Relationship between iron bioavailability and Salmonella Typhimurium fitness in raw and pasteurized liquid whole egg

Salmonella Enteritidis growth rates in liquid whole egg have been shown to be dependent on the initial inoculum dose and on the egg product's thermal history. This study's objective is to obtain further insight into the mechanisms underlying both phenomena. First we verified that Salmonella Typhimurium ATCC 14028s cells displayed the behavior already described for S. Enteritidis cells. Then, we carried out supplementation assays by adding different concentrations of egg-white antimicrobial proteins, iron, or siderophores to the egg samples (raw or pasteurized liquid whole egg, depending on the assay). These experiments revealed that addition of lysozyme (at the concentration at which it is present in liquid whole egg) did not affect Salmonella growth in pasteurized liquid whole egg, but that ovotransferrin as well as Ex-FABP caused a significant (p < 0.05) reduction in Salmonella growth rates in whole egg pasteurized at 70 °C for 1.5 min. Furthermore, we observed that the inactivation of ovotransferrin was dependent on treatment intensity within the range studied. On the other hand, addition of iron or siderophores to raw or low temperature (60 °C/3.5 min) pasteurized liquid whole egg increased the growth rate of Salmonella cells inoculated at a low initial dose. The concentration of these supplements required to reach the growth rate of cells inoculated at a high dose was lower for pasteurized than for raw egg. Finally, growth of a set of deletion mutants in genes coding for proteins related to different iron uptake systems, along with supplementation assays using spent medium revealed the key role of salmochelin in growth of S. Typhimurium in raw whole egg. In summary, our results strongly suggest that iron bioavailability determines the fitness (growth rates) of Salmonella cells in liquid whole egg. Thus, the higher the intensity of the thermal treatment applied to liquid egg, the more iron would be available, a phenomenon that would be linked to the denaturation of iron and/or siderophore binding egg proteins. Further work is still required to fully elucidate why lower Salmonella initial doses lead to lower growth rates, but it can be hypothesized that this might be related to a lower amount of siderophores being released to the medium (especially salmochelin), which would also limit iron bioavailability

Comparative resistance of bacterial foodborne pathogens to non-thermal technologies for food preservation

In this paper the resistance of bacterial foodborne pathogens to manosonication (MS), pulsed electric fields (PEFs), high hydrostatic pressure (HHP), and UV-light (UV) is reviewed and compared. The influence of different factors on the resistance of bacterial foodborne pathogens to these technologies is also compared and discussed. Only results obtained under harmonized experimental conditions have been considered. This has allowed us to establish meaningful comparisons and draw significant conclusions. Among the six microorganisms here considered, Staphyloccocus aureus is the most resistant foodborne pathogen to MS and HHP and Listeria monocytogenes to UV. The target microorganism of PEF would change depending on the treatment medium pH. Thus, L. monocytogenes is the most PEF resistant microorganism at neutral pH but Gram-negatives (Escherichia coli, Salmonella spp., Cronobacter sakazakii, Campylobacter jejuni) would display a similar or even higher resistance at acidic pH. It should be noted that, in acidic products, the baroresistance of some E. coli strains would be comparable to that of S. aureus. The factors affecting the resistance of bacterial foodborne pathogens, as well as the magnitude of the effect, varied depending on the technology considered. Inter- and intra-specific differences in microbial resistance to PEF and HHP are much greater than to MS and UV. Similarly, both the pH and aw of the treatment medium highly condition microbial resistance to PEF and HHP but no to MS or UV. Growth phase also drastically affected bacterial HHP resistance. Regarding UV, the optical properties of the medium are, by far, the most influential factor affecting its lethal efficacy. Finally, increasing treatment temperature leads to a significant increase in lethality of the four technologies, what opens the possibility of the development of combined processes including heat. The appearance of sublethally damaged cells following PEF and HHP treatments could also be exploited in order to design combined processes. Further work would be required in order to fully elucidate the mechanisms of action of these technologies and to exhaustively characterize the influence of all the factors acting before, during, and after treatment. This would be very useful in the areas of process optimization and combined process design

Desarrollo de una aplicación en Android para promocionar y enseñar el patrimonio cultural de Castilla y León

El Trabajo de Fin de Grado que se presenta en las siguientes páginas consiste en la creación de una aplicación móvil para fomentar el interés patrimonial ubicado en la zona de Castilla y León. Se trata de una aplicación que intenta ubicar sitios del patrimonio histórico dentro de la comunidad de Castilla y León, ofreciendo información relevante sobre ellos, de tal forma que se pueda examinar a los usuarios de esos contenidos. La aplicación se ha desarrollado para la Cátedra de Comercio Exterior de la Universidad de Valladolid mediante la participación en el proyecto TIMMIS.Grado en Ingeniería Informátic

Release of mannoproteins during Saccharomyces cerevisiae autolysis induced by pulsed electric field

The potential of the application of pulsed electric fields (PEF) to induce accelerate autolysis of a commercial strain of Saccharomyces cerevisiae for winemaking use was evaluated. The influence of PEF treatments of different intensity (5–25 kV/cm for 30–240 µs) on cell viability, cytoplasmic membrane permeabilization and release of mannoproteins and compounds absorbing at 260 and 280 nm has been investigated. After 8 days of incubation at 25¿C the Abs600 of the suspension containing the control cells was kept constant while the Abs600 of the suspension containing the cells treated by PEF decreased. The measurement of the absorbance at 260 and 280 nm revealed no release of UV absorbing material from untreated cells after 8 days of incubation but the amount of UV absorbing material released drastically increased in the samples that contained cells treated by PEF after the same storage period. After 18 days of storage the amount of mannoproteins released from the untreated cell was negligible. Conversely, mannoprotein concentration increased linearly for the samples containing cells of S. cerevisiae treated by PEF. After 18 days of incubation the concentration of mannoproteins in the supernatant increased 4.2 times for the samples containing cells treated by PEF at 15 and 25 kV/cm for 45 and 150 µs. Results obtained in this study indicates that PEF could be used in winemaking to accelerate the sur lie aging or to obtain mannoproteins from yeast cultures

Assessing the efficacy of PEF treatments for improving polyphenol extraction during red wine vinifications

The influence of the electric field intensity and pulse width on the improvement of total polyphenol index (TPI) and colour intensity (CI) during extraction in an ethanolic solution (30%) and during fermentation-maceration has been investigated in different grape varieties: Grenache from two harvesting times, Syrah and Tempranillo. The aim of this study was to develop a procedure to establish the PEF treatment conditions that cause enough permeabilization in the skin cells of different grape varieties to obtain a significant improvement in the vinification process in terms of increment on the polyphenol content or reduction of maceration time.Results obtained in this investigation indicate that extraction of polyphenols in a solution of ethanol (30%) for 2 h could be a suitable procedure to know if the PEF technology is effective for improving extraction of polyphenols from the grapes during vinification and to determine the most suitable PEF treatment conditions to obtain this objective. Improvement in the extraction during vinification only was observed with those grapes and under treatment conditions in which the improvement of the polyphenol extraction was higher than 40%. Other interesting observation from this research is the highest efficacy of PEF when treatments of the same duration are applied using longer pulses. Therefore, in a continuous process, where the flow processed is determined by the frequency applied by the PEF generator, it is possible to increase the processing capacity of the PEF installation.Industrial relevance. Benefits from PEF treatment of the grapes before the maceration step in the vinification process have been demonstrated. Nevertheless, the characteristics of the grapes may change in different vintages and grape varieties. Therefore, it is of high importance to be able to determine the optimum PEF conditions in order to obtain the desired benefit during the vinification. The rapid method developed permits to determine PEF process parameters before the application of the PEF treatment with the objective of facilitating the phenolic extraction and therefore, reducing the maceration time. In these cases, it would be possible to remove the skins from the rest of the wine earlier, and therefore, increase the processing capacity of the winery

Potential of Pulsed Electric Fields for the preparation of Spanish dry-cured sausages

The aim of this investigation was to lay the groundwork of the potential application of Pulsed Electric Fields (PEF) technology for accelerating the drying process of meat and meat products, and specifically in this work of Spanish dry-cured sausages “longaniza”. PEF treatments were applied to pork loin samples, and the influence of different PEF parameters on the process were evaluated. An optimal PEF treatment of 1 kV/cm, 200 µs of pulse width and 28 kJ/kg was determined as the most suitable to electroporate meat cells and to improve water transfer by achieving a water content reduction of 60.4% in treated-meat samples dried at 4 °C. The influence of PEF on meat drying rate was also studied on minced pork and the results showed that with a particle size of 4.0 mm higher drying rates were achieved. To validate the results, Spanish cured sausages were prepared from treated and untreated minced pork and stuffed into gauzes and natural pork casings at pilot plant scale. After the curing process, the application of PEF to sausages stuffed into gauze reduced the drying time from 17 to 9–10 days, a reduction of 41–47%, confirming the effects described at lab scale and the potential of PEF for accelerating the sausage-drying process

Relationship between growth ability, virulence, and resistance to food-processing related stresses in non-typhoidal Salmonellae

The ability of Salmonella to resist and adapt to harsh conditions is one of the major features that have made this microorganism such a relevant health hazard. However, the impact of these resistance responses on other aspects of Salmonella physiology, such as virulence and growth ability, is still not fully understood. The objective of this study was to determine the maximum growth rates (in three different media), virulence (adhesion and invasion of Caco-2 cells), and other phenotypic characteristics (biofilm-forming ability and antimicrobial resistance) of 23 Salmonella strains belonging to different serovars, and to compare them with their previously determined stress resistance parameters. Significant differences (p < 0.05) in growth rates, virulence, and biofilm-forming ability were found among the 23 strains studied. Nevertheless, whereas less than 3-fold change between the lowest and the highest growth rate was observed, the percentage of cells capable of invading Caco-2 cells varied more than 100-fold, that to form biofilms more than 30-fold, and the antibiotic MICs varied up to 512-fold, among the different strains. Results indicate that those strains with the highest cell adhesion ability were not always the most invasive ones and suggest that, in general terms, a higher stress resistance did not imply a reduced growth ability (rate). Similarly, no association between stress resistance and biofilm formation ability (except for acid stress) or antibiotic resistance (with minor exceptions) was found. Our data also suggest that, in Salmonella, acid stress resistance would be associated with virulence, since a positive correlation of that trait with adhesion and a negative correlation with invasion was found. This study contributes to a better understanding of the physiology of Salmonella and the relationship between bacterial stress resistance, growth ability, and virulence. It also provides new data regarding intra-specific variability of a series of phenotypic characteristics of Salmonella that are relevant from the food safety perspective

Direct Contact Ultrasound in Food Processing: Impact on Food Quality

Consumers' demand for “minimally processed” products that maintain the “fresh-like” characteristics has increased in recent years. Ultrasound (US) is a non-thermal technology that enhances mass and energy transfer processes resulting in improved food quality. A new method of applying US to food without using a liquid or gaseous medium for the propagation of acoustic waves has recently been under research. It is known as direct contact US, since the food is directly placed on a plate where the transducers are located. In this type of systems, the main effect is not cavitation but acoustic vibration, which encourages mass and energy transfer processes due to the “sponge effect.” Furthermore, as the product is not immersed in a liquid medium, the loss of hydrophilic nutritional compounds is reduced; systems such as these can thus be more easily implemented on an industrial level. Nevertheless, the very few studies that have been published about these systems mainly focus on dehydration and freezing. This article summarizes published research on the impact of direct contact US in nutritional and organoleptic quality of food in order to assess their potential to meet new market trend

La objeción de conciencia en la función pública. Especial mención a los miembros de las Fuerzas y Cuerpos de Seguridad del Estado.

En este trabajo abordo el problema de la objeción de conciencia (complicado de por sí) en la función pública. He decidido centrarme en los empleados públicos en sentido general en una primera parte, para luego entrar dentro de los miembros de las fuerzas y cuerpos de seguridad del Estado

Vulneración del artículo 18 de la Constitución española de 1978 en la jurisdicción penal en el caso de grabación mediante aeronave no tripulada

El presente Trabajo de Fin de Máster contiene un dictamen contextualizado en un procedimiento judicial cuyo orden jurisdiccional es el penal. Los hechos suscitados son los de una persona de nacionalidad francesa que graba, en la costa de Portacolom, mediante una aeronave no tripulada a las mandantes que piden asesoramiento jurídico haciendo topless en un bote de recreo. Las cuestiones que se suscitan y se resuelven en el dictamen son las derivadas de la vulneración de la intimidad y la propia imagen del artículo 18 de la Constitución española de 1978. Para mayor abundamiento, se ha tratado el procedimiento y la estrategia procesal a seguir para poder llevar a cabo con éxito las pretensiones de las patrocinadas