Associate Professor

Deptt. of Dairy Sc. & Tech. (Formerly A.H & Dairying)

R.K. (P.G.) College

 Shamli, U.P., India  

Milk fat is the most important and significant constituents of milk. Estimation of price of milk chiefly depends on the fat content of milk, Milk fat (ghee) an account of its higher nutritive value by virtue its colorie-dense (provide 2-25 times more energy than carbohydrate or protein), excellent source of fat soluble vitamins (A, D, E & K) content. Rich in antioxidant, presence of essential medium chain fatty acids (which the liver can absorbed directly and burn immediately) indispensable to life occupies most privileged position of being the best of all oil and fat used for human consumption. NO other food element has got as much bad press as well. It make the food tasty and palatable when taken alongwith food. Milk fat also adds to softness, sponginess and consumer acceptability of the milk products.

"Ghee has been recognised as Indian medicine in Ayurveda also religious significance in India that no important religious or festive Hindu rite omits the use of ghee" owing to all these amazing attributes of milk fat it is costly product as such it arouses temptations of adulteration with cheaper foreign fats. The risk involved in adulteration is not easy because the composition of ghee varies widely depending up on the feed, climate season etc. Adulteration of ghee has become a serious menace to public health. It may be defined "an addition of some foreign fatty or non fatty substances of a low value to the genuine product with the view to increase its amount or bulk or to lower the quality of product and thus to sell it off as genuine product in order to obtain high margin of profit.

For systematic marketing of ghee clearly, defined quality with purity is a pre-requisite. A part from the self-imposed discipline of quality control, there are several quality control agencies and legislative measure the quality assurance in our country. The important quality control agencies concerning ghee are PFA Act 1954, Bureau of Indian standard (BIS), FSSAI & AGMARK.

Standard of ghee under AGMARK Scheme (1937)

Fat  constants	Special Ghee (Red Level)	General Ghee (Green Level)	Cow Ghee (Yellow Level)	Buffalo Ghee (Blue Level)
Moisture (%) max	0.5	0.5	0.5	0.5
Free fatty acid (%) max	1.5	2.5	1.5	1.5
RI (40°C) B.R.	40.5-42.5	40.5-43.5	40.5-42.5	40.5-42.5
Saponification value	222-234	220-236	222-226	222-234
Richert-Mischil value	>28	>26	26-28	>30
Polenskey value	1.0-2.0	0.5-2.5	1.5-2.5	1.0-1.75
Iodine value	26-40	26-40	26-28	26-40
Krishchner value	20-26	20-26	20-25	>25
Biodine & Phytosterol acetate Test	Negative	Negative	Negative	Negative

Types of Ghee Adulteration

Detection of Adulteration in Ghee:

1.     Specific tests for specific ghee adulterants.

2.     Detection based on physico-chemical constants

3.     Technique based on Fatty acids content.

4.     Technique based on specific fatty acid content.

5.     Household method.

1.     Specific Test for Specific ghee Adulterants:

(i)     Fatty Substances:

Vegetable oil and Fats (Hydrogenated oil-Dalda or Vanaspati Ghee)

(a)   Baudouin's Test for Sesame oil:

Put 2ml melted sample ghee in a test tube and add 1ml of Baudouin's reagent (Prepared by adding 1gm of sucrose into 100ml Conc. HCl) shake well and allow the test tube in stand for 30 min. without disturbed. The development of pink colour denotes the presence of seasam oil or Dalda or Vanaspati Ghee. The presence of Dalda or Vanaspati oil as low as 3.0% can be detected.

(b)   Halphen's Test for Cotton Seed Oil:

Take 2ml of sample ghee and equal volume of Halphen's reagent (1ml of amyl alcohol and 1ml of 1% solution of carbon disulphide) in a test tube Mix thoroughly by shaking and heat gently on a water bath for 30 min. A red colour at the end of period denotes the presence of cotton seed oil. By this test, the addition of cotton seed oil into pure ghee as low as 1%.

(c)   Bomer's Phyto sterol Acetate Test for Veg. oil & fat:

This test is based on the principle that ghee is an animal fat contains cholesterol, while all vegetable oil contain sterols of other types which are together termed phyto sterols. This test will not be suitable for the presence of animal body fat such as tollow's and lards in ghee since these also contain cholesterol. The acetate of these sterols have characteristics melting point. Cholesterol acetate melts at 112-117°C whereas, the phytosterol acetate melts at 125°C. It the observed melting point of test sample is greater 117°C phytosterol from vegetable fat is assumed to be present and test is confirmed.

(ii)    Animal Fats:

(a)   Valenta Test:

About equal parts of milk ghee sample and glacial acetic acid and are mixed in a test tube and test tube placed in water bath. The test tube is shaken gently and note the temperature at which the fat melts. The value of genuine ghee ranges from 29 to 39°C if the temperature is above 39°C it denotes the presence of ghee with animal body fat. Temperature below 29°C it indicate the presence of coconut oil into ghee sample.

(b)   Nitric Acid Test:

Put 3ml of melted sample ghee in a test tube add 2-3 drops of pure and colourless nitric acid (HNO₃) mixed and tube is placed in water bath for few minute. The development of different colours denotes the presence of different adulterants as under:

Colours                 Adulterants

Colourless            Pure butter fat

Deep Yellow         Vegetable fat

Orange                  Animal body fat

Reddish brown     Wax

(c) Holde's Test for detecting mineral oil:

It has become a common practice to admixture mineral oil like heavy and light fuel oil, paraffin oil, petroleum jelly etc. and facts because of wide range of price differences. Nearly 2g of sample ghee is saponified with 25ml of 50% alcoholic potassium hydroxide for one hour. Then the saponified content is transferred to a beaker containing 100ml of water development of turbidity denotes the presence of mineral oil in ghee. Since mineral oil are unsaponifiable material so this characteristics is allowed for their detection.

(iii) Non-fatty substances:

(a)  Iodine Test for detection of Starch:

This test is based upon the fact that starch gives blue colour with Iodine solution.

Put nearly 3ml of tested sample in a test tube add 5ml of hot water and mix gently. Add 2-3 drop of Iodine solution into it. Development of blue colour shows the presence of starch (Potato, Sweet Potato and Other starches).

(b) Soda ash test for detecting alkalis:

The test is based on the fact that the genuine butter fat solidifies very slowly with Na₂CO₃ whereas vegetable fat or oil, or animal fat or wax is solidifed very quickly.

Take 10gm of suspected sample and equal amounts of saturated solution of sodium carbonate are mixed in a test tube and then placed in water bath. Genuine ghee does not give any turbidity and also does not form soap. It the ghee is adulterated the content develop turbidity due to formation of soap. The animal of soap formed depends an quantity of impurity.

(c) Phenolphthalein for detecting alkalies:

When pure ghee is stored for a longer period of time it develops hydrolytic rancidity. In order to neutralize this acidity same types of alkalis are added into it. Put 10gm of suspected ghee sample and 20ml of hot distilled water in a separating funnel into a beaker and mix gently. Allow the funnel to stand for some time. When the two layer separate the lower aqueous layer is drawn in a beaker and as few drop of phenolphthalein indicates are added. If pink colour develops it sure the presence of alkali into ghee sample.

Detection based on physico-chemical constant

Physical constants:

(a) Specific gravity: It varies from 0.91 to 0.94.

(b) Melting Point: It does not have an exact melting point due to mixture of glyceride. It ranges from 28 to 44°C.

(c) Solidifying Point: Solidifying point of cow ghee varies from 15 to 25°C and in case of buffalo ghee from 16 to 28°C.

(d) Refractive Index: RI of mixed ghee varies from 0.93 to 0.94.

(e) Microscopic test in Polarized light: Butter fat is optically inactive and non-crystalline, whereas vegetable fats and animal body fats are optically active and crystalline. This test is very competent and can be applied to detect the presence of other fats into butter fat.

Chemical Constants

(a) Reichert-Meissl (RM) value: It is the number of ml of N/10 alkali solution required to neutralize the steam-volatile, water soluble fatty acids from 5gm of butter fat. It ranges from 17 to 35. This value is the measure of butyric, caprice, caprylic acids. If RM value is below 17 there are very few chances of the ghee sample being pure which is higher than the value 1.0 for all fats & oils except coconut oil (6-8) and palm oil (4-8).

(b) Polenske value (P.V.): It is the number of ml of N/10 alkali required to neutralize the steam volatile and water-insoluble fatty acids from 5gm of fat. It ranges from 1.5 to 3.0 which is lower than that of coconut oil (15-20) Palm oil (17-22), beef tallow and lard (1-1.2).

(c) Kirschner value (K.V.): This denotes number of ml of N/10 alkali solution required to neutralize the steam-volatile and water-soluble fatty acids, the silver salts of which are soluble in water obtained from5gms. of butter fat. It varies from 20 to 26.

Thus RM, PV and KV can be determined from one sample and also only one process. The process being called RM, Pand K process.

(d) Iodine value: The denotes the percentage of iodine absorbed from the specific solutions of active iodine in organic solvents. It is the measure of unsaturated fatty acids. It ranges from 25 to 45 which is lower than that of cotton seed oil (103-112), Tallow (35-43) and Lard (50-80).

(e) Saponification value (S.V.): It indicate the number of milligram of caustic alkali (KOH) to saponify 1gm of butter fat. It ranges from 220 to 234 S.V. is the measure of the average molecules weight of the fatty acids coconut oil has a S.V. of about (245-260), tallow & lard (195-200).

(f) Acid value (A.V.): It indicate the number of mg of alkali required to neutralize the free fatty acids present in 1gm of butter fat. The acid value of butter varies from 0.45 to 3.5.

Techniques based on fatty acid content:

Recently many advanced and sensitive techniques such as Thin-layer chromatography, paper chromatography and Gas-liquid chromatography have been developed for detection of adulteration but these techniques are very expensive and also time consuming.

Technique based on specific fatty acid content:

Certain fatty acids like butyric acid, iso-veleric acid, cyclo propenoic acid etc. are not present in milk or if occasionally present in less amount as compared to adulterated fats. Therefore these fatty acids are used as an index for the detection of adulterants fats into milk fat.

(a) Butyric Acid: It's occurs only in milk fat and is not found in other type of fat. If butyric acid content of suspected ghee sample 9-6 mole percent, it denotes impurity with foreign fats.

(b) Iso-valeric Acid: The presence of this fatty acid in dolphin oil has been properly used as basis for its detection is suspected ghee sample by ascending paper chromatography technique.

(c) Cyclopropenoic Acid: the occurrence of this fatty acids in cotton seed oil. It is not found in milk fat which forms a basis for detection of cotton seed oil into pure ghee.

Factors Affecting The Constants Of Butter Fat:

There are many factors which influence the constants of butter fat or variation of composition of ghee are– 1. Technique of manufacture, 2. Breed of milk animal, 3. Season and climate of the year, 4. Stage of lactation of milch animal, 5. Feed & feeding of animal, 6. Degree of its nourishment, 7. Effect of hormones, 8. Affect of disease, 9. Rancidity of ghee.

Renovation of ghee

                This allude to the market mal practice of seeking to enhance the old and ranad ghee so as to make it marketable as a product of substandard quality in which long stored ghee is mixed with curd, betel leaves, chhachh etc. and heat up it upto 120°C temperature and subsequently straining it sometime, a yellow substances such as saffron, annatto, turmeric extract etc. are added to make it look like cow ghee. it is a crude manner practice followed by ghee seller.

Household Methods

(a) Smell and Taste Test: Genuine ghee has a distinct rich and nutty aroma whereas impured ghee may have a rancid or abnormal small.

(b) Appearance Test: Pure ghee is most often clear and has a yellow in colour where as impured ghee may appear cloudly or a have a greenish tint.

(c) Colour Test: The actual colour of genuine ghee is yellowish or golden. The granular part of the ghee that settle down at the bottom of transparent glass container is whiter than the fluid golden or yellowish part of ghee that float of the top.

(d) Melting Point Test: The genuine ghee will melt at a high temperature while impured ghee has a low melting point. We can test the ghee by taking a small quantity in a teaspoon and perceiving its melting behaviour.

(e) Palam Test: Take a teaspoon of tested ghee at palm. If it starts to melt by itself then it is genuine else the tested ghee you are using is impured. Genuine ghee melt on the body temperature.

(f) Heat Test: Heating a teaspoon of sample ghee in a vessel. It ghee melts quickly and turns dark brown colour, then it is genuine. If it is taken time to melt and turns into yellowish, then it is mixed with adulterants.

(g) HCl Test: take a teaspoon full of tested ghee in a test tube and heat it up, add an equal volume of conc. HCl with a pinch of sugar and leave a side for 5 min. The occurrence of pink or red colour in the bottom layer of ghee indicate the tested sample adulterated with Vanaspati Ghee or oil.

(h) Coaltar dyes Test: Take one teaspoon of melted sample ghee add 5ml dil. H₂SO₄. Pink colour developed that means tested ghee contain coaltar dyes.

References

1. Jauhar, Indrajeet & Gupta, Ramji (2022). Food Processing & Safety issues, Rama Publication House, Meerut, ISBN : 978-93-88821-43-8.

2. Singh, R.K. and Saraswat, B.L. (2008). Dairy Chemistry & Animal Nutrition, Kushal Publishers & Distributor, Varanasi, ISBN : 81-86099-646.

3. Singh, Vinay – Dairy Chemistry & Animal Nutrition, Bharti Bhandar, Meerut.

4. Bhati, S.S. and Lavana, G.S. (2000). Dairy Science, V.K. Prakashan, Baraut.

5. Chaudhary, A.C. (1959). Practical Dairy Science & Laboratory Method, Scientific Book Agency, Calcutta.

6. Manual Dairy Chemistry (1982), NDRI Press ICAR-NDRI, Bangalore.

7. Jauhar, Indrajeet – Dairy Technology & Quality Control, Rama Publishing House, Meerut.