Download - Biochemical tests for purity of fats & oils
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 )