Milk Adulteration and Milk Properties

7/27/2019 Milk Adulteration and Milk Properties

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Milk Adulteration


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What is Food Adulteration?

Food adulteration - quality is lowered or affected

addition of substances which may be injurious to health

removal of substances which are nutritious.

Definition:

Act of intentionally debasing the quality of food offered for sale either

by the admixture or substitution of inferior substances or by the

removal of some valuable ingredient.


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When you state that a food is adulterated?

If any inferior or cheaper substance has been substituted wholly or in part,

If any constituent of the article has been wholly or in part removed

If the food has been prepared, packed or kept under insanitary conditions

If the food consists in part filthy, rotten, decomposed or diseased animal orvegetable or is infested with insects

If the article contains any poisonous ingredient

If the food has un-prescribed colouring substance or the colouring substanceis in excess of the prescribed limits.

If the food contains any prohibited or excessive preservatives.

If the quality or the purity of the article falls below prescribed standard

As per Prevention of Food Adulterant Act 1954


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Types of milk adulterants

1. Addition of water

2. Addition of colouring matter

3. Addition of preservatives

4. Addition of thickening agents


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Addition of water

Increase the quantity

most difficult to detect

pure - does no harm other than to defraud the consumer

impure - drawn from wells near manure heaps, in

barnyards, it may prove fatal.


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Addition of colouring matter

The normal whiteness and opacity of milk is due to its fat globules.

Carotene

Annotto is the commonest dye used to impart a yellow colour to milk,cream, and butter.

Annotto - seeds of a tropical American tree (Bixa orellana).

It is detected by allowing the milk to stand in a tall glass, where thelower stratum will contain the pigment associated with the caseininstead of remaining colourless, while the naturally yellower creamfloats on top.

The cow's milk red or pink, and it may be so stained by traces of blood


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Addition of preservatives

To keep them from souring.

To increase the shelf life or keeping quality of milk.

Preservatives: sodium bicarbonate, borax, or boric acid.Salicylic acid and formaldehyde are less often used.

In small quantities they do not affect its taste or hurt thedigestion of adults, but they may be injurious and evenfatal to infants, and their use should never be tolerated.


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Addition of thickening agents

To bring back the consistency of milk to normal

To raise the specific gravity

To adjust the Solid Non Fat content of the milk

Starch, Flour, arrowroot, chalk, carbonate of magnesia,

Sugar, etc


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Detection of Neutralizers in milk

Rosalic acid test (Soda Test) Test for detection of hydrogen peroxide

Test for detection of formalin

Test for detection of sugar in milk

Test for detection of starch

Test for detection of glucose Phosphomolybdic or Barford Test

Diacetic test

Test for detection of urea

Test for detection of ammonium sulphate

Test for detection of salt

Test for detection of pulverized soap

Detection of detergents in milk

Detection of water in milk

Detection of skim milk powder in milk

Detection of vegetable fat in milk

Detection of buffalo milk in cow milk

Detection of benzoic and salicylic acid in milk

Detection of borax and boric acid in milk

Test to detect milk adulterants


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Mixture of water, pulverized detergent or soap, sodium hydroxide,vegetable oil, salt and urea

Synthetic milk

Differentiating

tests

Genuine Milk Synthetic Milk

Physical tests

Colour White White

Storage On storage, it remains white It turns pale yellow after some time

Texture When rubbed on the palm, it doesnt form

foam

When rubbed on the palm, foam formation

noticed.

pH 6.6 to 6.8 1011 (Highly alkaline)

Fat 4.55.0% 4.55.0%

Solids Not Fat 89% 89%

Chemical tests

Heat No change in colour on heating It turns yellow on boiling

Urea test Pale yellow colour develops Dark yellow colour develops


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Milk allergy

adverse reactions - immunoglobulin E (IgE) antibodies

to one or more protein fractions of milk, whether

belonging to the casein or whey protein group.

Proteins belonging to the casein group are heat-stable, i.e., they cannot be broken down using heat.

Thus, individuals allergic to casein proteins cannot

tolerate any cow's milk, including boiled milk.

whey proteins can be broken down by heat.

occur in any individual. (young children, although

people can develop milk allergy at any age)


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Milk intolerance

Milk intolerance occurs as a result of the decrease or

absence of an enzyme, called lactase, in the

gastrointestinal tract that is required to metabolise the

milk sugar lactose.

mainly seen in individuals over the age of five.

Particularly black children partially or completely lose

this enzyme.


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localized, cutaneous, and mostly benign infection

caused by a DNA virus of the genus Parapoxvirus.

common in cattle worldwide.

Infections in cattle are also known as bovine papular stomatitis. Human disease is contracted through direct transmission (ie,

handling of infected cow teats, calf muzzles, or other sites ofactive bovine infection) or through indirect transmission (ie,handling of virally contaminated objects).

The course of milker's nodule is usually self-limited, running from14-72 days, with infrequent systemic symptoms and little or noscarring.

Milker's nodule


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Milk Properties

Milk proteins- consist mainly of casein, b -lactoglobulin, a -lactalbumin, etc.

Casein exists only in milk and is found in the form of a calcium caseinate-phosphate complex.

It is present in the colloidal state.

8 per cent of the total protein in milk. Casein itself is composed of a , b , g fractions.

b -lactoglobulins and a -lactalbumin are also known as whey or serum-proteins. They are also present in the colloidal state and are easily coagulableby heat.

Phospholipids:three types of phospholipids, viz. Lecithin, cephalin andsphingomylin. Lecithin, which forms an important constituent of the fat globule membrane,

contributes to the richness of flavour of milk.

highly sensitive to oxidative changes, giving rise to oxidized/ metallic flavours.

Phospholipids are excellent emulsifying agents, and no doubt serve tostabilize the milk fat emulsion.


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Density and Specific Gravity:

Milk is heavier than water.

The average specific gravity ranges

cow milk -1.028 to 1.030 for, buffalo milk -1.030 to 1.032

skim milk - 1.035 to 1.037 for.

Freezing point of milk Milk freezes at temperatures slightly lower than water due to the

presence of soluble constituents such as lactose, soluble salts,etc.,

Indian cow milk - 0.5470C (31.020F) and

buffalo milk - 0.5490C (31.010F).

Milk Properties


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Enzymes: 1) Analase (diastase)starch splitting,

2) Lipasefat splitting, leading to rancid flavour,

3) Phosphatecapable of splitting certain phosphoric acid esters (basis of phosphatasetest for checking pasteurization efficiency);

4) Pro-teaseprotein splitting;

5) Peroxidase and Catalasedecomposes hydrogen peroxide.

Vitamins:

Fat-soluble vitamins A, D, E and K; and

Water-soluble vitamins of the B-complex group (such as thiamine or B1, riboflavin or B2,pantothenic acid, niacin, pyridoxine or B6, biotin, B12, folic acid, etc.)

PH: cow milk - 6.4 to 6.6

buffalo milk - 6.7 to 6.8.

Higher pH values for fresh milk indicate udder infection (mastitis) and lower values,bacterial action.

Milk Properties


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Pigments:These are 1) fat soluble, such as carotene andxanthophyll, and

2) water soluble, such as riboflavin.

Carotene is the colouring matter of all green leaves, where it ismasked by chlorophyll. Carotene (the pure substance of whichhas a reddish-brown colour) is fat soluble and responsible for theyellow colour of milk, cream, butter, ghee and other fat-rich dairyproducts. Besides contributing to the colour of cow milk, caroteneacts as an anti-oxidant and also as a precursor of vitamin A.

Riboflavin, besides being a vitamin, is a greenish-yellowpigment, which gives the characteristic colour to whey.

Milk Properties


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Spoilage of Milk


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Milk

Rich source of nutrients

Also an efficient vehicle for a variety of pathogens

Sources of infection or contamination of milk

Dairy animal

Human handler or

Environment,

e.g., contaminated vessels, polluted water, flies, dust, etc.


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Spoilage occurs when microorganisms degrade the carbohydrates,

proteins, fats of milk and produce noxious, end products.

Spoilage of Milk and Milk Products


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Spoilage type Organisms involved Signs of spoilage

Souring Lactobacillus sp.

Streptococcus sp.

Sour milk,

curd formation

Sweet curdling Bacillus sp.

Proteus sp.

Micrococcus sp.

Alkaline pH

Curd formation

Gas production Clostoridium sp.

Coliform bacteria

Explosion of curds

Ropiness Alcaligenes sp.,Klebsiella

sp.,Enterobacter sp.

Stringy or slimy milk

Red rot Serratia marcescens Red colaration

Gray rot Clostridium sp. Gray colaration, Foul smell

Dairy mould Penicilium sp.,Geotrichum sp. Mouldy appearance

Different types of Spoilage of Milk and Milk Products


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Flavour of Milk

The flavour of milk is also due to the short chain fatty acidsproduced, particularlybutyric acid.

Acid/sourflavour - lactic acid bacteria which ferment lactose.

Fruityflavours may arise due to psychrotrophs such as Pseudomonasfragi.

Bitter or putrid- caused by psychrotrophic bacteria which produceprotease. It is the proteolytic action of protease that usually causesspoilage in milk.

Maltyflavours - caused by Streptococcus lactisvar. maltigenesand ischaracterized by a corn flakes type flavour.

Ropymilk is also caused by bacteria, specifically those which produceexopolysaccharides.

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Milk Adulteration and Milk Properties