Range of methods used today

The methods of analysis for fatty acids (AOCS, 1990) are now one of the most frequent methods used in the analysis of fats. Further to total fatty acid determinations, it became possible, after reaction with pancreatic lipase, to determine the average fatty acid composition at the 2-position of a fat (Christie, 1986) and thus detect inter-esterification. This previously could only be detected 

It was not only fatty acids that could be analysed by GC. Triglycerides were also found to be separable, at least with respect to molecular weight. Thus triglycerides could be separated by carbon number. Later developments produced columns which also separated unsaturated triglycerides, but problems with recoveries of the more unsaturated components mean that it is only carbon number separation that is suitable for authentication purposes. The main uses of this procedure are for cocoa butters and milk fats. 

GC of sterols was also found to be a very useful technique. This could be carried out either on the sterol core or on the sterol ester. Oils can contain both but, for historical reasons, and because it is a simpler procedure, the pattern and level of the sterols themselves, rather than the esters, is the more commonly used technique. Because of this there is far more data available for ranges in oils for the former (Codex Alimentarius, 1997 AOCS, 1997 Gutfinger and Letan, 1974 Itoh et al, 1973 Rossell, 1991) than the latter. It is possible that differences between free sterols and sterol esters will become useful in checking adulteration (Youk et al., 1999). 

Three other GC analyses now used in authentication, largely for olive and other oils which should not be refined or solvent extracted, are the determination of waxes, aliphatic alcohols, triterpene alcohols (uvaol and erythrodiol), and stigmastadiene and other sterol-dehydration products (EEC, 1991). These analyses are used at present not to detect adulteration with other oils, but with solvent-extracted or refined oils. However, it is possible that, with solvent-extracted oils, wax, aliphatic alcohol and terpene alcohol compositions, could prove useful in differentiating or detecting different oils. 

With its development, HPLC was found to be useful in many authenticity determinations, either for the same or different components to those detected by GC. Triglycerides were the most immediate application. With the exception of milk fat, now that the major components of commercial fats can be completely separated by HPLC, the patterns of components can be analysed to detect adulteration. Cocoa butter adulteration with palm fractions can be detected by the presence of excess monounsaturated and diunsaturated components from the palm fraction, while more sophisticated products may be detected by measuring dipalmitoyl-monooleoyl glycerol (POP), palmitoyl-oleoyl-stearoyl glycerol (POS) and distearoyl-monooleoyl glycerol (SOS) components. In other oils, apart from the pattern of components, the presence of any significant level of 

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