1,720,960 research outputs found
Determination of acrylamide in dried fruits and edible seeds using QuEChERS extraction and LC separation with MS detection
Full text linkAcrylamide is a carcinogenic and neurotoxic process contaminant that is generated from food components during heat treatment, while it is absent in raw foodstuffs. Its level in food arouses great concern. A method for acrylamide extraction and determination in dried fruits (dried prunes and raisins) and edible seeds (almonds, hazelnuts, peanuts, pine nuts, pistachios, and walnuts) using a QuEChERS-LC-ESI-MS-Triple Quadrupole approach was set up. Linearity, sensitivity, accuracy, and precision of the method were satisfactory. Dried prunes and peanuts were the only samples appreciably contaminated, 14.7–124.3 and 10.0–42.9 μg/kg, respectively, as a consequence of the drying process. In fact, prunes are dried at 70–80 °C for a quite long time (24–36 h), while peanuts undergo a roasting process at 160–180 °C for 25–30 min. The relative standard deviations, accuracy, LOD, and LOQ show that the method provides a reliable approach to acrylamide determination in different matrices
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
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
Development of a method for acrylamide determination in dried fruits and edible seeds available on the Italian market
No full textAcrylamide is a process contaminant due to thermal processing and absent in raw food (1). It is carcinogenic and neurotoxic and its level in food arouses great concern (2), although it still does not exist a legal limit for its concentration in foodstuffs. However, European Union recently fixed a recommended level of 1000 μg kg-1 for potato chips. This work focuses on the development of extraction and analytical method for acrylamide determination in dried fruits and based edible seeds using a QuEChERS approach. Sixty-eight samples of packed dried fruits (dried prunes and raisins) and edible seeds (almonds, hazelnuts, peanuts, pine nuts, pistachios, and walnuts) were purchased on the Italian market. After grinding, an aliquot of each sample was suspended in water and acetonitrile and then added of the content of a QuEChERS pouch (MgSO4 4.0 g + NaCl 0.5 g) in order to achieve the separation of water from acetontrile and to induce the migration of acrylamide into the acetonitrile phase. The suspension was vigorously shacked and centrifuged. The upper organic phase was transferred and dried by a gentle nitrogen stream and redissolved in water before analysis. The acrylamide determination was carried out by liquid chromatography coupled with mass spectrometry using a RP-HPLC-ESI-MS-Triple Quadrupole (TQ) equipment. Linearity, sensitivity, matrix effect, accuracy, and precision of the method were studied, also using food matrix reference materials. Then, the method was applied to samples. Results showed that only dried prunes (from 14.7 to 124.3 μg/kg) and peanuts (from 10.0 to 42.9 μg/kg) were appreciably contaminated with acrylamide, as a result of the processing techniques. Prunes are not subjected to high temperature during drying (70-80 °C) but the exposure time is quite long (24-36 h), while peanuts undergo the roasting process (160-180 °C; 25-30 min). These conditions are both critical and they promote the formation of acrylamide. All the other samples showed values below the limit of detection or the limit of quantification. The relative standard deviations, accuracy and good LOD and LOQ show that QuEChERS associated to LC-MS-TQ could be considered a good approach for acrylamide determination in dried fruits and based edible seeds, and it is promising also for other food matrices
A SURVEY ABOUT ACRYLAMIDE IN DRIED FRUITS COLLECTED ON ITALIAN MARKET
No full textAs acrylamide is considered a carcinogen and neurotoxic, its level in food raises great concern
although it still does not exist a legal limit for its concentration in foodstuffs. Acrylamide is a
process contaminant, absent in raw foods and only formed during thermal processing due to
Maillard reaction among reducing sugars (glucose, fructose) and L-asparagine (Mottram et al.,
2002; Stadler et al., 2002).
This work focuses on the development of a method for acrylamide determination in dried fruits based on a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) approach for sample preparation (Schenck et al., 2004) and HPLC-ESI-MS-Triple Quadrupole for sample analysis.
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