Triacylglycerol compositions

In another experiment we might be interested in the monthly evolution of some constituents present in the olive oil. Therefore, we decide to measure the total amount of free fatty acids and the triacylglycerol composition in a set of olive oil... 

Mayer, B. X., Reiter, C., and Bereuter, T. L. (1997). Investigation of the triacylglycerol composition of iceman s mummified tissue by high-temperature gas chromatography. /. Chromatogr. B 692, 1-6. 

The Padley and Timms (1980) method has been the subject of a collaborative trial which showed the method to be suitable for use by competent laboratories for the analysis of fats that did not contain added milk fat, hazelnut oil or the CBE Calvettta , which has a rather different triacylglycerol composition to other CBEs (FSA, 2001). 

In the analysis of sterols and other components of CBAs, in particular the minor components it must be borne in mind that it is selected fractions of the parent fats obtained by crystallization that are used in confectionery and are potential adulterants. These fat fractions are produced with a view to obtaining desired physical properties, which depend on the triacylglycerol composition, and while they do contain measurable levels of some minor components of varying polarity their composition is likely to vary significantly from that of the parent fat. 

Ruiz-Sala et al. (1996) compared the triacylglycerol composition of the milkfat of sheep, cow and goat by HPLC, using ELSD detection. They... 

Physical modification of milk fat by fractionating milk fat or by blending milk fat or milk fat fractions with other oils and fats results in products with an altered triacylglycerol composition, but one in which the fatty acids in milk fat maintain their original position in the triacylglycerol molecules (Kaylegian, 1999). 

The fractions obtained by supercritical CO2 extraction are different from those by dry fractionation. There are differences in the fatty acid and triacylglycerol compositions and melting profiles (Table 8.1). As the characteristics of the fractions depend on the conditions of the processes and the number of fractions obtained, any comparison between fractions should take into account not only the type of processes employed but also the specific process conditions. 

From the 50% solid fat line in the isosolid diagram of physical blends of milk fat and beef tallow, it was evident that there were eutectic and compound interactions but these were absent in interesterified blends with a more complex triacylglycerol composition (Timms, 1979). 

The possibility of CB fractionation with supercritical carbon dioxide (SC-C02) has not yet been fully explored. Coenen Kriegel [7] claimed that fats can be fractionated using SC-C02 without giving examples. Rossi et al. [8] only observed minor changes in the triacylglycerol compositions of fats extracted from cocoa nibs and shells as a function of time, temperature and pressure. A real fractionation of the fat, however, was not achieved. 

Only oils that are rich in one fatty acid contain much monoacid triacylglycerol, for example, olive (Table 5), sunflower, and linseed oils containing OOO, LLL, and LnLnLn, respectively. Compilations of the triacylglycerol composition of commodity and other oils are available (8, 9). 

TABLE 5. Contrasting Triacylglycerol Composition of Some Commodity Oils [Molecular Species (wt%)]. 

Acidolysis. This reaction can be acid or enzyme catalyzed and may be used to modify triacylglycerol composition. Acidolysis of an oil containing only Cis and Cjg fatty acids with fatty acids rich in lauric acid (e.g., from palm-kemel oil) results in a triacylglycerol enriched in medium-chain fatty acids. 

Figure 8. Operational phase diagram for high-melting components of milk fat dissolved in low-melting components of milk fat based on triacylglycerol composition (acyl carbon number) (4).

There follows a brief account of the commodity oils. This includes the nature of the oil and any special features, its production levels, and major areas of production. Most of these oils are discussed in greater detail elsewhere in this series and in Gunstone (1). Triacylglycerol composition is indicated by three-letter symbols that include all of the isomeric triacylglycerols containing the acids designated where P = palmitic, St = stearic, S = saturated, O = oleic, L = linoleic, and Ln = linolenic. 

Rice bran oil is reported to lower serum cholesterol by reducing LDL and VLDL without changing the level of HDL. This effect seems not to be related to fatty acid or triacylglycerol composition but to the unsaponifiable fraction and probably to the oryzanols (1.5-2.0% of the oil). These can be isolated in concentrated form from rice bran oil soapstock but have not yet been accepted for food use (46-51). 

Almond Prunus dulcis, P. amygdalis, Amygdalis communis). Almond oil is generally considered as an oleic-rich oil (65-70%), but its fatty acid composition can vary widely. The triacylglycerol composition of the oil has also been reported. Low-saturated, high-monounsamrated oils show high oxidative and cold weather stability (i.e., they are slow to deposit crystals) (65, 66). 

Pistachio (Pistachio vera). Pistachio nuts, produced mainly in Iran, are widely consumed as shelled nuts. They contain about 60% of an oil that may be used for cooking and frying. Mean fatty acid values for hve varieties are given as palmitic (10%), stearic (3%), oleic (69%), and linoleic (17%). Triacylglycerol composition has been suggested as a method of determining the country of origin of pistachio nuts (161-163). 

Natural oils and fractionated oils usually have their acyl chains organized in a nonrandom manner, but they become randomized after interesterification with a chemical catalyst. There is no change in fatty acid composition, only in triacylglycerol composition, but this leads to a modification of the physical properties. More selective interesterification can be achieved with enzymic catalysts (Section 8.5). 

TABLE 6. Acyl and Triacylglycerol Composition in mol% of Soybean Oils Having a Wide Range of Fatty Acyl Compositions (48, 49). 

Figure 6. Triacylglycerol composition of reguiar sunflower oil as calculated from random distribution and experimentally determined (17). (Key Sat = saturated acid, 0= oleic acid, L = linoleic acid.)...

TABLE 10. Fatty Acid and Triacylglycerol Composition (%) of Reguiar Sunfiower Oii and of High-Oieic Sunfiower Oii [based on (25)]. 

The fatty acid composition, various analytical constants, and triacylglycerol composition of different cocoa butters are presented in Tables 1-3, respectively. These results show that Malaysian cocoa butter contains the highest levels of mono-unsaturated triacylglycerols. The Brazihan cocoa butter contains the lowest levels of monounsaturated triacylglycerols and the highest levels of other unsaturated triacylglycerols. The cocoa butters from India and Sri Lanka are close to Malaysian cocoa butter in terms of hardness and triacylglycerol composition. 

There is a good correlation between the triacylglycerol composition and solid fat content of these cocoa butters. Malaysian, Sri Lankan, and Indian cocoa butters are the hardest, and Brazilian is the softest, whereas others lie in between. The quality of the Brazilian cocoa butter can be unproved by mixing it with Malaysian cocoa butter, which will result in higher solid fat content at various temperatures. 

This category offers a range of confectionery fats with different levels of physical properties, but all having triacylglycerol compositions that make them incompatible with cocoa butter i.e. they are aU used in formulations with cocoa powder, mainly for compound coating. 

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