Unit 3 - Fats & Oils Flashcards
Structure of Fats and Oils
Edible fats and edible oils are esters formed from the condensation of glycerol (propane1,2,3-triol) and three carboxylic acid molecules.
The carboxylic acids are known as ‘fatty acids’ and can be saturated or unsaturated straight-chain carboxylic acids, usually with
long chains of carbon atoms.
Each of the OH groups in glycerol undergo condensation reactions to form an ester link with a fatty acid. The ratio of glycerol molecules to fatty acids is 1:3. The 3 fatty acids can be the same or different.
Glycerol Molecule
H
|
H-C-OH -
|
H-C-OH -
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H-C-OH -
|
H
Properties of Fats and Oils - Differences Between Fats and Oils
Fats are solid at room temperature and oils are liquids.
The main ‘chemical’ difference between fats and oils is the higher level of unsaturation in oils - oil molecules containn many more C=C double bonds than fats
Bromine Solution
Unsaturated compounds quickly decolourise bromine solution, The bromine molecules add across the carbon-carbon double bonds in an addition reaction. The greater the number of double bonds present in a substance, the more bromine solution can be decolourised,
Properties of Fats and Oils - Melting Points
Fats have a high melting point so are more saturated than oils (fewer double bonds).
Oils have a low melting point so are more unsaturated than margarine and other fats.
Properties of Fats and Oils - LDFs and MP/BP
Fat molecules containing saturated hydrocarbon chains can pack neatly together, even at high temperatures.
Hence, saturated fats have a high melting point due to increased LDFs. The double bonds in fatty acid chains prevent oil molecules from packing closely together, so the greater the number of double bonds present, the weaker the LDFs of attraction.
The weaker LDFs result in lower melting points for unsaturated fats.
Uses of Fats and Oils in the Body
Fats and oils are a concentrated source of energy. They provide more energy than carbohydrates but it is released more slowly.
Fats and oils are essential for the transport and storage of fat-soluble vitamins in the body.
