Cow milk varieties, processing and health

 

In the framework of a balanced diet, milk can provide several essential nutrients required for proper growth, bones and teeth. It is a valuable source of calcium, a 200 ml glass providing a third of the recommended daily allowance. It is also important for protein, energy, vitamin B₂, vitamin B₁₂, phosphorus and iodine. Furthermore, milk contributes vitamin B₁, niacin, folate, vitamins A, D and C, potassium, magnesium and zinc to the diet.

 

 

Milk consumption varies widely between the different European countries. Most of us have a choice between whole, semi-skimmed and skimmed milks (Table 1). As about half of milk fat is saturated, switching to reduced fat milk can help limit saturated fat intake, especially in high milk consumers.

 

 

 

Fat is a concentrated source of energy, so reducing milk fat will help cut down calories. Semi-skimmed milk has about two thirds of the calorie content of whole milk and skimmed milk has only half. However, most health authorities recommend that children under the age of two years should not have reduced fat milks as they need the concentrated source of energy for rapid growth, and specifically the proper development of their nervous system. Skimmed milk should not be introduced until the age of five.

 

 

Calcium, protein and most other nutrients in milk are hardly found in the cream, so are retained when this is taken away. Vitamin A and a small amount of vitamin D are found in the cream as they are fat soluble vitamins, so are removed when milk is skimmed.

 

 

Most milk we drink is pasteurised, ESL (Extended Shelf Life)-treated or UHT (Ultra-High Temperature)-treated (Table 2). Pasteurisation has minimal effects on either taste or nutritional quality of milk and helps to increase shelf life. ESL milk keeps for ca. 3 weeks and tastes like fresh milk. UHT milk keeps for several months without refrigeration, when packed in air-tight containers, but once opened will go off like fresh milk. Like pasteurisation, the effects on nutritional quality are small, but it does have a distinctive taste. The more thorough heat treatment of sterilised milk destroys about half its vitamin C and B₁.

 

Filtering milk through very small-pored membranes, a process called microfiltration, can remove >99% of bacteria. The bacteria-enriched fraction held back by the membrane is then heat-treated separately and added back to the filtered milk. This minimises nutrient losses and heat-induced flavour changes.

 

Raw milk has a short shelf life and is less safe to drink than treated milk because of the possible presence of food-poisoning micro-organisms.

 

 

Most milk in shops has been homogenised so you do not see a creamy layer forming at the top. This is because the milk fat globules are broken up mechanically so they are distributed evenly (homogeneously) throughout the milk. Homogenisation does not affect the nutritional value.

 

Condensed or evaporated milk has double the concentration of most nutrients and energy as fresh milk as about half the water is removed, but it is sterilised so will have lost vitamins B₁ and C.

 

Dried whole or skimmed milk, when made up with water has similar amounts of protein, fat, calories and minerals as fresh milk but some of the vitamins are destroyed by the heat process. Vitamins are sometimes added to dried milk.