Browsing by Author "Gonzales-Barron, Ursula"
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- An alternative framework to conduct inferential statistics for low microbial counts in foods: the poisson-gamma regressionPublication . Gonzales-Barron, Ursula; Cadavez, Vasco; Butler, FrancisThe objective of this article was to compare four Poisson-gamma regression models to assess the effect of chilling on the concentration of coliforms from beef carcasses. A total of 600 carcasses were sampled before and after chilling at eight large Irish abattoirs, and the total coliforms were determined. With a coded variable (pre-chill/post-chill) as treatment, and extracting the variability of batches nested in abattoirs, random-effects models confirmed that chilling had a decreasing effect on the overall recovery of coliforms. Furthermore, the expected coliforms concentrations on pre-chill and post-chill carcasses were estimated on a CFU/cm2 scale, as well as their between-batch variability. This study introduced an alternative conceptual framework that can find interesting applications in stochastic risk assessment and in the design of more efficient sampling plans.
- An assessment of the processing and physicochemical factors contributing to the microbial contamination of salpicão, a naturally-fermented Portuguese sausagePublication . Cadavez, Vasco; Gonzales-Barron, Ursula; Pires, P.; Fernandes, E.; Pereira, Ana Paula; Gomes, Aline; Araújo, José Pedro; Lopes-da-Silva, M.F.; Rodrigues, Paula; Fernandes, Conceição; Saavedra, Maria José; Butler, Francis; Dias, TeresaComplete microbiological, physicochemical and environmental longitudinal data were obtained from factory surveys in order to elucidate risk factors leading to the survival of Enterobacteriaceae, Staphylococcus aureus and Listeria monocytogenes in salpicão sausage. A total of six batches were surveyed from two factories; one added nitrite and polyphosphates in their formulation (Factory II). The addition of polyphosphates slowed down fermentation, which favoured the increase in Enterobacteriaceae (∼0.5 log CFU/g), S. aureus (∼0.5 log CFU/g) and L. monocytogenes (∼70 CFU/g) until maceration. Maceration should be regarded as a critical stage in the control of S. aureus in salpicão, as longer maceration (p = 0.033), higher temperatures of maceration (p = 0.018) and pH of macerated meat (p = 0.079) led to higher S. aureus counts in the final product. The main hurdle controlling S. aureus in salpicão is the pH. For L. monocytogenes and Enterobacteriaceae, at least three hurdles hinder their viability: low Aw (p = 0.010; 0.012), smoking (p < 0.0001; 0.020) and nitrite (p = 0.158; 0.105). Cross-contamination, especially during mixing, should be avoided as it is an important factor explaining the increase in Enterobacteriaceae (p = 0.041), S. aureus (p = 0.015) and L. monocytogenes (p = 0.082) on a batch basis. There is a need to optimise the acidification process and reinforce good hygiene practices
- An extend bigelow-type meta-regression model descring the heat resistance of neosartorya sporesPublication . Gonzales-Barron, Ursula; Cadavez, Vasco; Alvarenga, Verônica O.; Prado-Silva, Leonardo; Sant'Ana, Anderson S.A meta-regression based on an extended-Bigelow equation was adjusted to 326 D-values of Neosartorya spp., taken from the literature, in order to summarise its heat resistance parameters. As the meta-regression accommodated relevant study characteristics, it was possible to estimate D*-values and z-values of temperature, pH and °Brix for the various beverages, inactivation methods, fruits and preservative use/no use.
- Anti-listerial activity of lactic acid bacteria isolated from artisanal cheeses produced in the State of Minas Gerais, BrazilPublication . Campagnollo, Fernanda B.; Margalho, Larissa P.; Kamimura, Bruna A.; Alvarenga, Verônica O.; Cadavez, Vasco; Gonzales-Barron, Ursula; Sant'Ana, Anderson S.Introduction: Brazilian artisanal cheeses, among them Minas cheeses, are highly appreciated by consumers. Nonetheless, some cheeses have been regularly found to harbour high-risk pathogens, such as Listeria monocytogenes, mainly arising from their elaboration with raw milk and informal production. However, cheese matrices are complex systems whose microbial competing factors (i.e., indigenous lactic acid bacteria (LAB)) and intrinsic properties (acidity, temperature, and water activity) can act as effective hurdles against L. monocytogenes proliferation. Purpose: The aim of this study was to evaluate the capacity of LAB strains isolated from Minas artisanal cheeses as anti-listerial agents. Methods: A total of 891 LAB strains were isolated from 244 Minas artisanal cheese samples (466 using MRS agar (MRSLAB) and 425 using M17 agar (M17LAB)), which were tested qualitatively for anti-listerial activity by the deferred antagonism assay at 30oC (24 h). Two L. monocytogenes strains, serotypes 1/2b and 4b, isolated from cheese and crude milk, respectively, were used. LAB strains with positive anti-listerial activity at 30oC were further tested at 7oC (10 days). Results: MRSLAB strains presented significantly better anti-listerial activity at 30oC (73.0% and 70.8% for serotypes 1/2b and 4b, respectively) compared to M17LAB strains (21.2% and 23.1%, respectively), and there was no significant difference between listeria serotypes (P<0.05). Selected MRSLAB and M17LAB strains were able to keep anti-listerial activity at 7oC, with no significant differences between MRSLAB (96.8% and 97.2% for listeria 1/2b and 4b, respectively) and M17LAB (95.2% and 96.8%, respectively) or between Listeria serotypes (P<0.05). Significance: These results suggested that LAB isolated from Minas cheeses using MRS agar present a better inhibitory effect against L. monocytogenes at different temperatures. These strains can be used as starter cultures in order to inhibit pathogen survival.
- Arthropod biodiversity associated to European sheep grazed pasturesPublication . Garcia, Rosa; Peric, Tanja; Cadavez, Vasco; Ko, Nathanael; Cerqueira, Joaquim; Stanganello, R. Pietro; Fernandes, E.; Celaya, Rafael; Gonzales-Barron, Ursula; Baratta, MarioWe analysed the biodiversity of foliage arthropods in nine sheep grazed pasturelands in five European countries. During the maximum flowering period in 2018, entomofauna was collected in 4-6 areas within each pasture, performing 6 transects/area and 25 sweeps per transect. Multivariate analyses tested the differences in total arthropod community composition among degrees of intensification, bioregions and types of pastures. A total of 51,474 arthropods from 3 classes, 17 orders and 95 taxonomical groups were recorded. Univariate analyses revealed that total arthropod abundance was higher in extensive than in intensive systems (P<0.01). It also differed between bioregions (higher in Alpine than in Continental, P<0.05) and between types of pastures (higher in mountain than in lowland pastures where animals are supplemented, P<0.05). Total taxa richness was not influenced by any of the three factors. However, multivariate analyses indicated that community composition differed among intensive and extensive systems, bioregions and types of pastures (P<0.001). The greatest differences occurred between Alpine and Mediterranean (P<0.001), and Mediterranean and Continental pastures (P<0.05), as well as between lowland seminatural and improved pastures (P<0.05), and seminatural and mountain pastures (P<0.001). These results reveal the complex and varied communities associated to the diverse sheep systems and valorise the role of the mo
- Arthropod biodiversity associated to European sheep production systemsPublication . Rosa García, Rocío; Peric, Tanja; Cadavez, Vasco; Geß, Andreas; Cerqueira, Joaquim; Gonzales-Barron, Ursula; Baratta, MarioThe rural territories linked to European sheep systems still cover wide areas and provide multiple ecosystems services although the current situation of the associated biodiversity is not fully understood. In this study the foliage arthropods (including pollinators), the vegetation cover and height, the number of flowers and plant species richness were evaluated in 9 sheep grazed lands from 5 EU countries with different livestock management strategies and dominant vegetation. The total abundance of arthropods, the abundance of Diptera and Heteroptera, sward height and plant species richness were higher in more extensive than in more intensively managed farms. The total abundance and the abundance of most of the orders were highest in mountain areas (MP) and lowest in improved pastures (IMP) whereas the total arthropod richness showed no differences and the richness of pollinators was lower in IMP than in MP (p < 0.01) and semi-natural pastures (SN, p < 0.01). The grass cover was higher in IMP than in the rest of the areas whereas forb cover was higher in SN than in IMP (p < 0.01). The plant species richness peaked in MP whereas the number of flowers showed no significant differences. Sward height correlated positively with forb cover, plant species richness, the richness of the whole arthropod community, the abundance of several orders like Araneae, Diptera or Homoptera, as well as with the richness of the pollinator community. The community composition of the total arthropod fauna (p < 0.01) and the pollinators in particular (p < 0.05) differed between management strategies and more diverse groups were linked to the areas under more extensive management. Both communities (total and pollinators) also differed in composition between the types of vegetation (p < 0.01) and less diverse assemblages with low abundant taxa were associated to IMP and SN whereas more diverse groups were linked to MP and grassland-forest (WP) in both cases. A better understanding of the flora-fauna dynamics in sheep grazed pasturelands is essential for the proper conservation of the biodiversity and other ecosystem services, as well as for the maintenance of sustainable sheep systems relying on the natural resources.
- A Bayesian approach to estimating the uncertainty in the distribution of Cronobacter spp. in powdered infant formula arising from microbiological criteria test outcomesPublication . Westerholt, Friedrich von; Gonzales-Barron, Ursula; Butler, FrancisThe application of microbiological criteria related to foods has become well established for the protection of public health. Sampling plans will more likely detect a microorganism when the level of contamination is high. However, as the concentration of the microorganism drops, detection becomes more and more infrequent. Cronobacter spp. is an opportunistic pathogen that can occur infrequently and in low concentrations in powdered infant formula (PIF) with a distribution that is typically heterogeneous. This paper developed a Bayesian approach to quantify the uncertainty in the concentration of Cronobacter spp. clusters that may be present in a batch of PIF depending on the outcome of a sampling plan. Two approaches were developed. The first was a Bayesian methodology using a spreadsheet approach to develop the appropriate likelihood and posterior distributions based on an uninformed prior distribution. The second approach was similar but used an algebraic approach rather than a spreadsheet numerical approximation to characterise the uncertainty. Different sampling plans were considered based on the EC Microbiological Criteria for Cronobacter spp. When a zero positive test was the outcome of the sampling plans considered, the Bayesian analysis indicated that while the most likely outcome for all the sampling plans considered was zero clusters present, the analysis indicated that the true number of clusters present could be as high as several thousand clusters per tonne of powder depending on the sampling plan. The algebraic approach demonstrated that for zero or one positive tests, the uncertainty distribution could be approximated by a gamma distribution. Choice of the prior distribution influenced the level of uncertainty. The Bayesian approach demonstrates that even when zero positives are detected for a given sampling plan, there remains a considerable uncertainty in the true number of microorganisms that may be present undetected in a consignment of powder.
- Behavior of Listeria monocytogenes in the presence or not of intentionally-added lactic acid bacteria during ripening of artisanal Minas semi-hard cheesePublication . Gonzales-Barron, Ursula; Campagnollo, Fernanda B.; Schaffner, Donald W.; Sant'Ana, Anderson S.; Cadavez, VascoThe fate of Listeria monocytogenes during ripening of artisanal Minas semi-hard cheese, as influenced by cheese intrinsic properties and by autochthonous (naturally present) or intentionally-added anti-listerial lactic acid bacteria (LAB) was modeled. Selected LAB strains with anti-listerial capacity were added or not to raw or pasteurized milk to prepare 4 cheese treatments. Counts of LAB and L. monocytogenes, pH, temperature and water activity were determined throughout cheese ripening (22 days, 22±1ᵒC). Different approaches were adopted to model the effect of LAB on L. monocytogenes: an independent approach using the Huang primary model to describe LAB growth and the linear decay model to describe pathogen inactivation; the Huang-Cardinal [pH] model using the effect of pH variation in a dynamic tertiary approach; and the Jameson-effect with Nmax tot model which simultaneously describes L. monocytogenes and LAB fate. L. monocytogenes inactivation occurred in both treatments with added LAB and inactivation was faster in raw milk cheese (−0.0260 h−1) vs. pasteurized milk cheese (−0.0182 h−1), as estimated by the linear decay model. Better goodness-of-fit was achieved for the cheeses without added LAB when the Huang primary model was used. A faster and great pH decline was detected for cheeses with added LAB, and the Huang-Cardinal [pH] model predicted higher pathogen growth rate in cheese produced with raw milk, but greater L. monocytogenes final concentration in pasteurized milk cheese. The Jameson-effect model with Nmax tot predicted that LAB suppressed pathogen growth in all treatments, except in the treatment with pasteurized milk and no LAB addition. The Huang-Cardinal [pH] model was more accurate in modeling L. monocytogenes kinetics as a function of pH changes than was the Jameson-effect model with Nmax tot as a function of LAB inhibitory effect based on the goodness-of-fit measures. The Jameson-effect model may however be a better competition model since it can more easily represent L. monocytogenes growth and death. This study presents crucial kinetic data on L. monocytogenes behavior in the presence of competing microbiota in Minas semi-hard cheese under dynamic conditions.
- Behavior of spoilage bacteria and Salmonella enterica subspecies enterica O:4,5 in vacuum-packaged beef during refrigerationPublication . Silva, Jorge Luiz da; Cadavez, Vasco; Machado, Maxsueli Aparecida Moura; Dias, Brendo da Conceição Lima; Cunha-Neto, Adelino da; Gonzales-Barron, Ursula; Figueiredo, Eduardo Eustáquio de SouzaIn this study, the kinetic parameters of mesophilic, psychrotrophic and lactic acid bacteria in vacuum-packed beef at 1 °C and 4 °C were estimated from experimental growth curves produced by samples stored during 21 and 60 days, respectively. In a separate experiment, the survival of multidrug resistant (MDR) Salmonella enterica O:4,5 at 1°C was also characterized. The shelf-life of vacuum-packed beef stored at 4 °C was estimated at 16.1 days (95% CI: 14.8 – 17.3 days), whereas at 1 °C it was longer than 21 days because the mesophiles count estimated towards the end of the experiment was 12.5 ln CFU.g-1 (95% CI: 11.8 – 13.3 ln CFU.g-1) which is lower than the shelf-life reference value. At 1 °C, inoculated Salmonella was reduced in 6.61 ln CFU.g-1 (2.87 log CFU.g-1). These results demonstrated the importance of establishing in legislation, especially in Brazil, standard values of deteriorating microorganisms in beef for maintaining product quality.
- Biodiversidad asociada a los sistemas de producción ovina en PortugalPublication . Fernandes, E.; Cadavez, Vasco; Celaya, Rafael; Gonzales-Barron, Ursula; Cerqueira, Joaquim; Rosa-García, R.Los consumidores demandan cada vez más alimentos asociados a sistemas productivos sostenibles que contribuyan a la conservación de la biodiversidad.