EVOO from two minor Tunisian cultivars Chladmi and Oueslati have been evaluated. Volatile composi... more EVOO from two minor Tunisian cultivars Chladmi and Oueslati have been evaluated. Volatile composition of monovarietal olive oil was determined using HS-SPME-GC-EIMS. Chladmi and Oueslati have very interesting olive oil quality and aroma. We can use these cultivars to improve Chemlali oil quality by blending oils or by crossings between varieties.
Virgin olive oils (VOOs) were extracted from Chetoui variety at early and advanced ripening stage... more Virgin olive oils (VOOs) were extracted from Chetoui 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.
Euro-Mediterranean Journal for Environmental Integration, 2021
Grains of Tunisian durum wheat varieties (Razzek, Karim, and Om Rabia) were collected from four g... more Grains of Tunisian durum wheat varieties (Razzek, Karim, and Om Rabia) were collected from four growing locations (Zaghouan, Jendouba, Kef, and Kairouan). The wheat kernels were evaluated for various chemical and technological quality parameters. The results showed strong effects of growing area and genotype on the chemical compositions of wheat grain samples. These two factors (growing area and genotype) had significant effects on all measured parameters such as the thousand kernel weight, test weight, grain vitreousness, ash content, and gluten and grain-protein levels, but not the fatty acid composition. This study showed that Northern Tunisia (Kef and Jendouba) appears to have a favorable environment for the production of high-quality Razzek durum wheat. Central Tunisia (Kairouan) seems to have the most suitable environment for growing Om Rabia and Karim. It is important to chemically characterize these cultivars in order to select varieties that produce good-quality durum wheat grains which are well adapted to the environmental conditions in Tunisia.
Monitoring the volatile and hydrophilic bioactive compounds status of fresh and oxidized Chemlali... more Monitoring the volatile and hydrophilic bioactive compounds status of fresh and oxidized Chemlali virgin olive oils over olive storage times.
Heating operation has been applied to Chétoui extra-virgin olive oils (EVOOs) extracted from frui... more Heating 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,
The aim of the present work is to study the effect of the olive fruit storage on the olive oil qu... more The 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 quality.
Olive leafy biomass constitutes an attractive source of biological substances, such as oleuropein... more Olive leafy biomass constitutes an attractive source of biological substances, such as oleuropein, which can be valuable for the production of functional extracts. The incorporation of this valorization in a biorefinery requires understanding how feedstock and extraction conditions affect the phenolic composition. Therefore, in this study, the phenolic composition of olive leaves from nine cultivars has been explored through using conventional maceration and ultrasound-assisted extraction (UAE). Two-way ANOVA suggested that both factors have a strong influence in the total extraction yield, total phenol content (TPC), and antioxidant activity of the extracts, but only the varietal type affected the solubilization levels. Pearson correlation showed different correlation trends between the TPC and the antioxidant activity depending on the extraction method. Hence, an in-depth analysis by liquid chromatography−mass spectrometry was performed. It showed that maceration and UAE provided the same solubilization of oleuropein. Nonetheless, the cultivar and extraction method affected the qualitative and quantitative phenolic composition of the extracts, including the content of oleuropein and some novel phenolic compounds. Furthermore, using principal component analysis, the extracts were clustered in four main groups, which could be useful for further standardization in potential biorefineries placed in Tunisia.
INTRODUCTION Tunisia is one of the countries where the olive oil production has increased fourfol... more INTRODUCTION Tunisia is one of the countries where the olive oil production has increased fourfold, making it the second largest producer after Spain. Tunisian olive farms cover more than one-third of arable land More than 1.76 million hectares planted with 74 million olives contributing to 45 of food export receipts, 4.5 of total exports, and 11 of the total agricultural production value. The Tunisian olive grove lands, is dominated by two major varieties, Chemlali and Chétoui. Chemlali cultivar is grown in the warm coastal area and low steppes region of the South and the Center of Tunisia. It accounts for nearly 85 of the area under olive cultivation and for more than 80 of domestic olive oil production. It shows a high capacity of adaptation to various pedoclimatic conditions 1, 2. However, the fatty acid composition of its extra virgin olive oil EVOO was reported to contain low levels of oleic acid
The aim of this study was to investigate the influence of the solvent type on the extraction of p... more The aim of this study was to investigate the influence of the solvent type on the extraction of phenolics and the antioxidant properties of the extracts obtained from Chétoui olive leaves. Extraction was conducted at room temperature using four solvents: deionized water (ddH2O), 80% methanol (80% MeOH), 70% ethanol (70% EtOH), and 80% acetone. Total phenols and total flavonoids were measured using the Folin-Ciocalteau and aluminum chloride colorimetric methods, respectively. The antioxidant properties have been determined by two Chétoui olive leaf extracts: influence of the solvent type on phenolics and antioxidant activities
Características sensoriales de aceites de oliva virgen procedentes de cultivares tunecinos monova... more Características sensoriales de aceites de oliva virgen procedentes de cultivares tunecinos monovarietales e híbridos con variedades europeas. Con el fin de definir su perfil organoléptico, se han evaluado sensorialmente seis aceites de oliva virgen procedentes de cinco cultivares establecidos en diferentes zonas de Túnez: Sayali, Sradki, Hor Kesra, Chétoui y Chemlali, y un cultivar de la provincia de Badajoz (España): Arbequina; así como los procedentes de seis cultivares híbridos igualmente establecidos en Túnez: Hd 031, Hd 034, Hd 038, Hd 039, Hd 044 y Hd 045. Un test de Duncan (a ϭ 0,05), teniendo en cuenta las puntuaciones dadas a los diferentes atributos evaluados, permite observar diferencias entre los aceites estudiados, destacando la encontrada entre el aceite procedente del híbrido Hd 044 de los restantes por su nivel de amargo. Así mismo, un análisis de Cluster, muestra la similitud entre ellos, teniendo en cuenta esos mismos atributos, observándose una clara diferencia entre el aceite con origen en el híbrido Hd 044 y los restantes.
Abstract The objective of this work is studying the opportunity of using a Solar Heating System, ... more Abstract The objective of this work is studying the opportunity of using a Solar Heating System, SHS, to prevail the Tunisian households’ air-heating needs by comparing the energetic performances of two solar heating technologies: the SHS with an integrated active layer in the floor and a SHS with an integrated active layer in the wall. The SHS mainly consists of flat-plate solar collectors, a hot water cylinder and an active layer integrated inside the heated building. The study is accomplished by means of TRNSYS 16 simulation software. The investigations of the energetic and thermal performances of the SHS were based on an experimental and simulation studies. A complete model is formulated by means of the TRNSYS simulation program. To validate the TRNSYS model, experimental tests under the typical North-African climate (Tunisia) was performed. The optimization of the SHP performances was achieved by considering the monthly/annual solar fraction, SF. Then, we evaluate the long-term performances of the solar heating system with an integrated active layer in the floor and a solar heating system with an integrated active layer in the wall. The results showed that the optimal sizing of the heating system that allows the supply of a maximum rate of the solar fraction consisted on using 6 m2 area of solar collector, a collector’s mass-flow rate of about 120 kg h−1, a hot water storage cylinder with a capacity of 450 L and a mass flow-rate inside the active layer about 300 kg h−1. The comparison of the long-term performance of the solar heating system showed that the use of the floor as a heat source presented a great potential with a solar fraction of about 78%. It was also found that the use of the solar heating system, SHS, reduced obviously the relative humidity inside the tested room of about 35%.
ABSTRACT This paper deals with the energetic performances of a Solar Heating Prototype (SHP) conc... more ABSTRACT This paper deals with the energetic performances of a Solar Heating Prototype (SHP) conceived in our laboratory to prevail the Tunisian households’ air-heating needs. The conceived SHP mainly consists of a flat-plate solar collector, solar hot water tank and an active layer integrated inside a single room. Firstly, a complete model is formulated taking into account various modes of heat transfer in the SHP by means of the TRNSYS simulation program. To validate the TRNSYS model, experimental tests under local weather conditions were performed for 2 days spread over 2 months (March and April 2013). Predicted results were compared to the measurements in order to determine the accuracy of the simulation program. A parametric study was then achieved by means of the TRNSYS program in order to optimize SHP design parameters (Collector area, collector mass flow rate, floor mass flow rate, storage tank volume and thickness of the active layer). The optimization of all design parameters shows that to achieve a maximum performances from the SHP it is essential to use a solar collector with an area equal to 6 m2 area, a collector mass flow rate equal to 100 kg h−1 and a hot water storage tank with a capacity equal to 450 l. Concerning the floor heating, the optimal values of mass flow rate and the active layer thickness are 200 kg h−1 and 0.06 m, respectively. The long-term SHP performances were afterward evaluated by means of the Typical Meteorological Year (TMY) data relative to Tunis, Tunisia. Results showed that for an annual total solar insolation of about 6493.37 MJ m−2 the average solar fraction obtained is about 84%. The results show also that the request of auxiliary energy is limited to the cold months of the year chiefly from December to Mars. The results show also that the SHP reduce the relative humidity inside the monozone room of about 40%.
Abstract The endeavor of the paper is the study the feasibility of using a locally made daily sol... more Abstract The endeavor of the paper is the study the feasibility of using a locally made daily solar storage system, SSS, for domestic hot water supply especially in urban and isolated households. In order to evaluate the system efficiency during the charging and discharging periods an experimental and a numeric investigation were simultaneously achieved. Results showed that the daily energy efficiency of the energy stored in the HSU ranged from 30 to 49.5% whereas the daily exergy efficiency ranged from 19 to 27%. The results show also that for wet sand the quantity of daily destocked energy varies in the array of 1.75–0.8 kW h. The results showed that 75% of the total DHW requirements can be achieved from the heat storage system during the night. The results of the economic analysis shows that the SSS, the annual energy kept (YES) and the payback period (PBP) were about 1317 kW h/year and 4 years based on electric water heater and about 460 m3 gas saving and 3.5 years based on gas water heater, respectively.
Food Science and Technology International, Feb 1, 2009
The aim of this work was to study some of the chemical characteristics of virgin olive oils produ... more The aim of this work was to study some of the chemical characteristics of virgin olive oils produced by three varieties grown in Tataouine (south of Tunisia). The oil samples studied were characterized by high levels of oleic acid (470%) and relatively low percentages of linoleic and palmitic acids (≤ 13% and≤ 10%, respectively). They were also characterized by three primary triacylglycerols: OOO, POO, and OOL, and three secondary triacylglycerols POL+ SLL, SOO, and PPO. The sterol and triterpenic dialcohol ...
Abstract: Two main olive oil varieties occured in Tunisia: Chétoui cultivated in the north and Ch... more Abstract: Two main olive oil varieties occured in Tunisia: Chétoui cultivated in the north and Chemlali in the centre and the south. The latter contributes up to 80% of the national olive oil production. Nevertheless, it contains high palmitic acid levels and relatively low levels of oleic acid. So, some approaches have been considered, last years, among them the genetic improvement of Chemlali variety by controlled crossings using other tunisian and foreign varieties having better olive oil quality. This work was focused on studying olive oil quality of five new cultivars obtained through controlled crossings on Chemlali variety and chosen among a population of fourty descendants according to their improved fatty acid composition as compared to that of Chemlali. To assess the chemical composition of their oils, some parameters have been evaluated which are: average olive weight, oil yield, fatty acid composition, total phenolic compounds and chlorophylls contents, oxidative stabili...
EVOO from two minor Tunisian cultivars Chladmi and Oueslati have been evaluated. Volatile composi... more EVOO from two minor Tunisian cultivars Chladmi and Oueslati have been evaluated. Volatile composition of monovarietal olive oil was determined using HS-SPME-GC-EIMS. Chladmi and Oueslati have very interesting olive oil quality and aroma. We can use these cultivars to improve Chemlali oil quality by blending oils or by crossings between varieties.
Virgin olive oils (VOOs) were extracted from Chetoui variety at early and advanced ripening stage... more Virgin olive oils (VOOs) were extracted from Chetoui 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.
Euro-Mediterranean Journal for Environmental Integration, 2021
Grains of Tunisian durum wheat varieties (Razzek, Karim, and Om Rabia) were collected from four g... more Grains of Tunisian durum wheat varieties (Razzek, Karim, and Om Rabia) were collected from four growing locations (Zaghouan, Jendouba, Kef, and Kairouan). The wheat kernels were evaluated for various chemical and technological quality parameters. The results showed strong effects of growing area and genotype on the chemical compositions of wheat grain samples. These two factors (growing area and genotype) had significant effects on all measured parameters such as the thousand kernel weight, test weight, grain vitreousness, ash content, and gluten and grain-protein levels, but not the fatty acid composition. This study showed that Northern Tunisia (Kef and Jendouba) appears to have a favorable environment for the production of high-quality Razzek durum wheat. Central Tunisia (Kairouan) seems to have the most suitable environment for growing Om Rabia and Karim. It is important to chemically characterize these cultivars in order to select varieties that produce good-quality durum wheat grains which are well adapted to the environmental conditions in Tunisia.
Monitoring the volatile and hydrophilic bioactive compounds status of fresh and oxidized Chemlali... more Monitoring the volatile and hydrophilic bioactive compounds status of fresh and oxidized Chemlali virgin olive oils over olive storage times.
Heating operation has been applied to Chétoui extra-virgin olive oils (EVOOs) extracted from frui... more Heating 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,
The aim of the present work is to study the effect of the olive fruit storage on the olive oil qu... more The 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 quality.
Olive leafy biomass constitutes an attractive source of biological substances, such as oleuropein... more Olive leafy biomass constitutes an attractive source of biological substances, such as oleuropein, which can be valuable for the production of functional extracts. The incorporation of this valorization in a biorefinery requires understanding how feedstock and extraction conditions affect the phenolic composition. Therefore, in this study, the phenolic composition of olive leaves from nine cultivars has been explored through using conventional maceration and ultrasound-assisted extraction (UAE). Two-way ANOVA suggested that both factors have a strong influence in the total extraction yield, total phenol content (TPC), and antioxidant activity of the extracts, but only the varietal type affected the solubilization levels. Pearson correlation showed different correlation trends between the TPC and the antioxidant activity depending on the extraction method. Hence, an in-depth analysis by liquid chromatography−mass spectrometry was performed. It showed that maceration and UAE provided the same solubilization of oleuropein. Nonetheless, the cultivar and extraction method affected the qualitative and quantitative phenolic composition of the extracts, including the content of oleuropein and some novel phenolic compounds. Furthermore, using principal component analysis, the extracts were clustered in four main groups, which could be useful for further standardization in potential biorefineries placed in Tunisia.
INTRODUCTION Tunisia is one of the countries where the olive oil production has increased fourfol... more INTRODUCTION Tunisia is one of the countries where the olive oil production has increased fourfold, making it the second largest producer after Spain. Tunisian olive farms cover more than one-third of arable land More than 1.76 million hectares planted with 74 million olives contributing to 45 of food export receipts, 4.5 of total exports, and 11 of the total agricultural production value. The Tunisian olive grove lands, is dominated by two major varieties, Chemlali and Chétoui. Chemlali cultivar is grown in the warm coastal area and low steppes region of the South and the Center of Tunisia. It accounts for nearly 85 of the area under olive cultivation and for more than 80 of domestic olive oil production. It shows a high capacity of adaptation to various pedoclimatic conditions 1, 2. However, the fatty acid composition of its extra virgin olive oil EVOO was reported to contain low levels of oleic acid
The aim of this study was to investigate the influence of the solvent type on the extraction of p... more The aim of this study was to investigate the influence of the solvent type on the extraction of phenolics and the antioxidant properties of the extracts obtained from Chétoui olive leaves. Extraction was conducted at room temperature using four solvents: deionized water (ddH2O), 80% methanol (80% MeOH), 70% ethanol (70% EtOH), and 80% acetone. Total phenols and total flavonoids were measured using the Folin-Ciocalteau and aluminum chloride colorimetric methods, respectively. The antioxidant properties have been determined by two Chétoui olive leaf extracts: influence of the solvent type on phenolics and antioxidant activities
Características sensoriales de aceites de oliva virgen procedentes de cultivares tunecinos monova... more Características sensoriales de aceites de oliva virgen procedentes de cultivares tunecinos monovarietales e híbridos con variedades europeas. Con el fin de definir su perfil organoléptico, se han evaluado sensorialmente seis aceites de oliva virgen procedentes de cinco cultivares establecidos en diferentes zonas de Túnez: Sayali, Sradki, Hor Kesra, Chétoui y Chemlali, y un cultivar de la provincia de Badajoz (España): Arbequina; así como los procedentes de seis cultivares híbridos igualmente establecidos en Túnez: Hd 031, Hd 034, Hd 038, Hd 039, Hd 044 y Hd 045. Un test de Duncan (a ϭ 0,05), teniendo en cuenta las puntuaciones dadas a los diferentes atributos evaluados, permite observar diferencias entre los aceites estudiados, destacando la encontrada entre el aceite procedente del híbrido Hd 044 de los restantes por su nivel de amargo. Así mismo, un análisis de Cluster, muestra la similitud entre ellos, teniendo en cuenta esos mismos atributos, observándose una clara diferencia entre el aceite con origen en el híbrido Hd 044 y los restantes.
Abstract The objective of this work is studying the opportunity of using a Solar Heating System, ... more Abstract The objective of this work is studying the opportunity of using a Solar Heating System, SHS, to prevail the Tunisian households’ air-heating needs by comparing the energetic performances of two solar heating technologies: the SHS with an integrated active layer in the floor and a SHS with an integrated active layer in the wall. The SHS mainly consists of flat-plate solar collectors, a hot water cylinder and an active layer integrated inside the heated building. The study is accomplished by means of TRNSYS 16 simulation software. The investigations of the energetic and thermal performances of the SHS were based on an experimental and simulation studies. A complete model is formulated by means of the TRNSYS simulation program. To validate the TRNSYS model, experimental tests under the typical North-African climate (Tunisia) was performed. The optimization of the SHP performances was achieved by considering the monthly/annual solar fraction, SF. Then, we evaluate the long-term performances of the solar heating system with an integrated active layer in the floor and a solar heating system with an integrated active layer in the wall. The results showed that the optimal sizing of the heating system that allows the supply of a maximum rate of the solar fraction consisted on using 6 m2 area of solar collector, a collector’s mass-flow rate of about 120 kg h−1, a hot water storage cylinder with a capacity of 450 L and a mass flow-rate inside the active layer about 300 kg h−1. The comparison of the long-term performance of the solar heating system showed that the use of the floor as a heat source presented a great potential with a solar fraction of about 78%. It was also found that the use of the solar heating system, SHS, reduced obviously the relative humidity inside the tested room of about 35%.
ABSTRACT This paper deals with the energetic performances of a Solar Heating Prototype (SHP) conc... more ABSTRACT This paper deals with the energetic performances of a Solar Heating Prototype (SHP) conceived in our laboratory to prevail the Tunisian households’ air-heating needs. The conceived SHP mainly consists of a flat-plate solar collector, solar hot water tank and an active layer integrated inside a single room. Firstly, a complete model is formulated taking into account various modes of heat transfer in the SHP by means of the TRNSYS simulation program. To validate the TRNSYS model, experimental tests under local weather conditions were performed for 2 days spread over 2 months (March and April 2013). Predicted results were compared to the measurements in order to determine the accuracy of the simulation program. A parametric study was then achieved by means of the TRNSYS program in order to optimize SHP design parameters (Collector area, collector mass flow rate, floor mass flow rate, storage tank volume and thickness of the active layer). The optimization of all design parameters shows that to achieve a maximum performances from the SHP it is essential to use a solar collector with an area equal to 6 m2 area, a collector mass flow rate equal to 100 kg h−1 and a hot water storage tank with a capacity equal to 450 l. Concerning the floor heating, the optimal values of mass flow rate and the active layer thickness are 200 kg h−1 and 0.06 m, respectively. The long-term SHP performances were afterward evaluated by means of the Typical Meteorological Year (TMY) data relative to Tunis, Tunisia. Results showed that for an annual total solar insolation of about 6493.37 MJ m−2 the average solar fraction obtained is about 84%. The results show also that the request of auxiliary energy is limited to the cold months of the year chiefly from December to Mars. The results show also that the SHP reduce the relative humidity inside the monozone room of about 40%.
Abstract The endeavor of the paper is the study the feasibility of using a locally made daily sol... more Abstract The endeavor of the paper is the study the feasibility of using a locally made daily solar storage system, SSS, for domestic hot water supply especially in urban and isolated households. In order to evaluate the system efficiency during the charging and discharging periods an experimental and a numeric investigation were simultaneously achieved. Results showed that the daily energy efficiency of the energy stored in the HSU ranged from 30 to 49.5% whereas the daily exergy efficiency ranged from 19 to 27%. The results show also that for wet sand the quantity of daily destocked energy varies in the array of 1.75–0.8 kW h. The results showed that 75% of the total DHW requirements can be achieved from the heat storage system during the night. The results of the economic analysis shows that the SSS, the annual energy kept (YES) and the payback period (PBP) were about 1317 kW h/year and 4 years based on electric water heater and about 460 m3 gas saving and 3.5 years based on gas water heater, respectively.
Food Science and Technology International, Feb 1, 2009
The aim of this work was to study some of the chemical characteristics of virgin olive oils produ... more The aim of this work was to study some of the chemical characteristics of virgin olive oils produced by three varieties grown in Tataouine (south of Tunisia). The oil samples studied were characterized by high levels of oleic acid (470%) and relatively low percentages of linoleic and palmitic acids (≤ 13% and≤ 10%, respectively). They were also characterized by three primary triacylglycerols: OOO, POO, and OOL, and three secondary triacylglycerols POL+ SLL, SOO, and PPO. The sterol and triterpenic dialcohol ...
Abstract: Two main olive oil varieties occured in Tunisia: Chétoui cultivated in the north and Ch... more Abstract: Two main olive oil varieties occured in Tunisia: Chétoui cultivated in the north and Chemlali in the centre and the south. The latter contributes up to 80% of the national olive oil production. Nevertheless, it contains high palmitic acid levels and relatively low levels of oleic acid. So, some approaches have been considered, last years, among them the genetic improvement of Chemlali variety by controlled crossings using other tunisian and foreign varieties having better olive oil quality. This work was focused on studying olive oil quality of five new cultivars obtained through controlled crossings on Chemlali variety and chosen among a population of fourty descendants according to their improved fatty acid composition as compared to that of Chemlali. To assess the chemical composition of their oils, some parameters have been evaluated which are: average olive weight, oil yield, fatty acid composition, total phenolic compounds and chlorophylls contents, oxidative stabili...
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