1,721,079 research outputs found
STUDY OF CHEMICAL AND MOLECULAR INFORMATION RELATED TO NIR AND IR SPECTROSCOPIC DATA FOR DAIRY SECTOR
Full text linkIn the last decades, the spectroscopic techniques have acquired reliability, since they are sufficiently accurate and precise for analysis of the macro-composition of food.
In this work, NIR and IR techniques were applied to study some aspects of cow milk casein and fat globules.
In dairy field, casein amount and quality have great influence on milk rennet properties and cheese yield. Caseins from milk of ruminants have been extensively studied, but the exact structure of the casein micelle is still debated.
The research activity was addressed to verify the ability of spectroscopic techniques in the evaluation of modifications of casein fractions and sub-fractions as a function of pH and temperature. The NIRS ability in predicting casein fractions content and in detecting bonds involved in the micelle complex were also evaluated.
The study was carried out on both commercial preparations of casein fractions and reconstituted casein samples. These were obtained by ultracentrifugation (native casein) and by precipitation at the iso-electric pH (acid casein) of individual milk samples, collected during two months periods in the Austria’s region.
The IR spectra of commercial caseins showed the phosphate band at 1100 cm-1, confirming its role in the stabilization of casein micelle structure. When NIR casein spectra were measured as a function of temperature, exclusively changes in water bands were detected, while regarding pH, Absorbance differences from the mean spectrum evidenced some modifications of linearity due to the number of negative charged amino acid residues at pH > 6.80 in the casein sub-fractions.
Casein fractions content of reconstituted samples was determined by Capillary Zone Electrophoresis analyses. PLS analyses, performed with electrophoretic and NIR data, revealed the NIRS ability to determine and quantify casein genetic variants useful for milk selection for its final purpose. Moreover, the PCA analysis on the same samples proved the NIRS ability also to discriminate between samples obtained by physical and chemical treatments and to detect bonds involved in the micelle structure, especially phosphate group and its binding to calcium.
FT-NIR spectroscopy was also applied to study the size distribution of fat globules: an aspect influencing the technological and sensorial milk characteristics. In this contest, the variability in the distribution of fat globules within cow breedings in Lombardy was studied during two years period. The reference particle size analyses of fat globules were performed using a granulometer. The Sauter Mean Diameter (SMD) was chosen as the best descriptor of particle size distribution.
This parameter resulted to be more influenced by genetic factors than seasonal aspects. The differences among farms could be determinant in planning the milk collection for the technological destination, while the differences among the breeding bulls can be used for the animals’ selection.
Despite the importance of this parameter in several dairy processes, instrumentation for particle size analysis are not available in dairy laboratories. NIR instrumentation, instead, is largely used in dairy labs. NIR spectrum of whole milk arises from absorbance due to both molecular vibrations and elastic scattering related to the presence of fat globules in emulsion. Moreover, the amount of scattered photons depends on their size and wavelength. A rapid and economic method for estimating the distribution of fat globules in milk through a physical-mathematical model based on the study of the scattering component in the NIR spectrum was developed. The model, working in Visual Basic for Excel, calculates the optical density produced by milk fat globules, given the fat concentration. On the basis of the Weibull distribution, the model calculates the amount of globules with a certain diameter range, returning a first distribution curve. After the generation of a theoretical NIR spectrum, the model inversion was performed by minimizing the sum of squared differences between measured and theoretical spectra. At the end of the process, the new distribution curve was given. The performances of the model was tested by analyzing an external data set with both NIR and reference diffractometric data. For the SMD a very high coefficient of determination in prediction was found.
In order to improve the applicability of the model, the use of a portable spectrometer for estimating the distribution of milk fat globules was evaluated trough standardization to bench-top instrument spectra. The calculation of milk fat globules diameter by a portable instrument standardized spectra through the mathematical model, gave comparable results with those calculated on master spectra
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
Characterization of phenolics in red grape skins recovered from winemaking by-products employable as a food ingredient or as a nutraceutical preparation
No full textThe grape transformation by wine industry generates a large volume of by-products, such as grape pomace, which still contains polyphenols and other beneficial compounds for the human health. Thus, the recovery of the active compounds for the production of ingredients for food and nutraceuticals might be of interest. The purpose of our research was to define the qualitative and quantitative composition of the polyphenols in products to be used later for the formulation of foods high in added value. Red grape skins samples of Barbera, Croatina, Freisa, Dolcetto, Grignolino, Neretto, Nebbiolo and Pinot Nero were recovered from winemaking by-products, within the Valorvitis project (AGER 2010-2222). Samples were analyzed for total phenolics (Folin Ciocalteu assay), proanthocyanidins (Porter assay), and individual polyphenols by UPLC coupled to diode array and mass spectrometry detector. A wide variability was observed in the contents of total phenolics (12-54 mg gallic acid Eq/kg), proanthocyanidins (0.7- 5%), total anthocyanins (0.2-1.4%) and flavonols (0.3-2.5%). Glucoside of malvidin, delphinidin, peonidin, petunidin and cyanidin were the main anthocyanins, respectively. Additionally, lower amount of these compounds was found esterified with acetic, p-coumaric and caffeic acid. The main flavonols were the aglycones quercetin and kaempferol, respectively, but also lower amount of their derivatives such as glucuronides and glucosides were found. Regarding proanthocyanidins, the found amount were comparable with those reported in literature and the chromatographic analysis showed that catechin, epicatechin and epigallocatechin-gallate monomers were the main constituents of the polymers. Among the samples considered, the cultivar Barbera, which is largely cultivated, was found to be one of the most promising sources of phenolics. Thus, this well characterized winemaking by-product could be used as food ingredient or in nutraceutical preparations
Physical and chemical properties of some italian opals
No full textThe physical and compositional properties of some opals from different parts of Italy have been investigated through several methodologies like optical analysis, specific gravity, refractive indices, XRPD, IR spectroscopy, LA-ICP-MS. The opals show different colors: white, brownish-white, yellowish-white, yellow-/greenish white and grey. Black and metallic inclusions, consisting of todorokite, are sometimes present. Play-of-color have not been observed but some opals show small iridescence zones; opals are inert to the long and short wavelength UV radiation (366 - 254 nm) with the exception of one sample; also phosphorescence is absent. Refractive index and specific gravity values are respectively 1.43 to 1.44 and 2.07 to 2.33 g/cm3 consistent with data available in the literature. XRPD analyses highlighted Italian opals are A, CT and C types, but most of them can be classified as opals- CT. IR spectroscopy data confirmed the opal classification. The most abundant impurities are Mg (between 400 and 900 ppm), Fe (35-400 ppm), Ca (72-96 ppm) and Ni (20-65 ppm). Similarly to what observed in other opals worldwide, Fe appears to be the principal factor that determines the brown to red to orange to yellow colors. Chromophore elements like V, Cr, Cu, Ti, Co are present in very low concentrations and probably do not influence the physical properties of the Italian opals analyzed. Ni is present in more relevant amounts and is probably related to clay minerals. Mn is clearly detected only in two samples and is related to the presence of dendrites. The investigated Italian opals show a rather homogeneous trace element composition which is in the range of worldwide opal’s composition, except for their noticeable amount in Ni
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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