I am Dr. Akram ZRIBI. I awarded a B.S. degree in industrial chemistry (2009), a M.S. degree in organic chemistry (2011), and a Ph.D. degree in chemistry (2015) from the Sfax Faculty of Science, Sfax University, Tunisia. I insured the instruction of practical works and tutorials in “chemical composition of oil” and "chromatographic techniques and detection of adulterations in olive oil" as a supply professor for the students of 3rd year of co-constructed bachelor’s degree in Production and Conditioning of Olive Oil during the academic years 2014/2015, 2015/2016 and 2016/2017 at the Sfax Higher Institute of Biotechnology. I have published 14 research articles in international peer-review journals since 2012 (h-index 8 via the scholar Google database) and one chapter in a collective book. Besides, I participated in various national and international symposiums. My research interest includes especially the oxidative stability of pure and enriched frying oils and also the influence of storage, filtration, adulteration, mechanical processing systems and geographical sites in the quality of extra-virgin olive oils (phytochemistry, lipid and analytical chemistry). I am currently looking for a postdoctoral position abroad.
Changes occurring in refined olive pomace oil (ROPO) blended with refined palm oil (RPO) during r... more Changes occurring in refined olive pomace oil (ROPO) blended with refined palm oil (RPO) during repeated frying cycles were monitored. Four ratios of ROPO/RPO blends were prepared: (100:0), (75:25), (50:50) and (25:75). The effect of deep-frying was studied by assessing the changes in iodine value, acid value, color value and fatty acids composition. The results show that the mixture ROPO/RPO (25:75) is the most stable compared with other blends. The fate of 3-MCPD and glycidyl esters during deep-frying was investigated showing no endogenous formation of the esters during 16 h of deep-frying.
The aim of the present research is to evaluate the chemical characterization of main compounds fr... more The aim of the present research is to evaluate the chemical characterization of main compounds from Tunisian monocultivar Extra virgin olive oil (EVOO) (‘Chemlali’, ‘Chétoui’, ‘Zalmati’ and ‘crossbreeding Chemlali by Zalmati’) extracted after the addition of different amounts (0% and 3%) of olive leaves. As expected for virgin olive oil, the main sterols found in all analyzed samples were β-sitosterol, ∆-5-avenasterol, campesterol and cholesterol. Stigmasterol, 24-methylene-cholesterol, clerosterol, campestanol, sitostanol, ∆-7-stigmastenol, ∆-5,24-stigmastadienol, and ∆-7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds were significantly affected by the cultivars but not to be affected by added leaves at 3% to olives prior to the extraction process. The obtained results revealed that 14 phenolic compounds belonging to different phenolic types were characterized and quantified by an effective HPLC-DAD-ESI-MS/MS method. In all the studied olive-oil samples, dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), oleuropein aglycon (3,4-DHPEA-EA), and ligstroside aglycon (p-HPEA-EA) were the most abundant compounds. In addition, EVOO from ‘Chétoui’ cultivar extracted with 3% of olive leaves presented the highest amount of individual phenolic compounds.
The oil extracted from olive paste is a turbid and opalescent juice which contains impurities tha... more The oil extracted from olive paste is a turbid and opalescent juice which contains impurities that can affect its quality. Before olive oil packaging, filtration has recently become a standard processing procedure in order to obtain more brilliant extra-virgin olive oil (EVOO), maintain its quality, and extend its shelf life. In this research work, changes occurring in the concentrations of some minor compounds during industrial filtration of Chemlali EVOO were studied. The chemical parameters with sensorial quality were also determined. After the filtration of oil, a slight increase in quality parameters was noticed, along with a slight influence on the sensory scores. The adopted filtration system reduces the moisture contents. However, non-filtered olive oil might be more stable. Nevertheless, the behavior of phenolic compounds during filtration differed for each family. Indeed, the secoiridoids are the most affected phenolic compounds during EVOO filtration. Their concentrations increase significantly (p < 0.05) except the decarboxylated ligstroside aglycon decreases during this process.
Practical applications: This work clearly demonstrates the usefulness of filtration process in the Chemlali EVOO treatment. After industrial-scale filtration process, the analysis of individual concentration of phenolic compounds indicated that the concentrations of secoiridoids increased significantly (p < 0.05) mainly 3,4-DHPEA-EA. Besides, olive oil brilliance is achieved by eliminating vegetable water and suspended particles; thus extending final product shelf life.
The aim of this study was to investigate the effect of the refined palm oil addition (20%) on the... more The aim of this study was to investigate the effect of the refined palm oil addition (20%) on the fatty acid and sterol compositions of refined olive oil or refined soya bean oil and also to investigate the formation of total polar compounds and volatile compounds in these oil blends during fifty successive deep-frying sessions of potato fries at 180 °C. The blend of refined olive oil and refined palm oil exhibited a higher chemical stability during the frying process than that of refined soya bean oil and refined palm oil. Indeed, the total polar compounds and volatile compounds formed, especially 2,4-decadienal, were found to be relatively increased in the refined soya bean oil/refined palm oil blend reaching 36.50% and 46.70%, respectively, after fifty deep-frying sessions. Moreover, the degradation of linoleic acid and β-sitosterol was significantly (P < 0.05) observed for the refined soya bean oil/refined palm oil blend. The results have proven that the proper blending of monounsaturated refined olive oil with refined palm oil increases its stability and hence improves the quality of such olive oil during frying process.
Refined oils including corn, sunflower, soybean, and palm oils as well as low-quality olive oil s... more Refined oils including corn, sunflower, soybean, and palm oils as well as low-quality olive oil such as refined lampante and pomace olive oils are commonly used for extra-virgin olive oil (EVOO) adulteration. Indeed, K 270 could be used as a parameter for the detection of EVOO fraud for each type of the studied refined oils, 10 % olive, 4 % pomace olive, 10 % palm, 5 % corn, and 2 % soybean oils. Moreover, the adulteration could also be detected by the increase of the trans fatty acid contents with 10 % pomace olive, 3 % soybean, 3 % sunflower, 2 % corn, and 10 % palm oils. Actually, stigmasta-3,5-diene content is one of the most effective means of detecting refined oils in EVOO at low levels: 2 % olive, 0.4 % pomace olive, 1 % palm, 0.2 % soybean, 0.5 % sunflower, and 0.1 % corn oils. Finally, the application of linear discriminant analysis could represent an alternative and innovative tool for faster and cheaper evaluation of EVOO adulteration.
Frying performance of blends of a monounsaturated oil like refined olive oil (ROO) or a polyunsat... more Frying performance of blends of a monounsaturated oil like refined olive oil (ROO) or a polyunsaturated oil such as refined soybean oil (RSO) with a refined oil rich in saturated fatty acids like refined palm oil (RPO) was investigated by assessing their chemical changes during 50 successive deep-frying sessions of potato fries at 180°C. The blends were prepared in the volume ratio of 80:20 (ROO:RPO and RSO:RPO). Indeed, the chemical properties of the frying oil blends were significantly (p<0.05) influenced by type and concentration of oil compounds. The ROO/RPO blend exhibited the highest chemical stability during the frying process and the RSO/RPO blend showed the lowest stability. In fact, 25% of total polar compounds were exceeded after 40 successive deep-frying sessions for the ROO/RPO blend, whereas after 30 sessions for the RSO/RPO blend. Finally, ROO/RPO blend revealed better frying performance than that of RSO/RPO, as confirmed by both statistical analyses such as principal component analysis (PCA) and repeated measures analysis of variance (ANOVA).
Practical Applications: The use of the newly-proposed product which characterized by a strong thermo-oxidative stability during repeated deep-frying like refined olive oil (ROO) / refined palm oil (RPO) blend, is a promising possibility. It is hoped that the data obtained from this research study may facilitate food manufacturers to decide on the suitable oils for their frying operations.
Refined olive, corn, soybean, and sunflower oils were used as cooking oils for deep-frying at two... more Refined olive, corn, soybean, and sunflower oils were used as cooking oils for deep-frying at two different temperatures, 160 and 190 °C, and for pan-frying of potatoes at 180 °C for 10 successive sessions under the usual domestic practice. Several chemical parameters were assayed during frying operations to evaluate the status of the frying oils. Refined olive oil, as frying oil, was found to be more stable than the refined seed oils. In fact, this oil has proven the greatest resistance to oxidative deterioration, and its trans-fatty acid contents and percentages of total polar compounds were found to be lower at 160 °C during deep-frying. Finally, chemometric analysis has demonstrated that the lowest deterioration of the quality of all refined oils occurred in the refined olive oil during deep-frying at 160 °C and the highest deterioration occurred in the refined sunflower oil during pan-frying at 180 °C.
The present paper accounts for the study of the storage of Chemlali olive fruits at two condition... more The present paper accounts for the study of the storage of Chemlali olive fruits at two conditions of limited aerobiosis: in closed plastic bags and in open perforated plastic boxes for different periods before oil extraction. The ultimate objective is to investigate the effect of the container type of the postharvest fruit storage on the deterioration of the olive oil quality. The results have shown that the oil quality of Chemlali olives deteriorated more rapidly during fruit storage in closed plastic bags than in perforated plastic boxes. Therefore, the use of perforated plastic boxes is recommended for keeping the olives for longer periods of storage. The repeated measures analysis of variance of all parameters analyzed indicated that the olive oil quality is mainly affected by the olives storage conditions (containers type and storage periods). Finally, blends of extra-virgin olive oil and mildly deodorized low-quality olive oils can be detected by their alkyl esters concentrations.
Fatty acids composition as an indicator of purity suggests that linolenic acid content could be u... more Fatty acids composition as an indicator of purity suggests that linolenic acid content could be used as a parameter for the detection of extra/virgin olive oil fraud with 5% of soybean oil. The adulteration could also be detected by the increase of the trans-fatty acid contents with 3% of soybean oil, 2% of corn oil and 4% of sunflower oil. The use of the ΔECN42 proved to be effective in the Chemlali extra-virgin olive oil adulteration even at low levels: 1% of sunflower oil, 3% of soybean oil and 3% of corn oil. The sterols profile is almost decisive in clarifying the adulteration of olive oils with other cheaper ones: 1% of sunflower oil could be detected by the increase of Δ7-stigmastenol and 4% of corn oil by the increase of campesterol. Linear discriminant analysis could represent a powerful tool for faster and cheaper evaluation of extra-virgin olive oil adulteration.
Refined olive and refined soybean oils (RSO) have been analyzed in order to evaluate their physic... more Refined olive and refined soybean oils (RSO) have been analyzed in order to evaluate their physicochemical behavior during potatoes pan-frying. These refined oils exhibit significant variations in the physicochemical parameters when heated. A significant decrease (p<0.001) was practically observed in all analytical determination values except the induction time which showed a significant increase (p<0.001) with the enrichment with hydrolyzate olive leaf hydroxytyrosol-rich extract at 500 ppm during pan-frying. In fact, such enrichment has shown a remarkable resistance to oxidative deterioration, and the formation of trans-fatty acids (TFA) was found to be lower in the enriched refined oil samples during pan-frying. Such results have proven that not only is hydroxytyrosol-rich extract excellent antioxidant enrichment for refined olive and RSOs during pan-frying, but also it can be useful as substitute for synthetic ones. This study has shown that enriching refined oils with easily-found and cheap natural plant extracts could extend their usage life. Practical applications: The results of this research study have shown that refined pan-frying oils can successfully be enriched with hydrolyzate olive leaf hydroxytyrosol-rich extract at 500 ppm in order to enhance thermo-oxidative stability and reduce significantly the formation of trans-fatty acids. The hydrolyzate extract was found to be very suitable for this purpose. These materials are common agro-food by-products and can be produced very easily at a low cost. Besides, this type of enrichment may enable consumers to get some beneficial phenolic compounds through fried food consumption. In addition, these types of applications may open another area for marketing the named extract of natural origin.
This study is undertaken to determine the storage stability of Chemlali extra-virgin olive oil (E... more This study is undertaken to determine the storage stability of Chemlali extra-virgin olive oil (EVOO) in different containers such as clear and dark glass bottles, polyethylene (PE) and tin containers. The different oil samples were stored under light at room temperature. Quality parameters monitored during a 6-month-storage period included: acidity, peroxide value (PV), spectrophotometric indices (K232 and K270), chlorophyll and carotene pigments, fatty acids and sterol compositions, total phenols, Rancimat induction time as well as sensory evaluation. Tin containers and dark glass bottles recorded the lowest oxidation values. In addition, oil packed in tin containers and dark glass bottles showed better physicochemical and organoleptic characteristics than that stored in clear glass bottles and PE containers. A significant decrease (p < 0.05) in the antioxidant contents (carotenes, chlorophylls and total phenols) was observed in the oil stored in the clear glass bottles and PE containers. Such results proved that the storage of oil in tin containers and dark glass bottles appeared most adequate, and showed a gradual loss of quality during storage, especially in PE containers and clear glass bottles. This study has shown that the best packaging materials for the commercial packing of Chemlali extra-virgin olive oil are tin containers and dark glass bottles.
The analysis of the effect of cultivar and olive leaves addition before the extraction on the dif... more The analysis of the effect of cultivar and olive leaves addition before the extraction on the different analytical values revealed significant differences (p < 0.05) in some parameters, mainly in peroxide value, phenols and tocopherol contents, and oxidative stability. Aroma profiles were also influenced by the different varieties and the addition of different amounts (0% and 3%) of olive leaves. Twenty-three compounds were characterized, representing 86.1−99.2% of the total volatiles. Chétoui cultivar has the highest amount of (E)-2-hexenal, followed by Chemlali cultivar, whereas (E)-2-hexen-1-ol was the major constituent of Zalmati and crossbreeding Chemlali by Zalmati cultivars. Sensory analysis showed that Chemlali and Chétoui Zarzis possessed a high fruity, bitter, and pungent taste, whereas the Zalmati and crossbreeding Chemlali by Zalmati had a ‘green’ taste among its attributes. Indeed, the taste panel found an improvement of the oil quality when an amount of olive leaves (3%) added to the olives fruits.
The present work has been carried out to ascertain the influence of different processing systems ... more The present work has been carried out to ascertain the influence of different processing systems employed in olive process on the chemical composition, quality and stability of three Chemlali olive oils. Among these oils, two were classified as extra-virgin olive oils and the third named repassed olive oil was classified as an ordinary virgin olive oil. The analysis of the effect of the processing (two- and three-phases) on the analytical determinations values, revealed statistically significant differences (p<0.05) in some parameters, mainly in oxidative stability, antioxidant activity, total waxes, total phenols, o-diphenols and α-tocopherol contents as well as phenolic composition. The phenolic composition values were higher in the extra-virgin olive oil obtained from the two-phase system than in that obtained from the three-phase processing because it does not require the addition of water to the olive paste. Nevertheless, they were lower in the ordinary virgin olive oil (repassed olive oil) which was obtained by introducing hot water to the wet residues into the centrifugation processing at two-phases, than those in the extra-virgin olive oils obtained from the two- and three-phase processing.
The present work aims at the characterizing chemlali extra-virgin olive oils from different locat... more The present work aims at the characterizing chemlali extra-virgin olive oils from different locations in northern, central and southern Tunisia in terms of their quality indices, fatty acids, sterol content, phenolic composition and sensory profiles to show the classification of oil samples according to the geographical area. The majority of the analytical parameters have presented statistically significant differences (p < 0.05). The main sterols found in all chemlali olive oils were β-sitosterol, ∆-5-avenasterol, campesterol and stigmasterol. The phenolic compounds present in five olive oil samples were analysed by high-performance liquid chromatography (HPLC) method, thus identifying 16 phenolic compounds belonging to different phenolic types. The results have shown no qualitative differences in the phenolic fractions among extra-virgin olive oils from different geographical regions. However, the quantitative differences were observed in a wide number of phenolic compounds. In all studied olive oil samples, secoiridoids were the most abundant, followed by lignans, phenolic alcohols and flavonoids, respectively. Although there is no significant influence on the sensory scores of oils, some slight changes in sensorial profiles were noted: slightly higher intensities of sensory characteristics that are pungent, fruity and bitter in chemlali olive oil from Hammamet and Gafsa.
Changes occurring in refined olive pomace oil (ROPO) blended with refined palm oil (RPO) during r... more Changes occurring in refined olive pomace oil (ROPO) blended with refined palm oil (RPO) during repeated frying cycles were monitored. Four ratios of ROPO/RPO blends were prepared: (100:0), (75:25), (50:50) and (25:75). The effect of deep-frying was studied by assessing the changes in iodine value, acid value, color value and fatty acids composition. The results show that the mixture ROPO/RPO (25:75) is the most stable compared with other blends. The fate of 3-MCPD and glycidyl esters during deep-frying was investigated showing no endogenous formation of the esters during 16 h of deep-frying.
The aim of the present research is to evaluate the chemical characterization of main compounds fr... more The aim of the present research is to evaluate the chemical characterization of main compounds from Tunisian monocultivar Extra virgin olive oil (EVOO) (‘Chemlali’, ‘Chétoui’, ‘Zalmati’ and ‘crossbreeding Chemlali by Zalmati’) extracted after the addition of different amounts (0% and 3%) of olive leaves. As expected for virgin olive oil, the main sterols found in all analyzed samples were β-sitosterol, ∆-5-avenasterol, campesterol and cholesterol. Stigmasterol, 24-methylene-cholesterol, clerosterol, campestanol, sitostanol, ∆-7-stigmastenol, ∆-5,24-stigmastadienol, and ∆-7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds were significantly affected by the cultivars but not to be affected by added leaves at 3% to olives prior to the extraction process. The obtained results revealed that 14 phenolic compounds belonging to different phenolic types were characterized and quantified by an effective HPLC-DAD-ESI-MS/MS method. In all the studied olive-oil samples, dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), oleuropein aglycon (3,4-DHPEA-EA), and ligstroside aglycon (p-HPEA-EA) were the most abundant compounds. In addition, EVOO from ‘Chétoui’ cultivar extracted with 3% of olive leaves presented the highest amount of individual phenolic compounds.
The oil extracted from olive paste is a turbid and opalescent juice which contains impurities tha... more The oil extracted from olive paste is a turbid and opalescent juice which contains impurities that can affect its quality. Before olive oil packaging, filtration has recently become a standard processing procedure in order to obtain more brilliant extra-virgin olive oil (EVOO), maintain its quality, and extend its shelf life. In this research work, changes occurring in the concentrations of some minor compounds during industrial filtration of Chemlali EVOO were studied. The chemical parameters with sensorial quality were also determined. After the filtration of oil, a slight increase in quality parameters was noticed, along with a slight influence on the sensory scores. The adopted filtration system reduces the moisture contents. However, non-filtered olive oil might be more stable. Nevertheless, the behavior of phenolic compounds during filtration differed for each family. Indeed, the secoiridoids are the most affected phenolic compounds during EVOO filtration. Their concentrations increase significantly (p < 0.05) except the decarboxylated ligstroside aglycon decreases during this process.
Practical applications: This work clearly demonstrates the usefulness of filtration process in the Chemlali EVOO treatment. After industrial-scale filtration process, the analysis of individual concentration of phenolic compounds indicated that the concentrations of secoiridoids increased significantly (p < 0.05) mainly 3,4-DHPEA-EA. Besides, olive oil brilliance is achieved by eliminating vegetable water and suspended particles; thus extending final product shelf life.
The aim of this study was to investigate the effect of the refined palm oil addition (20%) on the... more The aim of this study was to investigate the effect of the refined palm oil addition (20%) on the fatty acid and sterol compositions of refined olive oil or refined soya bean oil and also to investigate the formation of total polar compounds and volatile compounds in these oil blends during fifty successive deep-frying sessions of potato fries at 180 °C. The blend of refined olive oil and refined palm oil exhibited a higher chemical stability during the frying process than that of refined soya bean oil and refined palm oil. Indeed, the total polar compounds and volatile compounds formed, especially 2,4-decadienal, were found to be relatively increased in the refined soya bean oil/refined palm oil blend reaching 36.50% and 46.70%, respectively, after fifty deep-frying sessions. Moreover, the degradation of linoleic acid and β-sitosterol was significantly (P < 0.05) observed for the refined soya bean oil/refined palm oil blend. The results have proven that the proper blending of monounsaturated refined olive oil with refined palm oil increases its stability and hence improves the quality of such olive oil during frying process.
Refined oils including corn, sunflower, soybean, and palm oils as well as low-quality olive oil s... more Refined oils including corn, sunflower, soybean, and palm oils as well as low-quality olive oil such as refined lampante and pomace olive oils are commonly used for extra-virgin olive oil (EVOO) adulteration. Indeed, K 270 could be used as a parameter for the detection of EVOO fraud for each type of the studied refined oils, 10 % olive, 4 % pomace olive, 10 % palm, 5 % corn, and 2 % soybean oils. Moreover, the adulteration could also be detected by the increase of the trans fatty acid contents with 10 % pomace olive, 3 % soybean, 3 % sunflower, 2 % corn, and 10 % palm oils. Actually, stigmasta-3,5-diene content is one of the most effective means of detecting refined oils in EVOO at low levels: 2 % olive, 0.4 % pomace olive, 1 % palm, 0.2 % soybean, 0.5 % sunflower, and 0.1 % corn oils. Finally, the application of linear discriminant analysis could represent an alternative and innovative tool for faster and cheaper evaluation of EVOO adulteration.
Frying performance of blends of a monounsaturated oil like refined olive oil (ROO) or a polyunsat... more Frying performance of blends of a monounsaturated oil like refined olive oil (ROO) or a polyunsaturated oil such as refined soybean oil (RSO) with a refined oil rich in saturated fatty acids like refined palm oil (RPO) was investigated by assessing their chemical changes during 50 successive deep-frying sessions of potato fries at 180°C. The blends were prepared in the volume ratio of 80:20 (ROO:RPO and RSO:RPO). Indeed, the chemical properties of the frying oil blends were significantly (p<0.05) influenced by type and concentration of oil compounds. The ROO/RPO blend exhibited the highest chemical stability during the frying process and the RSO/RPO blend showed the lowest stability. In fact, 25% of total polar compounds were exceeded after 40 successive deep-frying sessions for the ROO/RPO blend, whereas after 30 sessions for the RSO/RPO blend. Finally, ROO/RPO blend revealed better frying performance than that of RSO/RPO, as confirmed by both statistical analyses such as principal component analysis (PCA) and repeated measures analysis of variance (ANOVA).
Practical Applications: The use of the newly-proposed product which characterized by a strong thermo-oxidative stability during repeated deep-frying like refined olive oil (ROO) / refined palm oil (RPO) blend, is a promising possibility. It is hoped that the data obtained from this research study may facilitate food manufacturers to decide on the suitable oils for their frying operations.
Refined olive, corn, soybean, and sunflower oils were used as cooking oils for deep-frying at two... more Refined olive, corn, soybean, and sunflower oils were used as cooking oils for deep-frying at two different temperatures, 160 and 190 °C, and for pan-frying of potatoes at 180 °C for 10 successive sessions under the usual domestic practice. Several chemical parameters were assayed during frying operations to evaluate the status of the frying oils. Refined olive oil, as frying oil, was found to be more stable than the refined seed oils. In fact, this oil has proven the greatest resistance to oxidative deterioration, and its trans-fatty acid contents and percentages of total polar compounds were found to be lower at 160 °C during deep-frying. Finally, chemometric analysis has demonstrated that the lowest deterioration of the quality of all refined oils occurred in the refined olive oil during deep-frying at 160 °C and the highest deterioration occurred in the refined sunflower oil during pan-frying at 180 °C.
The present paper accounts for the study of the storage of Chemlali olive fruits at two condition... more The present paper accounts for the study of the storage of Chemlali olive fruits at two conditions of limited aerobiosis: in closed plastic bags and in open perforated plastic boxes for different periods before oil extraction. The ultimate objective is to investigate the effect of the container type of the postharvest fruit storage on the deterioration of the olive oil quality. The results have shown that the oil quality of Chemlali olives deteriorated more rapidly during fruit storage in closed plastic bags than in perforated plastic boxes. Therefore, the use of perforated plastic boxes is recommended for keeping the olives for longer periods of storage. The repeated measures analysis of variance of all parameters analyzed indicated that the olive oil quality is mainly affected by the olives storage conditions (containers type and storage periods). Finally, blends of extra-virgin olive oil and mildly deodorized low-quality olive oils can be detected by their alkyl esters concentrations.
Fatty acids composition as an indicator of purity suggests that linolenic acid content could be u... more Fatty acids composition as an indicator of purity suggests that linolenic acid content could be used as a parameter for the detection of extra/virgin olive oil fraud with 5% of soybean oil. The adulteration could also be detected by the increase of the trans-fatty acid contents with 3% of soybean oil, 2% of corn oil and 4% of sunflower oil. The use of the ΔECN42 proved to be effective in the Chemlali extra-virgin olive oil adulteration even at low levels: 1% of sunflower oil, 3% of soybean oil and 3% of corn oil. The sterols profile is almost decisive in clarifying the adulteration of olive oils with other cheaper ones: 1% of sunflower oil could be detected by the increase of Δ7-stigmastenol and 4% of corn oil by the increase of campesterol. Linear discriminant analysis could represent a powerful tool for faster and cheaper evaluation of extra-virgin olive oil adulteration.
Refined olive and refined soybean oils (RSO) have been analyzed in order to evaluate their physic... more Refined olive and refined soybean oils (RSO) have been analyzed in order to evaluate their physicochemical behavior during potatoes pan-frying. These refined oils exhibit significant variations in the physicochemical parameters when heated. A significant decrease (p<0.001) was practically observed in all analytical determination values except the induction time which showed a significant increase (p<0.001) with the enrichment with hydrolyzate olive leaf hydroxytyrosol-rich extract at 500 ppm during pan-frying. In fact, such enrichment has shown a remarkable resistance to oxidative deterioration, and the formation of trans-fatty acids (TFA) was found to be lower in the enriched refined oil samples during pan-frying. Such results have proven that not only is hydroxytyrosol-rich extract excellent antioxidant enrichment for refined olive and RSOs during pan-frying, but also it can be useful as substitute for synthetic ones. This study has shown that enriching refined oils with easily-found and cheap natural plant extracts could extend their usage life. Practical applications: The results of this research study have shown that refined pan-frying oils can successfully be enriched with hydrolyzate olive leaf hydroxytyrosol-rich extract at 500 ppm in order to enhance thermo-oxidative stability and reduce significantly the formation of trans-fatty acids. The hydrolyzate extract was found to be very suitable for this purpose. These materials are common agro-food by-products and can be produced very easily at a low cost. Besides, this type of enrichment may enable consumers to get some beneficial phenolic compounds through fried food consumption. In addition, these types of applications may open another area for marketing the named extract of natural origin.
This study is undertaken to determine the storage stability of Chemlali extra-virgin olive oil (E... more This study is undertaken to determine the storage stability of Chemlali extra-virgin olive oil (EVOO) in different containers such as clear and dark glass bottles, polyethylene (PE) and tin containers. The different oil samples were stored under light at room temperature. Quality parameters monitored during a 6-month-storage period included: acidity, peroxide value (PV), spectrophotometric indices (K232 and K270), chlorophyll and carotene pigments, fatty acids and sterol compositions, total phenols, Rancimat induction time as well as sensory evaluation. Tin containers and dark glass bottles recorded the lowest oxidation values. In addition, oil packed in tin containers and dark glass bottles showed better physicochemical and organoleptic characteristics than that stored in clear glass bottles and PE containers. A significant decrease (p < 0.05) in the antioxidant contents (carotenes, chlorophylls and total phenols) was observed in the oil stored in the clear glass bottles and PE containers. Such results proved that the storage of oil in tin containers and dark glass bottles appeared most adequate, and showed a gradual loss of quality during storage, especially in PE containers and clear glass bottles. This study has shown that the best packaging materials for the commercial packing of Chemlali extra-virgin olive oil are tin containers and dark glass bottles.
The analysis of the effect of cultivar and olive leaves addition before the extraction on the dif... more The analysis of the effect of cultivar and olive leaves addition before the extraction on the different analytical values revealed significant differences (p < 0.05) in some parameters, mainly in peroxide value, phenols and tocopherol contents, and oxidative stability. Aroma profiles were also influenced by the different varieties and the addition of different amounts (0% and 3%) of olive leaves. Twenty-three compounds were characterized, representing 86.1−99.2% of the total volatiles. Chétoui cultivar has the highest amount of (E)-2-hexenal, followed by Chemlali cultivar, whereas (E)-2-hexen-1-ol was the major constituent of Zalmati and crossbreeding Chemlali by Zalmati cultivars. Sensory analysis showed that Chemlali and Chétoui Zarzis possessed a high fruity, bitter, and pungent taste, whereas the Zalmati and crossbreeding Chemlali by Zalmati had a ‘green’ taste among its attributes. Indeed, the taste panel found an improvement of the oil quality when an amount of olive leaves (3%) added to the olives fruits.
The present work has been carried out to ascertain the influence of different processing systems ... more The present work has been carried out to ascertain the influence of different processing systems employed in olive process on the chemical composition, quality and stability of three Chemlali olive oils. Among these oils, two were classified as extra-virgin olive oils and the third named repassed olive oil was classified as an ordinary virgin olive oil. The analysis of the effect of the processing (two- and three-phases) on the analytical determinations values, revealed statistically significant differences (p<0.05) in some parameters, mainly in oxidative stability, antioxidant activity, total waxes, total phenols, o-diphenols and α-tocopherol contents as well as phenolic composition. The phenolic composition values were higher in the extra-virgin olive oil obtained from the two-phase system than in that obtained from the three-phase processing because it does not require the addition of water to the olive paste. Nevertheless, they were lower in the ordinary virgin olive oil (repassed olive oil) which was obtained by introducing hot water to the wet residues into the centrifugation processing at two-phases, than those in the extra-virgin olive oils obtained from the two- and three-phase processing.
The present work aims at the characterizing chemlali extra-virgin olive oils from different locat... more The present work aims at the characterizing chemlali extra-virgin olive oils from different locations in northern, central and southern Tunisia in terms of their quality indices, fatty acids, sterol content, phenolic composition and sensory profiles to show the classification of oil samples according to the geographical area. The majority of the analytical parameters have presented statistically significant differences (p < 0.05). The main sterols found in all chemlali olive oils were β-sitosterol, ∆-5-avenasterol, campesterol and stigmasterol. The phenolic compounds present in five olive oil samples were analysed by high-performance liquid chromatography (HPLC) method, thus identifying 16 phenolic compounds belonging to different phenolic types. The results have shown no qualitative differences in the phenolic fractions among extra-virgin olive oils from different geographical regions. However, the quantitative differences were observed in a wide number of phenolic compounds. In all studied olive oil samples, secoiridoids were the most abundant, followed by lignans, phenolic alcohols and flavonoids, respectively. Although there is no significant influence on the sensory scores of oils, some slight changes in sensorial profiles were noted: slightly higher intensities of sensory characteristics that are pungent, fruity and bitter in chemlali olive oil from Hammamet and Gafsa.
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Practical applications: This work clearly demonstrates the usefulness of filtration process in the Chemlali EVOO treatment. After industrial-scale filtration process, the analysis of individual concentration of phenolic compounds indicated that the concentrations of secoiridoids increased significantly (p < 0.05) mainly 3,4-DHPEA-EA. Besides, olive oil brilliance is achieved by eliminating vegetable water and suspended particles; thus extending final product shelf life.
Practical Applications: The use of the newly-proposed product which characterized by a strong thermo-oxidative stability during repeated deep-frying like refined olive oil (ROO) / refined palm oil (RPO) blend, is a promising possibility. It is hoped that the data obtained from this research study may facilitate food manufacturers to decide on the suitable oils for their frying operations.
Practical applications: This work clearly demonstrates the usefulness of filtration process in the Chemlali EVOO treatment. After industrial-scale filtration process, the analysis of individual concentration of phenolic compounds indicated that the concentrations of secoiridoids increased significantly (p < 0.05) mainly 3,4-DHPEA-EA. Besides, olive oil brilliance is achieved by eliminating vegetable water and suspended particles; thus extending final product shelf life.
Practical Applications: The use of the newly-proposed product which characterized by a strong thermo-oxidative stability during repeated deep-frying like refined olive oil (ROO) / refined palm oil (RPO) blend, is a promising possibility. It is hoped that the data obtained from this research study may facilitate food manufacturers to decide on the suitable oils for their frying operations.