Powdered Milk is milk that has been dehydrated to remove all the water, leaving just the solids behind in a powdered form. It was originally designed as a way to preserve milk. To make it, first about 1/3 of the water is evaporated from the milk under vacuum, then the milk is forced through either spray nozzles or atomizing wheels that remove any remaining water and leave just particles of milk powder behind.
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 (aka skim) Powdered Milk, especially at stores where there's not a large turnover of it. Sometimes you're better off getting it at bulk food stores, where you can smell it first. It should have no smell at all, not even that of milk. Strangely enough, it's often more expensive at the bulk stores than it is at regular stores. If you get a bad batch from the store, march it back.
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 have to mix it up, let it sit overnight in the fridge, then give it a whisk in the morning. While many people agree that both Regular and Instant taste terrible to drink straight up, in baking there is no taste difference between fresh and powdered milk.
Most Powdered Milk is actually used commercially rather than in homes. 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.
As a general rule of thumb, 100 g (3 oz weight) of powdered milk will make up 1 litre (1 US quart / 32 oz) of milk, unless a manufacturer provides different directions.
1 pound (450g) = 14 cups / 3.3 litres reconstituted
1 cup (4.5 oz / 125g) dry = 3 cups / 24 oz / 750 ml reconstituted
1 1/3 cups (6 oz / 175g) dry = 1 quart / 1 litre reconstituted
1/3 cup (1.5 oz / 40 g) = 1 cup / 8 oz / 250 ml reconstituted
1 tablespoon dry = .03 oz / 8 g dry
1 kg dry = 128 tablespoons
While it's true that the Mongols preserved milk by evaporating it in the sun, what they ended up with was more like chewy hunks of dried, chalk-like cheese.
It's often wrongly attributed to Henri Nestlé (1814 - 1890). Nestlé, born in Frankfurt as Heinrich Matthias, moved to Vevey, Switzerland in 1833 to work as a pharmacist. In 1839, he changed his name to Henri Nestlé. The reason the "invention" of powdered milk is attributed to him is that in 1867 he created an infant milk formula he called "Farine Lactée Henri Nestlé". This was not Powdered Milk, however: to Powdered Milk he added wheat flour (processed to remove the starch and acids) and sugar. Clearly, he already knew how to make or source Powdered Milk in order to create his now-famous infant food.
The credit for inventing Powdered Milk is also often given to Maurice Guigoz (1868 - 1919) in 1908. This, however, is actually when he started small-scale production of it -- there is no record of it having been an idea he came up with or a process he conceived. Guigoz went on to establish a factory in 1915 in Vuadens, Gruyère, Switzerland. The Guigoz brand of milk products had became a part of Nestlé by 1971 and remains so today, even though his original factory was closed in 1991.
The American "National Dairy Shrine" organization weighs in, attributing the invention to a Chester E. Gray (1881-1944), but gives no more details.
The most likely candidate appears to be none other than the American Gail Borden (1801-1874), who in the 1850s experimented with ways to evaporate milk. At the beginning of his work, in 1851, he refined a process permitting powdered milk. Some sources give the exact date as 31 January 1851; others vary the date to 1855 or 1856, though that is more likely their confusing the date with the year he patented his process for condensed milk.
The first North American manufacturer is sometimes given to be the Brownsville Cheese Company in Brownsville, Ontario, Canada, starting production in 1903. In 1909 they switched to using a spray and hot rollers system.
Powdered milk production began in Japan in 1917, mostly for use with infants.
Literature & Lore
Powdered MilkHousehold Milk; Instant Skim Powdered Milk; Malted Milk Powder; National Dried Milk; Powdered Milk
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