Marco Polo in the 13th century reported that soldiers of Kublai Khan carried sun-dried milk on their expeditions. In more recent times, milk has been dried in thin films on heated rollers. The earliest patents for this process date from the turn of the century. Such roller drying was the main means of producing milk powders until the 1960s when spray drying took over. Milk powder manufacture is now very big business throughout the world. New Zealand alone produced and exported over 450 000 tonnes of milk powder during the 1993/94 dairying season, earning in excess of NZ$1 billion then and now it’s even a bigger trade commodity throughout the world with many countries producing to meet the worldly demand.
World producers manufacture a wide range of spray dried milk powders (> 100) to meet the diverse and special needs of customers. Milk powders may vary in their; gross composition (milkfat, protein, lactose), the heat treatment they receive during manufacture, powder particle size and packaging. Special “high heat” or “heat-stable” milk powders are required for the manufacture of certain products such as recombined evaporated milk. Milk powders of various types are used in a wide range of products such as baked goods, snacks and soups, chocolates and confectionary (e.g. milk chocolate), ice cream, infant formulae, nutritional products for invalids, athletes, hospital use etc., recombined milks and other liquid beverages.
Powdered milk or dried milk is a manufactured dairy product made by evaporating milk to dryness. One purpose of 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. Another purpose is to reduce its bulk for economy of transportation. Powdered milk and dairy products include such items as dry whole milk, nonfat dry milk, dry buttermilk, dry whey products and dry dairy blends. Many dairy products exported conform to standards laid out in Codex Alimentarius.
Advantages of Powdered Milk
Powdered Milk has a good storage life, because with almost all the water removed from the milk, microbes that would spoil it have nothing to live or grow on. To prolong its storage life even further, most powered milk is made from low-fat milk, because fat can go rancid. The downside is that with the lack of fat and aroma molecules, Powdered Milk is not very appealing when mixed with water and drunk straight up.
Powdered Milk will eventually spoil with age. Regular Powdered Milk will spoil faster than Non-fat (skim) Powdered Milk, especially at stores where there’s not a large turnover of it.
Regular Powdered Milk is less expensive than Instant Powdered Milk, because it is somewhat harder to mix up — it doesn’t dissolve in water right away, the way the Instant does. You pretty much has to mix it up, let it sit overnight in the fridge, then give it a whisk in the morning. There is no taste difference in baking between fresh and powdered milk.
Most Powdered Milk is actually used commercially rather than in homes due to the storage and long shelf life advantages. Chances are, if you buy something that says its ingredients include milk, powdered milk was used.
Powdered Milk is more popular in the developing world, where they don’t have dairy herds or refrigeration.
Analysis and nutritional values
Reconstitution The weight of nonfat dry milk (NFDM) to use is about 10% of the water weight. Alternatively, one cup of potable fluid milk from powdered milk requires one cup of potable water and one-third cup of powdered milk.
Nutritional value Milk powders contain all twenty-one 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 nonfat dry milk are (by weight) 36% protein, 52% carbohydrates (predominantly lactose), calcium 1.3%, potassium 1.8%. Whole milk powder, on the other hand, contains on average 25-27% protein, 36-38% carbohydrates, 26-40% fat, and 5-7% ash (minerals). However, inappropriate storage conditions such as high relative humidity and high ambient temperature can significantly degrade the nutritive value of milk powder.
While pasteurised milk needs refrigeration and lasts only days, dried milk can be stored for up to four years at 10 degrees Celsius. Care must be taken, however, to keep dried milk airtight and away from sunlight and high temperatures. Exposure to hot sunlight in tropical countries during disaster relief for example, greatly reduces dried milk’s lifespan.
Weight and Volume
Dried milk is lighter and takes up less space. This has storage and shipping advantages, and makes it ideal for backpackers. Reduced weight and volume, combined with longer shelf life and greater economy, make dried milk a staple for emergency relief and disaster preparedness. The same qualities make dried milk a staple of food production, especially baked goods. Using fresh milk would increase the cost of food production.
Safety and Taste
Dried milk powders require a safe water supply for mixing. This can be a problem in disaster relief situations–water may be contaminated and power supplies to boil water limited. There have been problems with supplying baby formula to third world countries without good water supplies, where breast feeding would be much safer. Due to their dusty texture, traditional dried milks mix poorly with water and retain a slightly gritty texture, leading some to dislike the taste.
Newer agglomerated products have improved solubility, while taste is a question of familiarity. Using dried milk for cooking, but fresh milk for drinking is one solution.
Although the calcium, protein and riboflavin content of milk is unaffected by drying, vitamin C, thiamine and vitamin B-12 are lost. Powdered milk is higher in sodium and sugars than fresh pasteurised milk. For shelf-life enhancement, dried skimmed milk is best. Milks with higher fat content do not store so well, but because dried skimmed milk has no fat, it also lacks the fat-soluble vitamins. Children under 2 years must have full milk because they need the fat and vitamins.
Full Cream Milk Powder is available in both 26% and 28% fat levels with a variety of Instant, Agglomerated and Regular products produced to the most exacting of specifications.
Standard powders, because of their fine dusty nature, do not reconstitute well in water. “Agglomerated” and “instant” powders were specifically developed to counter this. The manufacture of an agglomerated powder initially follows the standard process of evaporation and drying, described above. However, during spray drying small particles of powder leaving the drier (the “fines”) are recovered in cyclones and returned to the drying chamber in the close proximity of the atomiser. The wet concentrate droplets collide with the fines and stick together, forming larger (0.1-0.3 mm), irregular shaped “agglomerates”. Agglomerated powders disperse in water more rapidly and are less dusty and easier to handle than standard powders.
INSTANT WHOLE MILK POWDER
With WMP, an extra step is required after agglomeration to make the product truly “instant” and overcome the hydrophobic (water-hating) nature of traces of free fat on the surface of the particles. This extra step consists of spraying minute quantities of the natural surfactant or wetting agent, soy lecithin, on to the powder in a fluid bed. Soy lecithin is extracted from soy bean oil. Lecithins are widespread in nature and they occur naturally in milk.
World s leading manufactures, produce a wide range of spray dried milk powders (> 100) to meet the diverse and special needs of customers. Milk powders may vary in their gross composition (milkfat, protein, lactose), the heat treatment they receive during manufacture, powder particle size and packaging. Special “high heat” or “heat stable” milk powders are required for the manufacture of certain products such as recombined evaporated milk. Some powders are agglomerated and they may be instantised for easy use in the home. Instant powders must wet, sink and disperse quickly, with minimal stirring, when added to water. The resulting liquid should closely resemble fresh milk and be free from undissolved particles. Some powders are fortified with vitamins and minerals. It is very important to use a powder suited to the intended application. Milk powders of various types are used in a wide range of products including the following;
- Baked goods, snacks and soups
- Cheese milk extension (powder is added to local fresh milk to increase the yield of cheese)
- Chocolates and confectionery (e.g. milk chocolate)
- Dairy desserts
- Direct consumer use (home reconstitution)
- Ice cream
- Infant formulae
- Nutritional products for invalids, athletes, hospital use etc.
- Recombined “fresh”, UHT, evaporated and sweetened condensed milks
- Recombined cheeses, mainly “soft” or “fresh”
- Recombined coffee and whipping creams
- Recombined yoghurts and other fermented products
Powdered 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.
|Atomiser :||A device for producing fine droplets of liquid. Usually either a high pressure nozzle or a perforated spinning disk through which the liquid is pumped.|
|Concentrate :||Milk concentrated by evaporation, typically containing around 48% total solids.|
|Cyclone :||A device for separating air and powder particles.|
|Effect :||A single unit in an evaporator operating at a particular pressure and temperature. Evaporators commonly have three to seven effects to allow heat to be reused several times.|
|Fluid bed :||A piece of equipment used for drying or cooling milk powder. Air is blown through the powder from below, causing the powder particles to separate and behave rather like a fluid. Alternatively, a layer of fluid-like powder in which the particles are kept apart by an air flow.|
|Recombined :||Liquid milk or other “fresh” product made by mixing skim milk powder, milkfat, water and possibly other components.|
|Reconstituted :||Liquid milk or other “fresh” product made by mixing milk powder and water.|