Adulteration of milk

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various methods for detection of adulterants in milk

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ADULTERANTS IN MILK AND THEIR METHODS OF DETECTION :

ADULTERANTS IN MILK AND THEIR METHODS OF DETECTION

INTRODUCTION:

INTRODUCTION Milk is the nature's most nearly perfect food supplying wide range of nutrients. Milk has a very high nutrient density in relation to calorie content of the food. When it leaves the udder of the animal, all the interplay's of adulteration begin. Due to ease with which other additives resembling in physico- chemical make up can be mixed. Factors for adulteration: Skill-full addition Imperical detection tests

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Requirement of specific laboratory set up Mass awareness among the consumers about the quality culture. To safeguard the public health, continuous affords are made by local, state and national health authorities to adopt strict measures to prevent adulteration which promotes fraud and / or which might be detrimental to the health of consuming public. These efforts are still inadequate because of skillful adulteration and imperical detection techniques.

Definitions :

Definitions The term adulteration in general may be defined as the addition and / or subtraction of some of the legally prohibited substances into and / or from a more valuable genuine product. According to PFA act 1954 "adulterant" means any material, which is or could be employed for the purpose of adulteration. Under PFA act 1954 the adulterated food has been defined in a very specific perspective.

MILK ADULTERATION :

MILK ADULTERATION ♣ Milk adulteration may be defined as any change caused in the natural level of milk ingredients. These changes may be brought about by addition of some foreign matter to milk or by removing some more valuable ingredients e.g. fat out of it. Milk is the most frequently adulterated food product in developing countries .

Possible adulterants:

Possible adulterants Water Reconstituted milk/Recombined milk/Dried milk Whey Mixing of milk of one species with other Cow milk in goat milk/ sheep milk Cow milk in buffalo milk Buffalo milk in Cow milk Thickening agents Starch Cane sugar Gelatin Cellulose

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Preservatives Boric acid/borates Formaldehyde Benzoic acid Salicylic acid Hydrogen peroxide Hypochloride Neutralizers Lime water Sodium bicarbonate Sodium carbonate Sodium hydroxide

Fertilizers/Additive :

Fertilizers/Additive Urea Glucose Ammonium sulphate Potassium nitrate Salts

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Coloring matter Annatto Coal tar dies Miscellaneous Adulterants Vegetable oil Soybean Protein Urine Coconut water Dirt QAC Antibiotics Wash water/detergents

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Water Presence of extraneous water can be detected by: Lower % of fat Lower density of milk at 27 O c Lower % of SNF Depression in freezing point Methods for detection of Water Adulteration: The Vieth ratio: The ratio of % lactose : protein : ash for normal milk is 13 : 9 : 2. Detection of nitrate: Some natural water contains nitrates. The well known diphenyl test is used. This compound is oxidized by nitrate-diphenyl benzidine -intense blue quinone -ammonium salt

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3. Calculation from chemical constituents : Principle: To find out osmotic pressure of milk purely by chemical means i.e. by lactose and mineral salts. The values varies from 69.2 and 82.8. The method is very time consuming. 4. Freezing point test Freezing point test is the most dependable method Two standard (Hortvet and Thermister cryoscope) methods are used The cryoscope is able to detect addition of less than 2 % water 5. Spectrophotometric measurement : Detection of 10 % added water is possible.

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6. Refractrometric method : It measures the ability of solution to bend or refract light beams. Water has RI of 1.33 while that of cow's milk is 1.35 7. Specific gravity and density test : One of the most practical and simple test Watered milk has a fair % of fat but has very low percentage, which shows that water has been added. 8. Electrical conductivity method : EC of water is lower than milk. Addition of water decreases the EC. 9. Vapor pressure osmometer 10. Enzyme method: Trypsin digestion -The decrease in absorption 11. Other simple & quick test

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Thickening agents : When milk is watered and skimmed, it is deficient in viscosity/density/consistency. It may be restored by addition of some substances. Detection of Starch Take about 3 ml of well-mixed milk in test tube. Boil the milk in water bath. Cool the boiled milk. Add 2-3 drops of 1 % iodine solution and shake well. Development of blue colour indicates the presence of starch.

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Detection of Sucrose Take 10 ml of milk in test tube. Add 1 ml of concentrated hydrochloric acid and 0.3g of resorcinol and mix well. Place the tube in boiling water bath for 5 min. Development of red colour indicates presence of cane sugar. Detection of Gelatin Take 10 ml of milk in a flask and add 10 ml. of mercuric nitrate solution. Then add 20 ml. of distilled water, keep it for 5 min and, filter. Add equal volume of picric acid to the filtrate. Development of turbidity and / or yellow colour indicates presence of gelatin.

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Detection of Cellulose To the 10 g of milk add 50 ml of hot water & stir it for 2min. Then filter & wash the residue with 50 ml hot water. Place it in a spotting plate and stain one part with iodine- ZnCl 2 reagent and another with iodine. Development of blue colour with Iodine- ZnCl 2 and absence of blue colour in iodine solution indicates presence of cellulose. Detection of Skim Milk Powder Take 10 ml milk in each of two centrifuge tubes. Centrifuge the tubes at 3000 rpm for 30 min. Decant the supernatant and dissolve the residue in 2.5 ml of concentrated nitric acid. Dilute the solution with 5 ml of distilled water. Add 2.5 ml of liquid ammonia. Development of orange colour indicates the presence of smp.

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Fertilizers/Additives: Milk suppliers take an advantage of increasing the SNF of milk by adding various substances such as urea, glucose, ammonium sulphate, potassium nitrate and other such salts. Detection of Urea Take 5 ml of milk sample in 50 ml conical flask and dd 5 ml of acetate buffer & heat for 3 min or add 5 ml TCA solution. Filter through Whatman No.42 filter paper & collect 1ml filtrate in tube. Add 1 ml of sodium hydroxide solution to the filtrate followed by 0.5 ml of sodium hypochlorite solution. Mix thoroughly and finally add 0.5 ml of phenol solution.A characteristic blue or bluish green colour indicates presence of extraneous urea in the milk.

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Detection of Ammonium Sulphate Take 1 ml of milk in a test tube. Add 0.5 ml of NaOH and 0.5 ml of sodium hypochlorite solution. Mix thoroughly and to this add 0.5 ml phenol solution. Heat the tube in boiling water bath for 20 seconds. Development of blue colour, which turns deep blue, indicates the presence of extraneous ammonium sulphate in the milk. Detection of Glucose Take 1 ml of milk sample in test tube. Add 1 ml of Barfoed’s reagent. Heat the tube in boiling water bath for 3 min and cool under tap water for 3 min. Add 1 ml of phosphomolybdic acid reagent to the turbid solution. Immediate formation of deep blue colour indicates the presence of extraneous glucose in the milk.

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PRESERVATIVES In dairy industry "Preservatives" means a substance which when added to milk, cream or other milk products would retard sourness and decomposition. The practice of adding preservatives is very objectionable and should be forbidden and made illegal because of various reasons. Detection of Borax and Boric Acid Take 5 ml of milk in a test tube. Add 1 ml concentrated hydrochloric acid and mix. Dip the tip of turmeric paper in the acidified milk. Dry the paper in watch glass at 100 0 C or over small flame. If turmeric paper turns red it indicates presence of borax or boric acid.Add a drop of ammonia solution on the turmeric paper. If red colour changes to green it indicates presence of boric acid.

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Detection of Hydrogen Peroxide Take 5 ml of milk in test tube and add 2 drops of p-phenyldiamine hydrochloride solution and mix well. Development of intense blue colour indicates presence of hydrogen peroxide. Detection of Formaldehyde ( Hechner Test) Take 10 ml of milk in a test tube. Add 0.5 ml of ferric chloride solution and mix well. Add concentrated sulphuric acid slowly from the side so that it forms separate layer at the bottom without mixing with milk.Development of violet ring at the junction of two layers indicates presence of formaldehyde. Leach Test Take 5 ml of milk in a test tube & add equal volume of Hcl containing ferric chloride. Heat over a small flame for 5 min. Break the curd by rotating the tube & observe for the colour. Violet colour in the curd indicates presence

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Neutralizers: Milk is highly perishable and during storage, it undergoes microbial action and develops acidity. If such highly acidic milk is used for the manufacture of milk products, it will result in final product of inferior quality, so neutralizers in the form of limewater, sodium bicarbonate, sodium carbonate, sodium hydroxide etc. may be added. Such a practice is not permissible. Detection of Carbonate or bicarbonate (Rosalic acid test) Rosalic acid is an indicator, which shows a change in the colour on addition to alkaline milk. Take 5 milk in a test tube and add equal volumes of alcohol. Then add few drops of 1% rosalic acid solution. Development of rose red color indicates the presence of carbonate. In pure milk, it may be brownish or brownish yellow color.

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Detection of Benzoic and Salicylic Acid Take 5 ml of milk in test tube. Acidify the milk with concentrated sulphuric acid. Add 0.5 % ferric chloride solution drop by drop and mix well. Development of buff colour indicates presence of benzoic acid and violet colour indicates presence of salicylic acid.

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