Influence of bleaching by ultrasound on fatty acids and minor compounds of olive oil. Qualitative and quantitative analysis of volatile compounds (by SPME coupled to GC/MS).
The effects of bleaching using high power ultrasound (20 kHz) on the quality of olive oil were considered in this study, in order to verify the modifications that can occur in fatty acid composition and minor compounds. During the treatment of olive oil under ultrasonic waves, a rancid odour has been detected. Treated olive oils show no significant changes in their chemical composition but the presence of some volatile compounds, due to ultrasonic treatment. Some off-flavour compounds (hexanal, hept-2-enal and 2(E),4(E)-decadienal) resulting from the sonodegradation of olive oil have been identified. A wide variety of analytical techniques (GLC, HPLC and GC/MS) were used to follow the quality of bleached olive oils with ultrasonic waves by the determination of the amounts of certain minor compounds such as sterols and tocopherols. Steradienes, resulting from the dehydration of sterols, were detected with small quantities especially in severe conditions of sonication. Solid phase micro-extraction (SPME) coupled to gas chromatography was known to be a sensitive technique to follow changes in the oxidative state of vegetable oils by measuring the amount of volatile materials produced during the refining process.
Laboratoire de chimie appliquée: Hétérocycles, Corps gras et Polymères, Faculté des Sciences de Sfax, Route Soukra Km 3.5, 3018 Sfax, Tunisia.
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Jahouach-Rabai
Laboratoire de chimie appliquée: Hétérocycles, Corps gras et Polymères, Faculté des Sciences de Sfax, Route Soukra Km 3.5, 3018 Sfax, Tunisia. Electronic address: Mah.Trabelsi@fss.rnu.tn.
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Trabelsi
Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
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Van Hoed
Laboratoire de chimie appliquée: Hétérocycles, Corps gras et Polymères, Faculté des Sciences de Sfax, Route Soukra Km 3.5, 3018 Sfax, Tunisia.
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Adams
Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
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Verhé
Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
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De Kimpe
Laboratoire de chimie appliquée: Hétérocycles, Corps gras et Polymères, Faculté des Sciences de Sfax, Route Soukra Km 3.5, 3018 Sfax, Tunisia.
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Frikha
D002851:Chromatography, High Pressure Liquid; D004602:Elements; D005227:Fatty Acids / Q000737:chemistry* / Q000528:radiation effects*; D005230:Fatty Acids, Nonesterified / Q000737:chemistry / Q000528:radiation effects; D008401:Gas Chromatography-Mass Spectrometry; D008054:Lipid Peroxides / Q000737:chemistry / Q000528:radiation effects; D000069463:Olive Oil; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000737:chemistry* / Q000528:radiation effects*; D052617:Solid Phase Microextraction; D013261:Sterols / Q000737:chemistry; D024505:Tocopherols / Q000737:chemistry / Q000528:radiation effects; D014835:Volatilization
D004602:Elements; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D008054:Lipid Peroxides; D000069463:Olive Oil; D010938:Plant Oils; D013261:Sterols; D024505:Tocopherols