Dairy At Glance

RECENT TREDS IN DETECTION OF ADULTERATION OF MILK AND DAIRY PRODUCTS

MONIKA GUPTA AND M.P. GUPTA

Deptt. Of Dairy Science

U.P. Pt. D.D. Upadhyay Pashu Chikitsa Vigyan Vishwavidyalaya

Evam Go – Anusandhan Sansthan Mathura 281001 (U.P.)

PREAMBLE

          Adulteration of food stuffs is commonly practiced in our country by the trade. From the view point of protecting the health of the consumer, the Government of India promulgated the ‘Prevention of Food Adulteration Act’ (PFA Act) in 1954. The Act  came into force from 1st June , 1955 . It prohibits the manufacture, sale and distribution of not only adulterated foods but also foods contaminated with toxicants and misbranded foods.

          According to PFA Act, an article of food shall be deemed to be adulterated:

  1. If the article sold by the vendor is not of the nature , substance or quality demanded by the purchaser or is not of the nature , substance or quality which it proports or is represented to be ,
  2. If the article contains any other substance which affects injuriously the nature , substance or quality thereof,
  3. If any inferior or cheaper substance has been substituted wholly or partly which affects the quality of food .
  1. If any constituent of the food has been abstracted wholly or partly so

 

  1. Research Scholar, Deptt. Of Chemistry U.P. College Varanasi.
  2. Professor and Head to whom correspondence should be addressed .

as to affect injuriously the quality of food .

  1. If the food article has been prepared , packed or kept under insanitary conditions whereby it has become contaminated or injurious to health ,
  2. If the article consists wholly or in part of any filthy, putrid, rotten, decomposed or diseased animal or vegetable substance or is insect infested or otherwise unfit for human consumption .
  3. If the article is obtained from a diseased animal,
  4. If the article contains any poisonous or other ingredient which renders it injurious to health,
  5. If the container of article is composed , whether wholly or in part, of any poisonous or deleterious or deleterious substance which renders its contents injurious to health,
  6. If any colouring matter other than that prescribed or if the amounts of prescribed colouring matter are not within the prescribed limits of variability.
  7. If the article contains any prohibited preservative , or permitted preservatives in excess of the prescribed limits,
  8. If the quality or purity of the article falls below the prescribed standard or its constituents are present in quantities not within the prescribed limits of variability which renders it injurious to health.
  9. if the quality or purity of the article falls below the prescribed standard or its constituents are present in quantities not within the prescribed limits of variability but which does not render it injurious to health .

Provided that, where the quality or purity of the article, being primary food, has fallen below the prescribed standards or its constituents are present in quantities not within the prescribed limits of variability, in either case, solely due to natural causes and beyond the control of human agency, then, such article shall not be deemed to be adultered

The rules laid down under PFA Acct apply equally and essentially to all articles of food, including milk and milk products. It is evident from the PFA Act that food adulteration includes :

  1. Intentional addition, substitution or abstraction  of substances which adversely affect the quality of foods,
  2. Incidental contamination of foods with deleterious constituents such as toxins, pesticides, pathogenic micro organisms etc., due to ignorance, negligence or lack of proper storage facilities,
  3. Contamination of food with harmful micro organisms during production, packaging, storage and distribution.

FRAUDULENT CHARACTER :

As to the character of adulteration, generally encountered in market foods , 9 out of 10 adulterated foods are so classed by reason of the addition Of cheaper though harmless ingredients added for commercial profit rather than by the addition of actually poisonous or injurious substances, though occasional instances of the latter are found. Authentic instances of actual danger to health from the presence of injurious  ingredients are rare so that the question of food adulteration should logically be met largely  on the ground of its fraudulent character.

NATURE OF ADULTERATION :

Before going into the details of hazards of adulteration , we will have a look on the nature of adulterants generally encountered in milk and milk products.

Milk and milk products

Adulterants

Milk

water, removal of fat, addition of skim

 

Milk, reconstituted milk, skim milk

 

Powder thickening agents such as

 

Starch, arrowroot, flour, cane sugar

 

Glucose, urea, fertilizers pesticides,

 

NaCl, chlorine and pesticide residues,

 

Antibiotics and other drugs

 

Preservatives neutralizers, kerosene

 

Oil petroleum products heavy metals etc.

Cream

Other fats, thickening agents .

Butter

Hydrogenated fats, thickening agents animal  Fat, margarine, pea nut butter .

Ghee           

Vegetable oils, fats, animal fats, thickening Agents pesticides .

Condensed milk                   

 

 

Preservatives, colour, skim milk, Homogenized foreign fats

Ice cream                        

Prohibited colour, artificial sweeteners, Prohibited flavours, foreign fats.

Milk powder                                 

starch dextrins

Khoa, Rabari and other       

Starch, arrowroot, blotting paper arti

Concentrated indigeneous               

ficial sweeteners, colouring matters .

Milk products

Milk based sweets                         

 

Starch, colouring matter, artificial

Sweeteners .

Cheese

Starch, prohibited colouring matters, hydrogenated fats aflatoxins .

 

 

It is obvious from the above table that not only harmless adulterants but toxic and injurious substances also find their way in milk and milk products. Many cases of food poisoning from these dairy products have been noticed in the past. Despite food legislation , these have remained uncontrolled. Unscrupulous producers and traders in our country have never shirked to deal with adulterated or sub standard stuff for human consumption to make monetary gains. Where millions of producers and traders are involved where consumers are not fully initiated in checking malpractices and value of wholesome food, legal steps as laid down in PFA Act are extremely difficult to maintain Furthermore without adequate trained man power and laboratory facilities . It is almost impossible to deal with millions of producers and traders. More often than not the application of the PFA Act therefore, remains confined to large traders and organized dairies, the number of which is relatively small .

HEALTH HAZARDS :-

Sub standard  qualities of dairy products which are outcome of malpractice of adulteration besides affecting adversely the nutrient value of these products also pose potential health hazards to consumers owing to unhygienic practices followed during their preparation, storage and distribution. Food poisoning out breaks through consumption of Indian milk products and milk based sweets have been reported (Ghodekar et al. 1974 Batis et al 1981 The types of toxins elaborated by some micro organisms in milk and milk products have been listed below :

 

S.No

Causative organisms

Toxins

1.

Staphylococus

Enterotoxins A,B,C,D, E and F

2.

Clostridium botulinum

C, perfringens

Neurotixin, A to F

A to E Enterotoxin

3.

E, Coli

LT (Heal labile ) and ST (heat stable) enterotoxins

4.

B. cereus

Hemolysin, lecithinase and enterotoxin

5.

Aspergillus flavus

Aflatoxins  M1, M2, M4 etc

 

Cheese, milk powders , butter cream frozen milk products like kulfi and ice cream are all potential carrier or staphylococcal enterotoxins as revealed by several food poisoning outbreaks (Batish et al 1981) In these circumstances, it would be appropriate to suggest that the Public Health Authorities should see that regulations are strictly enforced at all stages beginning from procurement of good quality milk free from pathogens to marketing of final products passing through manufacture, handling, storage and transportation.

ADULTERATION RAMPANT :

The malpractice of adulteration in milk products has reached an alarming  stage, Besides milk the menace of adulteration is rampant in almost all dairy products but it is too widely rampant in such products as ice cream, butter and ghee, which are by and large, in great demand by consumers. Substandard qualities of these products containing various types of harmful adulterants including pesticide residues are available in the market. Indigenous milk products are also widely adulterated Khoa and paneer besides milk based sweets are widely adulterated as these are in great demand, Ghee he costliest dairy product is the most adulterated dairy product and most of the research work has been carried out to find out simple, rapid and reliable tests to detect various adulterants in ghee ( Kumar et al 2002) Reports on survey of market guality of dairy  products have revealed that about 50 percent of market samples were adulterated (Kumar et al 1981 subrahmanyam, 1981 Sharma  and Gupta 1982 Dubey and Gupta 1986 ; Sharma  1991; Rao et al 2002 and Arora et al 2004 ) Rao et al (2002) found 95% of samples from venders to be adulterated .

          Recently , Arora et al (2004) conducted a survey to detect adulteration in milk in some states of North India, using rapid test kit developed at NDRI, Karnal. The prominent adulterants detected were urea, starch, sugar, neutralizer, common salt and added water. The most common adulterant encountered was water followed by neutralizers and sugar. Adulteration was detected in all the states of North India which were surveyed and in some milk samples more than one adulterant was detected The following table depicts the status of milk adulteration in some states of North India :

Table – 1 : Status of Milk adulteration in some states of North India ,

 

Name of the State

Total No of samples 

Total adulterated (%)

No. of milk samples found containing

Urea

Starch

Glucose

Sugar

NeutraLizers

Salt (NaCI)

Added

Formain

More than one adulterant

Panjab

337

91 (25%)

1

1

3

0

22

0

51

1

12

U.P.

254

58(22%)

1

5

0

1

11

1

20

3

13

Delhi

64

25(39%)

0

0

0

1

16

0

0

0

8

Rajasthan

20

10(50%)

0

0

0

1

8

1

0

0

0

Haryana

321

120(37%)

4

2

4

20

35

4

46

0

5

Total

996

304

9

8

7

23

92

6

117

4

38

 

 

30.5%

0.9%

0.8%

0.7%

2,3%

9.2%

(0.6%)

(11.7%)

0.1%

(3.8%)

Arora et al (2004)

       

It is  obvious that Rajasthan, Delhi and Haryana are the prominent states , where adulteration is rampant . It is interesting to note that out of 321 samples collected from Haryana, 120 samples were found to be adulterated The samples from Haryana U.P. and Panjab also contained urea/ synthetic milk .

          Not only private sector but public sectors including organized dairies have also been found to be involved in this malpractice . Even today, quite a good percentage of samples bearing ISI or Agmark Standards would be found to be of substandard quality . Even reputed brands of milk products manufacturers are trying to maintain just the minimum prescribed standards and not the optimum standards of quality. Unless the laws are strictly enforced, it would be impossible to get rid of the heinous crime of adulteration .

SYNTHETIC MILK VERSUS ADULTERATED MILK :

Adulteration of milk has assumed new heights with the emergence of synthetic milk in few states of northern India. However the synthetic milk phenomenon in India is quite recent with report appearing from Kurukshetra, Haryana. Over the years, the reports of synthetic milk menace have also emerged from the states of Himachal Pradesh , Punjab, Rajasthan and Uttar pradesh (Kumar et al 1998).

          The word synthetic milk is a misnomer. By synthetic milk , one would normally understand a product analogous to natural milk in appearance physical chemical and nutritional properties but there is absolutely no similarity between the two . It is a high degree  of adulteration to increase the volume or quantity of milk for increasing the profit Normally it is mixture of water pulverized soap / detergent vegetable/ refined oil caustic soda salt urea etc An expert can detect synthetic milk in its pure form on the basis of its appearance, flavour and consistency but when it is mixed with natural milk it is difficult to detect through organoleptic testes the smell, flavour, colour, taste and consistency appear natural in skil fully adulterated milk Table 2 depicts the differences between synthetic and natural milk .

Table -2: COMPARISON OF SYNTHETIC MILK WITH NATURAL MILK

Sl. No

Characteristics

Synthetic milk

Natural milk

1.

Appearance

White

White

2.

Taste

Bitter

Palatable

3.

Odour

Soapy becomes distinct on boiling

Characteristic milky odour

4.

Texture

When rubbed between fingers, gives a soapy feeling

No soapy feeling when rubbed between fingers

5.

Ph

Alkaline, 8.0-10.0

6.6-6.8

6.

Urea test

Distinctly positive (Deep yellow colour)

Faint yellow due to natural urea in milk

7.

Sugar test (Sucrose,glucose)

Positive

Negative

8.

Neutraliser Test

Positive

Negative

9.

Vegetable oil/fat test

Positive

Negative

10.

On heating

Turns yellowish
 

Remains white

   

Adulterated milk differs from synthetic milk in the sense that the bulk of mixture is natural milk to which some additional components, viz. water skim milk sugar salt preservatives and / or neutralizers have been added to enhance the bulk or extend the shelf life of raw milk. On the other hand, the synthetic milk does not contain any natural milk constituent synthetic milk poses great risk to human health and life because of excessive use of harmful detergents/ chemicals like caustic soda urea ammonium sulphate formalin hydrogen peroxide etc sodium ions in caustic soda and detergents increase the risk of coronary heart diseases . and urea in synthetic milk causes deleterious effects on kidneys. In brief , synthetic milk is a toxic beverage .

 

DETECTION OF ADULTERANTS IN MILK :

 

          Simple and rapid methods have been developed to detect various adulterants in milk . The ingredients of synthetic milk are also detected by specific tests for urea, ammonium sulphate, detergents, vegetable oils etc.

Some of these tests have been delineated below :

 

  1. Detection of removal of fat by  skimming :

This is indicated by the following :

  1. Lower percentage of fat
  2. Higher density reading
  3. Higher ratio of SNF: fat
  1. Detection of added waster :

This is indicated by the following

  1. Lower percentage of fat.
  2. Lower percentage of SNF
  3. Lower density reading
  4. Depression of freezing point .

 

Water is the most common adulterant and its presence can be detected by testing the freezing point of milk the AOAc Specifies a freezing point for normal milk of – 0.550C and the percentage of dded water is calculated as follows :

Percentage of added water = 0.550- T  x 100

                                       0.550

T is the freezing point depression (FPD) of suspected milk sample. FPD of pure milk is 0.550.

          A tolerance of 3 percent is allowed , which is equivalent to specifying a minimum FPD for authentic milk of 0.53350C . The addition of preservatives and other soluble matters like sugar and salts decrease the freezing point of watered milk and thus escape the detection of adulteration .

3. DETECTION OF STARCH :

          Starch, cereal flours or arrowroot are added to make up the density of milk to prevent detection of added water . It is detected by starch- iodide test .

          Three ml well mixed sample is taken in a test tube . It is heated to boil over flame, cooled to room temp. A drop of 1 percent iodine solution is added and mixed . Appearance  of blue colour indicates the presence of starch which disappears on boiling and reappears on cooling.

4. Detection of cane sugar :

            It is added to raise the density to prevent detection of extraneous water.

          To about 10 ml milk in a test tube, add 1 ml conc. HCL and 0.1 g resorcinol and mix Place the test tube in boiling water bath for 5 min, In the presence of cane sugar (sucrose), red colour is produced .

5. Detection of glucose :

          Whereas the test for detection of cane sugar is simple, that of glucose is not so. For this reason, glucose may be added to milk instead of sucrose .

          Take 1 ml milk or protein- free filtrate and add 1 ml. modified Barfoed reagent. Heat in boiling water bath for 3 min and cool under tap water for 2 min Then add 1 ml phosphomolybdic acid reagent and mix. Development of deep blue colour indicates the presence of glucose in milk. Pure milk shows faint bluish due to diluted Barfoed reagent .

6. Detection of Sodium Chloride :

          Sodium choride ( common salt) is added to make up the density (lactometer reading) of watered milk.

          Take 2 ml of milk and add 0.1 ml of 5 percent  potassium chromate and 2 ml of 0.1 N silver nitrate . Appearance of Yellow precipitate indicates the presence of sodium chloride .

7. Detection of Ammonium Sulphate :

            Like  urea, ammonium sulphate is a chemical fertilizer, which is added to milk to raise the density of watered milk.

          Take 2 ml. milk in a test tube  and add 0.5 ml NaOH (2%) 0.5 ml sodium hypochlorite (2%) and 0.5 ml phenol (5%) Heat in boiling water bath for 20 sec. A bluish colour forms immediately, which turns deep blue afterward .

 

          Pure milk shows salmon pink colour which gradually changes to bluish after 2 hours .

8. Detection of Urea :

            Like ammonium sulphate, urea is a chemical fertilizer, which is added to watered milk to make up its density (lactometer reading) Being an important ingredient of synthetic milk, it is also used in milk to raise its SNF content Several methods have been developed to detect adulteration of milk with added urea. It is noteworthy that urea is also a natural constituent of milk. The average content of urea in cow milk is  about 50 mg/100 ml whereas in buffalo milk it is present to the extent of 35 mg/100 ml (average). It is also important to note that feeding of urea as a protein supplement in the ration of dairy animals does not help to increase the urea content of milk substantially. However , concerted investigations need to be taken up in this direction as the menace of urea adulteration in milk is rising day by day .

Test (i)

          Take 5 ml. milk and add equal volume of 24 percent trichloroacetic acid (TCA) to precipitate fat and proteins of milk. Filter and collect filtrate take 1 ml. filtrate and add 0.5 ml. sodium hypochlorite (2%),0.5ml. sodium hydroxide (2%) and 0.5 ml phenol solution (5%) and mix .

          A characteristic blue or bluish green colour develops in presence of added urea whereas pure milk remains colourless.

Test (ii)

            Take 5 ml milk in a test tube, add 0.2 ml urease (20 mg/ml) Shake well at room temperature and then add 0.1 ml Bromothymol Blue (BTB) solution (0.5%) Appearance of blue colour after 10-15 min. indicates the presence of urea in milk. Normal milk shows faint blue colour due to natural urea present in milk.

Test (iii)

          Take 5 ml milk in a test tube and add 5 ml of p – Dimethyl Amino Benzaldehyde ( DMAB) reagent (1.6% in ethyl alcohol containing 10% HCI) Development of distinct yellow colour denotes the presence of added urea. The pure milk sample shows a slight yellow colour due to the presence of natural urea in milk .

          Processing treatments such as chilling, pasteurization and boiling of milk as well as adulterants and neutralizers do not affect the determination of added urea in milk (Bector et al 1998)

          The  test is more sensitive when it is conducted on protein free filtrate obtained as in case of test (i).

9. Detection of Detergent in milk :

            Take  5 ml in a test tube and add 0.1 ml Bromocresol Purple (BCP) solution (0.5%) Appearance of violet colour indicates the presence of detergent in milk Pure normal milk shows only faint violet colour .

10. Detection of Pulverized soap:

            It is  also an ingredient of synthetic milk like detergents .Soaps are defined as sodium or potassium salts of fatty acids. Hence, to detect the presence of pulverized soaps, iodine value, refractive index, fatty acid  composition, salt ratio etc. are excellent methods. The presence can also be detected by qualitative method as follows .

          To 10 ml. of milk in a test tube, 10 ml. hot water is added followed by 2-3 drops of phenolphthalein indicator. Development of red/pink colour denotes the presence of soap in milk.

11. Detection of synthetic milk:

            Take  5 ml milk in a test tube and add 0.2ml urease (20 mg. per ml) Shake well and then add 0.1 ml of BTB solution (0.5%) Appearance of dark blue colour indicates the presence of synthetic milk. The methods for detection of urea and synthetic milk are same, the only difference is appearance of dark blue colour in  case of synthetic milk .

12. Detection of Neutralizers in milk :

          Neutralisers such as caustic soda , caustic potash sodium carbonate, sodium bicarbonate and lime water etc. are commonly added to milk to neutralize the developed acidity in milk. Some of these chemicals (neutralizers ) are also ingredients of detergents which  are major components of synthetic milk The neutralizers added to milk are detected as follows :

Test (i):

          To  above 5 ml milk in a test tube, add 5 ml of alcohol and a few drops of rosolic  acid (1 percent alcoholic solution) and mix well. Appearance of rose red colour indicates the presence of sodium carbonate or bicarbonate neutralizer in milk. Pure milk shows only a brownish colouration.

Test (ii) Determination of pH:

            The pH of milk to which neutralizers have been added is generally alkaline. The pH of such milk is always more than 8.0, which can be determined by using indicator dyes, pH paper or electrometrically using pH meter.

Test (iii) Alkalinity of Ash:

                        Neutralisation of milk with lime, soda ash or caustic soda increases the ash content, and total alkalinity of the ash from a fixed quantity of milk. This is detected by ashing accurately measured 20 ml of milk and titrating the ash after dispersing in 10 ml water. If the amount of standard 0.1 N hydrochloric  acid required to neutalise the alkalinity exceeds  1.20 ml, it indicates the presence of neutralisers in milk .

13.Detection of colouring matter :

          It is a common practice to adulterate buffalo milk with water and sell it as cow milk after adding some yellow colour to it. The following colours are generally used :

  1. Artificial colours
  2. Coaltar dyes
  3. Annatto
  4. Turmeric

Some of these dyes are permitted only in some dairy products but none in milk. Thee are often detected as follows :

Test (i):

          To 10 ml milk in a test tube, add 10 ml diethyl ether and shake vigorously. Allow to stand . Presence of any colour is indicated by yellow colour of the ethereal layer .

Test (ii)  

          Add sodium bicarbonate to milk to make it alkaline. Immerse a strip of filter paper for 2 hours. Red yellow colour observed on filter paper indicates the presence of annatto. Treatment of paper with stannous chloride turns pink.

Test (iii)

          Add a few drops of hydrochloric acid to milk. Development of pink colour indicates azo (coaltar) dyes .

14. Detection of Buffalo milk added to cow milk :

          Where there is a great demand for cow milk the buffalo milk is generally diluted with water and mixed with cow milk to meet the shortages  in demand. It is easily easily detected by Hansa test for this test Hansa test serum is required .

          First dilute the milk 1/10. Put  a drop of diluted milk on the centre of a glass slide. Now place a drops of Hansa test serum (duly preserved) on the drop of milk and mix together with a glass rod or clean tooth pick. curdy particles develop within half a minute in milk containing buffalo milk.

15. Detection of formaldehyde :

            Formalin (40 percent aqueous solution of formaldehyde) is the most common preservative added to milk. The addition of any kind of preservative to milk is legally prohibited. Yet, market samples of milk are occasionally found adulterated with formaldehyde or hydrogen peroxide . Formalin (formaldehyde ) added to milk is detected by Hehner test  as follow :

To about 10 ml milk is a test tube. About 5 ml concentrated sulphuric acid containing traces of ferric chloride is added slowly along the side of the test tube so that it forms a layer at the bottom, without mixing with the milk. The development of a violet or blue colour ring at the junction of the two liquids indicates the presence of formaldehyde The test may be combined with the determination of fat nothing whether a violet colour forms on addition of sulphuric acid in the butyro meter .

16. Detection of Hydrogen peroxide

          This is another preservative which is frequently used in milk to prolong its keeping quality .

          Add to about 5 ml of milk(suspected sample) in a test tube, an equal volume of raw milk and 5 drops of a 2 percent solution of paraphenylene  diamine. A blue colour  is developed in presencec of hydrogen peroxide.

Note : Hydrogen peroxide in destroyed when milk is heated or stored for a long period .

17. Detection of nitrates (pond water ) in milk :

          Sodium and potassium nitrates are oxidizing agents and hence act as preservative Pond water also contains appreciable quantities of nitrates and such water is usually admixed with milk by rural milk producers or vendors .

  1. Take 10 ml milk in a beaker and add 10 ml mercuric chloride solution (2.5%in 1% HCI) Mix well and filter through what man No 42 filter paper .
  2. Take 1 ml filtrate in a test tube and add 4 ml of diphenyl amine sulphate or diphenyl benzidine  reagent Development of blue colour indicates the presence of nitrates .

18. Detection of Vegetable fat :  

              In synthetic milk milk fat is replaced by vegetable fat or oil (refined oil) Thus, vegetable fat/oil is the chief source of fat in synthetic milk. When synthetic  milk is admixed with cow or buffalo milk, the presence of vegetable  oil/fat becomes evident, which can be easily detected by one or more of the following methods :

  1. Detection by measuring analytical constants :

The adulteration of vegetable fat in milk can be detected by extracting the fat either by Rose- Gottlieb method or fat extracted in butyrometer (special butyrometer having both end open) and measuring its physico- chemical characteristics such as Butyro refractometer (BR) reading, Reichert – Meissi and Polenske values.

  1. Baudouin test:

Hydrogenated vegetable oils (vanaspati) is a common adulterant in

milk fat. Its presence in milk fat can be detected by the fact that sesame oil (minimum 5%) is added in vanaspati by the law. Thus the presence of this oil in milk fat indicates the presence of vanaspati or sesame oil.

To 5 ml melted milk fat in a test tube, add 5 ml conc. HCI and 0.4 ml furfural solution (2% distilled not earlier than 24 hr. in alcohol.) Shake vigorously for 2 minutes and allow the mixture to separate. The development of red or pink colour in acid layer indicates the presence of sesame oil, which is confirmed by adding 5 ml water and shaking again. If colour in acid layer persists , sesame oil/ vanaspati is present .

19. Detection of Adulterants by using kits :

     Several test kits for detecting various adulterants viz  urea, neutralizers, sucrose, glucose, pesticides antibiotics, aflatoxins have been developed in our country at National Dairy Research Institute, Karnal, Central food technological Research Institute, Mysore, PCDF, Lucknow and elsewhere . For detection of mastitis, simple strip test has been developed further M/s Gist Brocades, Netherlands, have developed Delvotest kits testing presence of antibiotics and sulpher drug residues in milk.

Causes of Adulteration :

  1. Demand and Supply gap

More acute during summer due to low milk production and increased

demand .

  1. Physical nature of milk

Aqueous and opaque nature of milk can accommodate many

adulterants in milk .

 

  1. Degraded moral society

Wrecked moral status coupled with passion for profiteering .

  1. Spoiled socio- economic structure

Poor persons engaged in the business do so to increase their income and raise socio- economic status .

  1. Perishable nature of milk

The unscrupulous producers / traders use preservatives neutralizers

etc. to prolong the shelf life of sub standard milk .

  1. Low purchasing power of customer

Encourages the supplier to adulterate milk and sell at cheaper rate .

  1. Unorganised condition of dairy industry :

Most of the milk is procured and traded by unorganized dairies, which freely adulterate the milk .

  1. Low legal standards and their improper enforcement .
  2. Lack of suitable, rapid and sure tests

Consumers have no access to public analytical laboratories to get their samples analysed.

Adulteration of Ghee and its detection :

            Ghee is an expensive product costing 3 times as much as edible vegetable oils Thus its adulteration is a very profitable proposition and one widely practiced variable nature of the product is a further incentive to adulteration The analytical characteristics of ghee cover a very wide range permitting fairly high degrees of adulteration while still keeping within these natural limits .

          Aqueous emulsions of coconut, groundnut and other oils, or various starches are added to milk. On souring and churning. These pass into butter and thence into ghee, the latter still exhibiting its characteristic flavour.

          Various vegetable oils are in common use. Coconut oil approaches close to ghee in its analytical characteristics and is the bugbear  of the analyst Tallows and other animal body fats are procured from slaughter houses and being hard and firm and difficult to be detected visually in ghee even when present in considerable amount In fact blends of tallow and vegetable oil can be prepared which look remarkably like ghee .

Detection :

          Several methods have been developed for the detection of adulteration in milk fat (ghee) which are based on the differences in the nature and extents of major / minor components of milk fat and adulterant fat / oil No single test can detect all types of adulterant fat/ oil. Hence, often more than one test has to be employed o confirm the purity of milk fat .

          Adulterants in ghee are generally detected by following methods :

  1. Using different fat constants ( analytical characteristics )
  2. Using specific tests for different adulterants viz (a) vegetable fats

(b) Animal fats (c) Non fatty materials .

   1. Using different fat constants :

                   Fats and oils  exhibit certain physico chemical characteristics which have long been employed for their characterization and differentiation These analytical characteristics indicate the nature of constituents which make up the fat Ghee is unique among natural fats  in that it contains a large proportion of fatty acids of chain length lower than 12 C atoms and therefore its characteristics are quite distinctive .

          Five analytical characteristics are considered to be of prime importance. Of these, 3 characteristics, the Reichert Meissl Value (RV) Polenske Valve (PV) and iodine value (IV) measure certain specific constitnents of milk fat. Two other characteristics the specific   value (SV)  and Butyro refract meter (BR) reading (or refractive index ) give an indication of the overall average nature of the constitnent fatty acids present .

          Based on some of these analytical characteristics, the legal (PFA) and Agmark standards have been provided to keep a check on the adulteration of ghee .

Table – 3 describes the standards of ghee under prevention of food Adulteration (PFA) act .

Table 3 : Standards of Ghee under PFA Rules

S No

Name of the State & U.T

B.R Reading At 400 C

RM (Reichert) Meissl value (Min)

Percentage of FFA (as Oleic acid ) (Max)

Percentage of Moistur (Max)

1.

Bihar, Chandigarh, Delhi, Punjab, Haryana (Areas other than

cotton tract) Sikkim 

40-43

28

3

0.5

2.

Manipur Meghalaya Mizoram Arunachal Pradesh Orissa Nagland Tripura Assam Goa Kearla Himachal Pradesh U.P. J&K Maharashtra Rajasthan (Areas other than jodhpur Division ) Haryana (Cotton Tract Areas) Lakshadweep

40-43

26

3

0.5

3.

Kamataka Belgaum Distt Madhya Pradesh Areas sotehr than cotton tract areas Pondicherry

40-44

26

3

0.5

4.

Andhra Pradesh Daman & Diu Dadar & Nagar Haveli Kamattak (Areas other than Belgaum Distt)

40-43

24

3

0.5

5.

Andaman & Nicobar Island Tamil Nadu

41-44

24

3

0.5

6.

Gujarat (Areas other than cotton tract )

40-43.5

24

3

0.5

7.

Gujarat (Cotton tract areas) Madhya Pradesh (Cotton tract areas) Maharashtra (cotton tract areas) Rajasthan (Jodhpur sub division)

41.5-45

21

3

0.5

  • Baudouin  test shall be negative
  • By cotton tract is meant the areas in the state where cotton seed is extensively fed to the cattle and so notified by the state Govt concerned
  • Usually such cotton tract areas ghee has low RM value and high BR reading compared to other areas
  • Ghee may contain BHA not more than 0.02% as antioxidant .

 

 

Table -4:  Agmark  standards of Ghee

Sl.No

Tests

All India

Winter

Regional

Summer

1.

Baudouin

Negative

Negative

Negative

2.

Phytosterol Acetate

Negative

Negative

Negative

3.

B.R.reading(400C)

40.0-43.0

41.5-44.0

42.5-45.0

4.

R.M. Value (Minimum)

28

23.0

21.0

5.

Polenske Value

1.0-2.0

0.5-1.2

0.5-1.0

6.

Moisture (%)

---Maximum

0.3

 

7.

Free fatty acids ( as %Oleic acid)

 

 

 

 

(a)Special Grade (Red Label )

Not more than

1.4

-------------

 

(b) General Grade

(Green Label)

Not more than

2.5

 

 

(C) Standard Grade

(Chocolate Label)

Where cotton seed is exclusively fed to milch animal .

Not more than

3.0

-------

             

Analytical characteristics of adulterant oils and fats :

          It is necessary to understand the physico chemical characteristics of adulterant oils and fats to assess the nature and extent of changes in these characteristics of ghee as a consequence of adulteration . Table 5 describes some of these analytical characteristics .

Table 5: Some characteristics of Ghee and Adulterant oils and Fats

Oils / Fats

B.R Reading (at 400C)

R.M. Value

Polenske

Value 

Saponifi cation Value

Lodine Value

Bomer

Value

Opacity Time (at 230C)

Crystalli

Zaition Time**(at 170C)

Cow ghee

40-43

28-33

2-3

225-235

32-35

63-64

18-19 min

---

Buffalo ghee

40-43

30-36

1.5-2.5

230-237

31-37

63-64

14-15 min

18-20min

Buffalo ghee

 

 

 

 

 

 

 

 

(cottonseed fed)

44-45

15-22

0.5-0.7

210-220

41-44

66-68

11-12min

10.5-12.5 min

Groundnut oil

53-58

--

--

188-195

84-102

-

>40min

>35 min

Vanaspati

 

 

 

 

 

 

 

 

Hydrogenated oil

52-55

-

---

197-199

70-79

66-67

1.5-2.0 min

>35min

Coconut oil

38-39

6- 8

15-20

245-262

6-10

-

>40 min

>35min

Palm Oil

39-40

4-8

7-12

243-255

10-18

-

>40 min

>35min

Sesame Oil

60-64

-

--

185-195

100-120

-

>40 min

>35min

Buffalo body fat

45-46

0.5

0.5

192-199

30-36

68-69

5-7 sec 10-12 sec

Instant

Cow body fat

47-49

-

--

193-199

38-54

-

---

Instant

Goat body fat

44-46

0.5

0.5

197-198

33-37

68-69

30-40 sec

Instant

Pig body fat

48-51

0.5

0.5

197-200

56-64

75-76

---

Instant

Sheep body fat

45-46

0.5

0.5

199-200

36-41

68-69

 

Instant

*Time required to acquire opacity of 0.15 O.D

** Time required for the   appearance of crystals . 

Source : Kumar et al (2002)

 

          Besides analytical characteristics, some of other tests like opacity test , Bomer valve and crystallization test have been found highly useful in detecting adulteration of ghee with vegetable fat and / or animal body fat opacity test and crystallization tests are particularly useful and described below in some detail .

2. Using Specific test :

(1) Opacity test :

          Singhal (1980)  developed an opacity test to detect the Adulteration of ghee with animal body fat . Test is performed by taking a clear melted fat sample (5g) in a test tube and maintained at 500C for 30 min. Test tube is then transferred to 230C Water bath and the opacity time ( time taken by the clear melted fat sample to become opaque i.e., optical density > 0.5) is recorded at 590 nm in a colorimeter . Normal ghee takes more than 35 minutes while animal body fat (buffalo, goat and sheep ) take only 10 to 20 seconds to become opaque .

          In a modified test, Panda and Bindal (1998a) recorded the opacity time (table 5) as the time required by a fat sample at 230C to acquire the O.D in the range of 0.14 to 0.16 and consequent transmittance of 68 to 72 Opacity time of pure ghee (14-15 min) was found to be much higher than that of ghee adulterated with animal body fats (2-9 min at 10% level and 3-11 min at 5% level of adulteration ) and much lower than that of ghee adulterated with vegetable oils (21-25 min at 10% level and 19-21 min. at 5% level .

(2)Crystallisation test :

The crystallization test has been developed to detect the adulteration of ghee / milk with animal body fat and vegetable oils separately or in combination ( Panda and Bindal 1998 b) This test obviates the use of any spectrophotometer /colorimeter and can be easily used as a platform test .

          Melted and filtered fat (0.8ml) is taken in a glass stoppered tube, to which 2.5 ml of the solvent mixture ( acetone : benzene , 3.5:1) is added and mixed thoroughly. The tube is placed in waterbath maintained at 170C till the onset of csrystallisation . The time required for the occurrence of crystallization in fat sample is noted .

          Table 6 and 7 show that ghee adulterated ( as low as 5% level) with animal body fats ( cow buffalo and pg) crystallizes within 8 to 15 min. In comparison to genuine ghee which shows crystallization time of 19 min (Panda and Bindal 1998 b).

Table 6: Crystallization Time * at 170C of Ghee before and after Adulteration with Animal Body fats at 5% and 10% Level .

Ghee

Adulterant

Time (min) of crystallization at

0% Level

5%Level

10% Level

Buffalo ghee

---

19

-

---

 

Pig body fat

-

15

12

 

Cow body fat

-

10

5

 

Buffalo body fat

-

8

3

Cotton tract ghee

 

11

-

--

*Based on 8 observation

 

 

                                     

Table – 7: Crystallization Behaviour of Normal Ghee, Cotton Tract Ghee and Adulterated Ghee

Time /Temp

Normal Ghee

Cotton Tract Ghee

Adulterated Ghee with 5% Cow Body fat

At 170C

 

 

 

After 5.5 min

No crystals

No Crystals

Crystals appeared

After 6.0 min

--do--

Crystals appeared 

Crystals increased

After 6.5 min

--do--

Crystals increased

----do---

After 8.0 min

--do--

5.5 ml crystals

4.5 ml crystals

At 250C

 

 

 

After 11min

---do--

Crystals disappeared

Crystals persisted

After 25 min

---do---

---do---

--do--

 

          Ghee samples prepared from milk adulterated with animal body fats (crystallization time 4 to 12 min) and these of milk adulterated with vegetable oils (23 to 27 min) were also detected by this test. The crystallization time of all these samples was wither considerably lower (animal body fats as well as hydrogenated fats ) or higher (vegetable oils) than that of ghee sample prepared from normal milk (19 min) as is clear from table 8 ---)

Table -8: Crystallization Time at 170C of Ghee prepared from Normal Milk and Milk Adulterated with animal body fats and vegetable oils (10% level)

Milk Fat

Adulterant

Time (Min) of Crystallization

Ghee (Control)

------

Pig body fat

Cow body fat

Buffalo body fat

Safflower oil

Cottonseed oil

Soybean oil

Groundnut oil

Sunflower oil

Mustard oil

Coconut oil

Hydrogenated oil (Dalda)

19.0

12.0

4.5

4.0

23.0

25.5

26.0

26.0

27.0

26.5

25.0

15.5

* Based on 8 observation

 

  1. Baudouin Test :

Addition of 5 percent sesame oil to vanaspati is compulsory as a marker for detecting the adulteration of latter in ghee by Baudouin test the method has been described in detail earlier .

  1. Phytosteryl Acetate (PA) test :

The  detection of plant sterols (phytosterols) in association with cholesterol is important in detecting the adulteration of milk fat with vegetable fat .

The melting point of cholesteryl acetate (114-150C ) is lower than that of phytosteryl acetates (125-1370C) . If  the melting point of steryl acetate is 1150C the ghee sample is genuine and  free from vegetable fat If the melting point is higher than 1170C, the fat  sample is considered to contain vegetable fat.

  1. Halphen’s test for cotton- seed oil

This test can detect as low as one percent cotton seed oil. The ghee samples from cows fed with cotton seed meal give a positive test.

To 5 ml melted ghee in a test tube, add 5 ml iso amyl alcohol and 5 ml 1 percent solution of sulphur in carbon bisulphide Heat in boiling water bath for 30-35 min. The development of rose red colour indicates the presence of cotton seed oil.  

Note : If cotton seed oil has been heated above 2500C, the test fails completely .

  1. Methylene Blue Reduction (MBR) test for cotton seed oil :

This test is based on the cylopropenoic fatty acids present in cotton seed oil which quickly reduce the methylene blue dye. Reduction of  methylene blue denotes either the presence of cotton seed oil in milk fat or ghee from cotton tract area. Normal ghee does not reduce methylene blue .

  1. lodine test for presence of starch :

Starchy   materials are used when liquid oil are added to ghee to increase its consistency. These materials are insoluble in fat and therefore easily detected by mixing the ghee with hot water, removing aqueous layer and adding a few drops of 1 percent iodine solution. The formation of blue colour indicates the presence of starch.

          Remedial measures :

  1. There is need for rationalization of the standards prescribed under PFA  Act . Buffalo milk, for which minimum requirement for fat % is 6 in most of the states, is hardly available as such in the market for sale . Either it is watered and sold as cow milk or admixed with cow milk and sold as mixed milk . In lieu of buffalo milk, full cream milk has been introduced containing minimum of 6.0% fat and 9.0% SNF.
  2. The PFA Act and Rules must be strictly enforced and offenders punished adequately. The manpower limitation, lack of adequate training to the food inspectors and apathy of consumers encourages the menace of adulteration .
  3. The adulterated substandard and injurious food stuffs (including dairy products) should be discouraged from trade. The enforcement of the act should be rigidly carried out particularly against unorganized dairies and small traders and vendors, which are the root causes of this malpractice .
  4. Certain discrepancies exist in the standards prescribed under PFA Act and ISI and Agmark standards . These anomalies should be rectified and a uniform standard should be prescribed .
  5. Rapid, reliable and inexpensive tests to detect various harmless and harmful adulterants should be worked out so that cases of adulterations are detected readily .
  6. The milk producers should be given  incentives for clean milk production  and should be encouraged to supply the milk to the registered village societies, milk unions and dariries. The various intermediaries should be eliminated .
  7. Special provision should be made for packaging and distribution / sale of dairy products. Most of the market samples of dairy products are stored under unhygienic conditions and sold loose without any specification with regard to the nature and content of the product .
  8. Special provisions should be framed for rigorous control over the production, distribution and sale of milk and milk products including registration of premises where they are manufactured , maintenance of premises in a sanitary condition and maintenance of healthy states of human beings associated with the production, distribution and sale of such foods .

REFERENCES

Arora, S., Sharma, V; Raj,  D; Ram, M. and Kishore, K. (2004) . Status of        milk adulteration in some states of North India. Indian J. Dairy Sci. 57 :65-66

Bector, B.S., Ram , M. and Singhal, O.P. (1998) Rapid platform test for detection / determination of urea in milk. Indian Dairy man 50 : 59-60.

Batis, V.K., Garg, S.K., Chander, H. and Ranganathan, B. (1981) .Indian Dairyman 33,435.

Dubey, P.C. and Gupta , M.P. (1986) Studies on quality of rabri. J. Agric Sci Res 28:9-14.

Ghodekar, D.R., Dudani, A.J and Ranganathan, B (1974). J. Milk fd Techn 37,199.

Kumar A., Lal, D., Seth , R. and Sharma , R (2002) Recent trends in detection of adulteration in milk fat a review Indian J. Dairy Sci. 55: 319-330

Kumar M., Rao, Y.S and Gupta ., M.P. (1981) Chemical quality of milk based sweets sold in Agra and Mathura cities. J. Agric Sci Re 23:13-17

Kumar , R., Singh, D.K. and Chawla , N.K. (1998) . Adulteration / Contamination of milk demystified . Indian dairyman 50: 25-33

PFA Act (1954) Prevention of food Adulteration Act and rules . Govt of India publication as amended upto date .

Panda , D. and BIndla, M.P. (1998 a) Detection of adulteration in ghee with animal body fats and vegetable oils using opacity test . J. Dairying foods & Home Sci. 17:31-36 .

Panda ., D. and Bindal, M.P (1998 b) Detection of adulteration in ghee with animal body fats and vegetable oils using crystallization tests Indian Dairyman 50: 13-16 .

Rao, L.V., Ranganadham, M and Rao B.V.R (2002) Quality of milk and milk product marketed in Hyderabad City. Part I Chemical quality of milk and fermented milk Indian J. Diary Sci 55: 338-341.

Sharma G.S (1991) quality of creamery buller marketed in Agra City M.Sc Thesis submitted to Agra Univ. Agra .

Sharma M.B. Gupta M.P. (1982) Quality of Mawa Bhurfi sold in Agra city Asian J. Dairy Res 1 : 165-168

Singhal, O.P. (1980) . Adulterants and methods of detection . Indian Dairyman 32: 771-774 .

Subrahmanyam (1981). Indian Dairyman 33. 33.

Varadaraj, M.C. Kand Nambudripad, V.K.N. (1982). J. Fd. Sc. Techn . 19: 53.

Varadaraj, M.C. Mahadev, B.S. and Ahmed, Ashfaq (1983). Indian Dairyman 35: 301 .

Akshay Sadana

Posted Date : 31/03/2015 Posted By : Admin