Classification of Lipids:

Lipids can be classified into three main categories:


  1. Simple Lipids:

    • Fats and Oils (Triglycerides): Esters of fatty acids with glycerol.
    • Waxes: Esters of fatty acids with long-chain alcohols.

  2. Compound (Complex) Lipids:

    • Phospholipids: Lipids containing a phosphate group, such as lecithins and cephalins.
    • Glycolipids: Lipids containing carbohydrates.
    • Lipoproteins: Complexes of lipids with proteins.

  3. Derived Lipids:

    • Products of hydrolysis of simple and compound lipids, such as fatty acids, glycerol, and steroids (cholesterol).

Analytical Parameters of Oils and Fats:

  1. Acid Value:

    • Measures the free fatty acid content in fats or oils.
    • Indicator of hydrolytic rancidity.
    • Expressed in milligrams of KOH required to neutralize the free fatty acids in 1g of oil.

  2. Saponification Value:

    • The number of milligrams of KOH required to saponify 1g of fat or oil.
    • Indicates the average molecular weight of fatty acids.

  3. Iodine Value:

    • Measures the degree of unsaturation in fats and oils.
    • Expressed as grams of iodine absorbed by 100g of oil.
    • Higher iodine value means more unsaturated bonds.

  4. Peroxide Value:

    • Indicates the extent of oxidation in fats and oils.
    • Expressed as milliequivalents of active oxygen per kilogram of oil.
    • Higher peroxide value indicates rancidity due to oxidation.

  5. Refractive Index:

    • Measures the degree of refraction of light in oil.
    • Varies with the degree of unsaturation and purity of the oil.

  6. Melting Point/Cloud Point:

    • The temperature at which the fat or oil solidifies.
    • Used to characterize the physical properties of oils and fats.

  7. Unsaponifiable Matter:

    • Substances in the fat or oil that do not form soap, including sterols, hydrocarbons, and pigments.
    • Used to assess purity and quality.

  8. Moisture Content:

    • Measures the amount of water present in oils and fats.
    • Important for shelf life and quality control.

  9. Smoke Point:

    • The temperature at which oil begins to smoke, indicating thermal decomposition.
    • Lower smoke points can suggest degradation.

  10. Rancimat Test:

    • A method used to evaluate the oxidative stability of oils.
    • Provides information on how long oil can resist oxidation.

These parameters help in assessing the quality, purity, and stability of oils and fats used in various applications like food, cosmetics, and pharmaceuticals.