Cambios producidos en la composición de aceites vegetales debido al calentamiento en microondas. Se estudia el efecto del calentamiento en horno de microondas sobre aceites de diferente composición en ácidos grasos. Aceites de girasol, soja, cacahuete y una mezcla de soja y cacahuete al 50%, se calentaron durante 2, 4, 6, 8 10, 12, 15 y 18 minutos. Los valores de índice de peróxidos, acidez libre y absorbancia a 420 nm fueron proporcionales al tiempo de calentamiento. Otras determinaciones incluyeron el contenido total en tocoferoles mediante cromatografía en capa fina, la composición en ácidos grasos y en epoxiácidos mediante cromatografía gas líquido, y la formación de dienos y trienos conjugados mediante espectrofotometría UV. Los resultados indicaron que el contenido en tocoferoles disminuyó con el tiempo de calentamiento dependiendo del tipo de tocoferol predominante y que los cambios estaban relacionados con los encontrados para el índice de peróxidos. Los ácidos poliinsaturados también decrecieron con el tiempo de calentamiento. Finalmente, los resultados obtenidos con la mezcla de aceites de soja y cacahuete fueron muy útiles para interpretar los resultados obtenidos con los aceites individuales.

The kinetics of oxirane ring cleavage in epoxidized soybean oil have been studied using glacial acetic acid at 60, 70, 80 and 90~ It was shown that the reaction can be successfully modelled as first order with respect to the epoxide concentration and second order with respect to acetic acid. The reaction velocity constant at 70~ was found to be 2 • 10 -3 1-3 hrl mol-2, the frequency factor, A, = 2.321 • 107 hr I and the energy of activation, E a = 15.84 k cal mol -l. The effects of the concentration of acetic acid and the temperature on the net yield of epoxides by in situ epoxidation were also studied on the basis of the predicted kinetic parameters of the reaction system.

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Egyptian jojoba seeds newly cultivated in Ismailia desert in Egypt promoted us to determine its lipid components. Fatty alcohols, fatty acids, wax esters and sterols patterns were determined by capillary GLC whereas, tocopherols profile, isopropenoid alcohols and sterylglycosides were determined by HPLC. The Egyptian seeds are rich in wax esters (55 %) with fatty alcohols C20:1and C22:1 as major components and amounted to 43.0 % and 45.6 % respectively followed by C24:1 and C18:1(9.6 % and 1.3 % respectively). The fatty acids profile showed that C20:1 is the major constituent (60 %) followed by C18:1and C22:1 (14.5 and 11.8 % respectively) whereas C24:1 was present at low concentration amounted to 1.6 %. In addition, the Egyptian jojoba wax contained C18:2 fatty acid at a level of 8.7 %. Wax esters composition showed that the local wax had C42 and C40 esters as major components amounted to 51.1 and 30.1 % respectively. Also, it had C44 and C38 at reasonable amounts (10.0 and 6.3 % respectively). Whereas C36 and C46 were present at lower concentrations amounted to 1.4 and 1.1 respectively. The sterols analysis showed the presence of campe-, stigma-, b-sito-, and isofuco-sterol amounting to 18.4 %, 6.9 %, 68.7 %, and 6.0 % respectively. The tocopherols pattern revealed that the local seed wax contained g-tocopherol as major constituent (79.2 %) followed by a-tocopherol (20.3 %). b-tocopherol as well as dtocopherol were found as minor constituents. The isopropenoid alcohols and the sterylglycosides (free and acylated) were not detected. The wax is proposed to be used in oleo chemistry and cosmetics.

Eight lipid patterns of Salicornia seed oil have been elucidated using HPLC as the main tool of analysis in conjunction with capillary GLC. The whole oil is rich in linoleic (66.5%) with lower amount of linolenic acid (1.4%). Of the 22 triglycerides (TG) determined, three major TG containing 3 and 2 linoleic acyls were detected by HPLC. The total tocopherols content (720 ppm) was determined directly in the oil by HPLC and it was found that alpha-T (49.1%) and gamma-T (48.2%) are predominating.<br />The whole sterol profile, as determined by GLC, includes cholesterol (1.0%), brassicasterol (1.4%), campesterol (2.4%), 5-stigmasterol (8.7%), beta-sitosterol (23.0%), spinasterol (17.0%), isofucosterol (0.8%), 7-stigmastenol (42.0%) and 7-avenasterol (3.7%). Furthermore, sterols patterns of the free (nonacylated) sterols (FS), acylated sterols (AS), free sterylglycosides (FSG) and acylated sterylglycosides (ASG) were determined by HPLC as their anthroylnitriles. FS and AS were determined as their steryl-9-anthroylnitriles (S-9-AN) whereas FSG and ASG were analysed as their sterylglycosidyl-1-anthroylnitriles (SG-1-AN) at nanogram level. <br /> Comparing Salicornia SOS-7 oil with traditional freshwater seed oils, Salicornia exhibits mostly a unique lipids constitution.<br><br>Se han dilucidado ocho perfiles lipídicos de aceite de semilla de Salicornia usando HPLC como principal herramienta de análisis junto con la CGL capilar. El aceite completo es rico en linoleico (66.5%) con bajo contenido en ácido linolénico (1.4%). De los 22 triglicéridos (TG) determinados, los tres mayoritarios que contenían 3 y 2 cadenas de linoleico se detectaron por HPLC. El contenido en tocoferoles totales (720 ppm) se determinó directamente en el aceite por HPLC y se encontró al alfa-T (49.1%) y al gamma-T (48.2%) como predominantes. El perfil de esteroles completo, determinado por CGL, incluyó colesterol (1.0%), brasicasterol (1.4%), campesterol (2.4%), 5-estigmasterol (8.7%), beta-sitosterol (23.0%), espinasterol (17.0%), isofucosterol (0.8%), 7-estigmastenol (42.0%) y 7-avenasterol (3.7%).<br /> Además, los perfiles de esteroles de los esteroles libres (sin acilar) (FS), esteroles adiados (AS), esterilglicósidos libres (FSG) y esterilglicósidos acilados (ASG) se determinaron por HPLC como sus antroilnitrilos. FS y AS se determinaron como sus esteril-9-antroilnitrilos (S-9-AN) mientras que FSG y ASG se analizaron como sus esterilglicosidil-1-antroilnitrilos (SG-1-AN) a niveles de nanogramos. <br /> Comparando el aceite de Salicornia SOS-7 con los aceites de semillas de agua dulce tradicionales, el de Salicornia mostró principalmente una constitución lipídica característica

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During chemical refining steps (neutralization, bleaching and deodorization) of crude cottonseed oil (CSO), minor and major components, namely, tocopherols, sterols and fatty acids were evaluated by HPLC and GLC. HPLC analysis of total tocopherols (T) revealed that loss in these components were 7.12, 12.28 and 18.47 % in neutralized, bleached and deodorized oil respectively. On the other side, quantitative GLC analysis of sterols (as trimethylsilyl derivative, TMS), showed that the losses were 5.6, 8.7 and 16.4 % at the different refining steps respectively. In case of the fatty acids (as methyl esters, ME), as determined by GLC analysis, it was noticed that essential fatty acids (EFA), namely, linoleic and linolenic were nearly kept constant. The total amounts of sterols and tocopherols lost in the deodorized distillates (D D) as well as their patterns were also determined. It was found that total sterols content was 28500 ppm, whereas tocopherols content was 2640 ppm. Sterenes (reference samples) were also used to follow the formation of sterenes during the chemical refining steps of CSO.

Dielectric properties (dielectric constant ~-' and dielectric loss E') were compared to conventional methods of analysis (viscosity, refractive index, iodine value, peroxide value and free fatty adds) for evaluating the frying quality of a blend of cottonseed and sunflower oils. The apparent relaxation time, T, the activation energy H and the entropy change S for dielectric relAxAtion of the heated oil samples were calculated. Results indicate that dielectric constant and dielectric loss are useful tools for predicting deterioration occurring during heating of the oil.