Possible Adulterations in Milk

Possible Adulterations in Milk

Fig Milk

Milk at the time of the secretion comprises two liquid phases. The aqueous phase contain solubilized lactose, whey proteins, some minerals and water soluble vitamins which are present in the simple solution while protein and other ions are present in the colloidal suspension. The liquid phase contains fat globules, fat soluble vitamins and other compounds such as careteniods. Collectively milk is an emulsion of fat globules and a suspension of casein micelles (casein, calcium, phosphorous) all suspended in an aqueous phase.

The proximate composition of milk is given below:

Constituents	%
water	87.54
Fat	3.71
casein	2.63
Whey protien	0.42
Protease-peptone	0.13
Other nitrogenous matter	0.11
lactose	4.70
Ash	0.76
Total	100

Fig: proximate composition of milk

Adulteration normally people think the addition of unwanted things in the foods which it could be health hazardous. But additions of unwanted particles are not just adulteration but removal of necessary things such as removal of essential oil from cloves, removing of milk fat from milk etc.

Here is a typical video of adulterations shown in Indian Channel Aaj Tak

Talking about the milk adulteration the milk may be adulterated in following thing:

Addition of lime

In milk neutralisers like hydrated lime, sodium hydroxide, sodium carbonate or sodium bicarbonate are added which are prohibited. Milk starts to coagulate when the pH lowers or temperature higher. So in order to stop coagulation the milk normally agriculturist use neutralisers to stop coagulating milk. The acidity of milk can be checked with help of titration.

Addition of Formalin

Formalin i.e., 40% formaldehyde (HCHO) solution can also be added to preserve milk for the long time. This is very dangerous to health.

Take 10 ml of milk in test tube and 5 ml of concentrate sulphuric acid is added on the sides of the test tube without shaking. If a violet or blue ring appears at the intersection of the two layers, then it shows the presence of formalin.

Addition of Sugar

Sugar is also added to increase the solid not fat (SNF) content of milk to increase the lactometer (a device to measure the water content) reading of milk, which was already diluted with water.

Take 10 ml of milk in a test tube and add 5 ml of hydrochloric acid along with 0.1 g of resorcinol. Then shake the test tube well and place the test tube in a boiling water bath for 5 min. Appearance of red colour indicates the presence of added sugar in milk.

Addition of Starch

Addition of starch also increases the SNF content of milk. Apart from the starch, wheat flour, arrowroot, rice flour is also added.

Take 3 ml milk in a test tube and boil it thoroughly. Then milk is cooled to room temperature and added with 2 to 3 drops of 1% iodine solution. Change of color to blue indicates that the milk is adulterated with starch.

Fig: Rice Starch Powder

Addition of detergents

Detergents may be added to increase the corrected lactometer reading. For this analysis take 5 ml of milk in a test tube and add 0.1 ml of bromocresol purple solution. Appearance of violet color indicates the presence of detergent in milk. Unadulterated milk samples show a faint violet color. A video of adulteration of detergent seen in India is added.

Addition of vegetable fat

The characteristic feature of milk is its fatty acid composition, which mainly consists of short chain fatty acids such as butyric, caproic, caprylic acid; whereas the vegetable fats consist mainly of long chain fatty acids and hence adulteration of vegetable fat in milk can be easily found out by analysing the fatty acid profile by gas chromatography.