fresh-cut were packaged using passive modified atmosphere packaging or vacuum packaging and were stored at 4 ℃ for 15 days. stored under controlled atmosphere for 30 days presented better retention of quality and in turn, being more suitable for minimally processing. Vacuum packaging preserved the physicochemical quality of fresh-cut better after 15 days. Mesophilic aerobic counts were also higher in fresh-cut stored under modified atmosphere packaging, but all counts were below the recommended limits during and at the end of their shelf-life (15 days). The most suitable conservation strategy might be to store whole under controlled atmosphere for 30 days and after minimally processing, packaged under vacuum in order to extend the shelf-life of fresh-cut .
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http://dx.doi.org/10.1177/1082013219891007DOI Listing
July 2020

Strawberry sanitization by peracetic acid washing and its effect on fruit quality.

Food Microbiol 2019 Oct 15;83:159-166. Epub 2019 May 15.

Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198, Lleida, Catalonia, Spain. Electronic address:

The risk posed by outbreaks associated with strawberries together with the safety issues of by-products from chlorine disinfection in the fruit industry has led to a search for alternative sanitizers. The disinfection capacity of peracetic acid (PA) at three concentrations (20, 40 and 80 ppm) and washing times (1 and 2 min) was compared to sodium hypochlorite (200 ppm) (NaClO) treatments and a water control, and its influence on the physico-chemical, biochemical and nutritional quality of strawberries was also studied. Counts on total aerobic mesophilic microorganisms were comparable between NaClO and PA. For yeasts and molds, only NaClO and 80 ppm PA reduced contamination in washing water, but no differences wereobserved in strawberries. Artificially inoculated L.innocua was reduced by at least 4 log cfu/g in strawberry by all the PA treatments, except at 20 ppm PA for 1 min. Total soluble solids, pH, titratable acidity, antioxidant activity and total phenolic content values were maintained after all treatments. Only anthocyanin content was affected. Treatments of 20 and 40 ppm PA did not significantly affect fruit color, and there were no losses on strawberry firmness. PA, as a GRAS substance that has shown potential to reduce microorganisms present in strawberries without any major physicochemical or sensorial alteration, could be a suitable alternative to chlorine disinfection.
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http://dx.doi.org/10.1016/j.fm.2019.05.004DOI Listing
October 2019

Assessing water-assisted UV-C light and its combination with peroxyacetic acid and Pseudomonas graminis CPA-7 for the inactivation and inhibition of Listeria monocytogenes and Salmonella enterica in fresh-cut 'Iceberg' lettuce and baby spinach leaves.

Int J Food Microbiol 2019 May 1;297:11-20. Epub 2019 Mar 1.

Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Spain. Electronic address:

The effectiveness of ultraviolet C light (UV-C) delivered in water (WUV) or in peroxyacetic acid (PAA) for the inactivation and inhibition of L. monocytogenes and S. enterica in ready-to-eat 'Iceberg lettuce' and baby spinach leaves, was evaluated throughout chilled storage in modified atmosphere packaging (MAP). The inhibition of pathogen's growth by sequential pretreatments with UV-C in PAA and then biocontrol using Pseudomonas graminis CPA-7 was assessed during MAP storage at 5 °C and upon a breakage of the cold-storage chain. In fresh-cut lettuce, 0 1 kJ/m UV-C, in water or in 40 mg/L PAA, inactivated both pathogens by up to 2.1 ± 0.7 log, which improved the efficacy of water-washing by up to 1.9 log and showed bacteriostatic effects on both pathogens. In baby spinach leaves, the combination of 0 3 kJ/m UV-C and 40 mg/L PAA reduced S. enterica and L. monocytogenes populations by 1.4 ± 0.2 and 2.2 ± 0.3 log respectively, which improved water-washing by 0.8 ± 0.2 log. Combined treatments (0.1 or 0 3 kJ/m WUV and 40 mg/L PAA) inactivated both pathogens in the process solution from lettuce or spinach single sanitation, respectively. Pretreating lettuce with UV-C in PAA reduced L. monocytogenes and S. enterica's growth by up to 0.9 ± 0.1 log with respect to the PAA-pretreated control after 6 d at 5 °C in MAP. Upon a cold-chain breakage, CPA-7 prevented S. enterica growth in PAA-pretreated lettuce, whereas showed no effect on L. monocytogenes in any of both matrices. Low-dose UV-C in PAA is a suitable preservation strategy for improving the safety of ready-to-eat leafy greens and reducing the risk of cross contamination.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2019.02.024DOI Listing
May 2019

Evaluation of Pseudomonas graminis CPA-7 as a biopreservation method for fresh-cut pear: Physicochemical, enzymatic, and nutritional quality.

Food Sci Technol Int 2019 Jun 13;25(4):271-281. Epub 2018 Dec 13.

1 Institute of Agrifood Research and Technology, XaRTA-Postharvest, Lleida, Spain.

Biological preservation methods with bacterial antagonists have emerged as alternatives to chemical sanitizers for extending shelf-life and reducing the population of pathogenic microorganisms. In addition, calcium plays an important role in maintaining the quality of fruit, and postharvest calcium treatments might determine the potential of fruit for processing. The objective of this work was to evaluate the effect of the postharvest application of calcium and biopreservation with the CPA-7 strain of Pseudomonas graminis on the quality parameters of fresh-cut pears. After harvest, whole pears were dipped in calcium chloride solution (1%, w/v) or water (control) for 10 min at 25 ℃ and stored for five months at temperatures ranging from 0 to -0.5 ℃. Both batches of fruit were minimally processed and dipped in a solution containing CPA-7 and an antioxidant solution or kept untreated, and both groups were stored at 4 ℃ for six days. The postharvest calcium treatment had no remarkable effect on the quality of the whole and fresh-cut pears. The enzymatic activities (PPO, PME and PG) related to browning and softening were constant in fresh-cut pears after storage, and the application of P. graminis CPA-7 had a positive effect on the activity of PPO. Finally, a combined effect of the biocontrol agent and calcium treatment was not demonstrated.
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http://dx.doi.org/10.1177/1082013218816483DOI Listing
June 2019

Evaluation of biocontrol capacity of Pseudomonas graminis CPA-7 against foodborne pathogens on fresh-cut pear and its effect on fruit volatile compounds.

Food Microbiol 2018 Dec 27;76:226-236. Epub 2018 Apr 27.

Institute of Agrifood Research and Technology (IRTA), XaRTA-Postharvest, Lleida, Spain. Electronic address:

The application of microorganisms to control the growth of foodborne pathogens is an alternative to the use of chemical additives. In this work, Pseudomonas graminis CPA-7 was tested as a biocontrol agent against Salmonella enterica and Listeria monocytogenes on fresh-cut pear under conditions that simulate its commercial application at 5 ± 1 °C (under a modified atmosphere and antioxidant solution). The quality of the fresh-cut fruit, including the ethanol and acetaldehyde contents and the volatile profile, was determined. After the storage period, the L. monocytogenes population was reduced by 1-log unit by the presence of CPA-7; however, CPA-7 was not found to have antagonistic activity against S. enterica. The fruit quality (total soluble solids content and titratable acidity) was not negatively affected by CPA-7. The ethanol and acetaldehyde contents increased during the shelf-life of the fruit regardless of the presence of CPA-7. Some volatile compounds were key factors for discriminating samples from the two groups (the control group and the group that was inoculated with CPA-7). Some components are common in the volatile profile of pear (methyl acetate, 3-methylbutyl acetate, 1-butanol, 1-hexanol, and hexanal), and thus increases in their contents could enhance consumers flavour perception.
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http://dx.doi.org/10.1016/j.fm.2018.04.007DOI Listing
December 2018

Effects of thermal and non-thermal processing of cruciferous vegetables on glucosinolates and its derived forms.

J Food Sci Technol 2018 Jun 16;55(6):1973-1981. Epub 2018 Apr 16.

Institute of Agrifood Research and Technology (IRTA), XaRTA-Postharvest, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, Edifici Fruitcentre, 25003 Lleida, Catalonia Spain.

vegetables, which include broccoli, kale, cauliflower, and Brussel sprouts, are known for their high glucosinolate content. Glucosinolates and their derived forms namely isothiocyanates are of special interest in the pharmaceutical and food industries due to their antimicrobial, neuroprotective, and anticarcinogenic properties. These compounds are water soluble and heat-sensitive and have been proved to be heavily lost during thermal processing. In addition, previous studies suggested that novel non-thermal technologies such as high pressure processing, pulsed electric fields, or ultraviolet irradiation can affect the glucosinolate content of cruciferous vegetables. The objective of this paper was to review current knowledge about the effects of both thermal and non-thermal processing technologies on the content of glucosinolates and their derived forms in vegetables. This paper also highlights the importance of the incorporation of vegetables into our diet for their health-promoting properties beyond their anticarcinogenic activities.
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http://dx.doi.org/10.1007/s13197-018-3153-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5976619PMC
June 2018

Differential contribution of the two major polygalacturonases from Penicillium digitatum to virulence towards citrus fruit.

Int J Food Microbiol 2018 Oct 31;282:16-23. Epub 2018 May 31.

Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Catedrático Agustín Escardino 7, 46980-Paterna, Valencia, Spain. Electronic address:

The fungus Penicillium digitatum is the causal agent of the citrus green mould, the major postharvest diseases of citrus fruit. Lesions on the surface of infected fruits first appear as soft areas around the inoculation site, due to maceration of fruit. The macerating activity has been associated with pectinases secreted by the fungus during infection. In order to evaluate the contribution to virulence and macerating activity of the two major polygalacturonases (PGs) secreted by P. digitatum, we have obtained and characterized mutants lacking either pg1 or pg2, the genes encoding PG1 and PG2, respectively. Disease incidence of deletants in either gene was not different from that of the parental strain or ectopic transformants. However, disease progressed more slowly in deletants, especially in those lacking the pg2 gene. The lesions originated by the Δpg2 deletants were not as soft and the pH was not as acid as those originated by either the wild type strain or the ectopic transformants. Total PG activity in the macerated tissue was also lower in fruits infected with the Δpg2 deletants. Interestingly, the macerated tissue of oranges infected with Δpg2 deletants showed around 50% reduction in galacturonic acid content with respect to lesions caused by any other strain.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2018.05.031DOI Listing
October 2018

Evaluation of postharvest calcium treatment and biopreservation with Lactobacillus rhamnosus GG on the quality of fresh-cut 'Conference' pears.

J Sci Food Agric 2018 Oct 24;98(13):4978-4987. Epub 2018 May 24.

IRTA, XaRTA-Postharvest, Fruitcentre Building, Parc Científic i Tecnològic Agroalimentari. Parc de Gardeny, Lleida, Catalonia, Spain.

Background: Biological preservation with probiotic bacteria has arisen as an alternative to control the growth of foodborne pathogens on food. The objective of this work was to evaluate the effect of postharvest calcium application and biopreservation with Lactobacillus rhamnosus GG on the quality and bioaccessibility of total phenolic content and antioxidant activity in fresh-cut pears.

Results: The immersion of whole pears in a calcium chloride solution did not provide added value. Despite the increase in observed activity of PME and PPO enzymes in fresh-cut pears during storage, the browning index and firmness values were constant for all samples. The antioxidant properties, including antioxidant activity, total phenolic content and vitamin C content, were maintained during storage, but a significant decrease was observed after in vitro simulated digestion. Ca/LGG samples showed the lowest calcium content (1.75 ± 0.00 g kg ) after 9 d of storage at 4 °C. In general, the overall visual quality scores were higher in fresh-cut pears treated with L. rhamnosus GG than in non-treated pears, with the highest values in the NoCa/LGG (7.7 ± 0.2) samples after 9 d at 4 °C.

Conclusion: Fresh-cut pears with a postharvest treatment of calcium and immersed in a solution containing antioxidant agents and probiotic bacteria could be a suitable alternative to dairy products for maintaining the overall quality of fruit for up to 9 d of storage. © 2018 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.9031DOI Listing
October 2018

Effect of Pseudomonas graminis strain CPA-7 on the ability of Listeria monocytogenes and Salmonella enterica subsp. enterica to colonize Caco-2 cells after pre-incubation on fresh-cut pear.

Int J Food Microbiol 2017 Dec 12;262:55-62. Epub 2017 Sep 12.

Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain. Electronic address:

To further gain insight into the mechanism by which the biopreservative bacterium Pseudomonas graminis CPA-7 develops its antimicrobial activity, we have examined the effect that the prior interaction stablished by this bacterium and two foodborne pathogens on fresh-cut pear, has on their capacity to colonize human epithelial cells (Caco-2 cell line) which is crucial for establishing infection. CPA-7 inhibited the growth of L. monocytogenes and S. enterica subsp. enterica ser. Enteritidis by 5.5 and 3.1 log, respectively, after 7d of interaction at 10°C. Furthermore, CPA-7 attenuated the adherence of S. enterica to Caco-2 cells by 0.8 log regardless of the pre-adaptation on the fruit. Conversely, the adhesiveness of L. monocytogenes was not influenced by the interaction with the antagonist but it was reduced by 0.5 log after incubation on the food matrix. Pathogen-antagonist-food matrix interaction was associated to a significant reduction of the relative invasiveness of both pathogens, by 1.3 log in the case of L. monocytogenes and to an undetectable level (below 5CFU/g fruit) for S. enterica. CPA-7 can adhere to and internalize into intestinal epithelium which enables it for competition. Its adherence positively correlates to the multiplicity of infection (MOI) with respect to Caco-2 cells, increasing by 0.6 log in an MOI range of 0.1:1 to 100:1. For the same levels of inoculum, internalized cells could only be detected after 7d of pre-adaptation in the fruit (pH4.5-5.0). However, the combination of gastrointestinal digestion and habituation on the fruit resulted in a significant reduction of CPA-7 populations (by 2 log more after 7d of incubation than on inoculation day) as well as in the decrease of its adhesiveness (by 0.8 log) and invasiveness (to undetectable levels).
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http://dx.doi.org/10.1016/j.ijfoodmicro.2017.09.003DOI Listing
December 2017

Unravelling the contribution of the Penicillium expansum PeSte12 transcription factor to virulence during apple fruit infection.

Food Microbiol 2018 Feb 12;69:123-135. Epub 2017 Aug 12.

IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, Edifici Fruit centre, 25003 Lleida, Catalonia, Spain.

Blue mould disease caused by Penicillium expansum infection is one of the most important diseases of pome fruit accounting for important economic losses. In the present study, the PeSte12 transcription factor gene was identified, and deletant mutants were produced by gene replacement. Knockout mutants showed a significant decrease of virulence during apple fruit infection. Virulence was affected by the maturity stage of the fruit (immature, mature and over-mature), and disease severity was notably reduced when the apples were stored at 0 °C. The ΔPeSte12 mutants resulted defective in asexual reproduction, producing less conidia, but this characteristic did not correlate with differences in microscopic morphology. In addition, the ΔPeSte12 mutants produced higher quantity of hydrogen peroxide than the wild type strain. Gene expression analysis revealed that PeSte12 was induced over time during apple infection compared to axenic growth, particularly from 2 dpi, reinforcing its role in virulence. Analysis of transcriptional abundance of several genes in ΔPeSte12 mutants showed that in most of the evaluated genes, PeSte12 seemed to act as a negative regulator during axenic growth, as most of them exhibited an increasing expression pattern along the time period evaluated. The highest expression values corresponded to detoxification, ATPase activity, protein folding and basic metabolism. Gene expression analysis during apple infection showed that 3 out of 9 analysed genes were up regulated; thus, PeSte12 seemed to exert a positive control to particular type of aldolase. These results demonstrate the PeSte12 transcription factor could play an important role in P. expansum's virulence and asexual reproduction.
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http://dx.doi.org/10.1016/j.fm.2017.08.005DOI Listing
February 2018

Exposure to minimally processed pear and melon during shelf life could modify the pathogenic potential of Listeria monocytogenes.

Food Microbiol 2017 Apr 13;62:275-281. Epub 2016 Oct 13.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003, Lleida, Catalonia, Spain. Electronic address:

Survival and virulence of foodborne pathogens can be influenced by environmental factors such as the intrinsic properties of food as well as the extrinsic properties that contribute to food shelf life (e.g., temperature and gas atmosphere). The direct contribution of food matrix characteristics on the survival of L. monocytogenes during fresh-cut fruit shelf life is not very well understood. In addition, the gastrointestinal tract is the primary route of listeriosis infection and penetration of the intestinal epithelial cell barrier is the first step in the infection process. Hence, the pathogenic potential of L. monocytogenes, measured as the capability for the organism to survive a simulated gastrointestinal tract and the proportion of cells able to subsequently adhere to and invade differentiated Caco-2 cells, subjected to fresh-cut pear and melon shelf life, was investigated. Samples were inoculated, stored at 10 °C for 7 days and evaluated after inoculation and again after 2 and 7 days of storage. A decrease in L. monocytogenes' capacity to survive a simulated gastrointestinal tract was observed with increasing storage time, regardless of the fruit matrix evaluated. Furthermore, L. monocytogenes placed on fresh-cut pear and melon was subjected to an attachment and invasion assay after crossing the simulated gastrointestinal tract. After inoculation, pathogen on fresh-cut pear showed 5-fold more capacity to adhere to Caco-2 cells than pathogen on fresh-cut melon. After 2 days of storage, L. monocytogenes grown on fresh-cut melon showed similar adhesive capacity (1.11%) than cells grown on pear (1.83%), but cells grown on melon had the higher invasive capacity (0.0093%). We can conclude that minimally processed melon could represent a more important hazard than pear under the studied shelf life.
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http://dx.doi.org/10.1016/j.fm.2016.10.016DOI Listing
April 2017

The impact of a cold chain break on the survival of Salmonella enterica and Listeria monocytogenes on minimally processed 'Conference' pears during their shelf life.

J Sci Food Agric 2017 Jul 29;97(9):3077-3080. Epub 2016 Nov 29.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003, Lleida, Catalonia, Spain.

Background: In recent years, improved detection methods and increased fresh-cut processing of produce have led to an increased number of outbreaks associated with fresh fruits and vegetables. During fruit and vegetable processing, natural protective barriers are removed and tissues are cut, causing nutrient rich exudates and providing attachment sites for microbes. Consequently, fresh-cut produce is more susceptible to microbial proliferation than whole produce.

Results: The aim of this study was to examine the impact of storage temperature on the growth and survival of Listeria monocytogenes and Salmonella enterica on a fresh-cut 'Conference' pear over an 8 day storage period. Pears were cut, dipped in antioxidant solution, artificially inoculated with L. monocytogenes and S. enterica, packed under modified atmospheric conditions simulating commercial applications and stored in properly refrigerated conditions (constant storage at 4 °C for 8 days) or in temperature abuse conditions (3 days at 4 °C plus 5 days at 8 °C). After 8 days of storage, both conditions resulted in a significant decrease of S. enterica populations on pear wedges. In contrast, when samples were stored at 4 °C for 8 days, L. monocytogenes populations increased 1.6 logarithmic units, whereas under the temperature abuse conditions, L. monocytogenes populations increased 2.2 logarithmic units.

Conclusion: Listeria monocytogenes was able to grow on fresh-cut pears processed under the conditions described here, despite low pH, refrigeration and use of modified atmosphere. © 2016 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.8127DOI Listing
July 2017

Relevance of the transcription factor PdSte12 in Penicillium digitatum conidiation and virulence during citrus fruit infection.

Int J Food Microbiol 2016 Oct 22;235:93-102. Epub 2016 Jul 22.

Laboratorio de Micología, Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Apartado Oficial. 46113- Moncada, Valencia, Spain. Electronic address:

Green mould, resulting from Penicillium digitatum, is the most important postharvest disease of citrus. In a previous study, the PdSte12 transcription factor gene was identified, and disruption mutants were obtained. In the present study, the ΔPdSte12 mutants generated through gene replacement showed significantly reduced virulence during citrus fruit infection. Virulence was affected not only in mature fruit but also in immature fruit, and disease severity was markedly reduced when the oranges were stored at 20 or 4°C. In addition, the ΔPdSte12 mutants were defective in asexual reproduction, producing few conidia. The conidiophores of these mutants had longer metulae with fewer branches at the tip of the hyphae. Gene expression analysis revealed that PdSte12 might act as a negative regulator of several transporter-encoding genes and a positive regulator of two sterol demethylases, all of which are involved in fungicide resistance and fungal virulence. Moreover, PdSte12 exhibited the negative regulation of another transcription factor PdMut3, putatively involved in fungal pathogenesis but with no effect on the MAPK SLT2 P. digitatum orthologue belonging to different transcription pathways relevant to cell integrity. These results indicate the PdSte12 transcription factor is functionally conserved in P. digitatum for infection and asexual reproduction, similar to other Ste12 fungal plant pathogens.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2016.07.027DOI Listing
October 2016

DNA-based methodologies for the quantification of live and dead cells in formulated biocontrol products based on Pantoea agglomerans CPA-2.

Int J Food Microbiol 2015 Oct 20;210:79-83. Epub 2015 Jun 20.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida, Catalonia, Spain. Electronic address:

Pantoea agglomerans strain CPA-2 is an effective biocontrol agent (BCA) against the major postharvest pathogens present on pome and citrus fruits. Dehydration, such as freeze-drying, spray-drying and fluidized bed drying is one of the best ways to formulate BCAs. In this work, the survival of CPA-2 cells after formulation was determined by dilution plating and molecular methods as qPCR alone and combined with a sample pretreatment with a propidium monoazide dye (PMA-qPCR) and they were used to calculate treatment concentrations in efficacy trials on postharvest oranges. Furthermore, no significant differences in CPA-2 survival were observed as determined by dilution plating and PMA-qPCR after both the freeze drying and fluidized bed drying processes; however, an interesting significant difference was observed in the spray dried product comparing all quantitative methods. A difference of 0.48 and 2.17 log10 CFU or cells g/dw was observed among PMA-qPCR with qPCR and dilution plating, respectively. According to our study, dilution plating was shown to be an unreliable tool for monitoring the survival of CPA-2 after spray drying. In contrast, the combination of PMA and qPCR enabled a quick and unequivocal methodology to enumerate viable and VBNC CPA-2 cells under stress-dried conditions. Efficacy trials showed that, after 3 days, spray drying formulation rehydrated with 10% non-fat skimmed milk (NFSM) was as effective as fresh cells to control Penicillium digitatum in oranges.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2015.06.013DOI Listing
October 2015

Effect of ripeness stage during processing on Listeria monocytogenes growth on fresh-cut 'Conference' pears.

Food Microbiol 2015 Aug 10;49:116-22. Epub 2015 Feb 10.

Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center. Rovira Roure, 191, 25198-Lleida, Catalonia, Spain.

There are several factors that affect the shelf life of fresh-cut fruit, including the cultivar, the ripeness stage of the fruit during processing and the fruit's storage atmosphere and temperature. The effect of fruit ripeness during processing on the survival and growth of Listeria monocytogenes on fresh-cut 'Conference' pear slices at different temperatures (5, 10 and 20 °C) was studied. The four ripeness stages studied in this work (assessed by a fruit's firmness) were mature-green (54-60 N), partially ripe (43-53 N), ripe (31-42 N) and overripe (<31 N). In our studies, pH, acidity and soluble solids content did not significantly change during conditioning at 20 °C. L. monocytogenes grew under all experimental conditions, showing an increase of approximately 2 log CFU g(-1) after 8 days of storage at 5 °C. There were significant differences in the L. monocytogenes population between different ripeness stages at the end of the experiments at 10 and 20 °C. Regardless of the ripeness stage of a fresh-cut pear, the growth potential of L. monocytogenes increased with increasing temperature. A pear's ripeness stage during processing is an important consideration to ensure the quality of a fresh-cut pear, but it is not as important for preventing L. monocytogenes growth at common storage temperatures.
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http://dx.doi.org/10.1016/j.fm.2015.01.019DOI Listing
August 2015

Exploring the effects of pulsed electric field processing parameters on polyacetylene extraction from carrot slices.

Molecules 2015 Mar 2;20(3):3942-54. Epub 2015 Mar 2.

Department of Food Biosciences, Teagasc Food Research Centre Ashtown, Dublin 15, Ireland.

The effects of various pulsed electric field (PEF) parameters on the extraction of polyacetylenes from carrot slices were investigated. Optimised conditions with regard to electric field strength (1-4 kV/cm), number of pulses (100-1500), pulse frequency (10-200 Hz) and pulse width (10-30 μs) were identified using response surface methodology (RSM) to maximise the extraction of falcarinol (FaOH), falcarindiol (FaDOH) and falcarindiol-3-acetate (FaDOAc) from carrot slices. Data obtained from RSM and experiments fitted significantly (p < 0.0001) the proposed second-order response functions with high regression coefficients (R2) ranging from 0.82 to 0.75. Maximal FaOH (188%), FaDOH (164.9%) and FaDOAc (166.8%) levels relative to untreated samples were obtained from carrot slices after applying PEF treatments at 4 kV/cm with 100 number of pulses of 10 μs at 10 Hz. The predicted values from the developed quadratic polynomial equation were in close agreement with the actual experimental values with low average mean deviations (E%) ranging from 0.68% to 3.58%.
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http://dx.doi.org/10.3390/molecules20033942DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6272167PMC
March 2015

Characterizing the proteome and oxi-proteome of apple in response to a host (Penicillium expansum) and a non-host (Penicillium digitatum) pathogen.

J Proteomics 2015 Jan 20;114:136-51. Epub 2014 Nov 20.

IRTA, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain. Electronic address:

Unlabelled: Apples are subjected to both abiotic and biotic stresses during the postharvest period, which lead to large economic losses worldwide. To obtain biochemical insights into apple defense response, we monitored the protein abundance changes (proteome), as well as the protein carbonyls (oxi-proteome) formed by reactive oxygen species (ROS) in 'Golden Smoothee' apple in response to wounding, Penicillium expansum (host) and Penicillium digitatum (non-host) pathogens with select transcriptional studies. To examine the biological relevance of the results, we described quantitative and oxidative protein changes into the gene ontology functional categories, as well as into de KEGG pathways. We identified 26 proteins that differentially changed in abundance in response to wounding, P. expansum or P. digitatum infection. While these changes showed some similarities between the apple responses and abiotic and biotic stresses, Mal d 1.03A case, other proteins as Mal d 1.03E and EF-Tu were specifically induced in response to P. digitatum infection. Using a protein carbonyl detection method based on fluorescent Bodipy, we detected and identified 27 oxidized proteins as sensitive ROS targets. These ROS target proteins were related to metabolism processes, suggesting that this process plays a leading role in apple fruit defense response against abiotic and biotic stresses. ACC oxidase and two glutamine synthetases showed the highest protein oxidation level in response to P. digitatum infection. Documenting changes in the proteome and, specifically in oxi-proteome of apple can provide information that can be used to better understand how impaired protein functions may affect apple defense mechanisms. Possible mechanisms by which these modified proteins are involved in fruit defense response are discussed.

Biological Significance: Mechanical damage in apple fruits is linked annually to large economic losses due to opportunistic infection by postharvest pathogens, such as P. expansum. Despite the current use of chemical fungicides and the implementation of new alternative strategies, blue mold remains a critical disease of these stored fruits worldwide. Actual trends are focused on acquiring the knowledge of the host-pathogen interactions because it may help on finding new rational and environmentally friendly control alternatives. Despite the economic importance of some postharvest diseases, proteomics has only been applied in a few cases to study fruit-pathogen interactions. On the one hand, this is the first study that monitored changes at the proteome and oxi-proteome level in 'Golden Smoothee' apple fruits in response to P. expansum (compatible) and P. digitatum (non-host) pathogens. On the other hand, the main technological innovation of the reported research is the detection and quantification of oxidized (carbonylated) proteins to assess protein oxidative damage, avoiding the immunoblotting technique. The importance of the biological process investigated lies in the different mechanisms induced in fruit in response to P. expansum and P. digitatum. Results revealed that fruit recognizes and reacts to P. expansum in a similar manner to wounding, while its response to P. digitatum exhibits few differences in the protein profile. Documenting changes in the proteome and, specifically in oxi-proteome of apple can provide information that can be used to better understand how impaired protein functions may affect apple defense mechanisms. It also provides new biomarkers for oxidative damage mainly caused by the oxidative response occurring in fruit tissue in response to a host and a non-host pathogen.
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http://dx.doi.org/10.1016/j.jprot.2014.11.007DOI Listing
January 2015

Development of PMA real-time PCR method to quantify viable cells of Pantoea agglomerans CPA-2, an antagonist to control the major postharvest diseases on oranges.

Int J Food Microbiol 2014 Jun 13;180:49-55. Epub 2014 Apr 13.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida Catalonia, Spain. Electronic address:

Dilution plating is the quantification method commonly used to estimate the population level of postharvest biocontrol agents, but this method does not permit a distinction among introduced and indigenous strains. Recently, molecular techniques based on DNA amplification such as quantitative real-time PCR (qPCR) have been successfully applied for their high strain-specific detection level. However, the ability of qPCR to distinguish viable and nonviable cells is limited. A promising strategy to avoid this issue relies on the use of nucleic acid intercalating dyes, such as propidium monoazide (PMA), as a sample pretreatment prior to the qPCR. The objective of this study was to optimize a protocol based on PMA pre-treatment samples combined with qPCR to distinguish and quantify viable cells of the biocontrol agent P. agglomerans CPA-2 applied as a postharvest treatment on orange. The efficiency of PMA-qPCR method under the established conditions (30μM PMA for 20min of incubation followed by 30min of LED light exposure) was evaluated on an orange matrix. Results showed no difference in CFU or cells counts of viable cells between PMA-qPCR and dilution plating. Samples of orange matrix inoculated with a mixture of viable/dead cells showed 5.59log10 CFU/ml by dilution plating, 8.25log10 cells/ml by qPCR, and 5.93log10 cells/ml by PMA-qPCR. Furthermore, samples inoculated with heat-killed cells were not detected by dilution plating and PMA-qPCR, while by qPCR was of 8.16log10 cells/ml. The difference in quantification cycles (Cq) among qPCR and PMA-qPCR was approximately 16cycles, which means a reduction of 65,536 fold of the dead cells detected. In conclusion, PMA-qPCR method is a suitable tool for quantify viable CPA-2 cells, which could be useful to estimate the ability of this antagonist to colonize the orange surface.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2014.04.011DOI Listing
June 2014

Detection and quantification by PCR assay of the biocontrol agent Pantoea agglomerans CPA-2 on apples.

Int J Food Microbiol 2014 Apr 31;175:45-52. Epub 2014 Jan 31.

IRTA, Postharvest XaRTA, Av. Rovira Roure, 191, 25198 Lleida, Catalonia, Spain. Electronic address:

The registration of biological control agents requires the development of monitoring systems to detect and quantify the agent in the environment. Pantoea agglomerans CPA-2 is an effective biocontrol agent for postharvest diseases of citrus and pome fruits. The monitoring of CPA-2 in postharvest semi-commercial trials was evaluated by Rodac impression plates and the colonies isolated were confirmed by conventional PCR using the SCAR primers PAGA1 and PAGB1. Samples were taken from different surfaces that had contact with CPA-2, the surrounding environment and working clothes worn by handlers. Moreover, population dynamics of the strain CPA-2 were determined on apple surfaces using both the classical plating technique and real-time quantitative PCR (qPCR). A qPCR assay using a 3'-minor groove-binding (MGB) probe was developed for the specific detection and quantification of P. agglomerans strain CPA-2. Based on the nucleotide sequence of a SCAR fragment of CPA-2, one primer set and TaqMan MGB probe were designed. The primers SP2-F/SP2-R and the TaqMan MGB probe showed a specific detection of strain CPA-2 on apple surfaces, which was verified tested against purified DNA from 17 strains of P. agglomerans, 4 related Pantoea species, and 21 bacterial strains from other genera isolated from whole and also freshly-cut fruit and vegetables. The detection level was approximately 10(3) cells per reaction, and the standard curve was linear within a range of 5log units. Results from semi-commercial trials showed that CPA-2 had a low impact. The maximum persistence of P. agglomerans CPA-2 was not longer than 5days in plastic boxes stored at 0°C. Significant differences in CPA-2 population level dynamics were observed in results obtained by qPCR and dilution plating. These differences may indicate the presence of non-degraded DNA from non-viable cells. In conclusion, qPCR is a novel potential tool to quickly and specifically monitor recent surface colonisation by CPA-2 populations on apple surfaces during large-scale experiments that could ensure efficient and successful treatments.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2014.01.014DOI Listing
April 2014

Potential secondary inoculum sources of Botrytis cinerea and their influence on bunch rot development in dry Mediterranean climate vineyards.

Pest Manag Sci 2014 Jun 2;70(6):922-30. Epub 2013 Oct 2.

Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Lleida, Catalonia, Spain.

Background: Epidemiological studies have described the life cycle of B. cinerea in vineyards. However, there is a lack of information on the several infection pathways and the quantitative relationships between secondary inoculum and bunch rot at harvest.

Results: Over two seasons, different spray programmes were used to determine key phenological stages for bunch rot development. Secondary inoculum sources within the bunch were also studied. The relative importance of flowering was evidenced in the given conditions, as treatments that included two fungicide applications at flowering were the most effective. In 2010, under conducive meteorological conditions for B. cinerea development after veraison, an extra application provided significantly higher control. Infections of necrotic tissues inside the bunch and latent infections developed mainly during flowering, while very low quantities of B. cinerea conidia were recovered from the fruit surface at veraison. Regression analysis correlated the incidence of latent infections and B. cinerea incidence on calyptras and aborted fruits at veraison with incidence of Botrytis bunch rot at harvest, presenting R2 = 0.95 for the overall regression model.

Conclusion: This work points out key phenological stages during the season for bunch rot and B. cinerea secondary inoculum development and relates quantitatively inoculum sources at veraison to bunch rot at harvest. Recommendations for field applications of antibotrytic products are also suggested.
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http://dx.doi.org/10.1002/ps.3629DOI Listing
June 2014

Suppression of Botrytis cinerea on necrotic grapevine tissues by early-season applications of natural products and biological control agents.

Pest Manag Sci 2014 Apr 1;70(4):595-602. Epub 2013 Jul 1.

Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Lleida, Catalonia, Spain.

Background: Necrotic tissues within grape (Vitis vinifera) bunches represent an important source of Botrytis cinerea inoculum for Botrytis bunch rot (BBR) at harvest in vineyards. This research quantified the incidence of B. cinerea on necrotic floral and fruit tissues and the efficacy of biologically based treatments for suppression of B. cinerea secondary inoculum within developing bunches.

Results: At veraison (2009 and 2010), samples of aborted flowers, aborted fruits and calyptras were collected, and the incidence and sporulation of B. cinerea were determined. Aborted fruits presented significantly higher incidence in untreated samples. Early-season applications of Candida sake plus Fungicover®, Fungicover alone or Ulocladium oudemansii significantly reduced B. cinerea incidence on aborted flowers and calyptras by 46-85%. Chitosan treatment significantly reduced B. cinerea incidence on calyptras. None of the treatments reduced B. cinerea incidence on aborted fruits. Treatments significantly reduced sporulation severity by 48% or more.

Conclusions: Treatments were effective at reducing B. cinerea secondary inoculum on necrotic tissues, in spite of the variable control on aborted fruits. This is the first report to quantify B. cinerea on several tissues of bunch trash and to describe the effective suppression of saprophytic B. cinerea inoculum by biologically based treatments.
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http://dx.doi.org/10.1002/ps.3587DOI Listing
April 2014

Control of foodborne pathogens on fresh-cut fruit by a novel strain of Pseudomonas graminis.

Food Microbiol 2013 Jun 31;34(2):390-9. Epub 2013 Jan 31.

Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.

The consumption of fresh-cut fruit has substantially risen over the last few years, leading to an increase in the number of outbreaks associated with fruit. Moreover, consumers are currently demanding wholesome, fresh-like, safe foods without added chemicals. As a response, the aim of this study was to determine if the naturally occurring microorganisms on fruit are "competitive with" or "antagonistic to" potentially encountered pathogens. Of the 97 and 107 isolates tested by co-inoculation with Escherichia coli O157:H7, Salmonella and Listeria innocua on fresh-cut apple and peach, respectively, and stored at 20 °C, seven showed a strong antagonistic capacity (more than 1-log unit reduction). One of the isolates, CPA-7, achieved the best reduction values (from 2.8 to 5.9-log units) and was the only isolate able to inhibit E. coli O157:H7 at refrigeration temperatures on both fruits. Therefore, CPA-7 was selected for further assays. Dose-response assays showed that CPA-7 should be present in at least the same amount as the pathogen to adequately reduce the numbers of the pathogen. From the results obtained in in vitro assays, competition seemed to be CPA-7's mode of action against E. coli O157:H7. The CPA-7 strain was identified as Pseudomonas graminis. Thus, the results support the potential use of CPA-7 as a bioprotective agent against foodborne pathogens in minimally processed fruit.
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http://dx.doi.org/10.1016/j.fm.2013.01.013DOI Listing
June 2013

Antagonistic effect of Pseudomonas graminis CPA-7 against foodborne pathogens in fresh-cut apples under simulated commercial conditions.

Food Microbiol 2013 Apr 9;33(2):139-48. Epub 2012 Oct 9.

University of Lleida, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.

Recently, we reported that the application of the strain CPA-7 of Pseudomonas graminis, previously isolated from apple, could reduce the population of foodborne pathogens on minimally processed (MP) apples and peaches under laboratory conditions. Therefore, the objective of the present work was to find an antioxidant treatment and a packaging atmosphere condition to improve CPA-7 efficacy in reducing a cocktail of four Salmonella and five Listeria monocytogenes strains on MP apples under simulated commercial processing. The effect of CPA-7 application on apple quality and its survival to simulated gastric stress were also evaluated. Ascorbic acid (2%, w/v) and N-acetyl-l-cysteine (1%, w/v) as antioxidant treatments reduced Salmonella, L. monocytogenes and CPA-7 recovery, meanwhile no reduction was observed with NatureSeal(®) AS1 (NS, 6%, w/v). The antagonistic strain was effective on NS-treated apple wedges stored at 10 °C with or without modified atmosphere packaging (MAP). Then, in a semi-commercial assay, efficacy of CPA-7 inoculated at 10(5) and 10(7) cfu mL(-1) against Salmonella and L. monocytogenes strains on MP apples with NS and MAP and stored at 5 and 10 °C was evaluated. Although high CPA-7 concentrations/populations avoided Salmonella growth at 10 °C and lowered L. monocytogenes population increases were observed at both temperatures, the effect was not instantaneous. No effect on apple quality was detected and CPA-7 did not survived to simulated gastric stress throughout storage. Therefore, CPA-7 could avoid pathogens growth on MP apples during storage when use as part of a hurdle technology in combination with disinfection techniques, low storage temperature and MAP.
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http://dx.doi.org/10.1016/j.fm.2012.09.007DOI Listing
April 2013

Microbiological and physicochemical quality of fresh-cut apple enriched with the probiotic strain Lactobacillus rhamnosus GG.

Food Microbiol 2011 Feb 18;28(1):59-66. Epub 2010 Aug 18.

University of Lleida, Centre UdL-IRTA, XaRTA-Postharvest, Lleida, Catalonia, Spain.

The effectiveness as protective culture of the probiotic Lactobacillus rhamonosus GG (L. rham. GG) against Salmonella and Listeria monocytogenes on minimally-processed apples throughout storage as well as its effect on apple quality and natural microflora was evaluated. Survival to subsequent exposure to gastric stress was also reported. Apples were cut into wedges and dipped in a solution containing Salmonella and L. monocytogenes (10(5) cfu mL(-1)) and/or L. rham. GG (10(8) cfu mL(-1)). Apple wedges were packed and stored at 5 and 10 °C. Periodically, microbial population, bacterial survival to gastric stress and quality of apple wedges were evaluated. Although Salmonella was not affected by co-inoculation with L. rham. GG, L. monocytogenes population was 1-log units lower in the presence of L. rham. GG. L. rham. GG population maintained over recommended levels for probiotic action (10(6) cfu g(-1)) along storage, however, viable cells after gastric stress were only above this level during the first 14 days. Pathogen survival after gastric stress was <1% after 7 days at 5 °C. Moreover, apple wedges quality was not affected by L. rham. GG addition. Thus, L. rham. GG could be a suitable probiotic for minimally-processed apples capable to reduce L. monocytogenes growth; nevertheless shelf life should not be higher to 14 days to guarantee the probiotic effect.
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http://dx.doi.org/10.1016/j.fm.2010.08.006DOI Listing
February 2011

Fate of Escherichia coli O157:H7, Salmonella and Listeria innocua on minimally-processed peaches under different storage conditions.

Food Microbiol 2010 Oct 15;27(7):862-8. Epub 2010 May 15.

University of Lleida, Centre UdL-IRTA, XaRTA-Postharvest, Rovira Roure, 191, 25198 Lleida, Catalonia, Spain.

Consumption of fresh-cut produce has sharply increased recently causing an increase of foodborne illnesses associated with these products. As generally, acidic fruits are considered 'safe' from a microbiological point of view, the aim of this work was to study the growth and survival of Escherichia coli O157:H7, Salmonella and Listeria innocua on minimally-processed peaches. The three foodborne pathogens population increased more than 2 log(10)units on fresh-cut peach when stored at 20 and 25 degrees C after 48 h. At 10 degrees C only L. innocua grew more than 1 log(10)unit and it was the only pathogen able to grow at 5 degrees C. Differences in growth occurred between different peach varieties tested, with higher population increases in those varieties with higher pH ('Royal Glory' 4.73+/-0.25 and 'Diana' 4.12+/-0.18). The use of common strategies on extending shelf life of fresh-cut produce, as modified atmosphere packaging and the use of the antioxidant substance, ascorbic acid (2%w/v), did not affect pathogens' growth at any of the temperatures tested (5 and 25 degrees C). Minimally-processed peaches have shown to be a good substrate for foodborne pathogens' growth regardless use of modified atmosphere and ascorbic acid. Therefore, maintaining cold chain and avoiding contamination is highly necessary.
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http://dx.doi.org/10.1016/j.fm.2010.05.008DOI Listing
October 2010

Factors affecting growth of foodborne pathogens on minimally processed apples.

Food Microbiol 2010 Feb 27;27(1):70-6. Epub 2009 Aug 27.

University of Lleida, Centre UdL-IRTA, XaRTA-Postharvest, Rovira Roure, 191, 25198-Lleida, Catalonia, Spain.

Escherichia coli O157:H7, Salmonella and Listeria innocua increased by more than 2 log(10) units over a 24 h period on fresh-cut 'Golden Delicious' apple plugs stored at 25 and 20 degrees C. L. innocua reached the same final population level at 10 degrees C meanwhile E. coli and Salmonella only increased 1.3 log(10) units after 6 days. Only L. innocua was able to grow at 5 degrees C. No significant differences were observed between the growth of foodborne pathogens on fresh-cut 'Golden Delicious', 'Granny Smith' and 'Shampion' apples stored at 25 and 5 degrees C. The treatment of 'Golden Delicious' and 'Granny Smith' apple plugs with the antioxidants, ascorbic acid (2%) and NatureSeal (6%), did not affect pathogen growth. The effect of passive modified atmosphere packaging (MAP) on the growth of E. coli, Salmonella and L. innocua on 'Golden Delicious' apple slices was also tested. There were no significant differences in growth of pathogens in MAP conditions compared with air packaging of 'Golden Delicious' apple plugs, but the growth of mesophilic and psychrotrophic microorganisms was inhibited. These results highlight the importance of avoiding contamination of fresh-cut fruit with foodborne pathogens and the maintenance of the cold chain during storage until consumption.
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http://dx.doi.org/10.1016/j.fm.2009.08.005DOI Listing
February 2010

Efficacy of neutral electrolyzed water (NEW) for reducing microbial contamination on minimally-processed vegetables.

Int J Food Microbiol 2008 Mar 30;123(1-2):151-8. Epub 2008 Jan 30.

IRTA, Centre UdL-IRTA, XaRTA-Postharvest, 191 Rovira Roure, 25198-Lleida, Catalonia, Spain.

Consumption of minimally-processed, or fresh-cut, fruit and vegetables has rapidly increased in recent years, but there have also been several reported outbreaks associated with the consumption of these products. Sodium hypochlorite is currently the most widespread disinfectant used by fresh-cut industries. Neutral electrolyzed water (NEW) is a novel disinfection system that could represent an alternative to sodium hypochlorite. The aim of the study was to determine whether NEW could replace sodium hypochlorite in the fresh-cut produce industry. The effects of NEW, applied in different concentrations, at different treatment temperatures and for different times, in the reduction of the foodborne pathogens Salmonella, Listeria monocytogenes and Escherichia coli O157:H7 and against the spoilage bacterium Erwinia carotovora were tested in lettuce. Lettuce was artificially inoculated by dipping it in a suspension of the studied pathogens at 10(8), 10(7) or 10(5) cfu ml(-1), depending on the assay. The NEW treatment was always compared with washing with deionized water and with a standard hypochlorite treatment. The effect of inoculum size was also studied. Finally, the effect of NEW on the indigenous microbiota of different packaged fresh-cut products was also determined. The bactericidal activity of diluted NEW (containing approximately 50 ppm of free chlorine, pH 8.60) against E. coli O157:H7, Salmonella, L. innocua and E. carotovora on lettuce was similar to that of chlorinated water (120 ppm of free chlorine) with reductions of 1-2 log units. There were generally no significant differences when treating lettuce with NEW for 1 and 3 min. Neither inoculation dose (10(7) or 10(5) cfu ml(-1)) influenced the bacterial reduction achieved. Treating fresh-cut lettuce, carrot, endive, corn salad and 'Four seasons' salad with NEW 1:5 (containing about 50 ppm of free chlorine) was equally effective as applying chlorinated water at 120 ppm. Microbial reduction depended on the vegetable tested: NEW and sodium hypochlorite treatments were more effective on carrot and endive than on iceberg lettuce, 'Four seasons' salad and corn salad. The reductions of indigenous microbiota were smaller than those obtained with the artificially inoculated bacteria tested (0.5-1.2 log reduction). NEW seems to be a promising disinfection method as it would allow to reduce the amount of free chlorine used for the disinfection of fresh-cut produce by the food industry, as the same microbial reduction as sodium hypochlorite is obtained. This would constitute a safer, 'in situ', and easier to handle way of ensuring food safety.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2007.12.008DOI Listing
March 2008

Evaluation of food additives and low-toxicity compounds as alternative chemicals for the control of Penicillium digitatum and Penicillium italicum on citrus fruit.

Pest Manag Sci 2002 May;58(5):459-66

Area de Postcollita, CeRTA, Centre UdL-IRTA, Av Rovira Roure 177, 25198 Lleida, Catalonia, Spain.

The effectiveness of low-toxicity chemicals as possible alternatives to synthetic fungicides for the control of post-harvest green and blue moulds of citrus was evaluated. A preliminary selection of chemicals, mostly common food additives, was made through in vivo primary screenings with oranges artificially inoculated with Penicillium digitatum or P italicum. Selected compounds and mixtures were tested as heated solutions in small-scale trials. Immersion of artificially inoculated oranges or lemons for 120 s in solutions at 40.6 degrees C and natural pH of potassium sorbate (0.2 M), sodium benzoate (0.2 M) or mixtures (0.1 + 0.1 M) of potassium sorbate with sodium benzoate, sodium propionate or sodium acetate were the most effective organic acid salts tested and reduced green mould by 70-80% after 7 days of storage at 20 degrees C. The mixtures did not significantly enhance the effectiveness of potassium sorbate or sodium benzoate alone. These solutions were as effective as sodium carbonate or calcium polysulphide treatments and, in general, they were more effective on lemons than on oranges. Satisfactory control of green and blue moulds was obtained by dipping oranges for 150 s in solutions of sodium molybdate (24.2 mM) or ammonium molybdate (1.0 mM) at 48 or 53 degrees C, but not at 20 degrees C. At 53 degrees C, however, the effectiveness of hot water was not enhanced by either molybdate. Molybdenum salts at higher concentrations were phytotoxic and stained the fruit. At non-phytotoxic concentrations, the effectiveness of these solutions was more influenced by temperature than by concentration. In general, the inhibitory effects of all compounds tested were not fungicidal but fungistatic and not very persistent. In conclusion, potassium sorbate, sodium benzoate and ammonium molybdate, among the wide range of chemicals tested, were superior for the control of post-harvest Penicillium decay of citrus fruit.
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http://dx.doi.org/10.1002/ps.477DOI Listing
May 2002