Classification of fixed oils and Analysis of Lipids

Classification of fixed oils and Analysis of Lipids

Classification of fixed oils and Analysis of Lipids


• Classification of fixed oils and Analysis of Lipids


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

• Classify fixed oils

• Discuss the parameters involved in analysis of lipids

Fixed or Fatty oils

• Reserve food materials of plant and animals

• 15.5oC to 16.5oC

• Solid and semi-solid


• Thick, viscous, yellow, characteristic odour

• Non-volatile, non-distillable

• Food value

• Saponifiable

• Rancid- free acidity

Fats and oils: Esters of glycerol and straight chain mono carboxylic acids

Fatty acids may be

• Saturated

• Unsaturated

– Monounsaturated

– Polyunsaturated


of carbon



Butyric acid



Butter fat

Caproic acid



Palm kernel oil

Caprylic acid



Coconut oil

Capric acid



Palm oil

Lauric acid



Coconut oil

Myristic acid



Palm oil

Palmitic acid



Arachis oil

Palmitoleic acid


Cotton seed oil

Oleic acid


Corn oil

Linoleic acid


Sunflower oil

Linolenic acid


Palm oil

Classification of fixed oils

Fixed oils can be classified into various categories based on their sources and properties. Some common classifications include:

1. Monounsaturated Oils

These oils are primarily composed of monounsaturated fatty acids, such as oleic acid. Olive oil and avocado oil are notable examples.

2. Polyunsaturated Oils

Rich in polyunsaturated fatty acids like linoleic acid and alpha-linolenic acid, these oils include sunflower oil, corn oil, and flaxseed oil.

3. Saturated Oils

Saturated fatty acids dominate these oils. Coconut oil and palm oil fall into this category.

4. Hydrogenated Oils

These are artificially saturated oils created through hydrogenation. They are often used in processed foods.

5. Essential Oils

Extracted from aromatic plants, these oils are used in perfumes, flavorings, and aromatherapy.

Oils and Fats (Vegetable)


Non-drying oils

Semi-drying oils

Non-drying oils

Cocoa butter

Olive oil

Castor oil

Linseed oil

Kokum butter

Peanut oil

Mustard oil

Poppy seed oil


Almond oil

Sesame oil

Hemp oil


Croton oil

Cotton seed oil

Walnut oil

Coconut oil

Rice bran oil

Safflower oil


Animal oil and Fats 

Marine animals

Terrestrial animals





Bone tallow

Cod liver oil

Shark liver oil

Whale oil


Mutton tallow

Butter suet

Lard oil

Chemical properties of fats

• Hydrolysis

• Addition reactions

• Oxidation

• Rancidification

Analysis of lipids

• Physical constants

• Chemical constants

Physical constants include,

• Viscosity

• Specific gravity

• Refractive index

• Solidification point etc.,

Chemical Constants

• Acid value

• Saponification value

• Polenski value

• Iodine value

• Ester value

• Acetyl value

• Hydroxyl value

• Kries test (Rancidity index)

• Unsaponifiable matter

• Reichert meissle value

• Peroxide value

Acid value:

It is defined as the number of milligrams of potassium hydroxide required to neutralize the free fatty acids present in one gram of the sample.

Generally rancidity causes free fatty acid liberation. Acid value is used as an indication of rancid state.

Saponification value:

It is defined as the number of milligrams of potassium hydroxide required to neutralize the fatty acids resulting from complete hydrolysis of one gram of the sample.

Saponification value occurs in an inverse proportion to the average molecular weight of fatty acid present in the sample.

Ester value:

It is defined as the number of milligrams of potassium hydroxide required to combine with fatty acids which are present in glyceride form in 1 gram of the sample. Ester value is the difference between the saponification value and acid value.

Iodine value:

It is defined as the weight of iodine absorbed by 100 parts by weight of the sample. It is the measure of extent of unsaturation. Rancidity increases iodine value.

Hydroxyl value:

It is defined as the number of milligrams of potassium hydroxide required to nuetralise the acetic acid capable of combining by acetylation with 1 gram of the sample.

Acteyl value:

It is the number of milligrams of potassium hydroxide required to neutralize the acetic acid obtained when 1 gram of acetylated sample is saponified.

Unsaponifiable matter:

It is the matter present in fats and oil, which after saponification by caustic alkali and subsequent extraction with an organic solvent, remains non-volatile on drying at 80oC. It includes sterols, oil soluble vitamins, hydrocarbons, and higher alcohols.

Peroxide value:

It is the measure of peroxide present in the sample. Peroxide values are generally less than 10 mEq/kg in fresh samples. Due to temperature or storage, rancidity occurs causing increase in peroxide value.

Kries test: (Rancidity index)

Due to rancidity, epihydrin aldehyde or malonaldehyde aremincreased which are detected by kries test using phloroglucinol which produces red colour with oxidized fat.

Reichert meisslemvalue:

This value is a measure of volatile water soluble acidmcontent of the sample.

It is the number of milligram of potassium hydroxide required to neutralize volatile water soluble acids obtained from 5 gram of the sample.

Polenski value:

It is defined as the number of milligram of N/10 potassium hydroxide required to neutralize water insoluble, steam distillable acid liberated obtained by hydrolysis of 5 gram of sample.

Significance in Various Industries

Fixed oils and lipid analysis have far-reaching applications:

– Food Industry

Fixed oils are used for cooking, frying, and as ingredients in various food products. Lipid analysis ensures quality and nutritional information.

– Cosmetics Industry

Lipids are used in cosmetics for their moisturizing and emollient properties. Analysis guarantees the desired lipid composition.

– Pharmaceutical Industry

Lipids play a role in drug delivery systems. Analyzing lipids aids in formulating effective medications.


• Fatty oils – Saturated/ unsaturated

• Fixed oils – drying, semi drying and non-drying oils

• Physical and chemical constants are used for analysis of lipids

• Physical constants include Specific gravity, Melting point etc

• Chemical constants include Acid value, Saponification value, Ester value, Iodine value, Peroxide value, Hydroxyl value, Acetyl value, unsaponifiable matter, Polenski value, Reissert meissle value and Kries test


  1. Are all fixed oils edible? While many fixed oils are edible and used in cooking, some are better suited for non-edible applications like cosmetics and industrial uses.
  2. Can lipid analysis help diagnose medical conditions? Yes, lipid analysis is used to assess lipid profiles in blood, aiding in diagnosing conditions like high cholesterol levels.
  3. Are hydrogenated oils unhealthy? Hydrogenated oils can contain trans fats, which are considered unhealthy. It’s advisable to limit their consumption.
  4. Are essential oils the same as fixed oils? No, essential oils are volatile compounds extracted from plants, while fixed oils are non-volatile fatty oils.
  5. Where can I find more information about lipid analysis techniques? For detailed information, consider referring to scientific literature and research papers in the field of lipid analysis.

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