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ELEMENTARY IDEA OF

FATS AND OILS

B.Sc. Vth semester

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Triglycerides: Esters of glycerol with fatty

acidsFats are solids at room temperature Oils are

liquids at room temperature.

Oils contain a larger proportion of the glycerides

of lower fatty acids and unsaturated fatty acidswhile fats contain a larger proportion of the

glycerides of higher saturated fatty acids having

high melting point.

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Fats (solid triglycerides) and

an oil (a liquid triglyceride)

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C

O

OH Carboxyl end

Polar head

Long hydrocarbon chainNonpolar tail

General Fatty Acid Structure

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Saturated FatsContain no C=C double bonds

Generally are solids or semisolids at room

temp

Animal fat is a major sourceShould not make up more than 30% of your

total fat intake per day

Unsaturated FatsContain one or more C=C double bondsGenerally are liquids at room temp

Vegetable oils are major source

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Fatty Acid

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Micelle Formation

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COOH

COOH

COOH

COOH

COOH

COOH

Palmitic acid

Stearic Acid

Saturated Fatty Acids

Unsaturated Fatty Acids

Oleic Acid

Linoleic Acid

Linolenic Acid

Arachidonic Acid

NOTE: Linoleic, linolenic, and aracidonic acids are examples of polyunsaturated fatty acids.Linoleic and linolenic acids are also the two essential fatty acids your body needs.

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HOOC CH312 C's

HOOC CH314 C's

HOOC CH316 C's

HOOC CH316C's 1 C=C

HOOC CH316C's 2 C=C

HOOC CH316C's 3 C=C

Myristic Acid14 C's

Palmitic Acid16 C's

Stearic Acid18 C's

Oleic Acid18 C's 1 C=C

Linoleic Acid18 C's 2 C=C

Linolenic Acid18 C's 3 C=C

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Molecular factors affecting

Melting Points

Molecular Weight

Myristic Acid 58 oC

Palmitic Acid 63 oC

Stearic Acid 71 oC

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COOH

COOH

COOH

COOH

COOH

COOH

COOH

COOH

COOH

semisolid atroom temp

liquid atroom temp

solid atroom temp

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Degree of unsaturationMonounsaturated one C=C

Polyunsaturated 2 or more C=C

Oleic Acid 16 oC

Linoleic Acid -5 oC

Linolenic Acid -11 oC

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Saponification Value

Saponification - hydrolysis of ester under alkalinecondition.

The saponification value of an oil or fat is definedas the number of mg of potassium hydroxide(KOH) required to neutralize the fatty acidsresulting from the complete hydrolysis of 1 g of

the sample.

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Saponification Value Determination

Saponification # --mgs of KOH required to saponify 1 g of fat.

1. 5 g in 250 ml Erlenmeyer.

2. 50 ml KOH (0.5 N) in Erlenmeyer.

3. Boil for saponification.

4. Titrate with HCl (0.5 N) using phenolphthalein.

5. Conduct blank determination.

B - ml of HCl required by Blank.

S - ml of HCl required by Sample.

N- Factor of 0.5 N HCL.

SP# =56.1(B -S) x N of HCl

Gram of Sample

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Iodine Number

The iodine value of an oil or fat is defined as the mass of iodine absorbedby 100 g of the sample.

The unsaturated fatty acid residues of the glycerides react with iodine, andthus the iodine value indicates the degree of unsaturation of the fatty acidresidues of the glycerides.

It is constant for a particular oil or fat, but depends on the method used.Animal fats (butter, dripping, lard) 30 - 70 Iodine Value

Non-drying oils (olive, almond) 80 - 110 Iodine Value

Semi-drying oils (cottonseed, sesame, soya) 80 - 140 Iodine Value

Drying oils (linseed, sunflower) 120 - 200 Iodine Value

The iodine value is often most useful in identifying the source of an oil.Generally, the higher iodine values indicate oils and the lower values fats.Iodine values are normally determined using Wigs or Hanus methods.

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Determination of Iodine Number

Iodine Value = (ml of Na2S2O3 volume for blank - ml of Na2S2O3volume for sample) N of Na2S2O3 0.127g/meq 100

Weight of Sample (g)

CH CH CH CH

Cl I

ICl

Iodine chloride

+

ICl KI KCl

I2

I2

Na2S2O3 Na2S4O6 NaI

+

+ 2 2+

+

Excess unreacted ICl