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LIPIDS

Lipids encompass a diverse group of organic compounds defined by solubility, with fats and oils formed by glycerol and fatty acids. Fatty acids are saturated or unsaturated, impacting the physical properties of lipids. Learn about essential fatty acids, oxidation sensitivity, rancidity factors, and the determination of acid value. Understand the importance of lipid quality assessment through acid value calculations.

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LIPIDS

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  1. LIPIDS

  2. LIPIDS • The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in non-polar organic solvents (e.g. ether, chloroform, acetone & benzene) and general insolubility in water. • Lipids are defined by their physical behavior rather than by their chemical structures. As a result there is great structural variety among the lipid class.

  3. LIPIDS • Fats and oils are made fromtwo kinds of molecules:glycerol(a type of alcohol with a hydroxyl group on each of its three carbons) and three fatty acids joined by dehydration synthesis. Since there are three fatty acids attached, these are known as triglycerides.

  4. LIPIDS • The main distinction between fats and oils is whether they’re solid or liquid at room temperature, and this is based on differences in the structures of the fatty acids they contain.

  5. The main functions of lipids include: 1- Source of energy. 2- Some fat soluble vitamins have regulatory or coenzyme functions. 3- Structural functions (cell membrane).

  6. 1. Fatty Acids (FA): • The “tail” of a fatty acid is a long hydrocarbon chain, making it hydrophobic. • The “head” of the molecule is a carboxyl group which is hydrophilic. These long-chain carboxylic acids are generally referred to by their common names, which in most cases reflect their sources. Natural fatty acids may be saturated or unsaturated.

  7. 1. Fatty Acids (FA): • The terms saturated,mono-unsaturated, and poly-unsaturated refer to the number of hydrogen atoms attached to the hydrocarbon tails of the fatty acids as compared to the number of double bonds between carbon atoms in the tail.

  8. 1. Fatty Acids (FA): • Fats, which are mostly from animal sources, have all single bonds between the carbons in their fatty acid tails, thus all the carbons are also bonded to the maximum number of hydrogen atoms possible.

  9. 1. Fatty Acids (FA): • Since the fatty acids in these triglycerides contain the maximum possible amount of hydrogen atoms, these would be called saturated fats. The hydrocarbon chains in these fatty acids are, thus, fairly straight and can pack closely together, making these fats solid at room temperature.

  10. 1. Fatty Acids (FA): • Oils, mostly from plant sources, have some double bonds between some of the carbons in the hydrocarbon tail, causing bends or “kinks” in the shape of the molecules.

  11. 1. Fatty Acids (FA): • Because some of the carbons share double bonds, they’re not bonded to as many hydrogen atoms as they could if they weren’t double bonded to each other. Therefore these oils are called unsaturated fats. • Because of the kinks in the hydrocarbon tails, unsaturated fats can’t pack as closely together, making them liquid at room temperature.

  12. Essential Fatty Acids: • Are those that the body can not synthesize them and therefore must be supplied in the diet. • Two of FAs are essential in humans: - Linoleic acid - Linolenic acid.

  13. DETERMINATION OF ACID VALUE

  14. Sensitivity of Fats to Oxidation (Rancidity): • Saturated FAs are relatively resistant to oxidation outside the body. • Unsaturated FAs are slowly but spontaneously oxidize in the presence of air.

  15. Rancidity: • Oxidative cleavage of the double bonds in unsaturated FA and peroxide formation which results in unpleasant taste and smell. • It produces aldehyde and carboxylic acids of shorter length.

  16. Rancidity: • Rancidity is caused by: 1. Atmospheric air. 2. Hydrolysis by microorganisms.

  17. Rancidity: • The amount of free fatty acids present therefore gives an indication of the: 1- Age. 2- Quality of oil.

  18. Rancidity: • Acid Value: Is the number of mg KOH required to neutralize the free fatty acids present in 1g of fat.

  19. Method: • Weigh out 2g of the test compound (fresh and rancid). • Suspend the melted fat in about 10ml of fat solvent. • Add 2 drops of ph.ph. (Indicator). • Mix well. • Titer with 0.1M KOH. • End point: faint pink color persists 20-30s • Record the volume of KOH required.

  20. 0.1M KOH Phenolphthalein (Ph.ph) 10 ml fat solvent 2g of the test compound (fresh or rancid). Mix Well

  21. Calculations: 1M KOH 1L contains 56 g/ L of fat 0.1M KOH 1L contains 5.6 mg/ ml of fat So: 5.6 mg 1ml ? mg titer No. 5.6 × titer No. = Y (No. of mg of KOH) Y 2g of fat ? 1g of fat Y × 1 = No of mg of KOH 2 that required to neutralize 1g of fat (i.e. acid value).

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