1,720,959 research outputs found
In vitro antimicrobial activity of essential oils from Mediterranean Apiaceae, Verbenaceae and Lamiaceae against foodborne pathogens and spoilage bacteria
No full textThe aim of this work was to investigate the antimicrobial activity of twelve essential oils, against Gram-positive and Gram-negative bacteria, for a potential use in food industry.
The antimicrobial activity of essential oils was determined by an agar diffusion method against foodborne pathogens and spoilage bacteria. Further, bacteriostatic and bactericidal concentrations were determined for each strain that evidenced sensitivity to the oils. All the oils showed bacteriostatic and bactericidal activity against E. coli O157:H7 and Salmonella Typhimurium, while B. thermosphacta was inhibited by eight of 12 tested oils. Finally, the pathogenic microorganism L. monocytogenes and lactic acid bacteria strains were affected only by thyme, oregano and vervain oils.
The essential oils considered in this research showed a satisfactory antimicrobial activity.
The essential oils could be used for the development of novel systems for food preservation
Impiego di sostanze di aroma di origine vegetale per il miglioramento della qualità microbiologica dei prodotti alimentari
No full textExpression of DnaK, HtpG, GroEL and Tf chaperones and the corresponding encoding genes during growth of Salmonella Thompson in presence of thymol alone or in combination with salt and cold stress
No full textThe expression of four different proteins (DnaK, HtpG, GroEL and Trigger factor Tf) commonly involved in stress response, and the corresponding encoding genes, was studied in Salmonella enterica serovar Thompson. The growth of S. Thompson MCV1 was monitored in the presence of sublethal concentrations of thymol (0.1%) alone or in combination with salt stress (NaCl 0.7%) or cold stress (15°C). Salmonella growth was also monitored in the presence of salt stress (NaCl 0.7%) and also in the presence of cold stress (15°C) alone. During the different growth phases (lag, exponential and early stationary) the expression of dnaK, htpG, groEL and tig genes was studied by quantitative reverse transcription-PCR (qRT-PCR), while the regulation of the corresponding proteins was monitored by 2D-PAGE analysis. Thymol increased the expression of chaperone proteins in all cases except when salt stress was also present. The cold stress increased the levels of expression of the chaperones and this was further enhanced by the presence of thymol. Each stress alone induced a variation in the chaperone regulation and the combination of different stresses together did not always lead to a cumulative response. Our evidence suggests that the response to thymol, salt and cold involves the regulation of all the studied chaperones. This process starts in the lag phase but the chaperones keep working in the further growth phases in order to help Salmonella cells to face the adverse conditions. Our study suggests that adaptation to stress conditions related to food storage takes place through a global response where DnaK, HtpG, GroEL and TF are only part of the protein network that gives support to the adaptation
Decarboxylase gene expression and cadaverine and putrescine production by Serratia proteamaculans in vitro and in beef
No full textStudies of the molecular basis of microbial metabolic activities that are important for the changes in food quality are valuable in order to help in understanding the behavior of spoiling bacteria in food. The growth of a psychrotrophic Serratia proteamaculans strain was monitored in vitro and in artificially inoculated raw beef. Two growth temperatures (25°C and 4°C) were tested in vitro, while growth at 15°C and 4°C was monitored in beef. During growth, the expression of inducible lysine and ornithine-decarboxylase genes was evaluated by quantitative reverse transcription-PCR (qRT-PCR), while the presence of cadaverine and putrescine was quantified by LC-ESI-MS/MS. The expression of the decarboxylase genes, and the consequent production of cadaverine and putrescine were shown to be influenced by the temperature, as well as by the complexity of the growth medium. Generally, the maximum gene expression and amine production took place during the exponential and early stationary phase, respectively. In addition, lower temperatures caused slower growth and gene downregulation. Higher amounts of cadaverine compared to putrescine were found during growth in beef with the highest concentrations corresponding to microbial loads of ca. 9CFU/g. The differences found in gene expression evaluated in vitro and in beef suggested that such activities are more reliably investigated in situ in specific food matrices
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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