1,720,984 research outputs found
Physiological response of Saccharomyces cerevisiae to citral combined with thermal treatment
No full textYeasts are responsible for spoilage of fruit juices and beverages because of their low pH and high sugar content. Their control is generally guaranteed by thermal treatments that however can affect organoleptic and nutritional properties. A strategy to reduce thermal damage is the combination of mild treatments with natural antimicrobials. This work studied the effect of citral on thermal inactivation of a Saccharomyces cerevisiae strain isolated from spoiled beverages, also in relation to medium pH, through plate counting and flow cytometry (FCM), to assess cell viability and membrane integrity. The results of treatments at 60 °C for 30 min showed that sublethal concentrations of citral increased death kinetics, especially at lower pH. Conversely, FCM analysis performed on cells treated at 60 °C for 10 min evidenced higher mortality at pH 6.0, while at pH 4.0 the population was mainly injured. This different behavior was likely due to higher membrane permeability observed at pH 6.0. No recovery of injured cells to a viable status was observed after 3 h of incubation. Since the fate of these cells in foods is a great concern, these results are helpful to increase knowledge about the physiological response of S. cerevisiae and to optimize strategies for food stability
Modelling of Listeria monocytogenes Scott A after a mild heat treatment in the presence of thymol and carvacrol: Effects on culturability and viability
No full textThe combined effect of thymol, carvacrol and mild heat treatments against Listeria monocytogenes Scott A was assessed in buffered system by plate counting and flow cytometry (FCM). The susceptibility of cells increased when heat treatment was combined with terpenes. The data modelling with Bigelow and Weibull equations showed that the latter was more appropriate to describe the inactivation kinetics. After treatments, cells were no longer able to form colonies on plates; nevertheless, FCM indicated that most of the cells were damaged rather than dead. Treated cells were not able to recover the damage after 6 h. This opens the question if they could recover in a food matrix. FCM can be a helpful technique to better comprehend the physiological state of microorganisms. In the perspective of industrial applications, studies based on predictive microbiology, as well as a deeper comprehension of the action mechanisms of antimicrobials, play a key role for process optimization
Listeria monocytogenes sensitivity to antimicrobial treatments depends on cell origin
Get PDFAbstract In this study we investigated how cell origin could affect the efficacy of an antimicrobial treatment (mild heating combined with terpenoids) in Listeria monocytogenes Scott A, considering cells from: 1. single colony, 2. glycerol stock, 3. cold adapted culture, and 4. fresh culture in stationary phase. After treatment, culturability on BHI medium and viability assessed by flow cytometry were evaluated. Our results showed that the cell origin significantly impacted viability and culturability of L. monocytogenes towards antimicrobial treatment. The mild heat treatment combined or not with terpenoids mainly affected culturability rather than viability, although the culturability of cells from single colony was less impacted. Therefore, to mimic the worst scenario, these latter were selected to contaminate Gorgonzola rind and roast beef slices and we evaluated the ability of L. monocytogenes cells to recover their culturability (on ALOA agar medium) and to growth on the food matrix stored at 4 °C for 7 days. Our results suggest that only Gorgonzola rind allowed a partial recovery of the culturability of cells previously heated in presence or not of terpens. In conclusion, we found a connection between the cell history and sensitivity toward an antimicrobial treatment, underlying the importance to standardize the experimental procedures (starting from the cells to be used in the assay) in the assessment of cell sensitivity to a specific treatment. Finally, our study clearly indicated that VBNC cells can resuscitate under favorable conditions on a food matrix, becoming a threat for consumer’s health
Occurrence, diversity, and persistence of antibiotic resistant enterococci in full-scale constructed wetlands treating urban wastewater in Sicily
Get PDFEnterococci isolated from different sites of an urban wastewater treatment plant (consisting of three horizontal subsurface flow constructed wetlands) were investigated. One-hundred-thirty isolates were identified at species level and tested for resistance to eleven antibiotics, by microdilution method, and their clonal relatedness was established by SmaI-PFGE analysis. Results highlighted the persistence of enterococcal population in all effluents and the dominance of E. faecium species. A high incidence of antibiotic resistance against erythromycin, chloramphenicol, rifampicin and ampicillin was observed, with 120 strains (93%) showing a multi-drug-resistance. Numerous pulso-types with a unique pattern were detected indicating a high diversity within enterococcal population. The recurrence of some pulso-types in different effluents was disclosed and, within the same pulso-types, different resistance patterns were observed. Comparing the MIC values of strains from inlet and outlet, different trends were observed, highlighting a certain variability among constructed wetlands in affecting the antibiotic resistance among enterococcal population
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
