chapter  6
20 Pages

Extraction and Analysis of Food Lipids

Lipids are often de‘ned as a group of biomolecules that are insoluble in water and soluble in organic solvents such as hexane, diethyl ether, or chloroform. W.W. Christie, an international authority on lipids, de‘nes them as follows: “Lipids are fatty acids and their derivatives and substances related biosynthetically or functionally to these compounds.”1 Sterols, tocopherols, and carotenoids are also common components of lipid extracts. Methods for the analysis of the sterols are described in this chapter (tocopherol analysis is covered in Chapter 9 and carotenoid analysis in Chapter 10). Triacylglycerols (TAGs) (Figure 6.1a) are the main storage lipid (storing energy and carbon skeletons) in plants and animals. TAGs include fats (which are solid at 20°C) and oils (which are liquid at 20°C). In general, most fats are found in animal tissues, and most oils are found in plant tissues. Since fats and oils comprise about 40% of

6.1 Introduction: A Description of the Common Types of Lipids Found in Foods .......................................................................................................115 6.2 Methods for the Determination of the Total Fat Content in Foods .............. 119 6.3 Methods for the Extraction of Total Lipids in Foods (for Subsequent

Analysis) ....................................................................................................... 122 6.4 Methods for the Separation and Quantitative Analysis of Intact Lipid

Classes ..........................................................................................................124 6.5 Methods for the Quantitative Analysis of Fatty Acids, Trans Fatty

Acids, and Sterols via Gas Chromatography ................................................ 126 6.6 Methods for the Quantitative Analysis of the Molecular Species of

Various Common Classes of Lipids via HPLC ............................................ 129 6.7 Lipidomics-An Emerging Field of Lipid Analysis .................................... 130 6.8 Conclusion .................................................................................................... 130 References .............................................................................................................. 131

the dietary calories consumed in Western Europe and North America, an understanding of their composition is essential to the ‘eld of nutrition.1 “Crude fat” is a compositional term that includes all of the nonpolar lipids that are extractable with diethyl ether (primarily TAGs, but also other nonpolar lipids such as waxes, sterols, free fatty acids, and tocopherols).