Fatty acids composition determination

Calculated based on fatty acid composition determined by GC. 

In practice, even if this method is very reliable for the detection of adulterated VOOs by using other edible oils at a percentage of 2.5%, it remains expensive and time-consuming, as it demands an initial purification of the VOO samples, TAGs separation and grouping according to their equivalent carbon numbers, fatty acid composition determined by GC, and the determination of differences between the analytical results obtained by HPLC and the theoretical content, calculated starting from the fatty acid composition. 

To determine the phosphoHpid and fatty acid compositions chromatographic methods (28) like gas chromatography (gc), thin-layer chromatography (tic), and high performance Hquid chromatography (hlpc) are used. Newer methods for quantitative deterrnination of different phosphoHpid classes include P-nmr (29). 

Ethanol and choline glycerolipids were isolated from calf brain and beef heart lipids by PTLC using silica gel H plates. Pure ethanol amine and choline plasmalogens were obtained with a yield of 80% [74]. Four phosphohpid components in the purple membrane (Bacteriorhodopsin) of Halobacterium halobium were isolated and identified by PTLC. Separated phosphohpids were add-hydrolyzed and further analyzed by GC. Silica gel G pates were used to fractionate alkylglycerol according to the number of carbon atoms in the aliphatic moiety [24]. Sterol esters, wax esters, free sterols, and polar lipids in dogskin hpids were separated by PTLC. The fatty acid composition of each group was determined by GC. 

After the extraction of lipid and nonlipid components from the leaves of mandarin orange Citrus reticulata, the lipid fraction was further separated by PTLC to determine different lipid classes that affect the chemical deterrence of C. reticulata to the leaf cutting ecat Acromyrmex octopinosus. These lipids seem to be less attractive to the ants [81a]. The metabolism of palmitate in the peripheral nerves of normal and Trembler mice was studied, and the polar lipid fraction purified by PTLC was used to determine the fatty acid composition. It was found that the fatty acid composition of the polar fraction was abnormal, correlating with the decreased overall palmitate elongation and severely decreased synthesis of saturated long-chain fatty acids (in mutant nerves) [81b]. 

One way to determine the fatty acid composition of a plant oil is by the technique of high-performance liquid chromatography. This technique is a separation... 

General requirements Identification. Unhydrogenated lard exhibits the following composition profile of fatty acids, determined as directed under Fatty Acid Composition, Appendix VII ... 

Fats are solid triacylglycerols, oils are liquid triacylglycerols it is the fatty acid composition of the triacylglycerol that determines its physical properties. Triacylglycerols with a high proportion of unsaturated fatty acids have lower melting points than those rich in sam-rated fatty acids, so the former are oils - that is, they are liquid at room temperature. The unsaturated fatty acids are identified by the number of carbon atoms and the position of the double bonds (see below). 

In order to determine the fatty acid composition of the triglycerides, they have to be first hydrolysed and the liberated fatty acids converted to their methyl esters, which have a good chromatographic peak shape compared to the free acids. A convenient method for achieving hydrolysis and methylation in one step is shown in Figure 11.8. 

Fang, J.-L., Vaca, C.E., Valsta, L.M. Mutanen. M. (1996) Determination of DNA adducts of malonaldehyde in humans effects of dietary fatty acid composition. Carcinogenesis, 17, 1035-1040... 

The number of fatty acids and related compounds in milk lipids grew from 16 in 1959 (Jenness and Patton, 1959) to 142 in 1967 (Jensen et al. 1967) to over 400 in 1983. However, there are only 10 fatty acids of quantitative importance. The amounts (weight percent) as butyl esters prepared by three methods of esterification were determined by Iverson and Sheppard (1977). Because of the widely differing molecular weights of the fatty acids (4 0-18 0), fatty acid compositions of ruminant milk fats are often presented as a mole percent. The nutritionist needs the data calculated in yet another manner weight of fatty acid/100 g or 100 ml of edible portion. Analyses of food fatty acids should always be accompanied by the fat content so that the actual weights of the fatty acids and be calculated. A compilation of this type was made by Posati et al. (1975). Since these analyses were done with methyl esters, the contents of 4 0 are low. Data from Feeley et al. (1975), obtained from careful analyses, are more reliable, and USDA Handbook 8-1 (Posati and Orr 1976) has data for many milk and dairy products. 

Table 4.7. Fatty Acid Composition of Butter Oil as Determined by GLC-Mass Spectrometry (Weight Percent) of Total Methyl Esters...

ABLE 9.2 FATTY ACID COMPOSITION OF FATS AND OILS DETERMINED BY GLC1 (19)... 

Accurate determination of lipids in foods is required for nutritional labeling, certification, or for evaluation of standard of identity and uniformity, as well as examination of their effects on functional and nutritional properties of foods. Following lipid extraction and precise quantitative analysis, lipids so obtained may be used for analysis of other lipid characteristics and properties provided that nondestructive and mild extraction procedures are employed that retain the integrity of lipids. Thus, determination of lipid classes, fatty acid composition (unit du), and oxidative state of lipids (Chapter D2), amongst others, may be pursued following the extraction process. 

The fatty acid composition of the trans-free reference fat plays a critical role. If the selected trans-free fat is significantly different from the matrix of the fat investigated, it may have an adverse impact on accuracy, particularly near the official method s lowest trans level of quantitation, 5% (AOAC International, 2000) or 1% (AOCS, 1999a). This trans-free reference fat must be carefully selected and should represent as much as possible t e composition of the unknown trans fat or oil being determined. 

A nonaqueous reversed-phase high-performance liquid chromatography (NARP-HPLC) with refractive index (RI) detection was described and used for palm olein and its fractions obtained at 12.5°C for 12-24 h by Swe et al. (101). The objective of their research was to find the optimum separation for analysis of palm olein triglycerides by NARP-HPLC, and to find a correction factor to be used in calculating CN and fatty acid composition (FAC). The NARP-HPLC method used to determine the triglyceride composition was modified from the method of Dong DiCesare (88). Palm olein was melted completely at 70°C in an oven for 30 min prior to crystal-... 

The ELS detector was previously also referred to as a mass detector, pointing to the fact that the response is (mainly) determined by the mass of the sample rather than by its chemical structure. Van der Meeren et al., though, demonstrated that the ELSD calibration curves of phospholipid classes were also dependent on the fatty acid composition (52). The dependence on the fatty acid composition is, however, completely different in nature and much less pronounced than for UV detection. The reason for this behavior is to be found in the partial resolution of molecular species, even during normal-phase chromatography. Thus, the peak shape depends not only on the chromatographic system but also on the fatty acid composition and molecular species distribution of the PL sample (47). Because it was shown before, based on both theoretical considerations and practical experiments, that the ELS detector response is generally inversely proportional to peak width (62,104), it follows that the molecular species distribution of the PL standards used should be similar to the sample components to be quantified. It was shown that up to 20% error may be induced if an inappropriate standard is used (52). 

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