Powdered milk

Powdered milk

Powdered milk is a manufactured dairy product made by evaporating milk to dryness. The purpose in drying milk is to preserve it - milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content - and to reduce its bulk for economy of transportation. Available as Dry Whole Milk (DWM), it is most commonly produced as Non-Fat Dry Milk (NFDM), also known as Dried Skim Milk (DSM).

History and Manufacture

While Marco Polo wrote of Mongolian Tatar troops in the time of Kublai Kahn carrying sun-dried skimmed milk as "a kind of paste, the first usable commercial process to produce dried milk was invented by T.S. Grimwade and patented in 1855, though a William Newton had patented a vacuum drying process as early as 1837. Today, powdered milk is usually made by spray drying nonfat skim milk or whole milk. Pasteurized milk is first concentrated in an evaporator to about 50% milk solids. The resulting concentrated milk is sprayed into a heated chamber where the water almost instantly evaporates, leaving fine particles of powdered milk solids.

Alternatively, the milk can be dried by drum drying. Milk is applied as a thin film to the surface of a heated drum, and the dried milk solids are then scraped off. Powdered milk made this way tends to have a cooked flavor, due to caramelization caused by greater heat exposure.

Another process is freeze drying, which preserves many nutrients in milk, compared to drum drying.

The drying method and the heat treatment of the milk as it is processed alters the properties of the milk powder (for example, solubility in cold water, flavor, bulk density).

Uses

Powdered milk is frequently used in manufacture of infant formula, confectionery such as chocolate and caramel, baked goods, in recipes where adding liquid milk would render the product too thin to be used. Powdered milk is also widely used in various sweets such as the famous Indian milk sweet balls known as Gulab jamun.

It is also a common in UN food aid supplies, fallout shelters, warehouses and wherever fresh milk is not a viable option. It is widely used in many developing countries because of reduced transport and storage costs (reduced bulk and weight, no refrigerated vehicles). As with other dry foods, it is considered nonperishable and is favored by survivalists, hikers and others needing of nonperishable, easy to prepare food.

Reconstituting 1 cup of milk from powdered milk requires 1 cup of potable water and 1/3 cup of powdered milk.

Powdered milk is also used in Western blots as a blocking buffer to prevent nonspecific protein interactions, and is referred to as Blotto.

Food and health

Nutritional value

Milk powders contain all twenty standard amino acids (the building blocks of proteins) and are high in soluble vitamins and minerals. According to USAID the typical average amounts of major nutrients in the unreconstituted milk are (by weight) 36% protein, 52% carbohydrates (predominantly lactose), calcium 1.3%, potassium 1.8%. Their milk powder is fortified with Vitamin A and D, 3000IU and 600IU respectively per 100g. Inappropriate storage conditions (high relative humidity and high ambient temperature) can significantly degrade the nutritive value of milk powder.

Oxysterols

Commercial milk powders are reported to contain, in general, very low levels of oxysterols (OS). However, compared to fresh milk (trace levels), powdered milk is higher in oxysterols (oxidized cholesterol), up to 30μg/g, yet significantly lower than powdered eggs (200μg/g). The OS free radicals have been suspected of being initiators of atherosclerotic plaques.

Adulteration

In the 2008 baby milk scandal in China, melamine adulterant was found in Sanlu infant formula, added to fool tests into reporting higher protein content. Thousands became ill and some children died after consuming the product.

See also

References

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