Definition, Method of Extraction, Classification of Lipids

Contents

Definition, Method of Extraction, Classification of Lipids

Objectives

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

• Classify lipids

• Explain the method of extraction of lipids

Lipids

• 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

• Vegetable origin - expression in hydraulic presses

• Virgin oil or cold pressed oil

• Hot pressed oil

Extraction by expression

• Screw presses - better yield than hydraulic press

• Operate at higher pressures and continuously

• Cooking - seeds rich in proteins

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

Degumming

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

• Hydrated - Dense gel, separates from lighter oil

• Gel discarded, oil dried under vacuum

Neutralization

• Free fatty Acids - dilute sodium hydroxide

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

Bleaching

• Diatomaceous earth or activated charcoal

• Bleaching agent - removed by filtration

Wax removal

• Winterization

• Crystallized waxes - Filtration

Deodorization

• 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

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

Ø  Glycero phospho lipids- Lecithin, cephalin

Ø   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

Summary

• 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