Definition, Method of Extraction, Classification of Lipids

Lipids: Definition, Method of Extraction, Classification

Lipids: Definition, Method of Extraction, Classification of lipids, method of extraction of lipids,



Definition, Method of Extraction, Classification of Lipids


At the end of this lecture, student will be able to

• Classify lipids

• Explain the method of extraction of lipids


Lipids encompass a wide array of molecules, including fats, oils, phospholipids, and steroids. They are hydrophobic in nature, which means they do not readily dissolve in water. Lipids are crucial for energy storage, insulation, cushioning of vital organs, and serving as structural components of cell membranes.


• Fixed oil, fats and wax

• Esters of fatty acids and alcohols or polyols

• Insoluble in water

• Soluble in non-polar solvents

• Constituent of cell structures, coating elements and also reserve substances

• Fats and oils – esters of long chain fatty acids and trihydric alcohol (glycerol) – glycerides

• Waxes – esters of long chain fatty acids and long chain monohydric alcohol (Cetyl alcohol)

Method of Extraction of Lipids

The method of extraction of lipids from natural sources involves various techniques, depending on the lipid type and the source material. Common methods include:

1. Solvent Extraction

This method involves using organic solvents like chloroform, methanol, or ethanol to dissolve lipids from the sample. It is widely used for extracting lipids from tissues, seeds, and other biological materials.

2. Cold-Pressing

For oils, cold-pressing is often employed, especially for plant-based sources like seeds and nuts. This method involves mechanically pressing the source material to release the oil.

3. Soxhlet Extraction

Soxhlet extraction is a continuous extraction method that utilizes a combination of solvent circulation and evaporation-condensation cycles to efficiently extract lipids from solid samples.

• Vegetable origin – expression in hydraulic presses

• Virgin oil or cold pressed oil

• Hot pressed oil

Method of Extraction of Lipids,

Method of Extraction by Expression

• Screw presses – better yield than hydraulic press

• Operate at higher pressures and continuously

• Cooking – seeds rich in proteins

Method of Extraction by solvents

• Intact seeds/seeds partially extracted by expression

• Hexane

• Organic phase is recovered

• Miscella – Solvent + Oil      

Refining of crude oil

• Degumming

• Neutralization

• Bleaching

• Wax Removal

• Deodorization


• Lecithins, proteins, other impurities in the form colloidal suspension

• Hydrated – Dense gel, separates from lighter oil

• Gel discarded, oil dried under vacuum


• Free fatty Acids – dilute sodium hydroxide

• Soap – Colouring matter, phenols, sterols, wax esters, traces of metals and miscellaneous oxidation products


• Diatomaceous earth or activated charcoal

• Bleaching agent – removed by filtration

Wax removal

• Winterization

• Crystallized waxes – Filtration


• Aldehydes and ketones – unpleasant odour

• Eliminated by injecting steam into the very hot oil
(200oC) under high vacuum

Extraction of animal lipids

• Rendering with steam, with or without pressure

• Heat melts the fat, which rises to the top

• Separated by decantation

Classification of Lipids

1. Fats and Oils

Fats and oils, also known as triglycerides, are the most common form of lipids. They consist of glycerol and three fatty acid chains. Fats are solid at room temperature, while oils are liquid.

2. Phospholipids

Phospholipids are key components of cell membranes. They have a hydrophilic (water-attracting) head and two hydrophobic (water-repellent) tails.

3. Steroids

Steroids include cholesterol and hormones like testosterone and estrogen. They have a characteristic four-ring structure and serve various roles, from regulating metabolism to acting as signaling molecules.

4. Waxes

Waxes are esters of long-chain fatty acids and alcohols. They are found in nature as protective coatings on surfaces, such as the waxy cuticle of plants and the wax in animal fur.

Based on the nature of the product obtained on hydrolysis

• Simple lipids

• Compound lipids

• Derived lipids

Simple lipids:

• Ester of fatty acids and alcohols

– Fats and oils

– Waxes

Compound lipids:

• Esters of fatty acids and alcohols in combination with other compounds

– Phosholipids

Glycero phospho lipids- Lecithin, cephalin

Sphingo phospho lipids – Sphingomyelin

– Glycolipids

– Lipoproteins

Derived lipids:

• Compounds donot contain an ester linkage; obtained by hydrolysis of simple and compound lipids

– Fatty acids

Ø  Saturated

Ø  Unsaturated

v Poly unsaturated

v Mono unsaturated

– Alcohols

– Sterols (cholesterols), Fat-soluble vitamins, Ketone bodies, hydrocarbons

Significance in Biology and Health

Lipids are vital to numerous biological processes:

– Cellular Structure

Lipids form the lipid bilayer of cell membranes, providing structure and controlling what enters and exits the cell.

– Energy Storage

Triglycerides store energy in adipose tissue, serving as a reserve that can be broken down when needed.

– Hormone Regulation

Steroid hormones are essential for various physiological functions, including growth, reproduction, and metabolism.

– Insulation and Protection

Lipids, especially adipose tissue, provide thermal insulation and cushion vital organs.


Lipids are fundamental to life, with their diverse functions spanning energy storage, cellular structure, and hormonal regulation. Understanding their extraction methods and classification sheds light on their importance in biological systems.


• Lipids are esters of long-chain fatty acids and alcohols

• Lipids include fixed oils, fat and waxes

• They can be extracted by hydraulic or screw press or by steam

• Based on the product obtained on hydrolysis lipids are classified into simple, compound and derived lipids


Are all lipids fats? No, while fats are a type of lipid, lipids encompass a broader range of molecules including fats, oils, phospholipids, and steroids.

Are lipids bad for health? Lipids are essential for health, but their consumption in excess can lead to health issues. It’s important to maintain a balanced intake.

How are lipids used in cosmetics? Lipids are used in cosmetics for their moisturizing and emollient properties, helping to hydrate and protect the skin.

Can lipids be extracted from animal sources? Yes, lipids can be extracted from animal tissues, such as fatty cuts of meat or adipose tissue.

Are all steroids harmful? No, steroids have both physiological and pharmaceutical applications. Some steroids are used as anti-inflammatory medications and hormone therapies.

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