Abstract- Changes in concentrations of nickel present in cow's, ewe's and goat's m... more Abstract- Changes in concentrations of nickel present in cow's, ewe's and goat's milk were stud-ied monthly (n = 360 sampi es) by using graphite fumace atomic absorption spectrometry. The mean concentrations of nickel are 15.0 ± 3.81, 18.6 ± 2.50 and 13.6 ± 2.46 ug-kg ' of fresh weight for cow's, ewe's and goat's milk respectively. Two-factor (species and time period) variance analyses were made on the three types ofmilk investigated and Tuckey's mean homogeneity test (P < 0.05) was also carried out for the formation of homogeneous groups per species for nickel content. Significant changes (P < 0.001) were determined over time in the nickel content of the three species studied and two homogeneous groups were formed, one for cow's and goat's milk and an other for ewe's milk with the higher nickel content. For the three species, the monthly changes of the nickel content corre-spond to a mathematical model of)Cd grade and the...
It is a principal aim of governments to assure the safety of societies in all sectors. In the foo... more It is a principal aim of governments to assure the safety of societies in all sectors. In the food field, safety has been dealt with for a long time by making decisions in an empirical manner. Recently, risk management has been appointed as the formal scientific-based approach to address food safety issues. From a global perspective, food safety risk management can be described “as the process of weighting control alternatives by government (and international standard-setting bodies) in consultation with interested stakeholders, taking into account scientific information on risks to consumers as well as other relevant inputs (e.g. economics, technical feasibility, societal preferences), and choosing and implementing food safety measures as appropriate” (Food Agriculture Organization/World Health Organization [FAO/WHO], 2006b). Indeed, governments must make decisions, whose effects are especially noted during food crises. Nevertheless, other stakeholders should also manage food risks...
This work has evaluated the possibility by the application of the «IMAGO» image analysis and trea... more This work has evaluated the possibility by the application of the «IMAGO» image analysis and treatment programme in the study of morphological cell differences in the xylem bundles of asparagus. The variables were analysed due to their longitudinal and concentric location, the variety of asparagus and its diameter, as well as postharvest modifications it undergoes during its cold storage at different levels of temperature throughout a period of time. Lignin deposit was determined in the xylem bundles of asparagus as cellular wall thickness, the cellular parameter analysed were area, perimeter, maximum and minimum radius and spherecity. Statistically significant differences were found between variety, diameters and portions of asparagus, as well as the two zones of the same cut and the temperatures and time of storage.
Journal of the Science of Food and Agriculture, 2000
An evaluation was made of the degree of toughening of asparagus during its storage through a stud... more An evaluation was made of the degree of toughening of asparagus during its storage through a study of the morphological and cellular differences of the xylem vascular bundles as a function of the variety, thickness and portion of the asparagus spear. Light microscopic examinations were carried out to determine the thickness of the cell wall to quantify the extent of the toughening. At the same time a study was made of the fractions of dietary ®bre of the asparagus spear by means of chemical extraction techniques. Statistically signi®cant differences were observed in both methods between varieties, thicknesses and portions of the asparagus spear. Different factors such as variety, degree of maturing, portion of spear, moment of harvesting, and type and time of storage have an in¯uence on the toughening of white asparagus that should be taken into account in order to standardise its quality.
Ready-to-eat lettuce is a food commodity prone to contamination by pathogenic microorganisms if p... more Ready-to-eat lettuce is a food commodity prone to contamination by pathogenic microorganisms if processing and distribution conditions as well as handling practices are not effective. A challenge testing protocol was applied to ready-to-eat iceberg-lettuce samples by inoculating different initial contamination levels (4.5, 3.5 and 2.5 log cfu/g) of Escherichia coli strain (serotype O158:H23) subsequently stored at 8, 12, 16, 20 and 24°C for 6 h. A polynomial regression model for log difference (log diff) was developed at each inoculum level studied through the calculation of the effective static temperature (T eff). Furthermore, the developed model was integrated within a risk-based approach with real time/Temperature (t/T) data collected in three Spanish foodservice centers: school canteens, long-term care facilities (LTCF) and hospitals. Statistical distributions were fitted to t/T data and estimated log diff values were obtained as model outputs through a Monte Carlo simulation (10,000 iterations). The results obtained at static conditions indicated that the maintenance of the lettuce at 8°C slightly reduced the E. coli population from −0.4 to −0.5 log cfu/g. However, if chill chain is not maintained, E. coli can grow up to 1.1 log cfu/g at temperatures above 16°C, even at low contamination levels. Regarding log diff estimated in foodservice centers, very low risk was obtained (log diff b 1.0 log cfu in all cases). Mean T eff values obtained in hospitals were the lowest ones (11.1°C) and no growth of E. coli was predicted in >92% of simulated cases. The results presented in this study could serve food operators to set time/Temperature requirements for ready-to-eat foods in foodservice centers, providing a scientific basis through the use of predictive modeling. These findings may also serve to food safety managers to better define the control measures to be adopted in foodservice centers in order to prevent food-borne infections.
ABSTRACTThe effects of storage temperature and time on the microflora of fresh, vacuum packaged, ... more ABSTRACTThe effects of storage temperature and time on the microflora of fresh, vacuum packaged, and modified atmospheres packaged asparagus (Asparagus officinalis) were analyzed. Total aerobic mesophilic, psychrophilic, lactic acid bacteria, Enterobacteriaceae, and yeast and molds were determined as a function of time. The effect of washing on the original microflora of the asparagus and the growth of the different microbial groups during the storage time were checked. From day 8, a progressive increase in the mesophile and psychrophile counts in both types of packaging was observed. At the end of the experiment (day 21), the mesophile and psychrophile counts were all 107 CFU/g, for both types of packaging. In the vacuum packaging, the final enterobacteria counts (2.5 × 102 CFU/g) and yeast and molds (10 CFU/g) were lower than in the polyethylene bag packaged asparagus, which showed enterobacteria counts of 7.3 × 104 CFU/g) and yeast and mold counts of 2.3 × 104 CFU/g. The non‐pack...
The power of computational neural networks (CNN) for microbiological growth prediction was evalua... more The power of computational neural networks (CNN) for microbiological growth prediction was evaluated. The training set consisted of growth responses data from a combination of three strains of Salmonella in a laboratory medium as affected by pH level, sodium chloride concentration and storage temperature. The architecture of CNN was designed to contain three input parameters in the input layer and one output parameter in the output layer. For their optimization, algorithms were developed to prune the net connections, obtaining an improvement in the generalization and a decrease in the number of necessary patterns for the training. The standard error of prediction (%SEP) obtained was under 5% using twenty inputs to the net, and the result was significantly smaller than the one obtained using regression equations. Therefore, the usefulness of CNN for modeling microbial growth is appealing, and its improvement promises results that will be better than those obtained by other estimation...
ABSTRACT Microbial survival on inert surfaces should be considered as an important factor to unde... more ABSTRACT Microbial survival on inert surfaces should be considered as an important factor to understand and quantify bacterial transfer to foods (i.e. cross contamination). The present work studied the survival of Escherichia coli O157:H7 and Salmonella spp. on stainless steel surfaces with different soiling substrates based on leafy vegetable juices. Furthermore, predictive models were proposed to describe survival patterns shown by both pathogens in the different substrates. E. coli O157:H7 and Salmonella spp. could be recovered until 192 and 168 h, respectively from surfaces soiled with chard, red cabbage, iceberg lettuce and romaine lettuce. However, in spinach and parsley juice substrates, microorganisms were not detected after 48 h. This survival 10/5/2013; Time:1:31:57time was much lower than that obtained in saline solution (120 h), used to simulate clean surfaces. The reduction rates observed in a period of time of 2 and 24 h for E. coli O157:H7 depended on the type of substrate and ranged 1.03-2.27 and 0.14-027 log cfu/cm(2) h, respectively. For Salmonella spp. results showed slightly lower drops, with 0.89-1.62 and 0.15-0.25 log cfu/cm(2)h, for 2 and 24 h, respectively. The Weibull model and Weibull + tail model seemed to be the most suitable mathematical functions describing survival of both microorganisms in the different substrates (adj-R-2 = 0.94-0.99). Experiments were developed simulating environmental conditions given in fresh-cut vegetable factories. Therefore, results and models generated in this study could be applied in quantitative risk assessment studies to obtain a more accurate representation of cross contamination, in addition to enabling the assessment of control strategies of both pathogens in the fresh-cut vegetable industry.
A stochastic simulation modelling approach was taken to determine the extent of Escherichia coli ... more A stochastic simulation modelling approach was taken to determine the extent of Escherichia coli O157:H7 contamination in fresh-cut bagged lettuce leaving the processing plant. A probabilistic model was constructed in Excel to account for E. coli O157:H7 cross contamination when contaminated lettuce enters the processing line. Simulation of the model was performed using @Risk PalisadeÓ Software, providing an estimate of concentration and prevalence in the final bags of product. Three different scenarios, named S1, S2, and S3, were considered to represent the initial concentration on the contaminated batch entering the processing line which corresponded to 0.01, 1 and 100 cfu/g, respectively. The model was satisfactorily validated based on Standard Error of Prediction (SEP), which ranged from 0.00-35%. ANOVA analysis performed on simulated data revealed that the initial concentration in the contaminated batch (i.e., S1, S2, and S3) did not influence significantly (p ¼ 0.4) the E. coli O157:H7 levels in bags derived from cross contamination. In addition, significantly different (p < 0.001) prevalence was observed at the different levels simulated (S1; S2 and S3). At the lowest contamination level (0.01 cfu/g), bags were cross-contaminated sporadically, resulting in very low E. coli O157:H7 populations (mean: 2 cfu/bag) and prevalence levels (<1%). In contrast, higher average prevalence levels were obtained for S2 and S3 corresponding to 3.05 and 13.39%, respectively. Furthermore, the impact of different interventions on E. coli O157:H7 cross-contamination (e.g., pathogen testing, chlorination, irradiation, and cleaning and disinfection procedures) was evaluated. Model showed that the pathogen was able to survive and be present in the final bags in all simulated interventions scenarios although irradiation (0.5 KGy) was a more effective decontamination step in reducing prevalence than chlorination or pathogen testing under the same simulated conditions.
Listeria monocytogenes, when present, could be able to grow on Ready-to-Eat (RTE) iceberg lettuce... more Listeria monocytogenes, when present, could be able to grow on Ready-to-Eat (RTE) iceberg lettuce. This investigation demonstrates that L. monocytogenes grows on packaged shredded iceberg lettuce held at 13 or 5°C (maximum growth rate of 0.019 and 0.013 log cfu/ h, respectively), with increments of 4.85 and 2.66 log cfu/g, respectively, after 14 days. No lag time was observed at 13°C, in contrast with that at 5°C (5.6 days). Initial atmosphere inside the packages was 4.65-6.2% CO 2 , 2.1-4.3% O 2 and a balance of N 2. Five predictive models taken from literature gave conservative predictions at 13°C, although at 5°C they were closer. Lactic acid and psychrotrophic bacteria showed similar growth at both temperatures. In general, the MAP system reported here retarded the growth of L. monocytogenes in comparison with other works without initial flushing of gases.
Bulletin of Environmental Contamination and Toxicology, 1986
The fluvial waters of Andalusia can be considered as having a lower degree of mercury pollution t... more The fluvial waters of Andalusia can be considered as having a lower degree of mercury pollution than other more highly industrialized areas, according to the annual reports on points in the fluvial network inspected for the quality of its water set up by the Department of Hydraulics at the Ministry of Works (Ministerio de Obras P6blicas y Urbanismo 1985). Some authors have demonstrated the positive use of marine organisms as biological indicators of environmental contamination by mercury (Sorentino 1979; Pens and Alberto 1984).
Page 1. 115 re v ista d e l co m ité cie n tífi co n º 1 2 Resumen La irradiación de alimentos es... more Page 1. 115 re v ista d e l co m ité cie n tífi co n º 1 2 Resumen La irradiación de alimentos está autorizada en numerosos países aunque con diferentes restricciones en cuanto al tipo de alimento, dosis absorbida, etc. La Unión ...
Understanding the role of food-related factors on the efficacy of protective cultures is essentia... more Understanding the role of food-related factors on the efficacy of protective cultures is essential to attain optimal results for developing biopreservation-based strategies. The aim of this work was to assess and model growth of Latilactobacillus sakei CTC494 and Listeria monocytogenes CTC1034, and their interaction, in two different readyto-eat fish products (i.e., surimi-based product and tuna pâté) at 2 and 12 • C. The existing expanded Jamesoneffect and a new expanded Jameson-effect model proposed in this study were evaluated to quantitatively describe the effect of microbial interaction. The inhibiting effect of the selected lactic acid bacteria strain on the pathogen growth was product dependent. In surimi product, a reduction of lag time of both strains was observed when growing in coculture at 2 • C, followed by the inhibition of the pathogen when the bioprotective L. sakei CTC494 reached the maximum population density, suggesting a mutualism-antagonism continuum phenomenon between populations. In tuna pâté, L. sakei CTC494 exerted a strong inhibition of L. monocytogenes at 2 • C (<0.5 log increase) and limited the growth at 12 • C (<2 log increase). The goodness-of-fit indexes indicated that the new expanded Jameson-effect model performed better and appropriately described the different competition patterns observed in the tested fish products. The proposed expanded competition model allowed for description of not only antagonistic but also mutualism-based interactions based on their influence on lag time.
The occurrence of various foodborne disease outbreaks linked to the consumption of cucumbers worl... more The occurrence of various foodborne disease outbreaks linked to the consumption of cucumbers worldwide in the last years raised concerns regarding the survival ability of foodborne pathogens on this food matrix. This work aimed at evaluating and quantifying the survival of Escherichia coli O157:H7 and Salmonella spp. on cucumber surfaces. Cucumbers were inoculated with a 5-strain cocktail of each microorganism and kept at 25 °C. The survival ability of two green fluorescent protein (GFP) labelled Salmonella strains inoculated individually on cucumbers was also evaluated. The inoculated areas were swabbed at different time intervals (maximum of 72 h) and cells were enumerated by plate count method (log CFU/cm2). The population of both pathogens decreased significantly on cucumber surfaces over time. E. coli O157:H7 could only be recovered up to 8 h while Salmonella spp. could be detected up to 24 h. The GFP-labelled Salmonella strains showed similar behaviour on cucumbers compared to the evaluated Salmonella cocktail. Survival kinetic parameters were estimated by fitting the Weibull model to the survival data. The data obtained in this study indicate that despite of the rapid decrease on concentrations of both pathogens evaluated on cucumbers surfaces, strategies to avoid their contamination during the supply chain as well as proper cleaning and disinfection protocols must be put forward to mitigate both E. coli O57:H7 and Salmonella on cucumbers and therefore, to decrease the exposure of consumers to microbial hazards and to avoid cross-contamination events during distribution, retail and in domestic environments.
Resumen del trabajo presentado a la 25th International ICFHM Conference FoodMicro, celebrada en D... more Resumen del trabajo presentado a la 25th International ICFHM Conference FoodMicro, celebrada en Dublin (Irlanda) del 19 al 22 de julio de 2016.-- et al.
In this study, the bioprotective potential of Lactobacillus sakei CTC494 against Listeria monocyt... more In this study, the bioprotective potential of Lactobacillus sakei CTC494 against Listeria monocytogenes CTC1034 was evaluated on vacuum-packed hot-smoked sea bream at 5 ºC and dynamic temperatures ranging from 3 to 12 ºC. The capacity of three microbial competition interaction models to describe the inhibitory effect of L. sakei CTC494 on L. monocytogenes was assessed based on the Jameson effect and Lotka-Volterra approaches. A sensory analysis was performed to evaluate the spoiling capacity of L. sakei CTC494 on the smoked fish product at 5 ºC. Based on the sensory results, the bioprotection strategy against the pathogen was established by inoculating the product at a 1:2 ratio (pathogen:bioprotector, log CFU/g). The kinetic growth parameters of both microorganisms were estimated in mono-culture at constant storage (5 ºC). In addition, the inhibition function parameters of the tested interaction models were estimated in coculture at constant and dynamic temperature storage using as input the mono-culture kinetic parameters. The growth potential (δ log) of L. monocytogenes, in mono-culture, was 3.5 log on smoked sea bream during the experimental period (20 days). In co-culture, L. sakei CTC494 significantly reduced the capability of L. monocytogenes to grow, although its effectiveness was temperature dependent. The LAB strain limited the growth of the pathogen under storage at 5 ºC (< 1 log increase) and at dynamic profile 2 (< 2 log increase). Besides, under storage at dynamic profile 1, the growth of L. monocytogenes was inhibited (< 0.5 log increase). These results confirmed the efficacy of L. sakei CTC494 for controlling the pathogen growth on the studied fish product. The Lotka-Volterra competition model showed slightly better fit to the observed L. monocytogenes growth response than the Jameson-based models according to the statistical performance. The proposed modelling approach could support the assessment and establishment of bioprotective culture-based strategies aimed at reducing the risk of listeriosis linked to the consumption of RTE hot-smoked sea bream. 7 foodborne pathogens such as Listeria monocytogenes (EFSA BIOHAZ Panel, 2018). 8 Biopreservation, also called bioprotection, is a biocontrol approach to enhance product 9 safety and shelf-life using microorganisms selected for their antimicrobial properties, so 10 called protective cultures (Leroi et al., 2015). Lactic-acid bacteria (LAB) are considered 11 a new generation of food additives and the basis of food biopreservation (Said et al., 12 2019). Protective cultures are considered by the regulatory agencies as 'new' food 13 additives, meaning that they require market authorization for their technological use in 14 foods. However, most LAB are Generally Recognized as Safe (GRAS) and many LAB 15 species (including Lactobacillus sakei) have been granted by EFSA with the Qualified 16 Presumption of Safety (QPS) status (EFSA, 2018). In the EU, microorganisms with the 17 latter food-grade standard do not need to undergo a further safety assessment other than 18 to provide evidence of efficacy and to satisfy the specified qualifications, if applicable, 19 for its market approval. Two recent studies have proved that the antilisterial sakacin K-20 producing Lactobacillus sakei strain CTC494 (from meat origin) is effective to inhibit L. 21 monocytogenes in filleted sea bream and cold-smoked salmon under refrigerated storage 22 (Aymerich et al., 2019; Costa et al., 2019). Nevertheless, the inhibitory capacity of this 23 bioprotective LAB strain has not been tested in other fish products where the differences 24 in product's characteristics and formulations might either favor its inhibition thanks to the antimicrobial hurdle combinations (Leistner, 2000) or hinder the ability of the strain 26
This study was aimed at characterizing microbiologically Gilthead sea bream (Sparus aurata) and S... more This study was aimed at characterizing microbiologically Gilthead sea bream (Sparus aurata) and Sea bass (Dicentrarchus labrax) produced in two estuarine ecosystems in Andalusia (Spain): the estuary of the river Guadalquivir (La Puebla del Río, Sevilla) (A), and the estuary of the river Guadiana (Ayamonte, Huelva) (B). The collected fish individuals and water were analysed for hygiene indicator microorganisms and pathogens. The statistical analysis of results revealed that microbial counts for the different microbiological parameters were not statistically different for fish type. On the contrary, considering anatomic part, viscera showed significantly higher concentrations for Enterobacteriaceae, total coliforms and for Staphylococcus spp. coagulase +. Furthermore, location A showed in water and fish higher levels for lactic acid bacteria, aerobic mesophilic bacteria, Enterobacteriaceae, total coliforms and Staphylococcus spp. coagulase +. Neither Listeria monocytogenes, nor Salmonella spp. were detected, though Vibrio parahaemolyticus was identified, molecularly, in estuarine water in location B. The predictive analysis demonstrated that the initial microbiological quality could have an impact on product shelf-life, being longer for location B, with better microbiological quality. Results stress the relevance of preventing the microbiological contamination of water in estuary production systems in order to assure the quality and safety of Gilthead sea bream and Sea bass.
Abstract- Changes in concentrations of nickel present in cow's, ewe's and goat's m... more Abstract- Changes in concentrations of nickel present in cow's, ewe's and goat's milk were stud-ied monthly (n = 360 sampi es) by using graphite fumace atomic absorption spectrometry. The mean concentrations of nickel are 15.0 ± 3.81, 18.6 ± 2.50 and 13.6 ± 2.46 ug-kg ' of fresh weight for cow's, ewe's and goat's milk respectively. Two-factor (species and time period) variance analyses were made on the three types ofmilk investigated and Tuckey's mean homogeneity test (P < 0.05) was also carried out for the formation of homogeneous groups per species for nickel content. Significant changes (P < 0.001) were determined over time in the nickel content of the three species studied and two homogeneous groups were formed, one for cow's and goat's milk and an other for ewe's milk with the higher nickel content. For the three species, the monthly changes of the nickel content corre-spond to a mathematical model of)Cd grade and the...
It is a principal aim of governments to assure the safety of societies in all sectors. In the foo... more It is a principal aim of governments to assure the safety of societies in all sectors. In the food field, safety has been dealt with for a long time by making decisions in an empirical manner. Recently, risk management has been appointed as the formal scientific-based approach to address food safety issues. From a global perspective, food safety risk management can be described “as the process of weighting control alternatives by government (and international standard-setting bodies) in consultation with interested stakeholders, taking into account scientific information on risks to consumers as well as other relevant inputs (e.g. economics, technical feasibility, societal preferences), and choosing and implementing food safety measures as appropriate” (Food Agriculture Organization/World Health Organization [FAO/WHO], 2006b). Indeed, governments must make decisions, whose effects are especially noted during food crises. Nevertheless, other stakeholders should also manage food risks...
This work has evaluated the possibility by the application of the «IMAGO» image analysis and trea... more This work has evaluated the possibility by the application of the «IMAGO» image analysis and treatment programme in the study of morphological cell differences in the xylem bundles of asparagus. The variables were analysed due to their longitudinal and concentric location, the variety of asparagus and its diameter, as well as postharvest modifications it undergoes during its cold storage at different levels of temperature throughout a period of time. Lignin deposit was determined in the xylem bundles of asparagus as cellular wall thickness, the cellular parameter analysed were area, perimeter, maximum and minimum radius and spherecity. Statistically significant differences were found between variety, diameters and portions of asparagus, as well as the two zones of the same cut and the temperatures and time of storage.
Journal of the Science of Food and Agriculture, 2000
An evaluation was made of the degree of toughening of asparagus during its storage through a stud... more An evaluation was made of the degree of toughening of asparagus during its storage through a study of the morphological and cellular differences of the xylem vascular bundles as a function of the variety, thickness and portion of the asparagus spear. Light microscopic examinations were carried out to determine the thickness of the cell wall to quantify the extent of the toughening. At the same time a study was made of the fractions of dietary ®bre of the asparagus spear by means of chemical extraction techniques. Statistically signi®cant differences were observed in both methods between varieties, thicknesses and portions of the asparagus spear. Different factors such as variety, degree of maturing, portion of spear, moment of harvesting, and type and time of storage have an in¯uence on the toughening of white asparagus that should be taken into account in order to standardise its quality.
Ready-to-eat lettuce is a food commodity prone to contamination by pathogenic microorganisms if p... more Ready-to-eat lettuce is a food commodity prone to contamination by pathogenic microorganisms if processing and distribution conditions as well as handling practices are not effective. A challenge testing protocol was applied to ready-to-eat iceberg-lettuce samples by inoculating different initial contamination levels (4.5, 3.5 and 2.5 log cfu/g) of Escherichia coli strain (serotype O158:H23) subsequently stored at 8, 12, 16, 20 and 24°C for 6 h. A polynomial regression model for log difference (log diff) was developed at each inoculum level studied through the calculation of the effective static temperature (T eff). Furthermore, the developed model was integrated within a risk-based approach with real time/Temperature (t/T) data collected in three Spanish foodservice centers: school canteens, long-term care facilities (LTCF) and hospitals. Statistical distributions were fitted to t/T data and estimated log diff values were obtained as model outputs through a Monte Carlo simulation (10,000 iterations). The results obtained at static conditions indicated that the maintenance of the lettuce at 8°C slightly reduced the E. coli population from −0.4 to −0.5 log cfu/g. However, if chill chain is not maintained, E. coli can grow up to 1.1 log cfu/g at temperatures above 16°C, even at low contamination levels. Regarding log diff estimated in foodservice centers, very low risk was obtained (log diff b 1.0 log cfu in all cases). Mean T eff values obtained in hospitals were the lowest ones (11.1°C) and no growth of E. coli was predicted in >92% of simulated cases. The results presented in this study could serve food operators to set time/Temperature requirements for ready-to-eat foods in foodservice centers, providing a scientific basis through the use of predictive modeling. These findings may also serve to food safety managers to better define the control measures to be adopted in foodservice centers in order to prevent food-borne infections.
ABSTRACTThe effects of storage temperature and time on the microflora of fresh, vacuum packaged, ... more ABSTRACTThe effects of storage temperature and time on the microflora of fresh, vacuum packaged, and modified atmospheres packaged asparagus (Asparagus officinalis) were analyzed. Total aerobic mesophilic, psychrophilic, lactic acid bacteria, Enterobacteriaceae, and yeast and molds were determined as a function of time. The effect of washing on the original microflora of the asparagus and the growth of the different microbial groups during the storage time were checked. From day 8, a progressive increase in the mesophile and psychrophile counts in both types of packaging was observed. At the end of the experiment (day 21), the mesophile and psychrophile counts were all 107 CFU/g, for both types of packaging. In the vacuum packaging, the final enterobacteria counts (2.5 × 102 CFU/g) and yeast and molds (10 CFU/g) were lower than in the polyethylene bag packaged asparagus, which showed enterobacteria counts of 7.3 × 104 CFU/g) and yeast and mold counts of 2.3 × 104 CFU/g. The non‐pack...
The power of computational neural networks (CNN) for microbiological growth prediction was evalua... more The power of computational neural networks (CNN) for microbiological growth prediction was evaluated. The training set consisted of growth responses data from a combination of three strains of Salmonella in a laboratory medium as affected by pH level, sodium chloride concentration and storage temperature. The architecture of CNN was designed to contain three input parameters in the input layer and one output parameter in the output layer. For their optimization, algorithms were developed to prune the net connections, obtaining an improvement in the generalization and a decrease in the number of necessary patterns for the training. The standard error of prediction (%SEP) obtained was under 5% using twenty inputs to the net, and the result was significantly smaller than the one obtained using regression equations. Therefore, the usefulness of CNN for modeling microbial growth is appealing, and its improvement promises results that will be better than those obtained by other estimation...
ABSTRACT Microbial survival on inert surfaces should be considered as an important factor to unde... more ABSTRACT Microbial survival on inert surfaces should be considered as an important factor to understand and quantify bacterial transfer to foods (i.e. cross contamination). The present work studied the survival of Escherichia coli O157:H7 and Salmonella spp. on stainless steel surfaces with different soiling substrates based on leafy vegetable juices. Furthermore, predictive models were proposed to describe survival patterns shown by both pathogens in the different substrates. E. coli O157:H7 and Salmonella spp. could be recovered until 192 and 168 h, respectively from surfaces soiled with chard, red cabbage, iceberg lettuce and romaine lettuce. However, in spinach and parsley juice substrates, microorganisms were not detected after 48 h. This survival 10/5/2013; Time:1:31:57time was much lower than that obtained in saline solution (120 h), used to simulate clean surfaces. The reduction rates observed in a period of time of 2 and 24 h for E. coli O157:H7 depended on the type of substrate and ranged 1.03-2.27 and 0.14-027 log cfu/cm(2) h, respectively. For Salmonella spp. results showed slightly lower drops, with 0.89-1.62 and 0.15-0.25 log cfu/cm(2)h, for 2 and 24 h, respectively. The Weibull model and Weibull + tail model seemed to be the most suitable mathematical functions describing survival of both microorganisms in the different substrates (adj-R-2 = 0.94-0.99). Experiments were developed simulating environmental conditions given in fresh-cut vegetable factories. Therefore, results and models generated in this study could be applied in quantitative risk assessment studies to obtain a more accurate representation of cross contamination, in addition to enabling the assessment of control strategies of both pathogens in the fresh-cut vegetable industry.
A stochastic simulation modelling approach was taken to determine the extent of Escherichia coli ... more A stochastic simulation modelling approach was taken to determine the extent of Escherichia coli O157:H7 contamination in fresh-cut bagged lettuce leaving the processing plant. A probabilistic model was constructed in Excel to account for E. coli O157:H7 cross contamination when contaminated lettuce enters the processing line. Simulation of the model was performed using @Risk PalisadeÓ Software, providing an estimate of concentration and prevalence in the final bags of product. Three different scenarios, named S1, S2, and S3, were considered to represent the initial concentration on the contaminated batch entering the processing line which corresponded to 0.01, 1 and 100 cfu/g, respectively. The model was satisfactorily validated based on Standard Error of Prediction (SEP), which ranged from 0.00-35%. ANOVA analysis performed on simulated data revealed that the initial concentration in the contaminated batch (i.e., S1, S2, and S3) did not influence significantly (p ¼ 0.4) the E. coli O157:H7 levels in bags derived from cross contamination. In addition, significantly different (p < 0.001) prevalence was observed at the different levels simulated (S1; S2 and S3). At the lowest contamination level (0.01 cfu/g), bags were cross-contaminated sporadically, resulting in very low E. coli O157:H7 populations (mean: 2 cfu/bag) and prevalence levels (<1%). In contrast, higher average prevalence levels were obtained for S2 and S3 corresponding to 3.05 and 13.39%, respectively. Furthermore, the impact of different interventions on E. coli O157:H7 cross-contamination (e.g., pathogen testing, chlorination, irradiation, and cleaning and disinfection procedures) was evaluated. Model showed that the pathogen was able to survive and be present in the final bags in all simulated interventions scenarios although irradiation (0.5 KGy) was a more effective decontamination step in reducing prevalence than chlorination or pathogen testing under the same simulated conditions.
Listeria monocytogenes, when present, could be able to grow on Ready-to-Eat (RTE) iceberg lettuce... more Listeria monocytogenes, when present, could be able to grow on Ready-to-Eat (RTE) iceberg lettuce. This investigation demonstrates that L. monocytogenes grows on packaged shredded iceberg lettuce held at 13 or 5°C (maximum growth rate of 0.019 and 0.013 log cfu/ h, respectively), with increments of 4.85 and 2.66 log cfu/g, respectively, after 14 days. No lag time was observed at 13°C, in contrast with that at 5°C (5.6 days). Initial atmosphere inside the packages was 4.65-6.2% CO 2 , 2.1-4.3% O 2 and a balance of N 2. Five predictive models taken from literature gave conservative predictions at 13°C, although at 5°C they were closer. Lactic acid and psychrotrophic bacteria showed similar growth at both temperatures. In general, the MAP system reported here retarded the growth of L. monocytogenes in comparison with other works without initial flushing of gases.
Bulletin of Environmental Contamination and Toxicology, 1986
The fluvial waters of Andalusia can be considered as having a lower degree of mercury pollution t... more The fluvial waters of Andalusia can be considered as having a lower degree of mercury pollution than other more highly industrialized areas, according to the annual reports on points in the fluvial network inspected for the quality of its water set up by the Department of Hydraulics at the Ministry of Works (Ministerio de Obras P6blicas y Urbanismo 1985). Some authors have demonstrated the positive use of marine organisms as biological indicators of environmental contamination by mercury (Sorentino 1979; Pens and Alberto 1984).
Page 1. 115 re v ista d e l co m ité cie n tífi co n º 1 2 Resumen La irradiación de alimentos es... more Page 1. 115 re v ista d e l co m ité cie n tífi co n º 1 2 Resumen La irradiación de alimentos está autorizada en numerosos países aunque con diferentes restricciones en cuanto al tipo de alimento, dosis absorbida, etc. La Unión ...
Understanding the role of food-related factors on the efficacy of protective cultures is essentia... more Understanding the role of food-related factors on the efficacy of protective cultures is essential to attain optimal results for developing biopreservation-based strategies. The aim of this work was to assess and model growth of Latilactobacillus sakei CTC494 and Listeria monocytogenes CTC1034, and their interaction, in two different readyto-eat fish products (i.e., surimi-based product and tuna pâté) at 2 and 12 • C. The existing expanded Jamesoneffect and a new expanded Jameson-effect model proposed in this study were evaluated to quantitatively describe the effect of microbial interaction. The inhibiting effect of the selected lactic acid bacteria strain on the pathogen growth was product dependent. In surimi product, a reduction of lag time of both strains was observed when growing in coculture at 2 • C, followed by the inhibition of the pathogen when the bioprotective L. sakei CTC494 reached the maximum population density, suggesting a mutualism-antagonism continuum phenomenon between populations. In tuna pâté, L. sakei CTC494 exerted a strong inhibition of L. monocytogenes at 2 • C (<0.5 log increase) and limited the growth at 12 • C (<2 log increase). The goodness-of-fit indexes indicated that the new expanded Jameson-effect model performed better and appropriately described the different competition patterns observed in the tested fish products. The proposed expanded competition model allowed for description of not only antagonistic but also mutualism-based interactions based on their influence on lag time.
The occurrence of various foodborne disease outbreaks linked to the consumption of cucumbers worl... more The occurrence of various foodborne disease outbreaks linked to the consumption of cucumbers worldwide in the last years raised concerns regarding the survival ability of foodborne pathogens on this food matrix. This work aimed at evaluating and quantifying the survival of Escherichia coli O157:H7 and Salmonella spp. on cucumber surfaces. Cucumbers were inoculated with a 5-strain cocktail of each microorganism and kept at 25 °C. The survival ability of two green fluorescent protein (GFP) labelled Salmonella strains inoculated individually on cucumbers was also evaluated. The inoculated areas were swabbed at different time intervals (maximum of 72 h) and cells were enumerated by plate count method (log CFU/cm2). The population of both pathogens decreased significantly on cucumber surfaces over time. E. coli O157:H7 could only be recovered up to 8 h while Salmonella spp. could be detected up to 24 h. The GFP-labelled Salmonella strains showed similar behaviour on cucumbers compared to the evaluated Salmonella cocktail. Survival kinetic parameters were estimated by fitting the Weibull model to the survival data. The data obtained in this study indicate that despite of the rapid decrease on concentrations of both pathogens evaluated on cucumbers surfaces, strategies to avoid their contamination during the supply chain as well as proper cleaning and disinfection protocols must be put forward to mitigate both E. coli O57:H7 and Salmonella on cucumbers and therefore, to decrease the exposure of consumers to microbial hazards and to avoid cross-contamination events during distribution, retail and in domestic environments.
Resumen del trabajo presentado a la 25th International ICFHM Conference FoodMicro, celebrada en D... more Resumen del trabajo presentado a la 25th International ICFHM Conference FoodMicro, celebrada en Dublin (Irlanda) del 19 al 22 de julio de 2016.-- et al.
In this study, the bioprotective potential of Lactobacillus sakei CTC494 against Listeria monocyt... more In this study, the bioprotective potential of Lactobacillus sakei CTC494 against Listeria monocytogenes CTC1034 was evaluated on vacuum-packed hot-smoked sea bream at 5 ºC and dynamic temperatures ranging from 3 to 12 ºC. The capacity of three microbial competition interaction models to describe the inhibitory effect of L. sakei CTC494 on L. monocytogenes was assessed based on the Jameson effect and Lotka-Volterra approaches. A sensory analysis was performed to evaluate the spoiling capacity of L. sakei CTC494 on the smoked fish product at 5 ºC. Based on the sensory results, the bioprotection strategy against the pathogen was established by inoculating the product at a 1:2 ratio (pathogen:bioprotector, log CFU/g). The kinetic growth parameters of both microorganisms were estimated in mono-culture at constant storage (5 ºC). In addition, the inhibition function parameters of the tested interaction models were estimated in coculture at constant and dynamic temperature storage using as input the mono-culture kinetic parameters. The growth potential (δ log) of L. monocytogenes, in mono-culture, was 3.5 log on smoked sea bream during the experimental period (20 days). In co-culture, L. sakei CTC494 significantly reduced the capability of L. monocytogenes to grow, although its effectiveness was temperature dependent. The LAB strain limited the growth of the pathogen under storage at 5 ºC (< 1 log increase) and at dynamic profile 2 (< 2 log increase). Besides, under storage at dynamic profile 1, the growth of L. monocytogenes was inhibited (< 0.5 log increase). These results confirmed the efficacy of L. sakei CTC494 for controlling the pathogen growth on the studied fish product. The Lotka-Volterra competition model showed slightly better fit to the observed L. monocytogenes growth response than the Jameson-based models according to the statistical performance. The proposed modelling approach could support the assessment and establishment of bioprotective culture-based strategies aimed at reducing the risk of listeriosis linked to the consumption of RTE hot-smoked sea bream. 7 foodborne pathogens such as Listeria monocytogenes (EFSA BIOHAZ Panel, 2018). 8 Biopreservation, also called bioprotection, is a biocontrol approach to enhance product 9 safety and shelf-life using microorganisms selected for their antimicrobial properties, so 10 called protective cultures (Leroi et al., 2015). Lactic-acid bacteria (LAB) are considered 11 a new generation of food additives and the basis of food biopreservation (Said et al., 12 2019). Protective cultures are considered by the regulatory agencies as 'new' food 13 additives, meaning that they require market authorization for their technological use in 14 foods. However, most LAB are Generally Recognized as Safe (GRAS) and many LAB 15 species (including Lactobacillus sakei) have been granted by EFSA with the Qualified 16 Presumption of Safety (QPS) status (EFSA, 2018). In the EU, microorganisms with the 17 latter food-grade standard do not need to undergo a further safety assessment other than 18 to provide evidence of efficacy and to satisfy the specified qualifications, if applicable, 19 for its market approval. Two recent studies have proved that the antilisterial sakacin K-20 producing Lactobacillus sakei strain CTC494 (from meat origin) is effective to inhibit L. 21 monocytogenes in filleted sea bream and cold-smoked salmon under refrigerated storage 22 (Aymerich et al., 2019; Costa et al., 2019). Nevertheless, the inhibitory capacity of this 23 bioprotective LAB strain has not been tested in other fish products where the differences 24 in product's characteristics and formulations might either favor its inhibition thanks to the antimicrobial hurdle combinations (Leistner, 2000) or hinder the ability of the strain 26
This study was aimed at characterizing microbiologically Gilthead sea bream (Sparus aurata) and S... more This study was aimed at characterizing microbiologically Gilthead sea bream (Sparus aurata) and Sea bass (Dicentrarchus labrax) produced in two estuarine ecosystems in Andalusia (Spain): the estuary of the river Guadalquivir (La Puebla del Río, Sevilla) (A), and the estuary of the river Guadiana (Ayamonte, Huelva) (B). The collected fish individuals and water were analysed for hygiene indicator microorganisms and pathogens. The statistical analysis of results revealed that microbial counts for the different microbiological parameters were not statistically different for fish type. On the contrary, considering anatomic part, viscera showed significantly higher concentrations for Enterobacteriaceae, total coliforms and for Staphylococcus spp. coagulase +. Furthermore, location A showed in water and fish higher levels for lactic acid bacteria, aerobic mesophilic bacteria, Enterobacteriaceae, total coliforms and Staphylococcus spp. coagulase +. Neither Listeria monocytogenes, nor Salmonella spp. were detected, though Vibrio parahaemolyticus was identified, molecularly, in estuarine water in location B. The predictive analysis demonstrated that the initial microbiological quality could have an impact on product shelf-life, being longer for location B, with better microbiological quality. Results stress the relevance of preventing the microbiological contamination of water in estuary production systems in order to assure the quality and safety of Gilthead sea bream and Sea bass.
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