ABSTRACT
Almost all foods contain “fat,” which is very loosely de ned as material that is soluble in any of several organic solvents such as hexane, diethyl ether, or chloroform. The major lipid classes commonly encountered in foods are shown in Figure 3.1. For this discussion, pigments, sterols, hydrocarbons, tocopherols, waxes, and so on will be ignored, although they are coextracted along with the major classes of lipids. The distinguishing feature of lipids in foods is the universal occurrence of medium-and long-chain (C14-C22) fatty acids. The hydrocarbon chains of these fatty acids are the main factor in the solubility already mentioned. As emphasized by the adjectives, the nomenclature is rather confused. Most nutritionists distinguish the C8, C10, and C12 fatty acids from the common C16 and C18 fatty acids by calling the former “short chain” and the latter “long chain.” The former are readily digested, and on absorption they pass directly to the liver via the portal vein, whereas the latter tend to transfer into the lymph in chylomicrons (Nelson and Ackman, 1988). For most foods, C22 fatty acids are the longest chain length present in any quantity, and in this chapter, “long chain” will mean C20 and C22.
