1,721,065 research outputs found
Storage of olives (Olea europaea): effect on the quality parameters and the radical scavenging activity ot total fraction, lipidic and metanol fractions of the VOO
No full textVariation in the different aromatic classes of virgin olive oils after heating at frying temperature
No full textFrying is one of the few methods of cooking common to the entire Mediterranean area. It is used for both domestic and industrial preparation of food. During frying, as a results of heating, virgin olive oil (VOOs) undergos a complex series of degradation reactions. In the present work, the changes in the different chemical families of the aroma of the virgin olive oil (VOO) subject to a heating at frying temperature (180°C) for 0, 2.5, 5, 7.5 and 10 hours, was carried out. The VOO volatile compounds were extracted by SPME, and analyzed and identified by GC/MS. In the untreated VOOs, the aromatic compounds showed different chemical families, with a predominance of the aldehydic class of the lipoxygenase products (75.2% of total peak area), followed by the class of sesquiterpenes (14.8%), esters (2.5%), monoterpenes (1.2%) and hydrocarbons (0.9%), other aromatic classes are present in trace. After olive oil heating, a newformed aldehydic compounds were observed reaching 84.4% of total peak area, whereas the lipoxygenase products, the mono-and sesquiterpenes showed a remarkable degradation after 2.5h of heating. Other volatile markers of thermoxidation were emitted with different levels depending to the heating time
Variation in the antioxidant activity of the lipidic fraction of the virgin olive oils and the refined vegetable oils during frying
No full textStorage of olives (Olea europaea): effect on the quality parameters and the radical scavenging activity of the total fraction, lipidic and methanolic fractions of the VOO
No full textThe aim of the present work is to study the effect of the olive fruit storage on the olive oil quality. ‘Chemlali’ used for oil production were stored in plastic containers, at room temperature during three different periods (0-3 weeks) before
oil extraction. After storage, the oils were extracted from the fruits and the acidity, peroxide value, coefficients of specific extinction at 232 and 270 nm, the radical scavenging activity of the total fraction, lipidic and methanolic fractions of the virgin olive oil (VOO) were determined. The effect of the olive fruit storage on the olive oil quality was investigated by measuring the radical-scavenging activity (RSA) toward
1,1-diphenyl-2-picrylhydrazyl radical (DPPH•).
The results showed that storage of fruits produced losses in all the VOO quality parameters. During storage, a marked decrease in the capacity of the total fraction of the VOO to scavenge the free radical DPPH (week 0: 77% - week 3:
60%). Similar changes were observed in the capacity of the polar fraction to scavenge the free radical DPPH (week 0: 4790 μmol Trolox/kg oil - week 3: 3357 μmol Trolox/kg oil). A drastic decrease was observed in the capacity of the lipidic
fraction to scavenge the free radical DPPH (week 0: 62% - week 3: 47%). The results demonstrate that the storage conditions of the olive fruits have a remarkable
impact on the VOO qualit
Variation of the different aromatic classes of virgin olive oil after heating at frying temperature
No full textIn the present work, the changes in the different chemical families of the aroma of the virgin olive oil (VOO), subject to a frying temperature (180 ° C) for 0, 2.5, 5, 7.5 and 10 hours, was carried out. The VOO volatile compounds were extracted by SPME, and analyzed and identified by GC/MS. In the untreated VOO, the aromatic compounds showed different chemical families with a predominance of the aldehydic class representing 75.2% of total peak area, followed by the class of sesquiterpenes (14.8%), the esters (2.5%), monoterpenes (1.2%) and hydrocarbons (0.9%), other aromatic classes are present in trace. After frying, the aldehydic class showed a remarkable increase, whereas the mono-and sesquiterpenes showed degradation. New aromatic classes such as the alcohols and ketones were detecte
Effect of cultivar on minor components in Tunisia olive fruits cultivated in microclimate
No full textThis paper evaluates the usefulness of three chemical parameters (composition of volatiles compounds, total phenols and fatty acids) as a tool to discriminate the olive oils obtained from three varieties (Oueslati, Chemlali and Chetoui). These varieties are included among the cultivars permitted by the disciplinary for the production of the ‘‘Kairouan olive oil’’, a Tunisian protected designation of origin (PDO) product. The olives were collected during the year crop 2009/2010 from the same orchard (calcareous soil), in order to eliminate geographical and climatic influences. Analysis of the effect of cultivar on the different analytical values, revealed statistically significant differences in some parameters, mainly in free fatty acid and phenol contents and oxidative stability. Furthermore, most of the quality indices and fatty acid composition showed significant variations among olive varieties. Oueslati variety had the highest values of oleic acid, whereas Chetoui was noteworthy for its high content of phenolic compounds. The major volatile component was the C6 aldehyde fraction whose content varied greatly between the different varieties: the (E)-2-hexenal content ranged from 20.9% in the oil obtained from the Oueslati variety to 7.7% in the case of Chemlali one; the amount of hexanal ranged from 10.2% in Oueslati to 3.7% in Chetoui. These results suggest that the genetic factor (cultivar) influences the volatiles formation
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
Chemical composition of virgin olive oils from the Chemlali cultivar with regard to the method of the olive tree propagation
Full text linkThis paper reports for the first time a discrimination study based on the antioxidant compounds, oxidative stability and volatile compounds of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivar (Chemlali) using two methods of olive tree propagation (suckers and cuttings). There were significant differences between the oils from the two methods. Olive oil samples obtained from the fruits of trees from suckers had a higher content of oleic acid (63.8%), higher contents of chlorophyll and carotenoids (3.01 mg/kg and 1.9 mg/kg respectively), a higher content of (E)-2 hexenal (66.1%) and a higher content in total phenols (890 mg/kg).
Interestingly, more stable oil was obtained from the olives from suckers compared to the olives from cuttings. These results can be used to discriminate and to characterize the Chemlali olive oils from each origin of olive tre
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
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