Valorización de los productos de las razas autóctonas a través de la dieta: la Gallina Murciana como caso de estudio

Uno de los principales valores nutricionales de la harina de algarroba es su alto contenido de antioxidantes, especialmente de taninos. Además se ha observado en el trabajo de Inserra y col (2015) que su inclusión en la dieta de cerdos de engorde aumentaba el contenido en ácidos grasos omega-3. En este sentido, en el presente trabajo se incluirá en la dieta de la gallina Murciana la harina de algarroba. Trascurridos 15 y 30 días del experimento, se realizará una toma de muestra de los huevos y se estudiará cómo se modifican los valores nutricionales del huevo (contenido en antioxidantes y perfil de ácidos grasos). Al mismo tiempo, se evaluará la producción de huevos, características del huevo (porcentaje de yema, clara y cáscara, y color)Universidad Politécnica de Cartagen

Exploiting the synergism among physical and chemical processes for improving food safety

This article provides an overview of recent published information on the subject of synergistic lethal effects that emerge from the combination of physical and/or chemical processes applied to enhance food safety. Despite important recent advances in non-thermal technologies, the greatest synergistic lethal effects emerge from combining them with traditional, relatively mild heat treatments. The combined application of antimicrobials has shown that their main constituents interact effectively, and great synergistic effects have been described with the capacity of either inhibiting or inactivating pathogens. Moreover, natural antimicrobials are more effective when pathogens are previously damaged sublethally by the application of physical technologies. Such combinations allow for a considerable reduction of treatment intensity and costs, along with a noticeable improvement in food quality and safety

Influence of environmental factors on bacterial biofilm formation in the food industry: a review

Formation and development of bacterial biofilms in the food industry could be a cause of food contamination, compromising food safety and shelf-life. Among the factors modulating biofilm formation, this review will focus in conditions normally encountered by bacteria in food environments, especially in biofilm initiation and development. The effect of environmental factors (substratum, temperature, oxygen concentration, hydrodynamic effects, food matrix composition, and microbial interactions) on biofilm formation is multifaceted and, in many circumstances, their influence could be compensatory. A better knowledge of these factors would allow for a better control of biofilm formation, either by avoiding and/or eradicating biofilms or by defining adequate Hazard Analysis and Critical Control Point systems in the food industry

Incubation with a complex orange essential oil leads to evolved mutants with increased resistance and tolerance

Emergence of strains with increased resistance/tolerance to natural antimicrobials was evidenced after cyclic exposure to carvacrol, citral, and (+)-limonene oxide. However, no previous studies have reported the development of resistance and tolerance to complex essential oils (EOs). This study seeks to evaluate the occurrence of Staphylococcus aureus strains resistant and tolerant to a complex orange essential oil (OEO) after prolonged cyclic treatments at low concentrations. Phenotypic characterization of evolved strains revealed an increase of minimum inhibitory and bactericidal concentration for OEO, a better growth fitness in presence of OEO, and an enhanced survival to lethal treatments, compared to wild-type strain. However, no significant differences (p > 0.05) in cross-resistance to antibiotics were observed. Mutations in hepT and accA in evolved strains highlight the important role of oxidative stress in the cell response to OEO, as well as the relevance of the cell membrane in the cell response to these natural antimicrobials. This study demonstrates the emergence of S. aureus strains that are resistant and tolerant to EO (Citrus sinensis). This phenomenon should be taken into account to assure the efficacy of natural antimicrobials in the design of food preservation strategies, in cleaning and disinfection protocols, and in clinical applications against resistant bacteria

Emerging mutant populations of Listeria monocytogenes EGD-e under selective pressure of Thymbra capitata essential oil question its use in food preservation

Due to their excellent antimicrobial properties, essential oils (EO) have been proposed as potential preservatives for certain kinds of foods, such as dairy products. However, the occurrence of pathogenic populations that are resistant to EOs could pose a health risk. This report seeks to assess the emergence of resistant populations in Listeria monocytogenes EGD-e growth at 37 °C under selective pressure of Thymbra capitata EO (TCO), to characterise their resistance in laboratory media, and to identify their genotypic changes, as well as to evaluate the resistance in skimmed milk. TCO cyclic treatment allowed the isolation of two L. monocytogenes EGD-e resistant strains against the EO: LmSTCO by sublethal doses (75 µL/L TCO) and LmLTCO by lethal doses (300 µL/L TCO) after 20 and 30 cycles, respectively. Both strains displayed an increase of the minimum inhibitory and bactericidal concentration against TCO and a higher survival rate after lethal treatments than the wild-type strain (LmWT). Growth kinetics revealed a better adaptation of LmSTCO in presence of TCO, while LmLTCO grew more slowly compared to LmWT, even in the absence of the antimicrobial. Moreover, a slight increase in cross-resistance to antibiotics was observed: LmSTCO to β-lactams and LmLTCO to a series of broad-spectrum antibiotics. The genomic study revealed one sole nucleotide change in LmSTCO located in plsC gene codifying an enzyme involved in the production of phosphatidic acid, a precursor in cell membrane synthesis. Five genetic variations were found in LmLTCO: among them, the deletion of an ATP-synthesis system involved in slowing bacterial growth. Inhibition and inactivation assays in skimmed milk confirmed the increased resistance of both strains, thereby indicating a safety risk in case these strains emerge in the food chain. These results strongly suggest that the occurrence of such resistances should be taken into account in order to ensure the efficacy of natural antimicrobials in the design of food preservation strategies

Antimicrobial activity of suspensions and nanoemulsions of citral in combination with heat or pulsed electric fields

The application of essential oils in form of nanoemulsions has been proposed as a method to improve their solubility in aqueous solutions, and hence their antimicrobial activity. The objective of this study was to evaluate the antimicrobial activity of citral, applied directly or in combined treatments with heat or pulsed electric fields (PEF), as a function of the inoculation procedure assayed: (i) a simple, vigorous shaking method by vortex agitation (suspension of citral; s-citral) or (ii) the previous preparation of nanoemulsions by the emulsion phase inversion (EPI) method (nanoemulsion of citral; n-citral). n-Citral was more effective in either inhibiting or inactivating Escherichia coli O157:H7 Sakai than s-citral. However, when combined with heat, a greater synergistic effect was observed with s-citral rather than with n-citral, either in lab media (pH 7·0 and 4·0) or apple juice. For instance, while almost 5 log10 cell cycles were inactivated in apple juice after 15 min at 53°C in the presence of 0·1 µl ml-1 of s-citral, the use of n-citral required 30 min. The use of nanoemulsions did not modify the slight synergism observed when citral and mild PEF were combined (150 µs, 30 kV cm-1). Significance and Impact of the Study: The exploration of different delivery systems of antimicrobial compounds such as citral in aqueous food products aids in the establishment of successful combined treatments for food preservation. While at room temperature, citral in form of a nanoemulsion shows a higher antimicrobial activity; its combination with heat would imply a partial loss of the outstanding synergistic lethal effect achieved when added in suspension form. Therefore, the most suitable procedure to magnify the synergism between heat and citral when processing juices would merely require an intense homogenization step prior to the combined treatment

Modified cyclodextrin type and dehydration methods exert a significant effect on the antimicrobial activity of encapsulated carvacrol and thymol

BACKGROUND The antimicrobial activity of essential oils and their constituents has led to increasing interest in using them as natural preservative agents. However, their high sensitivity to light and oxygen, their volatility and their low aqueous solubility are all obstacles to their application in the food, cosmetic or pharmaceutical industries. Encapsulation in cyclodextrins (CDs) is a solution for the application of such essential oils. RESULTS The complexation of carvacrol and thymol with hydroxypropyl (HP)‐α‐, HP‐β‐ and HP‐γ‐CD, the behavior of the solid complexes prepared by freeze‐drying and spray‐drying methods and the antibacterial activity of solid complexes were studied. Kc values of HP‐α‐ and HP‐γ‐CD complexes with carvacrol (118.4 and 365.7 L mol−1) and thymol (112.5 and 239.7 L mol −1) were far lower than those observed for HP‐β‐CD complexes with carvacrol (2268.2 L mol −1) and thymol (881.6 L mol −1). The lower stability of HP‐α‐ and HP‐γ‐CD complexes increased the release of compounds, thereby affecting the antimicrobial activity of carvacrol and thymol to a lesser extent than complexation with HP‐β‐CD, normally used in the encapsulation of carvacrol and thymol. HP‐β‐CD encapsulation of carvacrol and thymol markedly reduced their antimicrobial activity. The freeze‐drying method barely affected the antimicrobial activity of carvacrol and thymol after encapsulation, while spray drying could be considered for the production of solid complexes in combination with the appropriate CD. CONCLUSIONS It was thus demonstrated that HP‐α‐ and HP‐γ‐CD are very suitable alternatives for the encapsulation of carvacrol and thymol with the purpose of preserving their bacteriostatic and bactericidal activities

Bibliometric analysis of the literature on critical thinking: an increasingly important competence for higher education students

In recent years, interest in critical thinking(CT) has grown considerably. An evaluation of this research field and its challenges are provided in this paper. A bibliometric study was performed to analyse 1,295 papers on CT published in the last 50 years. The data were obtained from the WOS Core Collection database. The findings of this study improve the understanding of the CT domain by showing key studies, the main studies developing the field, key past studies and their influence in subsequent publications, emerging trends and potentially transformative ideas. Most publications and citations are from the last decade, reflecting the momentum of this concept over the period examined. The topic has also expanded geographically. Although the University of Iowa and the University of Alberta are the most prolific institutions, Asian universities have gained in prominence in recent years, as shown by the number of papers published. According to the analysis, the increase in the number of authors, publications and journals in this field and the rise in the number of publications written in collaboration with authors from different parts of the world are two trends that reflect the interest in CT as a way to understand the development of thinking skills

Salmonella enterica serovar Typhimurium genetic variants isolated after lethal treatment with Thymbra capitata essential oil (TCO) showed increased resistance to TCO in milk

The high prevalence of Salmonella enterica in milk poses a risk of considerable concern in the preservation of certain dairy products, mainly those elaborated from raw milk. Essential oils (EOs) have been proposed as a promising food preservative for such products due to their strong antimicrobial properties. Additionally, these natural antimicrobials have been shown to be effective against multi-drug resistant strains. They can thus also be utilized to prevent the dissemination of antimicrobial resistances (AMR). However, recent evidence of the development of bacterial resistance under EO treatments may call their use into question. This study sought to assess the emergence of antimicrobial resistant genetic variants of S. enterica serovar Typhimurium from survivors after cyclic exposure to lethal doses (>5 log10 cycles of inactivation) of Thymbra capitata EO (TCO), in order to evaluate the impact that it could have on milk preservation, to ascertain whether cross-resistance to antibiotics occurs, and to identify the genomic changes responsible for their phenotype. Isolated strains by TCO (SeTCO) showed a two-fold increase in minimum inhibitory and bactericide concentrations (MIC and MBC) of TCO compared to Salmonella enterica serovar Typhimurium wild-type strain (SeWT) in laboratory growth medium, as well as a greater adaptation and growth rate in the presence of the EOs and a higher survival to TCO treatments in buffers of pH 4.0 and 7.0. The increased resistance of SeTCO was confirmed in skimmed milk: 300 μL/L TCO reduced only 1 log10 cycle of SeTCO population, whereas it inactivated more than 5 log10 cycles in SeWT. Moreover, SeTCO showed an increased cross-resistance against aminoglycosides, quinolones and tetracyclines. Whole genome sequencing revealed 5 mutations in SeTCO: 2 in genes involved in O-antigens synthesis (rfbV and rfbX), 2 in genes related to adaptation to the growing medium (trkA and glpK), and 1 in a redox-sensitive transcriptional regulator (soxR). The phenotypic characterization of a constructed SeWT strain with mutant soxRSeTCO demonstrated that the mutation of soxR was the main cause of the increased resistance and tolerance observed in SeTCO against TCO and antibiotics. The emergence of resistant strains against EOs might jeopardize their use as food preservatives. Further studies will thus be required to determine under which conditions such resistant strains might occur, and to assess the food risk they may pose, as well as to ascertain their impact on the spread of AMR

Detection of thermal sublethal injury in escherichia coli via the selective medium plating technique: Mechanisms and improvements

In food preservation, the synergistic combination of different technologies aims to maximize the total lethality of the process and minimize the intensity of each hurdle. This is especially the case when at least one of the treatments can cause sublethal (reparable) injury in a great proportion of the population, so that sublethally injured cells can end up being entirely inactivated by the other hurdle(s). The selective medium plating technique (SMPT) is extensively used to enumerate bacterial sublethal injury after inimical treatments, being sodium chloride added to the recovery medium to detect damaged bacterial envelopes. However, little work has been done to explain the reasons for the inability of sublethally injured cells to outgrow in selective agar media, whereas they are able to grow in non-selective agar. In the present paper, the performance of SMPT on Escherichia coli cells after heat treatments is explored by applying different selective agents in the recovery media, using mutants lacking factors involved in osmoregulation, and also by examining the integrity of the cytoplasmic membrane. In view of the results, the possibility of a specific toxic effect of Na+ as the main mechanism under SMPT was discarded, since the same level of sublethal injury was detected using KCl instead of NaCl. The synthesis of the osmoprotectant trehalose determined the maximum osmotolerance of intact cells to the selective agents, but was not crucial in the quantification of sublethal injury. Moreover, for the first time, the extent of sublethal injury detected via SMPT was directly correlated with the physical loss of integrity of the cell membrane in 99.999% of the initial population. This was achieved through statistical analysis of flow cytometry data using propidium iodide-exclusion technique when that dye was added before thermal treatments. The present work confirms the adequacy of SMPT as a tool for detecting the occurrence and quantity of sublethally injured cells after thermal treatments and thus, for efficiently designing the combination of heat with other preservation techniques. We also propose the study of statistical analysis from flow cytometry data for a more rapid quantification of bacterial sublethal injury in a broad detection range