1,720,963 research outputs found
Botanical traceability of unifloral honeys by chemometrics based on head-space gas chromatography
No full textThe botanical origin of honey is subjected to severe controls by Food Control Institutions, both for health protection and for frauds prevention. The complexity of honey makes it very difficult to verify the botanical origin. Among the available validated methods, sensory analysis and melissopalynology are the most widely employed. These methods require a long time and deep consolidated expertise. To shorten analysis time while simplifying the analytical procedure, head-space flash gas chromatography was applied in the present study. Chromatographic peak areas were processed by chemometrics (in particular principal components analysis and linear discriminant analysis). Three hundred and thirty-nine honey samples from twelve categories of unifloral honey were analyzed: acacia, citrus, chestnut, thistle, tree heath, eucalyptus, sunflower, rhododendron, lime, French honeysuckle, fir honeydew, and wood honeydew. Each sample was a priori classified by sensory analysis. The multivariate models were validated by cross validation and test-set validation, with predictive abilities always higher than 80%: good results were obtained both in calibration and in prediction mode, showing a good agreement between this new approach and the traditional one for the determination of the botanical origin of honey
Determination of cholesterol oxidation products in cheese under photo-oxidative stress using QuEChERS and LC–MS
Full text linkThe QuEChERS approach was optimized for extracting cholesterol oxidation products in cheese, followed by LC-APCI-MS/MS analysis. Optimization of the method, including evaluations of saponification step, sample weight, and d-SPE purification resulted in good recoveries for each analyte, ensuring a reliable determination of these contaminants in cheese samples. In addition, the method was successfully validated by testing linearity of response, analytical limits (LOD and LLOQ), and precision. Sliced cheese samples wrapped in various packaging materials underwent a challenging test to simulate refrigerated storage conditions under fluorescent light, inducing photo-oxidative stress. The validated QuEChERS method revealed that only seasoned hard cow’s cheese showed an increase in the concentration of 7-ketocholesterol and its chemical precursors, 7β-hydroxycholesterol, and 7α-hydroxycholesterol, reaching levels of 0.45, 0.35, and 0.35 μg g−1, respectively. Conversely, opaque packaging and the use of a double film were found to be effective in preventing the formation of COPs in cheese samples subjected to photo-oxidative stress, such as smoked cheese and melted cheese slices (sottilette). A trade-off must be found between ensuring cheese protection and meeting the consumer’s desire to see the product
Morphogenesis in Cultured Thin Layers and Pith Explants of Tobacco. II. Early Hormone-modulated Polyamine Biosynthesis
No full textIn order to gain deeper insight into the interrelationships between polyamines and hormones, superficial thin layers and pith explants, excised from the stem of tobacco (Nicotiana tabacum L.) plants in the vegetative stage, were cultured under various hormonal conditions (IAA, IAA + BA, BA) and in a hormone-free medium, in the presence or in the absence of 100 μmol/L putrescine. In thin layers at 24 h, activation of putrescine biosynthesis via both arginine-(ADC) and ornithine decarboxylases (ODC) as well as free putrescine accumulation were detected in the IAA treatment, and via ADe alone in the presence of IAA + BA. BA caused an inhibition of or had no effect on putrescine biosynthesis. In pith explants, although some free putrescine accumulated in IAA treatment, no increase in its biosynthetic activity was detectable. No DAO activity could be detected in any treatment early in culture either in superficial or deep tissues. Exogenous putrescine did not affect this pattern. The modulation of polyamine biosynthesis by the different hormones in superficial and pith explants is discussed in relation to putrescine accumulation and oxidation and to early cytological events occurring in culture and previously described (Altamura et al., 1995). © 1995, Gustav Fischer Verlag, Stuttgart. All rights reserved
Pre-harvest polyamine and aminoethoxyvinylglycine (AVG) applications modulate fruit ripening in Stark Red Gold nectarines (Prunus persica L. Batsch).
No full textPutrescine (5, 10 and 20 mM), spermidine (0.5, 1 and 2 mM) and aminoethoxyvinylglycine (AVG; 0.32, 0.64 and 1.28 mM) were applied to peach trees (Prunus persica L. Batsch cv Stark Red Gold) under open field conditions. Treatments were performed 28 (polyamines; PAs) and 21 or 7 (AVG) days before harvest at 115 dAFB. Both PAs and AVG reduced ethylene production of fruit, delayed loss of firmness, retained titratable acidity, and prevented the increase in dry matter (DM) and soluble solids concentration (SSC). Fruit drop was consistently reduced by AVG at both application times, and by the highest spermidine concentration. Endogenous PA levels in treated fruit were transiently affected (7 d after treatment), but returned to control values at harvest in both mesocarp and epicarp tissues. Northern analysis of ethylene biosynthetic genes, aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO), and of those involved in PA biosynthesis, arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC), was performed in mesocarp tissue at harvest. AVG and putrescine reduced the accumulation of ACO and SAMDC messages, putrescine also influenced ACS transcript levels, while spermidine did not affect any of these genes. Results are discussed on the basis of the reduction by PA and AVG of ethylene production, and confirm the capacity of these naturally occurring substances to modulate fruit ripening
Applicazione di tecniche untarget molecolari e chimiche per la ricerca di allergeni vegetali in alimenti
Full text linkI frutti secchi ed i semi commestibili hanno comprovati benefici per la salute, essendo il loro consumo relazionato con la riduzione del rischio di malattie croniche. Tuttavia, questi alimenti hanno un elevato potenziale allergico per una parte della popolazione mondiale. A causa del fatto che le allergie alimentari sono in aumento, diventa importante conoscere tutti i componenti presenti in un alimento, anche se in tracce. Il Regolamento UE n°1169/2011 ha normalizzato le leggi sull’etichettatura delle sostanze che causano allergie ed intolleranze alimentari. Di conseguenza, vi è l'urgente necessità di metodi specifici e affidabili in grado di rilevare allergeni negli alimenti che permettano di garantire la sicurezza alimentare e la conformità delle etichette, migliorando così la vita dei consumatori allergici. Sebbene le tecniche immunologiche siano più specifiche per l’identificazione di proteine allergeniche, le tecniche basate sul DNA sono più adatte per matrici alimentari molto complesse o nel caso di alimenti che hanno subito numerosi processi di trasformazione, mostrandosi come metodi alternativi affidabili. L’obiettivo di questo lavoro di tesi è stato quello di sviluppare una metodica per il rilevamento di specie allergeniche vegetali (frutta a guscio e semi commestibili) in matrici alimentari usando la tecnica del DNA Barcoding e la tecnica della Real-Time PCR. I vantaggi di queste tecniche sono, oltre alla necessità di quantità minime di campione, la possibilità di identificare varie specie allergeniche in simultaneo, anche dopo che queste abbiano subito processi di lavorazione. Si è inoltre fatta un’analisi fingerprinting dei composti volatili su matrici alimentari attraverso il gascromatografo HERACLES II. Le metodiche sviluppate possono fungere come metodi di screening veloci ed affidabili nella riduzione di possibili contaminazioni dei prodotti alimentari, rilevando la presenza o confermando l'assenza di allergeni
Applicazione di metodi molecolari e di fingerprinting dei composti volatili per analisi di autenticità in spezie ed erbe aromatiche
Full text linkThe term “food” does not only indicate a nutritive concept, but it contains within itself an ethical, religious and cultural meaning, themes that are strongly felt by the public opinion. Food frauds, since ancient times, have always been considered criminal acts to be punished. Several different types of frauds can be associated to foods. Due to the relevance of this topic, continuous efforts have been made to the technological improvement of new techniques, faster and more accurate, able to detect potential adulteration in food. The aim of this work is to find and to optimize different analytical methods, such as DNA barcoding and fingerprinting of volatile compounds, for the identification of plant species in samples of spices, such as saffron, and aromatic herbs. Concerning the DNA-based methods, the identification of species through DNA, called DNA barcoding, features high specificity and sensitivity. In this work, DNA samples were amplified and sequenced either with capillary electrophoresis (Sanger method) and with Ion Torrent next generation sequencing (NGS) technology. In addition to DNA-based analysis, chemical methods can be employed for the authentication and traceability of several foods. In this study, the analysis of volatile compounds was performed by ultra-fast gas chromatography (Heracles II GC) and high performance liquid chromatography (HPLC). Data obtained with these methods were used for the statistical analysis based on chemometric approaches (PCA and LDA).
We can conclude that a synergistic study, including biological and chemical analysis, represents a powerful tool to identify food authenticity and frauds: analyses are simple, economically affordable, non-contaminating, quick and automated. Moreover, the approach used in this study could be improved by adding new samples of spices and aromatic herbs, in order to obtain more reliable results
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
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