Milk

Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals before they are able to digest solid food. Milk contains many nutrients, including calcium and protein, as well as lactose and saturated fat; the enzyme lactase is needed to break down lactose. Immune factors and immune-modulating components in milk contribute to milk immunity. The first milk, which is called colostrum, contains antibodies and immune-modulating components that strengthen the immune system against many diseases.
As an agricultural product, milk is collected from farm animals, mostly cattle, on a dairy. It is used by humans as a drink and as the base ingredient for dairy products. The US CDC recommends that children over the age of 12 months should have two servings of milk products a day, and more than six billion people worldwide consume milk and milk products. The ability for adult humans to digest milk relies on lactase persistence, so lactose intolerant individuals have trouble digesting lactose.
In 2011, dairy farms produced around of milk from 260 million dairy cows. India is the world's largest producer of milk and the leading exporter of skimmed milk powder. New Zealand, Germany, and the Netherlands are the largest exporters of milk products. Between 750 and 900 million people live in dairy-farming households.

Etymology and terminology

The term milk comes from "Old English meoluc, milc, from Proto-Germanic meluks ".
Since 1961, the term milk has been defined under Codex Alimentarius standards as "the normal mammary secretion of milking animals obtained from one or more milkings without either addition to it or extraction from it, intended for consumption as liquid milk or for further processing." The term dairy refers to animal milk and animal milk production.

Types of consumption

There are two distinct categories of milk consumption: all infant mammals drink milk directly from their mothers' bodies, and it is their primary source of nutrition; and humans obtain milk from other mammals for consumption by humans of all ages, as one component of a varied diet.

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. The early milk from mammals is called colostrum. Colostrum contains antibodies that provide protection to the newborn baby as well as nutrients and growth factors. The makeup of the colostrum and the period of secretion varies from species to species.
For humans, the World Health Organization recommends exclusive breastfeeding for six months and breastfeeding in addition to other food for up to two years of age or more. In some cultures it is common to breastfeed children for three to five years, and the period may be longer.
Fresh goats' milk is sometimes substituted for breast milk, which introduces the risk of the child developing electrolyte imbalances, metabolic acidosis, megaloblastic anemia, and a host of allergic reactions.

Food product for humans

In many cultures, especially in the West, humans continue to consume milk beyond infancy, using the milk of other mammals as a food product. Initially, the ability to digest milk was limited to children as adults did not produce lactase, an enzyme necessary for digesting the lactose in milk. People therefore converted milk to curd, cheese, and other products to reduce the levels of lactose. Thousands of years ago, a chance mutation spread in human populations in northwestern Europe that enabled the production of lactase in adulthood. This mutation allowed milk to be used as a new source of nutrition which could sustain populations when other food sources failed. Milk is processed into a variety of products such as cream, butter, yogurt, kefir, ice cream and cheese. Modern industrial processes use milk to produce casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additives and industrial products.
Whole milk, butter, and cream have high levels of saturated fat. The sugar lactose is found only in milk, and possibly in forsythia flowers and a few tropical shrubs. Lactase, the enzyme needed to digest lactose, reaches its highest levels in the human small intestine immediately after birth, and then begins a slow decline unless milk is consumed regularly. Those groups who continue to tolerate milk have often exercised great creativity in using the milk of domesticated ungulates, not only cattle, but also sheep, goats, yaks, water buffalo, horses, reindeer and camels. India is the largest producer and consumer of cattle milk and buffalo milk in the world.

Country	Milk	Cheese	Butter
	135.6	6.7	2.4
	127.0	22.5	4.1
	105.9	10.9	3.0
	105.3	11.7	4.0
	90.1	19.1	1.7
	78.4	12.3	2.5
	75.8	15.1	2.8
	62.8	17.1	3.6
	55.7	3.6	0.4
	55.5	26.3	7.5
	54.2	21.8	2.3
	51.8	22.9	5.9
	49.1	23.4	0.7
	47.5	19.4	3.3
	39.5	–	3.5
	9.1	–	0.1

History

Humans first learned to consume the milk of other mammals regularly following the domestication of animals during the Neolithic Revolution or the development of agriculture. This development occurred independently in several global locations from as early as 9000–7000BC in Mesopotamia to 3500–3000BC in the Americas. People first domesticated the most important dairy animals – cattle, sheep and goats – in Southwest Asia, although domestic cattle had been independently derived from wild aurochs populations several times since. Initially animals were kept for meat, and archaeologist Andrew Sherratt has suggested that dairying, along with the exploitation of domestic animals for hair and labor, began much later in a separate secondary products revolution in the fourth millennium BC. Sherratt's model is not supported by recent findings, based on the analysis of lipid residue in prehistoric pottery, that shows that dairying was practiced in the early phases of agriculture in Southwest Asia, by at least the seventh millennium BC.
From Southwest Asia domestic dairy animals spread to Europe, and South Asia. The first farmers in central Europe and Britain milked their animals. Pastoral and pastoral nomadic economies, which rely predominantly or exclusively on domestic animals and their products rather than crop farming, were developed as European farmers moved into the Pontic–Caspian steppe in the fourth millennium BC, and subsequently spread across much of the Eurasian steppe. Sheep and goats were introduced to Africa from Southwest Asia, but African cattle may have been independently domesticated around 7000–6000BC. Camels, domesticated in central Arabia in the fourth millennium BC, have also been used as dairy animals in North Africa and the Arabian Peninsula. The earliest Egyptian records of burn treatments describe burn dressings using milk from mothers of male babies. In the rest of the world, milk and dairy products were historically not a large part of the diet, either because they remained populated by hunter-gatherers who did not keep animals or the local agricultural economies did not include domesticated dairy species. Milk consumption became common in these regions comparatively recently, as a consequence of European colonialism and political domination over much of the world in the last 500 years.
In the Middle Ages, milk was called the "virtuous white liquor" because alcoholic beverages were safer to consume than the water generally available. Incorrectly thought to be blood diverted from the womb to the breast, it was also known as "white blood", and treated like blood for religious dietary purposes and in humoral theory.
James Rosier's record of the 1605 voyage made by George Weymouth to New England reported that the Wabanaki people Weymouth captured in Maine milked "Rain-Deere and Fallo-Deere." But Journalist Avery Yale Kamila and food historians said Rosier "misinterpreted the evidence." Historians report the Wabanaki did not domesticate deer. The tribes of the northern woodlands have historically been making nut milk. Cows were imported to New England in 1624.

Industrialization

The growth in urban population, coupled with the expansion of the railway network in the mid-19th century, brought about a revolution in milk production and supply. Individual railway firms began transporting milk from rural areas to London from the 1840s and 1850s. Possibly the first such instance was in 1846, when St Thomas's Hospital in Southwark contracted with milk suppliers outside London to ship milk by rail. The Great Western Railway was an early and enthusiastic adopter, and began to transport milk into London from Maidenhead in 1860, despite much criticism. By 1900, the company was transporting over annually. The milk trade grew slowly through the 1860s, but went through a period of extensive, structural change in the 1870s and 1880s.
Urban demand began to grow, as consumer purchasing power increased and milk became regarded as a required daily commodity. Over the last three decades of the 19th century, demand for milk in most parts of the country doubled or, in some cases, tripled. Legislation in 1875 made the adulteration of milk illegal– This combined with a marketing campaign to change the image of milk. The proportion of rural imports by rail as a percentage of total milk consumption in London grew from under 5% in the 1860s to over 96% by the early 20th century. By that point, the supply system for milk was the most highly organized and integrated of any food product. Milk was analyzed for infection with tuberculosis. In 1907 180 samples were tested in Birmingham and 13.3% were found to be infected.
The first glass bottle packaging for milk was used in the 1870s. The first company to do so may have been the New York Dairy Company in 1877. The Express Dairy Company in England began glass bottle production in 1880. In 1884, Hervey Thatcher, an American inventor from New York, invented a glass milk bottle, called Thatcher's Common Sense Milk Jar, which was sealed with a waxed paper disk. In 1932, plastic-coated paper milk cartons were introduced commercially.
In 1863, French chemist and biologist Louis Pasteur invented pasteurization, a method of killing harmful bacteria in beverages and food products. He developed this method while on summer vacation in Arbois, to remedy the frequent acidity of the local wines. He found out experimentally that it is sufficient to heat a young wine to only about for a brief time to kill the microbes, and that the wine could be nevertheless properly aged without sacrificing the final quality. In honor of Pasteur, the process became known as pasteurization. Pasteurization was originally used as a way of preventing wine and beer from souring. Commercial pasteurizing equipment was produced in Germany in the 1880s, and producers adopted the process in Copenhagen and Stockholm by 1885.
Homogenization, the process of distributing the milk fat evenly throughout the rest of the milk, was first invented in the late 1800s and exhibited by Auguste Gaulin at the 1900 World's Fair in Paris. Within 40 years, the use of homogenization spread to other countries and is now commonplace.