While Marco Polo wrote of Mongolian Tatar troops in the time of
Kublai Khan carrying sun-dried skimmed milk as "a kind of paste", the
first usable commercial production of dried milk was invented by the
Russian chemist M. Dirchoff in 1832. In 1855, T.S. Grimwade took a
patent on a dried milk procedure, 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, whole milk, buttermilk or whey.
Pasteurized milk is first concentrated in anevaporator 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).
Dried milk is frequently used in the manufacture of infant formula,
confectionery such as chocolate and caramel candy, and in recipes for
baked goods where adding liquid milk would render the product too thin.
Powdered milk is also widely used in various sweets such as the famous
Indian milk balls known as Rasa-Gulla and popular Indian sweet delicacy
(sprinkled with desiccated coconut) known as Chum chum (made with skim
Dried milk is also a common item 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 requiring nonperishable, easy-to-prepare food.
Reconstituting one cup of milk from powdered milk requires one cup of potable water and one-third cup of powdered milk.
Dried milk is also used in western blots as a blocking buffer to prevent nonspecific protein interactions, and is referred to as Blotto.
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.
Milk used in the production of milk powders is first clarified,
standardized and then given a heat treatment. This heat treatment is
usually more severe than that required for pasteurization. Besides
destroying all the pathogenic and most of the spoilage microorganisms,
it also inactivates the enzyme lipase which could cause lipolysis during
The milk is then evaporated prior to drying for the following reasons:
Homogenization may be applied to decrease the free fat content. Spray
drying is the most used method for producing milk powders. After
drying, the powder must be packaged in containers able to provide
protection from moisture, air, light, etc. Whole milk powder can then be
stored for long periods (up to about 8 months) of time at ambient
Skim milk powder (SMP) processing is similar to that described above except for the following points:
Low-heat SMP is given a pasteurization heat treatment and is used in the production of cheese, baby foods etc. High-heat SMP
requires a more intense heat treatment in addition to pasteurization.
This product is used in the bakery industry, chocolate industry, and
other foods where a high degree of protein denaturation is required.
Instant milk powder is produced by partially rehydrating the dried milk powder particles causing them to become sticky and agglomerate. The water is then removed by drying resulting in an increased amount of air incorporated between the powder particles.
Whey is the by-product in the manufacturing of cheese and casein.
Disposing of this whey has long been a problem. For environmental
reasons it cannot be discharged into lakes and rivers; for economical
reasons it is not desirable to simply dump it to waste treatment
facilities. Converting whey into powder has led to a number products
that it can be incorporated into. It is most desirable, if and where
possible, to use it for human food, as it contains a small but valuable
protein component. It is also feasible to use it as animal feed. Between
the pet food industry and animal feed mixers, hundred's of millions of
pounds are sold every year. The feed industry may be the largest
consumer of dried whey and whey products.
Whey powder is essentially produced by the same method as other milk powders. Reverse osmosis can be used to partially concentrate the whey prior to vacuum evaporation. Before the whey concentrate is spray dried, lactose crystallization is induced to decrease the hygroscopicity. This is accomplished by quick cooling in flash coolers after evaporation. Crystallization continues in agitated tanks for 4 to 24 h. A fluidized bed may be used to produce large agglomerated particles with free-flowing, non-hygroscopic, no caking characteristics.
Both whey disposal problems and high-quality animal protein shortages have increased world-wide interest in whey protein concentrates. After clarification and pasteurization, the whey is cooled and held to stabilize the calcium phosphate complex, which later decreases membrane fouling. The whey is commonly processed using ultrafiltration, although reverse osmosis, microfiltration, and demineralization methods can be used. During ultrafiltration, the low molecular weight compounds such as lactose, minerals, vitamins and nonprotein nitrogen are removed in the permeate while the proteins become concentrated in the retentate. After ultrafiltration, the retentate is pasteurized, may be evaporated, then dried. Drying, usually spray drying, is done at lower temperatures than for milk in order that large amounts of protein denaturation may be avoided.