1,720,962 research outputs found
Discrimination of some tunisian olive oil varieties according to their oxidative stability, volatiles compounds and chemometric analysis
No full textOxidation stability is a key property of olive oil quality and is affected by different antioxidant compounds whose levels may be influenced by several factors such as cultivar and place of production. Polyphenols, carotenoids, chlorophylls, fatty acids levels and some volatiles were correlated to oxidative stability in olive oils in five samples studied. Total polyphenols and saturated to polyunsaturated fatty acids (and/or oleic to linoleic acid ratio) ratio were shown to be the major parameters in oil antioxidant stability, according to analysis of variance and principal component analysis. The hexanal/E-2-hexenal ratio is a very important indicator of the freshness of the oils and can estimate their oxidation degre
Modification of pomological characteristics and flavor components of fruits and virgin olive oil following wastewater irrigation and soil tillage
No full textBACKGROUND
The experiment was carried out on olive trees cv. Chemlali, during two successive years (2013/2014). Two irrigation treatments (IT: Trees irrigated with wastewater; TRC: Trees grown under rainfed condition) were combined with two tillage practices (TTS: Trees grown in tilled soil; TNTS: Trees grown in non-tilled soil).
RESULTS
The results of the study showed that WW irrigation combined with soil tillage improved the pomological characteristics of olive fruits. The tree yield increase was substantial for IT and TTS. However, most of the identified phenolic compounds, especially oleuropein, mainly accumulated in olive fruits of the TC block (TNTS + TRC), suggesting a marked improvement in the nutritional value of these fruits. Moreover, fruits of TNTS had high contents of sugar compounds, required for the synthesis of the fruit storage material. The study also showed that the agronomic practices affected the amounts of some aromatic compounds responsible for the distinctive flavor notes of olive oil.
CONCLUSION
Hence, agronomic practices may affect considerably the commercial and nutritional values and the sensorial quality of the commodities
Butylated Hydroxytoluene (BHT) emitted by fungi naturally occurring in olives during their pre-processing storage for improving olive oil stability
No full textExtra virgin olive oil is widely consumed because of its nutritional benefits and sensory properties which are very important to be preserved in the product. Therefore, chemically synthesized compounds, such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), are widely used as antioxidants in oil products. It is well known that the activity of some micro-organisms able to oxidize free fatty acids can lead to the loss of the stability of the final product. Nevertheless, several researchers have been recently motivated to evaluate the potential of micro-organisms on the production of bioactive compounds. In this paper headspace solid micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were used for the characterization and investigation of Fungal Organic Volatile Metabolites (FOVCs) emitted by 14 fungal strains isolated from olives during their pre-processing storage. A wide range of volatile compounds were detected among them, Butylated Hydroxytoluene (BHT) was produced at levels ranging between 0.3 and 13.1%. This compound could be considered for the industry as natural antioxidant to substitute the synthetic ones used for ameliorating the stability of olive oil and other fatty food products.
Practical applications: As the pre-processing storage step is inevitable for several practical reasons, inducing the outgrowth of olive microflora (mainly fungi), which critically affect the physiological state of the fruit and thus the quality of the correspondent oil, this paper try to elucidate the potential of these naturally developing strains and their metabolites (FVOCs) of producing bioactive compounds mainly the Butylated Hydroxytoluene (BHT) which could be considered by the industry in order to substitute the synthetic one largely used to improve the stability of olive oil and other food products. Volatiles, when coupled with the power “omics” technologies represent a new frontier in bio-prospectin
Modification of Phenolic Compounds and Volatile Profiles of Chemlali Variety Olive Oil in Response to Foliar Biofertilization
No full textThe main objective of this work was to studythe effects of foliar biofertilizers on individual volatile pro-files and phenolic compounds of olive oil (Olea europaeaL. cv. Chemlali). Three foliar biofertilizers were used intwo successive application seasons: T1 (rich in nitrogen,phosphorus and potassium); T2 (rich in calcium); and T3(application of both T1 and T2). Results showed that foliarfertilization with T2 increased the phenolic compound con-tents (e.g., oleuropein aglycone and decarboxymethyl lig-stroside aglycone) of Chemlali olive oil. It also enhancedthe levels of many volatile compounds responsible for thegoodflavor of olive oil such as hexanal. However,T1-tested fertilizer led to a significant decrease in the con-tent of phenolic compounds, although they seemed toimprove significantly the levels of the majority of volatilecompounds, especially hexanal. Based on these results, asignificant relationship between plant nutrition and qualityof oil was observed. Our results demonstrated a potentialpositive influence on the concentration of sensory qualitycompounds under T2 (Ca2+-based fertilizer). This resultshould be considered in the design of foliar nutrient appli-cation management strategies for olive trees
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
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