Milk is a translucent white liquid produced by the mammary glands of mammals. It provides the primary source of nutrition for young mammals before they are able to digest other types of food. The early lactation milk is known as colostrum, and carries the mother's antibodies to the baby. It can reduce the risk of many diseases in the baby. The exact components of raw milk vary by species, but it contains significant amounts of saturated fat, protein and calcium as well as vitamin C. Cow milk has a pH ranging from 6.4 to 6.8, making it slightly acidic.[1][2]
Types of consumption
There are two distinct types of milk consumption: a natural source of nutrition for all infant mammals, and a food product for humans of all ages derived from other animals.
Nutrition for infant mammals
In almost all mammals, milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later. Some cultures, historically or currently, continue to use breast milk to feed their children until they are 7 years old.
Human infants are sometimes fed goat milk. There are known risks in this practice, including those of developing electrolyte imbalances, metabolic acidosis, megaloblastic anemia and a host of allergic reactions.[3]
Food product for humans
In many cultures of the world, especially the Western world, humans continue to consume milk beyond infancy, using the milk of other animals (especially cattle, goats and sheep) as a food product. For millennia, cow milk has been processed into dairy products such as cream, butter, yogurt, kefir, ice cream, and especially the more durable and easily transportable product, cheese. Modern industrial processes produce casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additive and industrial products.
Humans are an exception in the natural world for consuming milk past infancy, despite the fact that more than 75%[citation needed] of adult humans show some degree (some as little as 5%) of lactose intolerance, a characteristic that is more prevalent among individuals of African or Asian descent.[4] The sugar lactose is found only in milk, forsythia flowers, and a few tropical shrubs. The enzyme needed to digest lactose, lactase, reaches its highest levels in the small intestines after birth and then begins a slow decline unless milk is consumed regularly.[5] On the other hand, those groups that do continue to tolerate milk often have exercised great creativity in using the milk of domesticated ungulates, not only of cattle, but also sheep, goats, yaks, water buffalo, horses, and camels. The largest producer and consumer of cattle and buffalo milk in the world is India.[6]
| Country | Milk (litres) | Cheese (kg) | Butter (kg) |
|---|---|---|---|
 Finland |
183.9 | 19.1 | 5.3 |
 Sweden |
145.5 | 18.5 | 1.0 |
 Ireland |
129.8 | 10.5 | 2.9 |
 Netherlands |
122.9 | 20.4 | 3.3 |
 Norway |
116.7 | 16.0 | 4.3 |
 Spain |
119.1 | 9.6 | 1.0 |
 Switzerland |
112.5 | 22.2 | 5.6 |
 United Kingdom |
111.2 | 12.2 | 3.7 |
 Australia |
106.3 | 11.7 | 3.7 |
 Canada |
94.7 | 12.2 | 3.3 |
Terminology
The term milk is also used for white colored and/or milk-like tasting non-animal beverages such as soy milk, rice milk, almond milk, and coconut milk. Even the regurgitated substance secreted by glands in the mucosa of their upper digestive tract which pigeons feed their young is called crop milk though it bears little resemblance to mammalian milk.
Grade A vs Grade B milk
In the United States, there are two grades of milk, with Grade A primarily used for direct sales and consumption in stores, and Grade B used for indirect consumption, such as in cheesemaking or other processing.
The differences between the two grades are defined in the Wisconsin administrative code for Agriculture, Trade, and Consumer Protection, chapter 60.[8] Grade B generally refers to milk that is cooled in milk cans, which are immersed in a bath of cold flowing water, typically drawn up from an underground water well rather than using mechanical refrigeration.
- Grade A farms are inspected every 6 months, while Grade B farms are inspected every 2 years {WI-ATCP 60.24.2}
- Both types of farms are required to have two cleaning vats in the milkhouse for washing and rinsing of equipment {WI-ATCP 60.07.2(g)}. A farm must also have an additional separate sink and faucet provided for handwashing {WI-ATCP 60.07.2(h)}, unless the bulk tank was installed before Jan 1, 1979 or the farm uses milk cans.
- Grade A milk stored in a bulk tank is cooled to 45 degrees F within 2 hours of milking. Grade A milk in a tank may only rise to 50 F if milk from additional milking sessions are added to the tank (potentially requiring a plate cooler to reduce the temperature of a large volume influx quickly enough) and must be cooled back to 45 F within two hours. {WI-ATCP 60.2.4(b)}
- Grade B milk in milk cans is cooled to 50 degrees F within 2 hours of milking. Grade B farms cannot mix milk into cans from previous milking. {WI-ATCP 60.2.4(c)}
- The somatic cell count (SCC) of Grade A or B cow or sheep milk may not exceed 750,000 cells per mL, and the SCC of Grade A or B goat milk may not exceed 1,000,000 cells per mL. {WI-ATCP 60.15.4}
- The bacterial plate or loop count of Grade A milk may not exceed 100,000 per mL, while Grade B milk may not exceed 300,000 per mL. {WI-ATCP 60.15.2}
- A bacterial plate count test is required at least once a month. {WI-ATCP 60.18.3} If the bacterial count exceeds 100,000 per mL for Grade A or 300,000 per mL for grade B in 3 out of 5 tests, the license to sell milk is suspended. The license will be immediately revoked if the bacterial count ever exceeds 750,000 per mL. {WI-ATCP 60.18.6}
Evolution
Milk glands are highly specialized sweat glands. It has been suggested that the original function of lactation (milk production) was to keep eggs moist. Much of the argument is based on monotremes (egg-laying mammals):[9][10][11]
History
Animal milk is first known to have been used as human food during the Secondary Products Revolution, around 5000 BC. It is assumed that when animals such as cattle were first domesticated, it was only for purposes of meat. Dairy products obtained from the animals proved to be a more efficient way of turning uncultivated grasslands into sustenance: the food value of an animal killed for meat can be matched by perhaps one year's worth of milk from the same animal, which will keep producing milk — in convenient daily portions — for years.[5]
Milk byproducts found inside stone age pottery from Turkey indicate processed milk was consumed in 6500 BC, some thousands of years before adult humans had evolved the ability to digest raw milk.[12][13]
DNA evidence extracted from Neolithic skeletons indicates that in 5500 BC, people in Northern Europe, like all other peoples of the time, were still lactose intolerant. Earthenware vessels found in England and dated to 4500 BC contain milk byproducts, indicating milk was used in some form, although perhaps not drunk directly.[14]
In 1863, French chemist and biologist Louis Pasteur invented pasteurization, a method of killing harmful bacteria in beverage and food products.[15]
In 1884, Doctor Hervey Thatcher, an American inventor from New York, invented the first glass milk bottle, called 'Thatcher's Common Sense Milk Jar', which was sealed with a waxed paper disk[15]. Later, in 1932, plastic-coated paper milk cartons were introduced commercially as a consequence of their invention by Victor W. Farris.[15]
In America, milk was first delivered in bottles on January 11, 1878.[citation needed] The town of Harvard, Illinois celebrates milk with a summer festival known as "Milk Days". Their's is a different tradition meant to celebrate dairy farmers in the "Milk Capital of the World."[16]
Sources
In addition to cattle, the following livestock animals provide milk used by humans for dairy products:
In Russia and Sweden, small moose dairies also exist.[17]
According to the National Bison Association, American bison (also called American buffalo) are not milked commercially.[18] However, various sources report cows resulting from cross-breeding bison and domestic cattle are good milk producers, both during the European settlement of North America[19] and during the development of commercial Beefalo in the 1970s and 1980s.[20]
Human milk is not produced or distributed industrially or commercially; however, milk banks exist that allow for the collection of donated human milk and its redistribution to infants who may benefit from human milk for various reasons (premature neonates, babies with allergies or metabolic diseases, etc.).
All other female mammals do produce milk, but are rarely or never used to produce dairy products for human consumption.
Modern production
In the Western world today, cow milk is produced on an industrial scale, and is by far the most commonly consumed form of milk. Commercial dairy farming using automated milking equipment produces the vast majority of milk in developed countries. Dairy cattle such as the Holstein have been specially bred for increased milk production. About 90% of the dairy cows in the United States and 85% in Great Britain are Holsteins.[5] Other dairy cows in the United States include Ayrshire, Brown Swiss, Guernsey, Jersey, and Milking Shorthorn (Dairy Shorthorn). The largest producers of dairy products and milk today are India followed by the United States,[21] Germany, and Pakistan.
Increasing affluence in developing countries, as well as increased promotion of milk and milk products, has led to a rise in milk consumption in developing countries in recent years. In turn, the opportunities presented by these growing markets have attracted investment by multinational dairy firms. Nevertheless, in many countries production remains on a small scale, and presents significant opportunities for diversification of income sources by small farmers.[22] Local milk collection centers, where milk is collected and chilled prior to being transferred to urban dairies, are a good example of where farmers have been able to work on a cooperative basis, particularly in countries such as India.[23]
The table below shows the numbers of water buffalo milk production. Cattle milk is produced in a much wider range.
| Country | Production (tonnes) | Note |
|---|---|---|
 India |
59,210,000 | Unofficial/Semi-official/mirror data |
 Pakistan |
20,372,000 | official figure |
 People's Republic of China |
2,900,000 | FAO estimate |
 Egypt |
2,300,000 | |
 Nepal |
958,603 | official figure |
 Iran |
241,500 | FAO estimate |
 Myanmar |
220,462 | official figure |
 Italy |
200,000 | FAO estimate |
 Vietnam |
32,000 | |
 Turkey |
30,375 | official figure |
| World | 86,574,539 | Aggregate |
Open source encyclopedia content modification information:
Authorship and Review
Open source encyclopedia content provided here is not reviewed directly by MedLibrary.org. Content is sourced directly from Wikipedia and is authored by an open community of volunteers. It is not produced by or in any way affiliated with MedLibrary.org.
Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Milk", which is available in its original form here:
http://en.wikipedia.org/w/index.php?title=Milk
All material adapted used from Wikipedia is available under the terms of the GNU Free Documentation License. Wikipedia® itself is a registered trademark of the Wikimedia Foundation, Inc.