Publications by authors named "Pilar Colás-Medà"

7 Publications

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Bacterial Spore Inactivation in Orange Juice and Orange Peel by Ultraviolet-C Light.

Foods 2021 Apr 15;10(4). Epub 2021 Apr 15.

AGROTECNIO-CERCA Center, Food Technology Department, Universitat de Lleida, Rovira Roure 191, 25198 Lleida, Spain.

Spore-forming bacteria are a great concern for fruit juice processors as they can resist the thermal pasteurization and the high hydrostatic pressure treatments that fruit juices receive during their processing, thus reducing their microbiological quality and safety. In this context, our objective was to evaluate the efficacy of Ultraviolet-C (UV-C) light at 254 nm on reducing bacterial spores of , and at two stages of orange juice production. To simulate fruit disinfection before processing, the orange peel was artificially inoculated with each of the bacterial spores and submitted to UV-C light (97.8-100.1 W/m) with treatment times between 3 s and 10 min. The obtained product, the orange juice, was also tested by exposing the artificially inoculated juice to UV-C light (100.9-107.9 W/m) between 5 and 60 min. A three-minute treatment (18.0 kJ/m) reduced spore numbers on orange peel around 2 log units, while more than 45 min (278.8 kJ/m) were needed to achieve the same reduction in orange juice for all evaluated bacterial spores. As raw fruits are the main source of bacterial spores in fruit juices, reducing bacterial spores on fruit peels could help fruit juice processors to enhance the microbiological quality and safety of fruit juices.
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http://dx.doi.org/10.3390/foods10040855DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8103511PMC
April 2021

Application of an innovative water-assisted ultraviolet C light technology for the inactivation of microorganisms in tomato processing industries.

Food Microbiol 2021 Apr 30;94:103631. Epub 2020 Aug 30.

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

We aimed to study the efficacy of a water-assisted UVC light device (WUVC) as an innovative clean technology for the disinfection of fresh sound tomatoes and processing wash water and water turbidity was evaluated as a critical parameter. First, wash waters with different turbidities (from 0.4 to 828 NTU) were inoculated with Listeria innocua and treated in the WUVC device at different dosages. Secondly, fresh tomatoes, inoculated with L. innocua and non-inoculated ones, were treated using the WUVC device containing wash water of different turbidities for different times. The reduction of L. innocua populations on wash water and on the surface of tomato was influenced by turbidity; lower reduction values were observed at higher turbidities. Washing tomatoes with tap water with UVC lamps off (control treatment, TW) decreased L. innocua population on the surface of tomatoes but did not eliminate those bacteria that went into the water. Contrarily, when UVC lights were on, L. innocua population in wash water after treatment significantly decreased, those in clean water being the lowest populations. Reductions of native microbiota on the clean water treated with the highest UV-C radiation dose were lower than those obtained when tomatoes were artificially inoculated. We demonstrated that high reductions of L. innocua population on fresh tomatoes could be achieved using the WUVC system but some drawbacks related to the increase of turbidity should be solved for its implementation in real conditions.
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http://dx.doi.org/10.1016/j.fm.2020.103631DOI Listing
April 2021

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

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

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

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