56 research outputs found
Lipoxygenase pathways metabolites associated to antioxidant properties of tunisian monovarietal virgin olive oils
No full textOlive oil, rich in bioactive compounds and antioxidants, is renowned for its health benefits. The lipoxygenase pathway contributes to the formation of antioxidant metabolites in virgin olive oils. This study examined the impact of location on volatile compounds, fatty acids, and antioxidants in Chetoui monovarietal olive oil from thirteen Tunisian regions. Analysis detected 37 volatile compounds, displaying significant compositional differences across regions. The predominant volatile compound, (E)-2-hexenal, exhibited noteworthy variations, reaching peak levels in Dogga II and Thibar at 24.9% and 23.1% respectively. Fatty acid composition revealed varying percentages of linoleic acid (C18:2) and linolenic acid (C18:3). Amdoun exhibited the highest C18:2 content at 17.5%. Similarly, C18:3 ranged from 0.7% in Slouguia to 0.8% in Teboursouk. Comparative analysis of oxidative stability and antioxidant activity indicated significant differences among regions. Testour II (52 h) and Medjez El-Bab II (44 h) demonstrated higher stability. Regarding antioxidant activity, Teboursouk displayed the highest value at 96.46% and 83.13% for DPPH and ABTS assays, while Thibar scored the lowest at 93.64% and 77.52% for DPPH and ABTS assays. The correlation coefficients reveal that oxidative stability has a negative correlation with DPPH activity (-0.4106) and ABTS activity (-0.491). In contrast, there is a strong positive correlation between oxidative stability and 1-Hexanol (0.584). Furthermore, the fatty acids C18:2 (-0.599) and C18:3 (-0.273) demonstrates negative correlations with oxidative stability. They provide novel insights into the relationship between the lipoxygenase pathway and olive oil's antioxidant properties, contributing to the production of high-quality olive oils with enhanced antioxidant attributes
The compositional quality and volatile compounds from the blend of monovarietal olive oils cultivated in Tunisia
No full textChemlali olive oil has been blended with oils obtained from Oueslati and Chetoui varieties to improve the
quality of the former one. Parameters such as acidity, acids compositions, phenol content, oxidative stability
and volatile compounds were characterised for various blends Chemlali · Oueslati and Chemlali · Chetoui.
The accumulation of volatiles originating from the lipoxygenase pathway in the monovarietal oils was
different and closely dependent on the genetic store of each variety. The concentrations appeared to
proportionally vary according to the relative proportion of each monovarietal oil in the mixtures. The blending process improved fatty acids by increasing the oleic acid content and decreasing the palmitic and linoleic acids levels of Chemlali oil. At 40% blending, oleic acid increased from 54% to 62%, while palmitic acid decreased from 18.59% to 16% when Oueslati and Chetoui olive oil was used
Influence of olive storage period on volatile compounds and oil quality of two Tunisian cultivars of Olea europaea, Chemlali and Chetoui
No full textOlives (Olea europaea cv. Chemlali and Chetoui) used for oil production were stored, in plastic containers, at 5°C for four 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, stability, pigments, total phenols, fatty acids, and volatile compounds were determined. The results showed that storage of fruits produced losses in the olive oil quality. During storage, a marked decrease in total phenols content was observed. The cultivar richer in phenols (862.16 mg kg)1 in Che ́toui) had a lower loss (25%). On the contrary, in Chemlali olive oil, the starting value of 728.52 mg kg)1 decreased to 469.25 mg kg)1, with a loss of 35%. Che ́toui and Chemlali olive oils presented the highest oxidative stability before storage (58.76 and 47.05 h, respectively), while the lowest values were recorded using olives stored for 3 weeks (54.46 and 43.43 h, respectively). The changes in the volatile bouquet were determined using headspace solid phase microextraction (HS-SPME). Thirty compounds were characterised by GC–FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterised the volatile profile
How stresses associated with the operating conditions affect the balance between some non-enzymatic and enzymatic antioxidant activities in Haematococcus pluvialis cells
No full textInternational audienceIn the last decade, great interest in using microalgae for applications in several fields such as nutrition, cosmetic or sustainable chemicals manufacturing, e.g. plastic or pharmaceutical synthesis intermediates. Among the high-value products, some natural carotenoids such as β-carotene and astaxanthin are derived from microalgae biomass. For instance, astaxanthin, 3,3′-dihydroxy-4,4′-diketo-β-β carotene, is produced, mainly for its antioxidant activities, by the microalga Haematococcus pluvialis. The optimization of astaxanthin production by microalgae cultures still requires better control of the process leading to its intracellular over-accumulation. The present study aims to determine the contribution of different enzymatic and non-enzymatic antioxidants within vegetative and encysted cells of H. pluvialis before and after the application of stresses representative of operating conditions for industrial cultures under solar conditions.08H30 Arrivée des participants et inscriptions 09H30 OUVERTURE 10H00-10H45 CONFÉRENCE I : Monsieur Nabil BEN KHATRA Secrétaire Exécutif à l'Observatoire du Sahara et du Sahel La Comptabilité Ecosystémique pour une meilleure valorisation/gestion des Ressources Naturelles en Afrique. 10H45-11H45 Session POSTER (I) de P 001 à P 040 PAUSE CAFÉ Modérateurs : Pr Nabil BEN KHATRA, Pr Fethia HARZALLAH-SKHIRI 11H45-11H55 C.O. 01 Rihab MISSAOUI, Nessrine TEKA, Hatem MAJDOUB, Tarek REBAI Chemical characterization, antioxidant and anticoagulant properties of sulfated polysaccharides from fresh water algae Cladophora sp. 11H55-12H05 C.O. 02 Rabeb MANNAI, Nizar BARRAK, Sabrine FRADJ, Lotfi ACHOUR, Boulbaba SELMI Optimisation d'un prétraitement "Fenton-Microonde" des boues activées pour une production efficace de biogaz
How stresses associated with the operating conditions affect the balance between some non-enzymatic and enzymatic antioxidant activities in Haematococcus pluvialis cells
No full textInternational audienceIn the last decade, great interest in using microalgae for applications in several fields such as nutrition, cosmetic or sustainable chemicals manufacturing, e.g. plastic or pharmaceutical synthesis intermediates. Among the high-value products, some natural carotenoids such as β-carotene and astaxanthin are derived from microalgae biomass. For instance, astaxanthin, 3,3′-dihydroxy-4,4′-diketo-β-β carotene, is produced, mainly for its antioxidant activities, by the microalga Haematococcus pluvialis. The optimization of astaxanthin production by microalgae cultures still requires better control of the process leading to its intracellular over-accumulation. The present study aims to determine the contribution of different enzymatic and non-enzymatic antioxidants within vegetative and encysted cells of H. pluvialis before and after the application of stresses representative of operating conditions for industrial cultures under solar conditions.08H30 Arrivée des participants et inscriptions 09H30 OUVERTURE 10H00-10H45 CONFÉRENCE I : Monsieur Nabil BEN KHATRA Secrétaire Exécutif à l'Observatoire du Sahara et du Sahel La Comptabilité Ecosystémique pour une meilleure valorisation/gestion des Ressources Naturelles en Afrique. 10H45-11H45 Session POSTER (I) de P 001 à P 040 PAUSE CAFÉ Modérateurs : Pr Nabil BEN KHATRA, Pr Fethia HARZALLAH-SKHIRI 11H45-11H55 C.O. 01 Rihab MISSAOUI, Nessrine TEKA, Hatem MAJDOUB, Tarek REBAI Chemical characterization, antioxidant and anticoagulant properties of sulfated polysaccharides from fresh water algae Cladophora sp. 11H55-12H05 C.O. 02 Rabeb MANNAI, Nizar BARRAK, Sabrine FRADJ, Lotfi ACHOUR, Boulbaba SELMI Optimisation d'un prétraitement "Fenton-Microonde" des boues activées pour une production efficace de biogaz
Adapting authoritarianism: institutions and co-optation in Egypt and Syria
No full textThis PhD thesis compares Egypt and Syria’s authoritarian political systems. While the tendency in social science political research treats Egypt and Syria as similarly authoritarian, this research emphasizes differences between the two systems with special reference to institutions and co-optation. Rather than reducibly understanding Egypt and Syria as sharing similar histories, institutional arrangements, or ascribing to the oft-repeated convention that “Syria is Egypt but 10 years behind,” this thesis focuses on how events and individual histories shaped each states current institutional strengthens and weaknesses. Specifically, it explains the how varying institutional politicization or de-politicization affects each state’s capabilities for co-opting elite and non-elite individuals.
Beginning with a theoretical framework that considers the limited utility of democratization and transition theoretical approaches, the work underscores the persistence and durability of authoritarianism. Chapter two details the politicized institutional divergence between Egypt and Syria that began in the 1970s. Chapter three and four examines how institutional politicization or de-politicization affects elite and non-elite individual co-optation in Egypt and Syria. Chapter five discusses the study’s general conclusions and theoretical implications.
This thesis’s argument is that Egypt and Syria co-opt elites and non-elites differently because of the varying degrees of institutional politicization in each governance system. Rather than view one country as more politically developed than the other, this work argues that Syria’s political institutions are more politicized than their Egyptian counterparts. Syria’s political arena is, thus, described as politicized-patrimonialism. Syria’s politicized-patrimonial arena produces uneven co-optation of elites and non-elites as they are diffused through competing institutions. Conversely, the Egyptian political arena remains highly personalized as weak institutions and individuals are manipulated and molded according to the president’s ruling clique. This is referred to as personalized-patrimonialism. As a consequence, Egypt’s political establishment demonstrates more flexibility in ad hoc altering and adapting its arena depending on the emergence of crises.
This study’s theoretical implications suggest that, contrary to modernization and democratization theory’s adage that institutions lead to a political development, politicized institutions within a patrimonial order actually hinder regime adaptation because consensus is harder to achieve and maintain. It is within this context that Egypt’s de-politicized institutional framework advantages its top political elite. In this reading of Egyptian and Syrian politics, Egypt’s personalized political arena is more adaptable than Syria’s. These conclusions do not indicate that political reform is a process underway in either state
Volatile compounds and compositional quality of virgin olive oil from Oueslati variety: Influence of geographical origin
No full textHeadspace solid-phase microextraction (HS-SPME) was applied to the analysis of volatile compounds of virgin olive oils from Oueslati variety cultivated in different geographical areas. Thus, olives at the same stage of maturation were harvested from seven regions in the Centre and the South of the country for oil extraction and analysis. Twenty-seven compounds were characterised by GC-FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterised the volatile profiles. Significant differences in the proportion of volatiles from oils of different geographical origins were detected. The results suggest that, besides genetic factors, environmental conditions influence volatile formatio
Lipid composition and antioxidant activity of liver oils from ray species living in Tunisian coasts
No full textAbstractThe proximate composition, fatty acid profiles, physicochemical properties and radical scavenging activities of liver oil from three ray species, Dasyatis pastinaca, Dasyatis violacea and Rhinoptera marginata, were investigated. Lipid contents of D. pastinaca (58.27%) and D. violacea (57.33%) were significantly high compared to those of R. marginata (10.90%). Among minerals, K and Na were the most abundant elements and the highest values were observed for R. marginata (153.7 and 115.86mg/100g, respectively). The fatty acid profiles exhibited a dominance of unsaturated fatty acids exceeding 65% of the total fatty acids. C16:0, C18:0 and C14:0 were the major saturated fatty acids. The most abundant monounsaturated fatty acids were C18:1 (10.88–21.98%) and C16:1 (4.47–23.95%). Interestingly, omega-3 polyunsaturated fatty acid profiles exhibited a dominance of eicosapentaenoic acid (3.36–5.51%) and docosahexaenoic acid (9.07–30.50%). D. pastinaca contained the highest carotenoid and total phenolic content accompanied with the strongest free radical scavenging abilities. This study suggests that ray livers which were actually wasted, could be used as new raw material for omega-3 polyunsaturated fatty acid oil production and a good source of carotenoids and phenolic compounds
Influence of the Site of Cultivation on Chétoui Olive (Olea europaea L.) Oil Quality
No full textA comparative study was conducted to evaluate the effect of location on the chemical composition and quality of monovarietal virgin olive oils obtained from the Chétoui cultivar in relation to the fruit ripening stages. Three sites representative of two Tunisian olive growing regions were examined, Selten (region I (RI): original site of plantation of Chétoui variety in the north of the country), Ousletia and Jelma (region II (RII): in the central part of the country away from the original plantation site). In this study, Chétoui olive cultivar was found to have different responses to environmental conditions. Chétoui olive oils showed lower values in phenol and o-diphenol contents and were less stable to oxidation (weaker oxidative stability and antioxidant activity levels) when the olive trees were cultivated away from the original plantation site. These Chétoui olive oils are also characterized by decreased oil content and higher values of quality parameters such as free acidity, peroxide value and UV absorbance due probably to the drought during the flowering and olive ripening periods. Furthermore, many analytical parameters, i.e., chlorophyll pigments, carotenoids, oleic acid contents, total phenol and o-diphenol amounts, oxidative stability, antioxidative capacity and quality parameters showed nearly the same changes during fruit ripening but in different degrees depending on the site of the plantation
Sterolic composition and triacylglycerols of Oueslati virgin olive oil: comparison among different geographic areas
No full text- …
