Storage Lipids:- Many Foods Contain Triacylglycerols

Most natural fats, such as those in vegetable oils, dairy products, and animal fat, are complex mixtures of simple and mixed triacylglycerols. These contain a variety of fatty acids differing in chain length and degree of saturation (Fig. 10–4). Vegetable oils such as corn (maize) and olive oil are composed largely of triacylglycerols with unsaturated fatty acids and thus are liquids at room temperature. They are converted industrially into solid fats by catalytic hydrogenation, which reduces some of their double bonds to single bonds and converts others to trans double bonds. Triacylglycerols containing only saturated fatty acids, such as tristearin, the major component of beef fat, are white, greasy solids at room temperature. When lipid-rich foods are exposed too long to the oxygen in air, they may spoil and become rancid. The unpleasant taste and smell associated with rancidity result from the oxidative cleavage of the double bonds in  unsaturated fatty acids, which produces aldehydes and carboxylic acids of shorter chain length and therefore higher volatility.

FIGURE 10–4 Fatty acid composition of three food fats. Olive oil, butter, and beef fat consist of mixtures of triacylglycerols, differing in their fatty acid composition. The melting points of these fats—and hence their physical state at room temperature (25C)—are a direct function of their fatty acid composition. Olive oil has a high proportion of long-chain (C₁₆ and C₁₈) unsaturated fatty acids, which accounts for its liquid state at 25C. The higher proportion of long-chain (C₁₆ and C₁₈) saturated fatty acids in butter increases its melting point, so butter is a soft solid at room temperature. Beef fat, with an even higher proportion of long-chain saturated fatty acids, is a hard solid.

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مواضيع ذات صلة

Structural Lipids in Membranes:- Chloroplasts Contain Galactolipids and Sulfolipids

Structural Lipids in Membranes:- Some Phospholipids Have Ether-Linked Fatty Acids

Structural Lipids in Membranes:- Glycerophospholipids Are Derivatives of Phosphatidic Acid

Storage Lipids:- Triacylglycerols Provide Stored Energy and Insulation

Storage Lipids:- Triacylglycerols Are Fatty Acid Esters of Glycerol

Storage Lipids:- Triacylglycerols Are Fatty Acid Esters of Glycerol

Storage Lipids:- Fatty Acids Are Hydrocarbon Derivatives

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Genome Alterations and New Products of Biotechnology:- New Technologies Promise to Expedite the Discovery of New Pharmaceuticals

Genome Alterations and New Products of Biotechnology:- Manipulation of Animal Cell Genomes Provides Information on Chromosome Structure and Gene Expression

Genome Alterations and New Products of Biotechnology:- A Bacterial Plant Parasite Aids Cloning in Plants

Storage Lipids:- Triacylglycerols Are Fatty Acid Esters of Glycerol