Ácidos aldehídicos en aceites de fritura: formación, significado toxicológico y análisis

Aldehydic acids are generated in oxidized lipids as a result of decomposition of hydroperoxides by (β-scission reactions. Aldehydes are known to interact with proteins and DNA and to impair enzymatic functions. Aldehydic esters from oxidized lipids were reabsorbed to a significant extent in rats. This paper reviews the mechanism of formation of esterified aldehydic acids in frying oils and their physiological/toxicological effects. The paper also gives an overview of relevant basic analytical techniques that needs to be improved to establish reliable quantitative method (s).Ácidos aldehídicos son producidos en lípidos oxidados como resultado de la descomposición de hidroperóxidos por reacciones de (β-escición. Es conocido que los aldehídos interaccionan con las proteínas y el ADN y debilitan las funciones enzimáticas. Los esteres aldehídicos de lípidos oxidados fueron reabsorbidos en una cantidad significativa en ratas. Este artículo revisa los mecanismos de formación de ácidos aldehídicos esterificados en aceites de fritura y sus efectos fisiológicos/toxicológicos. El artículo también ofrece una visión de conjunto de las técnicas analíticas básicas que necesitan ser mejoradas para establecer métodos cuantitativos fiables

Sterols and sterol oxides in the potato products, and sterols in the vegetable oils used for industrial frying operations

The objective of this study was to determine the composition of sterols in vegetable oils used in industrial frying operations, and sterols and sterol oxides in the fried potato products. The sterols and sterol oxides were enriched by saponification of oils and by solid phase extraction. Preparative thin layer chromatography, capillary gas chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy, were used to give qualitative and quantitative data. The results revealed that the content of desmethylsterols in palm oil, sunflower oil, high oleic sunflower oil, and rapeseed oil/palm oil blend were, 790, 4501, 3550, and 4497 ppm, respectively. Sitosterol was the major desmethylsterol in all samples. Palm oil also contained the lowest levels of total unsaponifiables. The sterols and unsaponifiable contents in sunflower oil were, to some extent, higher than in higholeic sunflower oil. The compositions of sterols after two days of frying were neither markedly different in the oils nor in the potato products fried in these oils compared with the original oils. Isomerised sterols were tentatively quantified to account for 10 ppm, 50 ppm and 20 ppm, in rapeseed oil/palm oil blend, sunflower oil, and high-oleic sunflower oils, respectively. Lipids extracted from French fries prepared in rapeseed oil/palm oil blend contained the highest levels of total sterol oxides, 191 ppm, and epoxides of both sitosterol and campesterol were the major contributors, together at a level of 172 ppm. On the other hand, lipids extracted from French fries prepared in sunflower oil and high-oleic sunflower oil contained 7α-hydroxy-, 7β-hydroxy-, 7-keto- and both epimers of epoxysitosterol, generally in equal amounts. All samples also contained small amounts of different oxidation products of campesterol and stigmasterol

Characterisation of aldehydic acids in used and unused frying oils

Aldehydic acids, expected to be present in auto-oxidised lipids as a result of decomposition of hydroperoxides by β-scission reactions, were analysed in unused and in frying oils used for two days. The oils studied were partially hydrogenated rapeseed/palm oil mixture, conventional sunflower oil and high oleic acid sunflower oil. The method involved saponification of lipids, elimination of the unsaponifiable matter, transmethylation and further fractionation of the methyl esters into polar and non-polar fractions by silica column chromatography. Both fractions were analysed by high-performance size-exclusion chromatography to determine the levels of non-polar dimers, polar dimers and oxidised monomers. The polar fraction was also analysed by gas chromatography and gas chromatography–mass spectrometry. Using this approach, the aldehydic acid methyl esters: methyl 8-oxooctanoate, methyl 9-oxononoate, methyl 10-oxo-8-decenoate, methyl 11-oxo-9-undecenoate and methyl 12-oxo-9-dodecenoate were characterised in used as well as unused frying oils.This work was supported by Swedish National Board for Industrial and Technical Development (NUTEK, grant No. 5521-92-94718) as a part of an EU project (AIRI-CT92-0687).Peer reviewe