Milk- Milk Nutrients and Composition

Milk- Milk Nutrients and Composition

• Milk is a nutrient-rich liquid food produced by the secretion from mammary glands of mammals. As an agricultural product, dairy milk is collected from farm animals.
• It is the primary source of nutrition for young mammals until they are able to digest solid food. Since it contains numerous nutrients, it makes a significant contribution to meeting the body’s needs for calcium, magnesium, selenium, riboflavin, vitamin B12 and pantothenic acid (vitamin B5).
• Milk and dairy products play a key role in healthy human nutrition and development throughout life, but especially in childhood.
• Milk does not contain enough iron and folate to meet the needs of growing infants, and due to the low iron content animal milks are not recommended for infants younger than 12 months old.
• Colostrum is early-lactation milk contains antibodies that strengthen the immune system and thus reduces the risk of many diseases in infants.
• India is the world’s largest producer of milk and the leading exporter of skimmed milk powder. India is also the largest producer and consumer of cattle and buffalo milk in the world. Highest milk producing states are Rajasthan>U.P>M.P; whereas, in per capita availability, Punjab ranks 1st followed by Rajasthan and Haryana.
• World milk day is celebrated on June,1, whereas National milk day is on November,26.

Nutrition for infant mammals

• Almost all mammals use breastfeeding in order to feed milk to infants. World Health Organization recommends exclusive breastfeeding for six months for humans.
• The early milk (colostrum) provides nutrients, contains antibodies that provide protection to the newborn baby.
• Milk is the food source for the young as all of its contents provide benefits for growth. It provides major requirements like energy (lipids, lactose, and protein), essential amino acids, essential fatty acids, vitamins and inorganic elements, and water.
• Fresh goats’ milk is sometimes substituted for breast milk, but is not suitable because it develops electrolyte imbalances, metabolic acidosis, and allergic reactions in infants.

Composition

• Milk is an emulsion or colloid of butterfat globules within a water-based fluid that contains dissolved carbohydrates and protein aggregates with minerals. Butterfat is a triglyceride (fat) formed from fatty acids such as myristic, palmitic, and oleic acids.
• Milk and cream is an emulsion of “oil in water type”, while butter is “water in oil type”.
• Fat is present as emulsion in milk, protein and some minerals are present as colloidal suspension in milk, lactose with some minerals and soluble protein as true solution.

Proximate composition of milk (per 100 g of milk)

pH

• The pH of milk ranges from 6.4 to 6.8 and it changes over time.

Lipids

• Initially milk fat (triacylglycerols) is secreted in the form of a fat globule surrounded by membrane called phospholipids along with proteins. These act as emulsifiers which keep the individual globules from coalescing and protect the contents of these globules from various enzymes in the fluid portion of the milk.
• Although 97–98% of lipids are triacylglycerols, small amounts of di- and monoacylglycerols, free cholesterol and cholesterol esters, free fatty acids, and phospholipids are also present.
• Unlike protein and carbohydrates, fat composition in milk varies widely due to genetic, lactational, and nutritional factor difference among species.
• Like composition, fat globules vary in size from less than 0.2 to about 15 micrometers in diameter between different species.
• In unhomogenized cow’s milk, the fat globules have an average diameter of two to four micrometers and with homogenization, average around 0.4 micrometers.
• The fat-soluble vitamins A, D, E, and K along with essential fatty acids such as linoleic and linolenic acid are found within the milk fat portion of the milk.

Proteins

• Normal bovine milk contains 30–35 gm. protein/liter of which about 80% is arranged in casein micelles.
• Caseins- There are four different types of casein proteins: αs1-, αs2-, β-, and κ-caseins. Most of the casein proteins are bound into the micelles. The kappa-casein molecules have a negative electrical charge and therefore repel each other, keeping the micelles separated under normal conditions and in a stable colloidal suspension in the water-based surrounding fluid.
• Beside caseins, milk contains other types of proteins including enzymes. These other proteins are more water-soluble than caseins and do not form larger structures. Lactoglobulin is the most common whey protein.

Salts, minerals, and vitamins

• Calcium, phosphate, magnesium, sodium, potassium, citrate, and chloride occur at concentrations of 5-40
• The milk salts strongly interact with casein, most notably calcium phosphate.
• In addition to calcium, milk is a good source of many other vitamins. Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin, riboflavin, folates, and pantothenic acid are all present in milk.

Sugars

Milk contains lactose, glucose, galactose, and other oligosaccharides. The lactose gives milk its sweet taste and contributes approximately 40% of whole cow’s milk’s calories. Lactose is a disaccharide composite of two simple sugars, glucose and galactose.

Appearance

• Both the fat globules and the smaller casein micelles, which are just large enough to deflect light, contribute to the opaque white color of milk.
• The fat globules contain some yellow-orange carotene to impart a golden or “creamy” hue.
• The riboflavin in the whey portion of milk has a greenish color, which sometimes can be discerned in skimmed milk or whey products.
• Fat-free skimmed milk has only the casein micelles to scatter light, and they tend to scatter shorter-wavelength blue light more than they do red, giving skimmed milk a bluish tint.

Food product for humans

• Lactase, the enzyme needed to digest lactose, reaches its highest levels in the human small intestine immediately after birth, and then begins a slow decline unless milk is consumed regularly. People therefore converted milk to different products like curd, cheese etc.to reduce the levels of lactose.
• There are a variety of processed milk products such as cream, butter, yogurt, ice cream, and cheese. Now a day’s milk is used to produce casein, whey protein, lactose, condensed milk, powdered milk, and other food-additives.
• The sugar lactose is found only in milk, except few flowers and shrubs but is not well known.
• Pasteurization– In 1863, French chemist and biologist Louis Pasteur invented pasteurization. This method is used for killing harmful bacteria in beverages and food products.

Production Worldwide

Here are the top milk producing countries worldwide-

1. India
2. European union
3. United states
4. Pakistan
5. Brazil
6. China
7. Russia

Frequently Asked Questions (FAQ)

What dairy products have probiotics?

Both fermented and probiotic foods are made with microorganisms. However, all fermented foods are not considered probiotics. Probiotics are live microorganisms that, when consumed in adequate amounts may deliver health benefits. Yogurt can be a probiotic food because the traditional cultures or good bacteria have ability to help with lactose digestion. These live cultures can help digest lactose, the naturally occurring sugar in milk.

What is A2 milk?

All milk contains beta casein, a protein that has two common forms: A1 and A2. A2 milk is a type of milk from certain dairy cows that produce milk highly concentrated in A2 beta casein. A2 milk only contains the A2 beta casein, which is thought to be easier to digest. This theory is controversial.

What is difference in cow and goat milk?

Both cow and goat milk has similarities in nutritional content like fat, protein and carbohydrate and both are excellent source of calcium and riboflavin. But goat milk contains very little folic acid and also low in vit-12 as compared to cow milk.

Why cannot some people tolerate milk?

Lactose intolerant people have problem to consume milk.

Is consuming raw milk beneficial?

Fresh cow milk can contain unhealthy bacteria. So, it is advised to drink milk after boil first.