BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS

DR ROHINI C SANE

BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS

BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS (To check adulteration)

1. Iodine number

2. Saponification number

3. Reichert –Meissl number

4. Acid number

Significance of Characterization of FATS &OILS

BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS -Iodine number

1. Iodine number

Definition : Iodine number is defined as the grams ( number ) of iodine absorbed by 100 g of fat or oil.

Significance :

1. Iodine number : directly proportional to degree /content of unsaturated fatty acids .

2. Lower the iodine number ,less is the degree of unsaturation

3. Iodine number is useful to analyze the degree of adulteration

Iodine number

FAT/OIL Iodine number

Coconut oil 7-10

Butter 25-28

Palm oil 45-55

Olive oil 80-85

Groundnut oil 85-100

Cotton seed oil 100-110

Sunflower oil 125-135

Linseed oil 175-200

Iodine number of Butter adulterated with groundnut oil : >28 depending upon degree of adulteration /weight contribution by coconut oil

Iodine gets attached on double /triple bonds present in oil & fat molecule

1. Iodine number for degree of unsaturation of fat

Iodine number :Definition, Its use to detect Degree ofunsaturation,Adulteration &

biological value –energy yield of fat

Iodine number of Different types oils Indicating degree of unsaturation

Iodine number with suitable examples

BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS -Saponification number

2.Saponification number of Fat/oils

Definition : Saponification number is defined as the mg ( number ) of KOH required to hydrolyze ( saponify ) by 1 gram of fat or oil.

Significance :

1. Saponification number is a measure of the average molecular size of constituent fatty acids of given fat/oil.

2. higher Saponification number for fats containing short chain fatty acids egbutter –(SN 230-240),Coconut oil( SN250-260),Human fat (SN195-200)

Saponification number of FatChemical Reaction involved in determination of saponification number using NaOH /KOH

Saponification number helps to predict size of /chainlength of constituent fatty acids Examples of Saponification

number: Butter (with short chain fatty acid )& Oleomargarine (with long chain fatty acid ) Saponification number

inversely related with chain length of constituent fatty acids of fat/oil

Definition of Saponification number of Fat

its Use to Identify nature of constituent fatty acids ( short /long chainfatty acids )

Indication of Saponification numberButter & coconut oil contain short chain fatty acids & can be easily digested in human body.

Comparison of Saponification number of palm oil &corn oil indicates Palm oil has higher content of long chain fatty acids than corn oil .Corn oil is more digestible than Palm oil.

Comparison of Iodine number & saponification number of Cord liver oil , Soybean oil & Lard

Degree of unsaturation :Iodine adulteration :Lard <Tambaqui fat< Soyabean oil < Cod liver oil Content of short chain fatty acids : Saponication number : Tambaqui fat< Soyabean oil < Cod liver oil <Lard

BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS: Reichert –Meissl number

3. Reichert –Meissl number of Fat/oils

1. Definition : Reichert –Meissl number (RM ) of Fat/oils is defined as the number of ml of 0.1N KOH required to completely neutralize the soluble volatile fatty acids distilled from 5 gram of fat or oil.

Significance :

1. Higher content of Volatile fatty acids of butter (Butyric acid ,Caproic acid &Caprylic acid) responsible for its higher Reichert –Meissl number

2. Reichert –Meissl number for butter (RM -25-30 ) & negligible for fat /edible oils without volatile fatty acids (RM< 1)

3. Reichert –Meissl number of Fat/oils is useful in testing purity /adulteration of butter .

Reichert –Meissl number : indicates natural content of short chain fatty acids(<10 C )DERIVED BY DISTILATION OF FAT /OIL

Reichert –Meissl number-the analysis

TOAD SKIN DISEASE---PHRYNODERMA-deficiency of PUFA

BIOCHEMICAL TESTS FOR PURITY OF FATS & OILS – Acid number

4.Acid number of Fat/oils

1. Definition : Acid number is defined as the mg ( number ) of KOH required to completely neutralize free fatty acids present in 1 gram of fat or oil.

Significance :

1. Oils decompose on long standing due to bacterial /fungal contamination or chemical decomposition . Acid number is higher for oils stored for longer duration (manufacturing/packing date important )

2. Acid number : Refined oils should be free from any free fatty acids & have negligible acid number (AN - nil )

Determination of Acid number: using titration of a stored oil with alkali

Neutralization pointFor detection of acid number

Acid number of Fat :Use : to detect rancidityAcid number is directlyproportional to rancidity(shelf life /free fatty acids content of fat stored for longer duration )

Rancidity :fat/oil undergoes oxidation –producing undesired /dangerous metabolites-imparting unpleasant odor to stored fat/oils .Certain factors aggravate oxidation of fat /oils eg exposure to light ,oxygen & bacteria/fungi .

ACID NUMBER OF Coconut oil :Increases with contamination with Aspergillus Niger & imparts bad odor on prolonged storage on the shelf.

Acid number : Lipases of bacterial origin are responsible for rancidity & increase content of free fatty acids of stored fat/oil

Acid number :Exposure to Moisture /water responsible is for rancidity & increase content of free fatty acids of stored fat /oil

Lipid peroxidation of Polyunsaturated oils Producing aldehydes ,ketones ,acid & alcohol

High risk of cancer

OXIDATION OF FATTY ACIDS

• SATURATED FATTY ACIDS BETA OXIDATION yield ATP

• UNSATURATED FATTY ACIDS ---AUTOOXIDATION (REACTIVE DOUBLE BONDS )

• PEROXIDES

• ENEDIOLS HARMFUL PRODUCTS

• EPIOXIDES

• ALDEHYDES

ANTIOXIDANTS PREVENT OXIDATION OF FATTY ACIDS –FOOD PRESEVATION

1. BHA ---BUTYLATED HYDROXY ANISOL

2. BHT ----BUTYLATED HYDROXY TOLUENE

3. VITAMIN E

4. PROPYL GALLATE

5. HYDROQUINONE

Recommended shelf life of different oilsto prevent their Rancidity

Comparison of Saponification number, Reichert –Meissl number & Acid number:To detect purity /adulteration of fat/oil

Saponification number Reichert –Meissl number Acid number

Definition mg ( number ) of KOH required to hydrolyze ( saponify ) by 1 gram of fat or oil.

number of ml of 0.1N KOH required to completely neutralize the soluble volatile fatty acids distilled from 5 gram of fat or oil.

the mg ( number ) of KOH required to completely neutralize free fatty acids present in 1 gram of fat or oil.

KOH /NaOH & starting material in definition

mg KOH /1gram of fat /oil 0.1N KOH/ 5 gm. of fat/oil ( DISTILATION AS PRE-ANALYTICAL STEP )

mg KOH/1gm fat

APPLICATION / USE /SIGNIFICANCE

Identify nature of constituent fatty acids ( short /long chainfatty acids ) –MOLECULAR SIZE

To measure the soluble volatile fatty acids of fat/oil &is directly proportional toContent of the soluble volatile fatty acids

To detect rancidity& is directlyproportional to free fatty

acids content of fat stored for longer duration(rancidity/shelf life )