Milk: Definition, Composition and Nutritive Value

Definition

The mammary glands of mammals create milk, a nutrient-rich liquid diet. It is the main source of nutrition for young mammals until they can digest solid food. It includes vital elements, such as proteins, lipids, carbs, vitamins, and minerals, which are required for growth and development.

Constituents of Milk:

Milk is a complex emulsion and contains various components, which can be broadly categorized as:

1. Water: Approximately 87% is water.
2. Fat: Typically 3-5% of milk, depending on the type and breed of the animal. It is present in the form of tiny globules, forming an emulsion.
3. Proteins: Around 3.5%, with casein being the major protein (80%), and the rest are whey proteins.
4. Carbohydrates: Primarily lactose, which is about 4.8% of milk.
5. Minerals: Around 0.7%, including calcium, phosphorus, magnesium, sodium, potassium, chloride, etc.
6. Vitamins: Vitamins A, D, B1, B2, B6, B12, and niacin.
7. Enzymes: It also contains natural enzymes which assist in various metabolic processes.

Composition

It is made up of several essential components, each of which adds to its nutritious worth. Here’s a breakdown of the typical composition of cow’s milk, which may differ significantly depending on the type, breed, and nutrition of the animal:

Nutritive Value:

It is an excellent source of essential nutrients and provides a balanced mix of macronutrients and micronutrients, making it a highly valuable food, especially for growth and development.

1. Macronutrients

• Calories: Approximately 60-70 kcal per 100 ml (varies depending on the fat content).
• Proteins: Around 3.2 grams per 100 ml.
• Fats: Typically 3.5-5.0 grams per 100 ml, depending on the type of milk (whole, semi-skimmed, or skimmed).
• Carbohydrates: About 4.8 grams per 100 ml, mostly in the form of lactose.

2. Proteins

• High Biological Value (HBV): Milk proteins contain all essential amino acids required for growth and repair. Casein and whey proteins are the main protein fractions.
  • Casein: Provides slow-digesting protein, important for sustained nutrient supply.
  • Whey Proteins: Quickly digested, ideal for muscle repair and immune function.

3. Fats

• Milk fat provides essential fatty acids (linoleic and linolenic acids) and fat-soluble vitamins.
• The fat content varies depending on the milk type:
  • Whole milk: ~3.5-4% fat.
  • Semi-skimmed milk: ~1.5-2% fat.
  • Skimmed milk: Less than 0.5% fat.
• It also contains phospholipids and cholesterol, which play roles in cell membrane structure and hormone production.

4. Carbohydrates

• Lactose: The primary carbohydrate in milk. Lactose is a disaccharide composed of glucose and galactose, which provides energy and helps in calcium absorption.
• Lactose intolerance occurs when the enzyme lactase is deficient, making it hard to digest lactose.

5. Vitamins

• Vitamin A: Important for vision, immune function, and skin health.
• Vitamin D: Helps in calcium absorption and bone health. Fortified in many commercial milk products.
• B-Vitamins:
  • Vitamin B12: Vital for red blood cell formation and neurological function.
  • Riboflavin (Vitamin B2): Aids in energy metabolism.
  • Niacin, Thiamine: Support energy release and overall cellular function.

6. Minerals

• Calcium: One of the most abundant minerals in milk (120 mg per 100 ml), crucial for bone health, muscle function, and nerve transmission.
• Phosphorus: Works with calcium to strengthen bones and teeth.
• Magnesium, Potassium, Sodium: Play important roles in muscle function, nerve function, and maintaining electrolyte balance.
• Trace elements: Zinc, iodine, and selenium are present in small quantities and contribute to immune function, thyroid health, and antioxidant defense.

7. Water

Milk is about 87% water, making it a hydrating food that also supplies essential nutrients.

Frequently Asked Questions (FAQs)

Related Articles

• Cultivation, Establishment & Yield of Common Pasture Species
• Cultivation Practices of Annual and Perennial Fodder Legumes