1,720,976 research outputs found
The Chemical Properties and Volatile Compounds of Virgin Olive Oil from Oueslati Variety: Influence of Maturity Stages in Olives
No full textThe aim of the present work was to investigate the influence of fruit ripening on oil quality and volatile compounds in an attempt to establish an optimum harvesting time for Oueslati olives, the minor olive variety cultivated in Tunisia. Our results showed that many analytical parameters, i.e., peroxide value, UV absorbance at 232–270 nm, chlorophyll pigments, carotenoids and oleic acid contents decreased during ripening, whilst linolenic acid increased. Free acidity remained practically stable with a very slight rise at the highest maturity index. The volatile compounds emitted by the Oueslati olive oil were characterized and quantified by HS-SPME-GC-EIMS. Twenty-three volatile compounds were identified, mainly aldehydes, sesquiterpenes and esters. The results show variations in the volatile fractions and quality parameters of Oueslati extra virgin olive oil obtained at different olive-ripening stages. Fifteen sesquiterpenes were identified for the first time in this cultivar, mainly hydrocarbon derivatives, but also oxygenated ones. On the basis of the quality parameters and volatile fractions studied, the best stage of Oueslati olive fruits for oil processing seems to be at ripeness index about 3.0. Indeed, these results suggested the possibility of using sesquiterpenes for olive authenticity and traceability and demonstrated that the volatile fractions can be used as indicators of the degree of ripening of the olives used to obtain the corresponding virgin olive oils
Olive oil polyphenols extracts inhibit inflammatory markers in J774A.1 murine macrophages and scavenge free radicals
No full textHere we evaluate the olive oil antiradical and anti-inflammatory potential through its polyphenols extracts and examine the influence of olive maturity on olive oil quality properties, polyphenols composition and biological potentials. Samples have been obtained from minor Tunisian olive cultivars (Chemchali, Fouji and Zarrazi) at different maturity indices. Principal quality properties were evaluated and polyphenols analysis was carried out by Folin Ciocalteu reagent and HPLC-UV-MS. Antiradical activity was examined by DPPH and FRAP scavenging assays while J774A.1 murine macrophages were used to evaluate anti-inflammatory potential by analyzing NO production with Griess reagent method and iNOS and COX-2 expression by cytofluorimetric analysis. Our results revealed that quality characteristics, total phenol content, as well as phenolic compound concentrations were significantly affected by the olive maturity levels. On the other hand, the polyphenols extracts showed an interesting radical scavenging capacity and a potential ability to inhibit inflammatory markers at 90% for NO release and 75% for iNOS expression. Thus, our study establishes that olive oil through its polyphenols extracts has a substantial antiradical and anti-inflammatory potential. Likewise a lot of attention should be attributed to olive ripening level in order to decide the optimum harvesting time
Monitoring the volatile and hydrophilic bioactive compounds status of fresh and oxidized Chemlali virgin olive oils over olive storage times
Full text linkThe virgin olive oils (VOOs) under examination were from the main Tunisian cultivar ‘Chemlali’. Olive fruits used for oil production were stored in plastic containers for four weeks at ambient temperature. Hydrophilic bioactive compounds and volatile profiles of the corresponding oils were analyzed. Chemometric analysis showed that VOO obtained from fruits stored during one week is similar to that of freshly harvested
fruits. They preserved their bioactive and volatile molecular markers of freshness with the predominance of the secoiridoid aldehydic form of oleuropeine aglycon, and the C6 lipoxygenase products. However, VOO obtained from fruits stored for a long time, showed degradation of the derivatives of oleuropeine and ligstro- side aglycons, a decrease in the lignan, and flavonoid groups, whereas phenolic acids showed a remarkable in- crease. The volatile profile was characterized by a decrease in the LOX products, and biosynthesis of the volatile molecular markers of oxidation C7 -C1 0 aldehydes (nonanal, decanal, (Z) and (E)-2-heptenal, (E)-2-octenal, and (E,E)-2,4-heptadienal), and hydrocarbons (n-dodecane, and n-tetradecane). Mono and sesquiterpenes showed also an increase over storage time. Consequently, and in order to avoid deterioration of VOO composition, chemometric analysis showed that the olive fruits should be processed as soon as possible after being harvested, with a maximum storage time of one week
Effect of the Ripening Stage on the Volatile Composition of Chétoui Virgin Olive Oil
No full textirgin olive oils (VOOs) were extracted from Chétoui variety at early and advanced ripening stages. The volatile compounds were analyzed using HS-SPME coupled to GC-MS. The lipoxygenase products were the main identified compounds. Aldehydes formed most of the C6 fraction. The percentages of alcohols and esters differed with ripening index suggesting a strict dependence on the enzymatic store
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
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
Volatile molecular markers of VOO Thermo-oxidation: Effect of heating processes, macronutrients composition, and olive ripeness on the new emitted aldehydic compounds
No full textHeating operation has been applied to Chétoui extra-virgin olive oils (EVOOs) extracted from fruits with several ripening stages (RS). The studied samples, were subjected to microwave and conventional heating. Results showed that heated VOOs after 2.5 h and 7 min of conventional and microwave heating, respectively, gave rise to a drastically decrease of LOX products and allowed the detection of toxic new formed aldehydic volatiles (alkanal: nonanal, alkenals: (Z)-2-heptenal and (E)-2-decenal, and alkadienals: (E.E)-2.4-decadienal), which can be used as markers of VOO degradation. Their abundance in the VOO headspaces depends on their boiling points, the rate of their possible degradation to yield other compounds, on the heating processes and on the rate of macronutrients. The emission rate of the new synthesized volatiles during heating processes was mainly attributed to enzymatic oxidation of some fatty acids. Hexanal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,E) and (E,Z)-2,4-decadienal, and (E,E)-2,4-nonadienal, derived from linoleic acid, and heptanol, octanal, nonanal, decanal, (E) and (Z)-2-decenal, (E)-2-undecenal, and (E,E)-2,4-nonadienal, are emitted after degrada- tion of oleic acid. During thermo-oxidation, the ECN44 (LLO, and OLnO), and the ECN46 (OLO, and PLO + SLL) compounds decreased, whereas, the ECN48 (OOO, and PPO), and the ECN50 (SOO) compounds increased when temperature and heating time increased. The several variations of the studied biochemical compounds depend to the heating processes. Ripening stage of olive fruits can be used as a tool to monitor the emission rate of the aldehydic volatiles, but cannot be used for a chemometric discrimination
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