The Composition of Milk: Constituents, Their Importance & Nutritional Benefits

We all have heard that milk is good for health, do you know why it is so healthy? If not, read the article “The Composition Of Milk: Constituents, Their Importance & Nutritional Benefits” till the end, you will surely know.

When we talk about milk, we think it is a white liquid produced by the mammary glands of mammals. It’s not as simple as it looks. Milk contains various components such as proteins, fats, lactose, vitamins, minerals, and enzymes, which are essential for the growth and development of our body.  

As per FSSAI (a food regulatory body in India), Milk means the normal mammary secretion derived from the complete milking of a healthy milch animal, without either addition or extraction of milk components, unless otherwise provided in these regulations and it shall be free from colostrum. This means that milk should be free from any additives or extractions, except as permitted by the FSSAI regulations. Along with this, milk must be free from colostrum, which is the first milk produced after childbirth and is high in nutrients.

Table 1: FSSAI Standards for Cow and Buffalo Milk:

*SNF: Solid-Not-Fats.                                        (Reference: FSSAI Regulations, 2011)

Composition Of Milk

As we are aware of what milk means, let’s have a look at the composition of milk. 

Water

Milk contains 84-88% of water, everything except water is called total solids (12-15%). In milk, water acts as a continuous phase in which other milk constituents are dispersed.

Fat

The rich nutty profile of milk is due to the presence of fats. Milk fats are the glycerol esters of fatty acids.  It gives milk that creamy texture. The color varies from yellow (due to carotene) to whitish light blue (due to bilirubin). In milk, fat exists in the form of many small spherical globules, which are coated with a membrane rich in phospholipids & proteins known as milk fat globule membrane. This milk fat globule membrane prevents two fat globules from coming in close contact with each other, hence maintaining the individuality of these small spherical fat globules. One gram of milk fats provides 9 kcal of energy.

Protein 

Milk also contains 3.2-3.5 % of protein. Proteins are made up of amino acids attached to form a long chain.  The main protein in milk is casein, which is 80% of the total protein present, the rest are whey proteins.

Casein in the milk exists in the form of a number of submicelles which are connected to each other with a calcium phosphate bridge, together forming a large single micelle. Whey proteins are a group of globular proteins, which are present as highly structured molecules. One gram of protein provides energy of 4 kcal.

Lactose

Lactose, a carbohydrate found only in milk, gives a sweet profile to milk accounting for 4.8%. Lactose is not as sweet as table sugar. It is made of glucose & galactose molecules. When it breaks down, it provides energy to the body & helps in the absorption of calcium. One gram of lactose provides energy of 4 kcal.

Minerals

Milk contains essential minerals such as calcium, magnesium, sodium, potassium, etc. The mineral content of milk varies from 0.7-0.8%, giving a slightly salty profile to milk. Buffalo milk has a slightly higher salt content and hence slightly higher salty taste profile. Milk is a rich source of calcium, which helps to build & maintain strong bones.

Vitamins 

Along with this milk also contains vitamins, which are divided into water-soluble vitamins & fat-soluble vitamins. Vitamins B & C are water-soluble vitamins, whereas Vitamins A, D, E & K are fat-soluble vitamins. These vitamins are important for the normal functioning and development of the human body and are not synthesized by our body.

Enzymes

Milk also contains enzymes such as lactase, lactoperoxidase, protease, lipase, peroxide, and many more. This can be inactivated by heat. Some of these enzymes are responsible for the preservation of milk, whereas others are responsible for the spoilage of milk.

Nutritive value of milk:

Milk consists of almost all the nutrients essential for newborns as they cannot digest nutrients from any other food source. The nutrients are present in milk in such a way that it provides nutrients in an easy and palatable form as well as gives energy and provides daily nutritional needs. The constituents present in milk are responsible for growth, energy supply, body maintenance, and disease recovery in newborns as well as adults

References:

Principles of Dairy Chemistry by Jennes & Patton.

A textbook of Dairy Chemistry by Ling, E.R. (1956).

Fundamentals of Dairy Chemistry Book by Robert Jennes.

FSSAI Regulations, 2011.