Youssef Ouni

Triacylglycerols Composition and Volatile Compounds of Virgin Olive Oil from Chemlali Cultivar: Comparison among Different Planting Densities

The present study focused on the comparison the chemical composition of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivar (Chemlali) grown in four planting densities (156, 100, 69, and 51 trees ha−1). Despite the variability in the triacylglycerols and volatile compounds composition, the quality indices (free fatty acids, peroxide value, and spectrophotometric indices K232 and K270) all of the virgin olive oils samples studied met the commercial standards. Decanal was the major constituent, accounting for about 30% of the whole volatiles. Moreover, the chemical composition of the volatile fraction of the oil from fruits of trees grown at the planting density of 156, 100, and 51 trees ha−1 was also characterised by the preeminence of 1-hexanol, while oils from fruits of trees grown at the planting density of 69 trees ha−1 had higher content of (E)-2-hexenal (20.3%). Our results confirm that planting density is a crucial parameter that may influence the quality of olive oils.

Municipal solid waste compost application improves productivity, polyphenol content, and antioxidant capacity of Mesembryanthemum edule

Organic wastes were successfully used as soil amendment to improve agrosystems productivity. Yet, the effectiveness of this practice to enhance plant antioxidant capacities has received little attention. Here, we assess the effect of municipal solid waste (MSW) compost (at 40 t ha(-1)) on growth, polyphenol contents and antioxidant activities of Mesembryanthemum edule. MSW compost application significantly increased the soil contents of carbon, nitrogen, calcium, phosphorus and potassium. This was associated with higher nutrient (N, P, and K) uptake, which likely led to the significant improvement of the plant biomass and relative growth rate (RGR) (+93% on average) as compared to the control. In the same way, the fertilizing effect of the added organic matter significantly enhanced the antioxidant potential M. edule, assessed by radical scavenging activity, iron reducing power and β-carotene bleaching capacity. This was associated with significantly higher antioxidant contents, mainly total phenols and flavonoids. Heavy metal (Pb, Cd, Cu, and Zn) concentrations were slightly increased upon compost application, but remained lower than phytotoxic values. Overall, our results point out that short-term MSW compost application at 40 t ha(-1) is efficient in enhancing the productivity together with the antioxidant potentiality of M. edule without any adverse environmental impact.

The phenolic compounds and compositional quality of Chetoui virgin olive oil: effect of altitude

The differences in the chemical composition of virgin olive oils (VOO) obtained from trees of the Chetoui variety cultivated at different altitudes in Tunisia were evaluated. All samples were harvested using the same controlled procedures and were submitted to a controlled processing in the same laboratory mill. Several analytical parameters such as fatty acid composition, amounts of phenols; o-diphenols and pigments were analyzed. All these parameters showed an important effect on the fatty acids and phenols content of the oils. The total phenol content was positively correlated with the altitude, ranging from 817.33 mg/kg (403 m) to 131.91 mg/kg (10 m). However, the results of the regulated parameters in the potential quality classified all the analyzed oils into the ‘‘extra virgin’’ category. Key words : Orchard elevation, total antioxidant capacity, phenolic compounds, quality index.

EFFECTS OF THE HALOPHYTES TECTICORNIA INDICA AND SUAEDA FRUTICOSA ON SOIL ENZYME ACTIVITIES IN A MEDITERRANEAN SABKHA

In the present work, we studied the effectiveness of the predominant halophytes of Soliman sabkha (Tecticornia indica and Suaeda fruticosa) to promote soil biological activities and ecosystem productivity. Soil Arylsulphatese ARY, β-glucosidase β-GLU, phosphatase PHO, invertase INV, urease URE, and dehydogenase DES activities in Extra- and Intra-tuft halophytes and plant productivity were assessed. Results revealed a high increase of microbial community and ARY, β-GLU, PHO, INV, URE and DES activities (+298%, +400%, +800%, +350%, +320%, +25% and +759%, respectively) in Intra-tuft rhizosphere as compared to Extra-tuft one, which is likely due to the significant decrease of salinity in the rhizosphere of Tecticornia indica and Suaeda fruticosa. Both perennial plants exhibited high productivities (7.4 t dry weight ha−1 and 2.2 t dry weight ha−1, respectively) and Na+-hyperaccumulating capacities (0.75 t Na+ ha−1 and 0.22 t Na+ ha−1, respectively), reducing salt constraint and favouring soil fertility. This constitutes a promising alternative to enhance productivity in such a salt-affected biotope by offering suitable microhabitat for annual glycophytes.

Municipal Solid Waste Compost Application Improves the Negative Impact of Saline Soil in Two Forage Species

Inappropriate utilization of biosolids may adversely impact agrosystem productivity. This article addresses the response of H. vulgare and P. monspeliensis to different doses (0, 100, and 150 t ha−1) of municipal solid waste (MSW) compost in a greenhouse pot experiment. Plant growth, heavy-metal uptake, gas exchange, and photosynthetic pigment concentrations and photosynthesis parameters were considered. Results showed that compost supply significantly increased shoot and root dry weights of both species, and this was positively correlated with nutrient uptake. Chlorophyll and carotenoid contents were positively influenced, especially in H. vulgare at rate of 100 t ha−1. Furthermore, MSW compost application increased net photosynthetic rate (A), stomatal conductance (Gs), and water-use efficiency (WUE) in both species. Alternatively, MSW compost amendment increased plant heavy-metal contents but levels remained lower than phytotoxic thresholds. This preliminary study suggests that a MSW supply at moderate doses (100 t ha−1) could be highly beneficial for plant productivity on saline soils.

Characterization and quantification of phenolic compounds of extra-virgin olive oils according to their blending proportions

Chemlali olive oil was blended with oils obtained from Oueslati and Chetoui varieties to improve the quality of the former one. Parameters such as triacylglycerols and phenolic compounds were characterized for various blends of Chemlali x Oueslati and Chemlali x Chetoui. Results show that blended oils had an improved composition as compared to that of Chemlali. In fact, the highest percentage of Oueslati and Chetoui olive oils (60% of blending) could lead to 1,2,3-trioleylglycerol (OOO) of up to 30.20 and 33.44%, respectively. The amount of aldehydic form of oleuropeine aglucon was higher when Chemlali was blended using either 40 or 60% of Chetoui olive oil (from 99.17 to 299.63 and 334.16 mg kg -1 ). Key words: Oil blending, Chemlali x Oueslati, Chemlali x Chetoui, phenolic fraction, triacylglycerols African Journal of Biotechnoloy , Vol 13(12), Vol 1386-1392

Quality, stability and radical scavenging activity of olive oils after Chétoui olives (Olea europaea L.) storage under modified atmospheres

At the industrial scale, the major source of olive oil deterioration is the poor handling of the raw material during the time separating harvesting from processing. The objective of this work was to verify the effect of modified atmospheres and cold storage in relation to quality parameters of the extracted oils. Olives (cv Chétoui) intended for oil extraction, were stored for 21 days at two different temperatures (ambient temperature 14 ± 2 °C and 5 °C) and under two different modified atmospheres 21% O2 – 0% CO2 and 2% O2 – 5% CO2. Oils quality was ascertained with analytical parameters: free fatty acids, peroxide value, K232, K270 as suggested by European regulation. Oxidative stability, total phenols content, radical scavenging activity and fatty acids composition were carried out in order to measure the hydrolytic and oxidative degradation of oils. Olive oils quality parameters were significantly affected by treatments with especially a beneficial effect on primary oxidation indicators and free acidity. Most efficient treatments, with regard to oils phenolic content and involved parameters, were 21% O2 – 0% CO2 at ambient temperature (636.25 mg ca/kg) and 2% O2 – 5% CO2 under 5 °C (637.50 mg ca/kg). Those two treatments improved individually oil samples phenolic content of 25% but not at the same storage period.