268 OLIVE OILS AND HEALTH - trans fatty acids; trans fats; hydrogenated fats; trans (Topic covered in detail in Chapter 2)) Trans fatty acids are fatty acids that contain at least one double bond in trans configuration (or trans geometry), meaning that the hydrogen atoms adjacent to the double bond are oriented in opposite directions (see later in this chapter and Figure 1 of Chapter 2). This structural feature distinguishes trans fatty acids from physiological unsaturated fatty acids, most of which have their double bonds in cis configuration. The structure and biological activity of trans fatty acids are more similar to those of saturated fatty acids than to unsaturated ones. Partially hydrogenated oils contain large amounts of trans fatty acids, whereas fully hydrogenated oils do not, as all double bonds have been saturated. Dietary trans fatty acids come mainly (>90%) from fried foods, “fast food”, and packaged or processed products (for example, when manufacturers convert liquid oils into solid fats through partial hydrogenation), producing fats such as shortening or margarine. A small proportion (2–8%) comes from natural foods, such as dairy products and meat from ruminants. Trans fatty acids are harmful to health. · elaidic fatty acid A fatty acid with 18 carbon atoms and one trans double bond in the ω-9 position (C18H34O2; C18:1-trans ω-9). It is the trans isomer of oleic acid (C18H34O2; C18:1 cis ω-9), and one of the main trans fatty acids found in partially hydrogenated vegetable oils. · biohydrogenation; hydrogenation; hydrogenated Biohydrogenation is a natural process that occurs in ruminants and leads to the formation of trans fatty acids. This process is carried out by rumen bacteria. Consequently, fats from cattle and sheep, as well as derived products such as milk, cheese, and butter, contain between 2% and 8% trans fatty acids. Ruminant trans fatty acids differ from those produced by partial industrial hydrogenation in that they include different monounsaturated isomers derived from the original 18-carbon fatty acid involved in the biohydrogenation process. The most common trans fatty acids in the rumen and in ruminant lipids are elaidic acid (C18H34O2; C18:1—trans ω-9—) and trans-vaccenic acid (C18H34O2; C18:1—trans ω-7—) (See Figure 3 in Chapter 2) · cis configuration; cis unsaturated fats; cis · trans configuration; trans geometry; trans; trans isomers Trans and cis isomers are the same type of compound, but they differ in the spatial arrangement of the substituent groups attached to the carbon atoms of the double bond. Cis isomers have the substituent groups on the same side (B), while in trans isomers the groups are on opposite sides (A). cis A trans B Most of the natural fatty acids have a cis configuration in their double bonds. o ~OH
RkJQdWJsaXNoZXIy Njg1MjYx