1,720,992 research outputs found
Effect of Storage Temperature on the Microbial Composition of Ready-to-Use Vegetables
No full textFour different salad preparations were investigated from microbiological point of view: two were packaged in air and two under Modified Atmosphere. The samples were stored at 4°C and 10°C and analyzed at established times. Total Bacterial Count (TBC) was taken as the most relevant index to define their hygiene and quality at both temperatures. Lactic Acid Bacteria, yeasts and moulds were found only occasionally. In general the most important factor was the packaging technique: TBC was lower when the product is packed under modified conditions. The packaging technique also influences the microbial population: Gram negative aerobic rods are dominant in air-packaged products, while the presence of Enterobacteriaceae becomes important in salads packaged under modified atmosphere. Pseudomonas fluorescens, with all its biovars, was the most frequently found species among the aerobic isolates, while for the Enterobacteriaceae strains there was no dominant species
IDENTIFICATION AND CHARACTERIZATION OF SPECIFIC SPOILAGE ORGANISMS (SSOS) IN DIFFERENT FOOD MATRICES
Full text linkThis PhD thesis aims to improve the actual systems of management and quality control of food, expanding the knowledge about the microorganisms responsible of food spoilage (Specific Spoilage Organisms) and their degradative activities.
The analysed foods were of vegetable and animal origin: in particular they were ready-to-eat vegetables (carrots and green salads packaged in air and MAP), milk and dairy products (raw, pasteurized, UHT and micro-filtered milk and mozzarella cheese) and beef and hamburger packaged traditionally or in master bag.
Firstly the microbial quality of each food was monitored from the production, during the declared shelf life and even after the expiration date. The isolates were phenotypically and genotipically characterized and identified; for each food SSOs were recognized.
Some microorganisms appeared typical of each product, sometimes also depending on the packaging and storage conditions. Leuconostoc spp. was indicated as typical carrots spoiler; Enterobacteriaceae family was involved in spoilage of salads packaged under modified atmosphere; lactic acid bacteria were typical of food packaged in low oxygen concentrations (salads in MAP and meat in master bag) and Brochothrix thermosphacta was specific of beef.
Pseudomonas spp. appeared common to all the analysed products and dominant among the bacterial spoilers. For this genus more detailed studies were conducted: the classification was made up to the biotype and biovar level; the characterization focused on different enzymatic activities and in particular the proteolysis was qualitatively and quantitatively evaluated; a phylogenetic study, based on the gene codifying for the most common Pseudomonas protease, was made.
Subsequently each food was analysed with a different approach. For vegetables the influence of temperature on microbiota was verified, resulting that low temperature slowed down microbial growth and partially modified the composition of the microbiota. In milk proteolytic activity of Pseudomonas spp. was evaluated and the formation of Pseudo-GMPs, deriving from the cutting of K-casein (103-104 position), were recognized. In mozzarella the blue pigment formation was studied and a rapid method for the detection and the quantification of alive, dead and Viable But Non Colturable (VBNC) cells was set up. For meat, a primer specific for Brochothrix genus was built and the packaging conditions were studied to verify the evolution of microbiota and the possible effects on the growth of Listeria monocytogenes (challenge test)
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
Set up of a rapid method to distinguish among dead, alive and viable but not-cultivable cells of Pseudomonas spp. in mozzarella cheese
No full textPseudomonas spp. is the main psychrotrophic genus involved in the spoilage of raw milk and more in general of dairy products, such as mozzarella cheese. The members of this bacterial species are able to produce heat-resistant proteolytic enzymes, determining the casein hydrolysis, and as a consequence, a reduction of the shelf life and sensory quality of the products. Therefore, the spoilage activity could be attributed not only to viable, but also to viable but noncultivable (VBNC) cells. For this reason, the setup of a non-culture-based method is useful for a rapid detection of cells that are still alive, but no longer cultivable, such as VBNC cells. Here we propose a method based on DNA or RNA content (or both) to reveal the presence of dead, alive, and VBNC cells belonging to the genus Pseudomonas. The obtained results clearly indicate the limits of the classical plating count overcome by molecular detection of Pseudomonas spp. through DNA and RNA analysis, enabling us to establish the presence of different states of the cells
Attività antimicrobica di sostanze di origine naturale impiegabili in imballaggi plastici funzionali di vegetali minimamente trattati (IV gamma)
No full textLa ricerca, inserita nell’ambito del progetto Vegapack, relativo alla qualità e sicurezza dei prodotti vegetali minimamente trattati (IV gamma) attraverso imballaggi plastici funzionali, ha previsto la determinazione dell’attività antimicrobica di carvacrolo e timolo, oli essenziali (EO), unitamente al LAE (etil-lauroil-arginato), solubile in acqua. L’attività antimicrobica è stata inizialmente determinata nei confronti di microrganismi di collezione. I batteri Gram positivi (Listeria, Staphylococcus e Bacillus) sono risultati più sensibili al LAE, con MIC pari a 12 mg/L coltura, mentre i Gram negativi (E. coli e Pseudomonas) e S. cerevisiae hanno presentato sensibilità inferiore, con MIC da 24 mg/L. Il timolo non ha presentato attività significativa, anche ad elevate concentrazioni (30 g/L), mentre per il carvacrolo la MIC è risultata compresa tra 17 e 100 μl /L. L’impiego dei due antimicrobici in associazione ha prodotto un effetto sinergico, con MIC dell’ordine di 12 mg/L per LAE e 50 μl /L per carvacrolo.
L’attività antimicrobica dei due composti è stata inoltre valutata nei confronti di microrganismi isolati da prodotti vegetali minimamente trattati, e i risultati ottenuti hanno confermato l’efficacia delle molecole allo studio. L’approccio proposto di associazione delle due attività antimicrobiche, una attiva in fase vapore e una in fase liquida, potrebbero costituire quindi un’innovazione nel settore del packaging alimentare
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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