Classification of fixed oils and Analysis of Lipids

Contents

• Classification of fixed oils and Analysis of Lipids

Objectives

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

• 15.5^oC to 16.5^oC

• Solid and semi-solid

Properties:

• 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

Fatty acids	No. of carbon	Formula	Source
Butyric acid	4	CH3(CH2)2COOH	Butter fat
Caproic acid	6	CH3(CH2)4COOH	Palm kernel oil
Caprylic acid	8	CH3(CH2)6COOH	Coconut oil
Capric acid	10	CH3(CH2)8COOH	Palm oil
Lauric acid	12	CH3(CH2)10COOH	Coconut oil
Myristic acid	14	CH3(CH2)12COOH	Palm oil
Palmitic acid	16	CH3(CH2)14COOH	Arachis oil
Palmitoleic acid		CH3(CH2)5CH=CH(CH2)7COOH	Cotton seed oil
Oleic acid		CH3(CH2)5CH=CH(CH2)7COOH	Corn oil
Linoleic acid		CH3(CH2)4CH=CH-CH2-CH=CH(CH2)7COOH	Sunflower oil
Linolenic acid		CH3(CH2)7CH=CH(CH2)11COOH	Palm oil

Classification of fixed oils

Oils and Fats (Vegetable)
Fats	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
Nutmeg	Almond oil	Sesame oil	Hemp oil
butter	Croton oil	Cotton seed oil	Walnut oil
Coconut oil	Rice bran oil	Safflower oil

 

Animal oil and Fats
Marine animals		Terrestrial animals
Fats	Oils	Fats	Oils
Bone tallow	Cod liver oil Shark liver oil Whale oil	Lard 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 are increased which are detected by kries test using phloroglucinol which produces red colour with oxidized fat.

Reichert meissle value:

This value is a measure of volatile water soluble acid content 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.

Summary

• 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