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Coffee is a beverage brewed from roasted, ground coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content, but decaffeinated coffee is also commercially available. There are also various coffee substitutes. Typically served hot, coffee has the highest sales in the world market for hot drinks.^[2]

Coffee production begins when the seeds from coffee cherries (the Coffea plant’s fruits) are separated to produce unroasted green coffee beans. The “beans” are roasted and then ground into fine particles. Coffee is brewed from the ground roasted beans, which are typically steeped in hot water before being filtered out. It is usually served hot, although chilled or iced coffee is common. Coffee can be prepared and presented in a variety of ways (e.g., espresso, French press, caffè latte, or already-brewed canned coffee). Sugar, sugar substitutes, milk, and cream are often added to mask the bitter taste or enhance the flavor.

Espresso latte and black filtered coffee

Though coffee is now a global commodity, it has a long history tied closely to food traditions around the Red Sea. The earliest credible evidence of coffee drinking as the modern beverage appears in modern-day Yemen in southern Arabia in the middle of the 15th century in Sufi shrines, where coffee seeds were first roasted and brewed in a manner similar to how it is now prepared for drinking.^[3] The coffee beans were procured by the Yemenis from the Ethiopian Highlands via coastal Somali intermediaries, and cultivated in Yemen. By the 16th century, the drink had reached the rest of the Middle East and North Africa, later spreading to Europe.

The two most commonly grown coffee bean types are C. arabica and C. robusta.^[4] Coffee plants are cultivated in over 70 countries, primarily in the equatorial regions of the Americas, Southeast Asia, the Indian subcontinent, and Africa. Green, unroasted coffee is traded as an agricultural commodity. The global coffee industry is massive and worth $495.50 billion as of 2023.^[5] In the same year, Brazil was the leading grower of coffee beans, producing 35% of the world’s total, followed by Vietnam and Colombia. While coffee sales reach billions of dollars annually worldwide, coffee farmers disproportionately live in poverty. Critics of the coffee industry have also pointed to its negative impact on the environment and the clearing of land for coffee-growing and water use.

Etymology

The word coffee entered the English language in 1582 via the Dutch koffie, borrowed from the Ottoman Turkish kahve (قهوه), borrowed in turn from the Arabic qahwah (قَهْوَة).^[6] Medieval Arabic lexicons traditionally held that the etymology of qahwah meant ‘wine’, given its distinctly dark color, and was derived from the verb qahiya (قَهِيَ), ‘to have no appetite‘.^[7] The word qahwah most likely meant ‘the dark one’, referring to the brew or the bean; qahwah is not the name of the bean, which are known in Arabic as bunn and in Cushitic languages as būn. Semitic languages have the root qhh, ‘dark color’, which became a natural designation for the beverage. Its cognates include the Hebrew qehe(h) ‘dulling’ and the Aramaic qahey (‘give acrid taste to’).^[7] Although etymologists have connected it with a word meaning ‘wine’, it is also thought to be from the Kaffa region of Ethiopia.^[8]

The terms coffee pot and coffee break originated in 1705 and 1952, respectively.^[9]

History

Main article: History of coffee

Legendary accounts

Main article: Kaldi

There are multiple anecdotal origin stories which lack evidence. In a commonly repeated legend, Kaldi, a 9th-century Ethiopian goatherd, first observed the coffee plant after seeing his flock energized by chewing on the plant.^[3] This legend does not appear before 1671, first being related by Antoine Faustus Nairon, a Maronite professor of Oriental languages and author of one of the first printed treatises devoted to coffee, De Saluberrima potione Cahue seu Cafe nuncupata Discurscus (Rome, 1671), indicating the story is likely apocryphal.^[10][11][3] Another legend attributes the discovery of coffee to a Sheikh Omar. Starving after being exiled from Mokha (a port city in what is now Yemen), Omar found berries. After attempting to chew and roast them, Omar boiled them, which yielded a liquid that revitalized and sustained him.^[12]

Historical transmission

The earliest recorded reference to the coffee bean and its qualities appears in a treatise by Al-Razi, which describes the bean—referred to as “bunchum”—as “hot and dry and very good for the stomach”.^[13] Medieval sources indicate that coffee was first introduced in the land of Saʿd ad-Din—the heartland of the Adal Sultanate, which encompassed Somali territories and adjoining areas of the Horn of Africa.^[14]

Credible evidence of coffee drinking or knowledge of the coffee tree appears in the middle of the 15th century in the accounts of Ahmed al-Ghaffar in Yemen,^[3] where coffee seeds were first roasted and brewed in a similar way to how it is prepared now. Coffee was used by Sufi circles to stay awake for their religious rituals.^[15] Accounts differ on the origin of the coffee plant before its appearance in Yemen. From Ethiopia, coffee could have been introduced to Yemen via trade across the Red Sea.^[16] One account credits Muhammad Ibn Sa’d for bringing the beverage to Aden from the African coast,^[17] other early accounts say Ali ben Omar of the Shadhili Sufi order was the first to introduce coffee to Arabia.^[17][18]

16th-century Islamic scholar Ibn Hajar al-Haytami notes in his writings that a beverage called qahwa developed from a tree in the Zeila region located in the Horn of Africa.^[15] Coffee was first exported from Ethiopia to Yemen by Somali merchants from Berbera and Zeila in modern-day Somaliland, which was procured from Harar and the Abyssinian interior. According to Captain Haines, who was the colonial administrator of Aden (1839–1854), Mokha historically imported up to two-thirds of its coffee from Berbera-based merchants before the coffee trade of Mokha was captured by British-controlled Aden in the 19th century. After that, much of the Ethiopian coffee was exported to Aden via Berbera.^[19]

By the 16th century, coffee had reached the rest of the Middle East and North Africa.^[20] The first coffee seeds were smuggled out of the Middle East by Sufi Baba Budan from Yemen to India during the time. Before then, all exported coffee was boiled or otherwise sterilized. Portraits of Baba Budan depict him as having smuggled seven coffee seeds by strapping them to his chest. The first plants from these smuggled seeds were planted in Mysore.

Coffee had spread to Italy by 1600 and then to the rest of Europe, Indonesia, and the Americas.^[21]

In 1583, Leonhard Rauwolf, a German physician, gave this description of coffee after returning from a ten-year trip to the Near East:

A beverage as black as ink, useful against numerous illnesses, particularly those of the stomach. Its consumers take it in the morning, quite frankly, in a porcelain cup passed around and from which each one drinks a cupful. It is composed of water and the fruit from a bush called bunnu.

— Léonard Rauwolf, Reise in die Morgenländer (in German)

Thriving trade brought many goods, including coffee, from the Ottoman Empire to Venice. From there it was introduced to the rest of Europe. Coffee became more widely accepted after it was deemed a Christian beverage by Pope Clement VIII in 1600, despite appeals to ban the “Muslim drink”. The first European coffee house opened in Venice in 1647.^[22]

As a colonial import

A late 19th-century advertisement for coffee essence

A 1919 advertisement for G Washington’s Coffee. The first instant coffee was invented by inventor George Washington in 1909.

The Dutch East India Company was the first to import coffee on a large scale.^[23] The Dutch later grew the crop in Java and Ceylon.^[24] The first exports of Indonesian coffee from Java to the Netherlands occurred in 1711.^[25]

Through the efforts of the British East India Company, coffee also became popular in England. In a diary entry of May 1637, John Evelyn recorded tasting the drink at Oxford in England, where it had been brought by a student of Balliol College from Crete named Nathaniel Conopios of Crete.^[26][27] Oxford’s Queen’s Lane Coffee House, established in 1654, is still in existence today. Coffee was introduced in France in 1657 and in Austria and Poland after the 1683 Battle of Vienna, when coffee was captured from supplies of the defeated Turks.^[28]

When coffee reached North America during the Colonial period, it was initially not as successful as in Europe, as alcoholic beverages remained more popular. During the Revolutionary War, the demand for coffee increased so much that dealers had to hoard their scarce supplies and raise prices dramatically; this was also due to the reduced availability of tea from British merchants,^[29] and a general resolution among many Americans to avoid drinking tea following the 1773 Boston Tea Party.^[30]

During the 18th century, coffee consumption declined in Britain, giving way to tea drinking. Tea was simpler to make, and had become cheaper with the British conquest of India and the tea industry there.^[31] During the Age of Sail, seamen aboard ships of the British Royal Navy made substitute coffee by dissolving burnt bread in hot water.^[32]

The Frenchman Gabriel de Clieu took a coffee plant to the French territory of Martinique in the Caribbean in the 1720s,^[33] from which much of the world’s cultivated arabica coffee is descended. Coffee thrived in the climate and was conveyed across the Americas.^[34] Coffee was cultivated in Saint-Domingue (now Haiti) from 1734, and by 1788 it supplied half the world’s coffee.^[35] The conditions that the enslaved people worked in on coffee plantations were a factor in the soon to follow Haitian Revolution. The coffee industry never fully recovered there.^[36]

Mass production

Meanwhile, coffee had been introduced to Brazil in 1727, although its cultivation did not gather momentum until independence in 1822.^[37] After this time, massive tracts of rainforest were cleared for coffee plantations, first in the vicinity of Rio de Janeiro and later São Paulo.^[38] Brazil went from having essentially no coffee exports in 1800 to being a significant regional producer in 1830, to being the largest producer in the world by 1852. In 1910–1920, Brazil exported around 70% of the world’s coffee, Colombia, Guatemala, and Venezuela exported 15%, and Old World production accounted for less than 5% of world exports.^[39]

Many countries in Central America took up cultivation in the latter half of the 19th century, and almost all were involved in the large-scale displacement and exploitation of the indigenous people. Harsh conditions led to many uprisings, coups, and bloody suppression of peasants.^[40] The notable exception was Costa Rica, where lack of ready labor prevented the formation of large farms. Smaller farms and more egalitarian conditions ameliorated unrest over the 19th and 20th centuries.^[41]

Rapid growth in coffee production in South America during the second half of the 19th century was matched by an increase in consumption in developed countries, though nowhere has this growth been as pronounced as in the United States, where a high rate of population growth was compounded by doubling of per capita consumption between 1860 and 1920. Though the United States was not the heaviest coffee-drinking nation at the time (Belgium, the Netherlands and Nordic countries all had comparable or higher levels of per capita consumption), due to its sheer size, it was already the largest consumer of coffee in the world by 1860, and, by 1920, around half of all coffee produced worldwide was consumed in the US.^[39]

Coffee has become a vital cash crop for many developing countries. Over one hundred million people in developing countries have become dependent on coffee as their primary source of income. It has become the primary export and economic backbone for African countries like Uganda, Burundi, Rwanda, and Ethiopia,^[42] as well as many Central American countries.

Biology

Main articles: Coffea and List of coffee varieties

Several species of shrub of the genus Coffea produce the berries from which coffee is extracted. The two main species commercially cultivated are Coffea canephora (predominantly a form known as ‘robusta’) and C. arabica.^[43] C. arabica, the most highly regarded species, is native to the southwestern highlands of Ethiopia and the Boma Plateau in southeastern Sudan and Mount Marsabit in northern Kenya.^[44] C. canephora is native to western and central Subsaharan Africa, from Guinea to Uganda and southern Sudan.^[45] Less popular species are C. liberica, C. stenophylla, C. mauritiana, and C. racemosa.

All coffee plants are classified in the large family Rubiaceae. They are evergreen shrubs or trees that may grow 5 m (15 ft) tall when unpruned. The leaves are dark green and glossy, usually 10–15 cm (4–6 in) long and 6 cm (2.4 in) wide, simple, entire, and opposite. Petioles of opposite leaves fuse at the base to form interpetiolar stipules, characteristic of Rubiaceae. The flowers are axillary, and clusters of fragrant white flowers bloom simultaneously. Gynoecium consists of an inferior ovary, also characteristic of Rubiaceae. The flowers are followed by oval berries of about 1.5 cm (0.6 in).^[46] When immature, they are green, and they ripen to yellow, then crimson, before turning black on drying. Each berry usually contains two seeds, but 5–10% of the berries^[47] have only one; these are called peaberries.^[48] Arabica berries ripen in six to eight months, while robusta takes nine to eleven months.^[49]

Coffea arabica is predominantly self-pollinating, and as a result, the seedlings are generally uniform and vary little from their parents. In contrast, Coffea canephora, and C. liberica are self-incompatible and require outcrossing. This means that useful forms and hybrids must be propagated vegetatively.^[50] Cuttings, grafting, and budding are the usual methods of vegetative propagation.^[51] On the other hand, there is great scope for experimentation in search of potential new strains.^[50]

• Illustration of Coffea arabica plant and seeds
• Coffea robusta flowers
• A flowering Coffea arabica tree
• Coffea arabica berries on the bush

Cultivation and production

Further information: Coffee production, Coffee production in Colombia, Coffee production in Ethiopia, Coffee production in India, and Coffee production in Vietnam

The traditional method of planting coffee is to place 20 seeds in each hole at the beginning of the rainy season. This method loses about 50% of the seeds’ potential, as about half fail to sprout. A more effective process of growing coffee, used in Brazil, is to raise seedlings in nurseries that are then planted outside after six to twelve months. Coffee is often intercropped with food crops, such as corn, beans, or rice during the first few years of cultivation as farmers become familiar with its requirements.^[46] Coffee plants grow within a defined area between the tropics of Cancer and Capricorn, termed the bean belt or coffee belt.^[52]

In 2020, the world production of green coffee beans was 175,647,000 60 kg bags, led by Brazil with 39% of the total, followed by Vietnam, Colombia, and Indonesia.^[53] Brazil is the largest coffee exporting nation, accounting for 15% of all world exports in 2019.^[54] As of 2021, no synthetic coffee products are publicly available but multiple bioeconomy companies have reportedly produced first batches that are highly similar on the molecular level and are close to commercialization.^[55][56][57]

Species variations

Of the two main species grown, arabica coffee (from C. arabica) is generally more highly regarded than robusta coffee (from C. canephora). Robusta coffee tends to be bitter and has less flavor but a better body than arabica. For these reasons, about three-quarters of coffee cultivated worldwide is C. arabica.^[43] Robusta strains also contain about 40–50% more caffeine than arabica.^[58] Consequently, this species is used as an inexpensive substitute for arabica in many commercial coffee blends. Good quality robusta beans are used in traditional Italian espresso blends to provide a full-bodied taste and a better foam head (known as crema).

Additionally, robusta is less susceptible to disease than arabica and can be cultivated in lower altitudes and warmer climates where arabica does not thrive.^[60] The robusta strain was first collected in 1890 from the Lomani River, a tributary of the Congo River, and was conveyed from the Congo Free State (now the Democratic Republic of the Congo) to Brussels to Java around 1900. From Java, further breeding resulted in the establishment of robusta plantations in many countries.^[59] In particular, the spread of the devastating coffee leaf rust (caused by the fungal pathogen Hemileia vastatrix), to which arabica is vulnerable, hastened the uptake of the resistant robusta. The pathogen and results in light, rust-colored spots on the undersides of coffee plant leaves.^[61] It grows exclusively on the leaves of coffee plants.^[62] Coffee leaf rust is found in virtually all countries that produce coffee.^[63]

Beans from different countries or regions can usually be distinguished by differences in flavor, aroma, body, and acidity.^[64] These taste characteristics are dependent not only on the coffee’s growing region but also on genetic subspecies (varietals) and processing.^[65] Varietals are generally known by the region in which they are grown, such as Colombian, Java, and Kona. Arabica coffee beans are cultivated mainly in Latin America, eastern Africa or Asia, while robusta beans are grown in central Africa, southeast Asia, and Brazil.^[43]

Coffee can also be blended with medicinal or functional mushrooms, of which some of the most frequently used include lion’s mane, chaga, Cordyceps, and reishi.^[66] Mushroom coffee has about half the caffeine of standard coffee.^[67] However, drinking mushroom coffee can result in digestive issues and high amounts can result in liver toxicity.^[67] There is little clinical evidence for the benefits of mushroom coffee.^[68]

Pests and treatments

Fungi

Coffee wilt disease or tracheomycosis is a common vascular wilt found in Eastern and Central Africa that can kill coffee trees it infects. It is induced by the fungal pathogen Gibberella xylarioides. It can affect several Coffea species, and could potentially threaten production worldwide.^[69]

Mycena citricolor, American leaf spot, is a fungus that can affect the whole coffee plant. It grows on leaves, resulting in leaves with holes that often fall from the plant. It is a threat primarily in Latin America.^[70]

Animals

Over 900 species of insect have been recorded as pests of coffee crops worldwide. Of these, over a third are beetles, and over a quarter are bugs. Some 20 species of nematodes, 9 species of mites, and several snails and slugs also attack the crop. Birds and rodents sometimes eat coffee berries, but their impact is minor compared to invertebrates.^[72] In general, arabica is the more sensitive species to invertebrate predation overall. Each part of the coffee plant is assailed by different animals. Nematodes attack the roots, coffee borer beetles burrow into stems and woody material,^[73] and the foliage is attacked by over 100 species of larvae (caterpillars) of butterflies and moths.^[74]

Mass spraying of insecticides has often proven disastrous, as predators of the pests are more sensitive than the pests themselves.^[75] Instead, integrated pest management has developed, using techniques such as targeted treatment of pest outbreaks, and managing crop environment away from conditions favoring pests. Branches infested with scale are often cut and left on the ground, which causes scale parasites to not only attack the scale on the fallen branches but in the plant as well.^[76]

The 2-mm-long coffee borer beetle (Hypothenemus hampei) is the most damaging insect pest of the world’s coffee industry, destroying up to 50 percent or more of the coffee berries on plantations in most coffee-producing countries. The adult female beetle nibbles a single tiny hole in a coffee berry and lays 35 to 50 eggs. Inside, the offspring grow, mate, and then emerge from the commercially ruined berry to disperse, repeating the cycle. Pesticides are mostly ineffective because the beetle juveniles are protected inside the berry nurseries, but they are vulnerable to predation by birds when they emerge. When groves of trees are nearby, the American yellow warbler, rufous-capped warbler, and other insectivorous birds have been shown to reduce by 50 percent the number of coffee berry borers in Costa Rica coffee plantations.^[71]

Ecological effects

See also: Sustainable coffee

Originally, coffee was grown in the shade of trees that provided a habitat for many animals and insects.^[77] Remnant forest trees were used for this purpose, but many species have been planted as well. These include leguminous trees of the genera Acacia, Albizia, Cassia, Erythrina, Gliricidia, Inga, and Leucaena, as well as the nitrogen-fixing non-legume sheoaks of the genus Casuarina, and the silky oak Grevillea robusta.^[78]

This method is commonly called “shade-grown coffee“. Starting in the 1970s, many farmers switched their production method to sun cultivation, in which coffee is grown in rows under full sun with little or no forest canopy. This causes berries to ripen more rapidly and bushes to produce higher yields, but requires the clearing of trees and increased use of fertilizer and pesticides, which damage the environment and cause health problems.^[79]

Unshaded coffee plants grown with fertilizer yield the most coffee, although unfertilized shaded crops generally yield more than unfertilized unshaded crops: the response to fertilizer is much greater in full sun.^[80] While traditional coffee production causes berries to ripen more slowly and produce lower yields, the quality of the coffee is allegedly superior.^[81] In addition, the traditional shaded method provides living space for many wildlife species. Proponents of shade cultivation say environmental problems such as deforestation, pesticide pollution, habitat destruction, and soil and water degradation are the side effects of the practices employed in sun cultivation.^[77][82]

The American Birding Association, Smithsonian Migratory Bird Center,^[83] National Arbor Day Foundation,^[84] and the Rainforest Alliance have led a campaign for ‘shade-grown’ and organic coffees, which can be sustainably harvested.^[85] Shaded coffee cultivation systems show greater biodiversity than full-sun systems, and those more distant from continuous forest compare rather poorly to undisturbed native forest in terms of habitat value for some bird species.^[86][87]

Coffee production uses a large volume of water. On average it takes about 140 litres (37 US gal) of water to grow the coffee beans needed to produce one cup of coffee. Growing the plants needed to produce 1 kg (2.2 lb) of roasted coffee in Africa, South America or Asia requires 26,400 litres (7,000 US gal) of water.^[88] As with many other forms of agriculture, often much of this is rainwater, much of which would otherwise run off into rivers or coastlines, while much water actually absorbed by the plants is transpired straight back into the local environment through the plants’ leaves (especially for cooling effects); broad estimates aside, consequential margins vary considerably based on details of local geography and horticultural practice. Coffee is often grown in countries where there is a water shortage, such as Ethiopia.^[89]

Used coffee grounds may be used for composting or as a mulch. They are especially appreciated by worms and acid-loving plants such as blueberries.^[90] Climate change may significantly impact coffee yields during the 21st century, such as in Nicaragua and Ethiopia which could lose more than half of the farming land suitable for growing (Arabica) coffee.^[91][92][93] As of 2016, at least 34% of global coffee production was compliant with voluntary sustainability standards such as Fairtrade, UTZ, and 4C (The Common Code for the Coffee Community).^[94]

Preprocessing

Coffee berries are traditionally selectively picked by hand, which is labor-intensive as it involves the selection of only the berries at the peak of ripeness. More commonly, crops are strip picked, where all berries are harvested simultaneously regardless of ripeness by person or machine. After picking, green coffee is processed by one of two types of method—a dry process method which is often simpler and less labor-intensive, and a wet process method, which incorporates batch fermentation, uses larger amounts of water in the process, and often yields a milder coffee.^[95]

Then they are sorted by ripeness and color, and most often the flesh of the berry is removed, usually by machine, and the seeds are fermented to remove the slimy layer of mucilage still present on the seed. When the fermentation is finished, the seeds are washed with large quantities of fresh water to remove the fermentation residue, which generates massive amounts of coffee wastewater. Finally, the seeds are dried.^[96]

The best (but least used) method of drying coffee is using drying tables. In this method, the pulped and fermented coffee is spread thinly on raised beds, which allows the air to pass on all sides of the coffee, and then the coffee is mixed by hand. The drying that then takes place is more uniform, and fermentation is less likely. Most African coffee is dried in this manner and certain coffee farms around the world are starting to use this traditional method.^[96] Next, the coffee is sorted, and labeled as green coffee. Some companies use cylinders to pump in heated air to dry the coffee seeds, though this is generally in places where the humidity is very high.^[96]

An Asian coffee known as kopi luwak undergoes a peculiar process made from coffee berries eaten by the Asian palm civet, passing through its digestive tract, with the beans eventually harvested from feces. Coffee brewed from this process^[97] is among the most expensive in the world, with bean prices reaching $160 per pound or $30 per brewed cup.^[98] Kopi luwak coffee is said to have a uniquely rich, slightly smoky aroma and flavor with hints of chocolate, resulting from the action of digestive enzymes breaking down bean proteins to facilitate partial fermentation.^[97][98] In Thailand, black ivory coffee beans are fed to elephants whose digestive enzymes reduce the bitter taste of beans collected from dung.^[99] These beans sell for up to $1,100 a kilogram ($500 per lb), achieving the world’s most expensive coffee,^[99] three times costlier than palm civet coffee beans.^[98]

Processing

Roasting

Main article: Coffee roasting

The next step in the process is the roasting of green coffee. Coffee is usually sold in a roasted state, and with rare exceptions, such as infusions from green coffee beans,^[100] coffee is roasted before it is consumed. It can be sold roasted by the supplier, or it can be home roasted.^[101] The roasting process influences the taste of the beverage by changing the coffee bean both physically and chemically. The bean decreases in weight as moisture is lost and increases in volume, causing it to become less dense. The density of the bean also influences the strength of the coffee and the requirements for packaging.

The actual roasting begins when the temperature inside the bean reaches approximately 200 °C (392 °F), though different varieties of seeds differ in moisture and density and therefore roast at different rates.^[102] During roasting, caramelization occurs as intense heat breaks down starches, changing them to simple sugars that begin to brown, which darkens the color of the bean.^[103]

Sucrose is rapidly lost during the roasting process, and may disappear entirely in darker roasts. During roasting, aromatic oils and acids weaken, changing the flavor; at 205 °C (401 °F), other oils start to develop.^[102] One of these oils, caffeol, is created at about 200 °C (392 °F), and is largely responsible for coffee’s aroma and flavor.^[24] The difference of caffeine content between a light roast and a dark roast is only about 0.1%.^[104]

Grading roasted beans

See also: Food grading

Depending on the color of the roasted beans as perceived by the human eye, they will be labeled as light, medium light, medium, medium dark, dark, or very dark. A more accurate method of discerning the degree of roast involves measuring the reflected light from roasted seeds illuminated with a light source in the near-infrared spectrum. This elaborate light meter uses a process known as spectroscopy to return a number that consistently indicates the roasted coffee’s relative degree of roast or flavor development. Coffee has, in many countries, been graded by size longer than it has been graded by quality. Grading is generally done with sieves, numbered to indicate the size of the perforations.^[105]

Roast characteristics

The degree of roast affects coffee flavor and body. The color of coffee after brewing is also affected by the degree of roasting.^[106] Darker roasts are generally bolder because they have less fiber content and a more sugary flavor. Lighter roasts have a more complex and therefore perceived stronger flavor from aromatic oils and acids otherwise destroyed by longer roasting times.^[107] Roasting does not alter the amount of caffeine in the bean, but does give less caffeine when the beans are measured by volume because the beans expand during roasting.^[108] A small amount of chaff is produced during roasting from the skin left on the seed after processing.^[109] Chaff is usually removed from the seeds by air movement, though a small amount is added to dark roast coffees to soak up oils on the seeds.^[102]

Decaffeination

Decaffeination of coffee seeds is done while the seeds are still green. Many methods can remove caffeine from coffee, but all involve either soaking the green seeds in hot water (often called the “Swiss water process”)^[110] or steaming them, then using a solvent to dissolve caffeine-containing oils.^[24] Decaffeination is often done by processing companies, and the extracted caffeine is usually sold to the pharmaceutical industry.^[24]

Storage

Main article: Coffee bean storage

Coffee is best stored in an airtight container made of ceramic, glass or non-reactive metal.^[111] Higher quality prepackaged coffee usually has a one-way valve that prevents air from entering while allowing the coffee to release gases.^[112] Coffee freshness and flavor is preserved when it is stored away from moisture, heat, and light. The tendency of coffee to absorb strong smells from food means that it should be kept away from such smells. Storage of coffee in refrigerators is not recommended due to the presence of moisture which can cause deterioration. Exterior walls of buildings that face the sun may heat the interior of a home, and this heat may damage coffee stored near such a wall. Heat from nearby ovens also harms stored coffee.^[111]

In 1931, a method of packing coffee in a sealed vacuum in cans was introduced. The roasted coffee was packed and then 99% of the air was removed, allowing the coffee to be stored indefinitely until the can was opened. Today this method is in mass use for coffee in a large part of the world.^[113]

Brewing

Main article: Coffee brewing

Coffee beans must be ground and brewed to create a beverage. The criteria for choosing a method include flavor and economy. Almost all methods of preparing coffee require that the beans be ground and then mixed with hot water long enough to allow the flavor to emerge but not so long as to draw out bitter compounds. The liquid can be consumed after the spent grounds are removed. Brewing considerations include the fineness of the grind, how the water is used to extract the flavor, the ratio of coffee grounds to water (the brew ratio), additional flavorings such as sugar, milk, and spices, and the technique to be used to separate spent grounds. Optimal coffee extraction occurs between 91 and 96 °C (196 and 205 °F).^[116] Ideal holding temperatures range from 85 to 88 °C (185 to 190 °F) to as high as 93 °C (199 °F) and the ideal serving temperature is 68 to 79 °C (154 to 174 °F).^[117]

Coffee beans may be ground with a burr grinder, which uses revolving elements to shear the seed; a blade grinder cuts the seeds with blades moving at high speed; and a mortar and pestle crush the seeds. For most brewing methods a burr grinder is deemed superior because the grind is more even and the grind size can be adjusted.^[118] The type of grind is often named after the brewing method for which it is generally used, Turkish grind being the finest, while coffee percolator or French press are the coarsest. The most common grinds are between these extremes: a medium grind is used in most home coffee-brewing machines.^[119]

Coffee may be brewed by several methods. It may be boiled, steeped, or pressurized. Brewing coffee by boiling was the earliest method, and Turkish coffee is an example of this method. It is prepared by grinding or pounding the seeds to a fine powder, then adding it to water and bringing it to a boil for no more than an instant in a pot called a cezve or, in Greek, a μπρίκι: bríki (from Turkish ibrik). This produces a strong coffee with a layer of foam on the surface and sediment (which is not meant for drinking) settling at the bottom of the cup.^[120]

Drip brewers and automatic coffeemakers brew coffee using gravity. In an automatic coffeemaker, hot water drips onto coffee grounds that are held in a paper, plastic, or perforated metal coffee filter, allowing the water to seep through the ground coffee while extracting its oils and essences. The liquid drips through the coffee and the filter into a carafe or pot, and the spent coffee grounds are retained in the filter.^[121]

In a coffee percolator, water is pulled under a pipe by gravity, which is then forced into a chamber above a filter by steam pressure created by boiling. The water then seeps through the grounds, and the process is repeated until terminated by removing from the heat, by an internal timer,^[122] or by a thermostat that turns off the heater when the entire pot reaches a certain temperature.

The espresso method forces hot pressurized water through finely-ground coffee.^[119] As a result of brewing under high pressure (typically 9 bar),^[123] the espresso beverage is more concentrated (as much as 10 to 15 times the quantity of coffee to water as gravity-brewing methods can produce) and has a more complex physical and chemical constitution.^[124] A well-prepared espresso has a reddish-brown foam called crema that floats on the surface.^[119] Other pressurized water methods include the moka pot and vacuum coffee maker. The AeroPress also works similarly, moving a column of water through a bed of coffee.

Cold brew coffee is made by steeping coarsely ground beans in cold water for several hours, then filtering them.^[125] This results in a brew lower in acidity than most hot-brewing methods.

Serving

“Black coffee” redirects here. For other uses, see Black Coffee (disambiguation).

See also: List of coffee drinks

Once brewed, coffee may be served in a variety of ways. Drip-brewed, percolated, or French-pressed/cafetière coffee may be served as white coffee with a dairy product such as milk or cream, or dairy substitute, or as black coffee with no such addition. It may be sweetened with sugar or artificial sweetener. When served cold, it is called iced coffee.

Espresso-based coffee has a variety of possible presentations. In its most basic form, an espresso is served alone as a shot or short black, or with hot water added, when it is known as Caffè Americano. A long black is made by pouring a double espresso into an equal portion of water, retaining the crema, unlike Caffè Americano.^[126] Milk is added in various forms to an espresso: steamed milk makes a caffè latte,^[127] equal parts steamed milk and milk froth make a cappuccino,^[126] and a dollop of hot foamed milk on top creates a caffè macchiato.^[128] A flat white is prepared by adding steamed hot milk (microfoam) to two espresso shots.^[129] It has less milk than a latte, but both are varieties of coffee to which the milk can be added in such a way as to create a decorative surface pattern. Such effects are known as latte art.^[130]

Coffee is frequently served iced. Popular options include Frappés, Iced lattes, or stronger brewed coffee served with ice.^[131]

Coffee can also be incorporated with alcohol to produce a variety of beverages: it is combined with whiskey in Irish coffee, and it forms the base of alcoholic coffee liqueurs such as Kahlúa and Tia Maria. Some craft beers have coffee or coffee extracts added to the beer,^[132] although porter and stout beers may have a coffee-like taste solely due to roasted grains.^[133]

Instant coffee

Main article: Instant coffee

Many products are sold for the convenience of consumers who do not want to prepare their coffee or who do not have access to coffeemaking equipment. Instant coffee is dried into soluble powder or freeze-dried into granules that can be quickly dissolved in hot water.^[134] A New Zealand invention and staple, instant coffee was originally invented in Invercargill in 1890, by food chemist David Strang.^[135] It rapidly gained in popularity in many countries in the post-war period, with Nescafé being the most popular product.^[136] Many consumers determined that the convenience of preparing a cup of instant coffee more than made up for a perceived inferior taste,^[137] although, since the late 1970s, instant coffee has been produced differently in such a way that is similar to the taste of freshly brewed coffee.^[138] Paralleling (and complementing) the rapid rise of instant coffee was the coffee vending machine invented in 1947 and widely distributed since the 1950s.^[139]

Economics

Main article: Economics of coffee

Country	Millions of tonnes
Brazil	3.00
Vietnam	1.85
Indonesia	0.77
Colombia	0.56
Ethiopia	0.46
Honduras	0.40
Peru	0.37
India	0.33
World	9.92

Over 90 percent of coffee production takes place in developing countries—mainly South America—while consumption happens primarily in industrialized economies. There are 25 million small producers who rely on coffee for a living worldwide. In Brazil, where almost a third of the world’s coffee is produced, over five million people are employed in the cultivation and harvesting of over three billion coffee plants; it is a more labor-intensive culture than alternative cultures of the same regions, such as sugar cane or cattle, as its cultivation is not automated, requiring frequent human attention.

World production

In 2021, world production of green coffee beans was 9.9 million tonnes, led by Brazil with 30% of the total (table). Vietnam, Indonesia, and Colombia were other major producers.

Nearly 90 countries export coffee cherries, 60 of them developing countries, with coffee constituting the main export revenue for countries such as Burundi, Ethiopia, Rwanda, and formerly Haiti.^[141] The largest producer by far is Brazil (almost 30% of world production in 2015), followed by Vietnam, Colombia, Indonesia, and Ethiopia.^[142]

Coffee production provides a living for about twenty-five million people, mainly small-scale producers, while imports, processing, and distribution provide a living for about one hundred to one hundred and ten million people.^[143]

Commodity market

Coffee retailing

Bag of coffee beans

Bag with ziplock and one-way valve to prevent mold

Coffee is bought and sold as green coffee beans by roasters, investors, and price speculators as a tradable commodity in commodity markets and exchange-traded funds. Coffee futures contracts for Grade 3 washed arabicas are traded on the New York Mercantile Exchange under ticker symbol KC, with contract deliveries occurring every year in March, May, July, September, and December.^{[144][145][146][147]} Higher and lower grade arabica coffees are sold through other channels. Futures contracts for robusta coffee are traded on the London International Financial Futures and Options Exchange and, since 2007, on the New York Intercontinental Exchange.^[148]

Dating to the 1970s, coffee has been incorrectly described by many, including historian Mark Pendergrast, as the world’s “second most legally traded commodity”.^[149][150] Instead, “coffee was the second most valuable commodity exported by developing countries,” from 1970 to circa 2000.^[151] This fact was derived from the United Nations Conference on Trade and Development Commodity Yearbooks which show “Third World” commodity exports by value in the period 1970–1998 with crude oil in first place, coffee in second, followed by sugar, cotton, and others. Coffee continues to be an important commodity export for developing countries, but more recent figures are not readily available due to the shifting and politicized nature of the category “developing country”.^[149] Coffee is one of seven commodities included in the EU Regulation on Deforestation-free products (EUDR), which aims to guarantee that the products European Union (EU) citizens consume do not contribute to deforestation or forest degradation worldwide.^[152]

International Coffee Day, which is claimed to have originated in Japan in 1983 with an event organized by the All Japan Coffee Association, takes place on 29 September in several countries.^[153] There are numerous trade associations and lobbying and other organizations representing the coffee industry.^[154][155]

Consumption

Nordic countries are the highest coffee-consuming nations when measured per capita per year, with consumption in Finland as the world’s highest.^[156]

1. Finland – 26.45 lb (12.00 kg)
2. Norway – 21.82 lb (9.90 kg)
3. Iceland – 19.84 lb (9.00 kg)
4. Denmark – 19.18 lb (8.70 kg)
5. Netherlands – 18.52 lb (8.40 kg)
6. Sweden – 18.00 lb (8.16 kg)
7. Switzerland – 17.42 lb (7.90 kg)
8. Belgium – 15.00 lb (6.80 kg)
9. Luxembourg – 14.33 lb (6.50 kg)
10. Canada – 14.33 lb (6.50 kg)

United States

An April 2024, National Coffee Association survey indicated that coffee consumption in the U.S. reached a 20-year high, with 67% of U.S. adults reporting drinking coffee in the past day. This is a significant increase compared to 2004 when fewer than half of U.S. adults reported coffee consumption in the past day. Drip coffee remains the most popular brewing method, but espresso-based beverages, particularly lattes, espresso shots, and cappuccinos, gained popularity.^[157]

Economic impacts

Further information: List of countries by coffee production

Market volatility, and thus increased returns, during 1830 encouraged Brazilian entrepreneurs to shift their attention from gold to coffee, a crop hitherto reserved for local consumption. Concurrent with this shift was the commissioning of vital infrastructures, including approximately 7,000 km (4,300 mi) of railroads between 1860 and 1885. The creation of these railways enabled the importation of workers, to meet the enormous need for labor. This development primarily affected the State of Rio de Janeiro, as well as the Southern States of Brazil, most notably São Paulo, due to its favorable climate, soils, and terrain.^[158]

Coffee production attracted immigrants in search of better economic opportunities in the early 1900s. Mainly, these were Portuguese, Italian, Spanish, German, and Japanese nationals. For instance, São Paulo received approximately 733,000 immigrants in the decade preceding 1900, whilst only receiving approximately 201,000 immigrants in the six years to 1890. The production yield of coffee increases. In 1880, São Paulo produced 1.2 million bags (25% of total production), in 1888 2.6 million (40%), and in 1902 8 million bags (60%).^[159] Coffee is then 63% of the country’s exports. The gains made by this trade allow sustained economic growth in the country.

The four years between planting a coffee and the first harvest extend seasonal variations in the price of coffee. The Brazilian Government is thus forced, to some extent, to keep strong price subsidies during production periods.

Fair trade

Main article: Fair trade coffee

See also: Fair trade debate

The concept of fair trade labeling, which guarantees coffee growers a negotiated preharvest price, began in the late 1980s with the Max Havelaar Foundation’s labeling program in the Netherlands. In 2004, 24,222 metric tons (of 7,050,000 produced worldwide) were fair trade; in 2005, 33,991 metric tons out of 6,685,000 were fair trade, an increase from 0.34% to 0.51%.^[160][161] A number of fair trade impact studies have shown that fair trade coffee produces a mixed impact on the communities that grow it. Many studies are skeptical about fair trade, reporting that it often worsens the bargaining power of those who are not part of it. The first fair-trade coffee was an effort to import Guatemalan coffee into Europe as “Indio Solidarity Coffee”.^[162]

Since the founding of organizations such as the European Fair Trade Association (1987), the production and consumption of fair trade coffee has grown as some local and national coffee chains started to offer fair trade alternatives.^[163] For example, in April 2000, after a year-long campaign by the human rights organization Global Exchange, Starbucks decided to carry fair-trade coffee in its stores.^[164] Since September 2009 all Starbucks Espresso beverages in UK and Ireland are made with Fairtrade and Shared Planet certified coffee.^[165]

A 2005 study done in Belgium concluded that consumers’ buying behavior is not consistent with their positive attitude toward ethical products. On average 46% of European consumers claimed to be willing to pay substantially more for ethical products, including fair-trade products such as coffee. The study found that the majority of respondents were unwilling to pay the actual price premium of 27% for fair trade coffee.^[164]

Specialty coffee and new trading relationships

Specialty coffee has driven a desire for more traceable coffee, and as such businesses are offering coffees that may come from a single origin, or a single lot from a single farm. This can give rise to the roaster developing a relationship with the producer, to discuss and collaborate on coffee. The roaster may also choose to cut out the importers and exporters to directly trade with the producer, or they may “fairly trade”, where any third-parties involved in the transaction are thought to have added value, and there is a high level of transparency around the price, although often there is no certification to back it up.^[166] This process tends to only be done for high-quality products since keeping the coffee separate from other coffees adds costs, and so only coffee that roasters believe can command a higher price will be kept separate.^[167]

Some coffee is sold through internet auction – much of it is sold through a competition, with coffees passing through local and international jurors, and then the best coffees being selected to be bid on. Some estates known for high-quality coffee also sell their coffee through an online auction. This can lead to increased price transparency since the final price paid is usually published.^[166]

Pharmacology

Main articles: List of chemical compounds in coffee and Health effects of coffee

Brewed coffee from typical grounds has no essential nutrients in significant content.^[168] In espresso, however, likely due to its higher amount of suspended solids, there are significant contents of magnesium, the B vitamins, niacin and riboflavin, and 212 mg of caffeine per 100 grams of grounds.^[169]

One psychoactive chemical in coffee is caffeine, an adenosine receptor antagonist that is known for its stimulant effects.^[170] Coffee also contains the monoamine oxidase inhibitors β-carboline and harmane, which may contribute to its psychoactivity.^[171] In a healthy liver, caffeine is mostly broken down by hepatic enzymes. The excreted metabolites are mostly paraxanthines—theobromine and theophylline—and a small amount of unchanged caffeine. Therefore, the metabolism of caffeine depends on the state of this enzymatic system of the liver.^[172]

Coffee is also known for its laxative effects, inducing defecation in some people within minutes of consumption.^{[173][174][175][176][177]} The specific mechanism of action and chemical constituents responsible are still unknown, but caffeine is likely not responsible.^[178][179]

Coffee is known to have a significant amount of water-soluble dietary fiber compared to other commonly consumed beverages such as factory orange juice. The amount of dietary fiber ranges from 0.47-0.75 g per 100 mL of prepared coffee in a 2007 experiment testing on espresso, drip coffee, and freeze-dried coffee with the beverage made from freeze-dried containing the highest amount fiber. Given the popularity of coffee and the low amount of fiber consumed by the average person in many developed nations, coffee may majorly contribute to the daily dietary fiber consumption for many people. (For instance, in Spain the mean fiber consumption of 7 grams per day with a moderate coffee drinker having 3 cups per day points to coffee accounting for 10% of Spanish dietary fiber.) ^[180][181]

Polyphenols in coffee have been shown to affect free radicals in vitro,^[182] but there is no evidence that this effect occurs in humans. Polyphenol levels vary depending on how beans are roasted as well as for how long. As interpreted by the Linus Pauling Institute and the European Food Safety Authority, dietary polyphenols, such as those ingested by consuming coffee, have little or no direct antioxidant value following ingestion.^{[183][184][185]}

A 2017 review of clinical trials found that drinking coffee is generally safe within usual levels of intake and is more likely to improve health outcomes than to cause harm at doses of 3 or 4 cups of coffee daily. Exceptions include possible increased risk in women having bone fractures, and a possible increased risk in pregnant women of fetal loss or decreased birth weight. Results were complicated by poor study quality, and differences in age, gender, health status, and serving size.^[186]

Caffeine content

See also: Low caffeine coffee

Depending on the type of coffee and method of preparation, the caffeine content of a single serving can vary greatly.^{[187][188][189]} The caffeine content of a cup of coffee varies depending mainly on the brewing method, and also on the coffee variety.^[190] According to the USDA National Nutrient Database, a 240-millilitre (8 US fl oz) cup of “coffee brewed from grounds” contains 95 mg caffeine, whereas an espresso (25 mL) contains 53 mg.^[191] According to an article in the Journal of the American Dietetic Association, coffee has the following caffeine content, depending on how it is prepared:^[188]

	Serving size	Caffeine content
Brewed	200 mL (7 US fl oz)	80–135 mg
Drip	200 mL (7 US fl oz)	115–175 mg
Espresso	45–60 mL (1+1⁄2–2 US fl oz)	100 mg

Caffeine remains stable up to 200 °C (392 °F) and completely decomposes around 285 °C (545 °F).^[192] Given that roasting temperatures do not exceed 200 °C (392 °F) for long and rarely if ever reach 285 °C (545 °F), the caffeine content of a coffee is not likely changed much by the roasting process.^[193]

Society and culture

Main article: Coffee culture

See also: Coffee culture in Australia and Coffee culture in former Yugoslavia

Coffee is often consumed alongside (or instead of) breakfast by many at home or when eating out at diners or cafeterias. It is often served at the end of a formal meal, normally with a dessert, and at times with an after-dinner mint, especially when consumed at a restaurant or dinner party.^[194]

Coffeehouses

Main article: Coffeehouse

Widely known as coffeehouses or cafés, establishments serving prepared coffee or other hot beverages have existed for over five hundred years. The first coffeehouse in Constantinople was opened in 1475 by traders arriving from Damascus and Aleppo.^[196]

A contemporary term for a person who makes coffee beverages, often a coffeehouse employee, is a barista. The Specialty Coffee Association of Europe and the Specialty Coffee Association of America have been influential in setting standards and providing training.^[197]

Break

The coffee break in the United States and elsewhere is a short mid-morning rest period granted to employees. It originated in the late 19th century in Stoughton, Wisconsin, with the wives of Norwegian immigrants. The city celebrates this every year with the Stoughton Coffee Break Festival.^[198] In 1951, Time noted that “[s]ince the war, the coffee break has been written into union contracts”.^[199] The term subsequently became popular through a Pan-American Coffee Bureau ad campaign of 1952 which urged consumers, “Give yourself a Coffee-Break – and Get What Coffee Gives to You.”^[200] John B. Watson, a behavioral psychologist who worked with Maxwell House later in his career, helped to popularize coffee breaks within the American culture.^[201]

Prohibition and condemnation

Historically, several religious groups have prohibited or condemned the consumption of coffee. The permissibility of coffee was debated in the Islamic world during the early 16th century, variously being permitted or prohibited until it was ultimately accepted by the 1550s.^[202] Contention existed among Ashkenazi Jews as to whether coffee was acceptable for Passover until it was certified kosher in 1923.^[203] Some Christian groups, such as Mormons and Seventh-day Adventists, discourage the consumption of coffee.^[204][205] Some Rastafarians also generally avoid coffee.^[206]

Furthermore, coffee has been prohibited for political and economic reasons. King Charles II of England briefly outlawed coffeehouses to quell perceived rebellion.^[31] King Frederick the Great banned it in Prussia, concerned about the price of importing of coffee without production colonies.^[207][208] Sweden prohibited coffee in the 18th century for the same reasons.^[209] Coffee has seldom been prohibited based on its intoxicating effect.^[210]

Folklore and culture

“Cup of joe” redirects here. For other uses, see Cup of Joe (disambiguation).

There are many stories about coffee and its impact on people and society. The Oromo people would customarily plant a coffee tree on the graves of powerful sorcerers. They believed that the first coffee bush sprang up from the tears that the god of heaven shed over the corpse of a dead sorcerer.^[211] Johann Sebastian Bach was inspired to compose the humorous Coffee Cantata, about dependence on the beverage, which was controversial in the early 18th century.^[212]

In the United States, coffee is sometimes called a “cup of Joe”. The origin of this phrase is in dispute; a common story is that in World War I the US Secretary of the Navy Josephus “Joe” Daniels banned alcohol on navy ships which meant that the strongest drink available aboard the ship was black coffee. Sailors began referring to coffee as a “cup of Joe” in reference to Daniels. However, this story may be apocryphal since the first written account of it was in 1930, some 15 years later. Another explanation is that a formerly popular nickname for coffee, jamoke, from mocha java, was shortened to Joe. A third origin story is that since coffee is such a commonly consumed beverage, it is the drink of the average Joe.^{[213][214][215]}

Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food.^[1] Milk contains many nutrients, including calcium and protein, as well as lactose and saturated fat.^[2] Immune factors and immune-modulating components in milk contribute to milk immunity. Early-lactation milk, which is called colostrum, contains antibodies and immune-modulating components that strengthen the immune system against many diseases. The US CDC agency recommends that children over the age of 12 months (the minimum age to stop giving breast milk or formula) should have two servings of dairy (milk) products a day,^[3] and more than six billion people worldwide consume milk and milk products.^[4]

As an agricultural product, dairy milk is collected from farm animals, mostly cattle. In 2011, dairy farms produced around 730 million tonnes (800 million short tons) of milk^[5] from 260 million dairy cows.^[6] India is the world’s largest producer of milk and the leading exporter of skimmed milk powder.^[7][8] New Zealand, Germany, and the Netherlands are the largest exporters of milk products.^[9] Between 750 and 900 million people live in dairy-farming households.^[4]

A glass of cow milk

Etymology and terminology

The term milk comes from “Old English meoluc (West Saxon), milc (Anglian), from Proto-Germanic *meluks “milk” (source also of Old Norse mjolk, Old Frisian melok, Old Saxon miluk, Dutch melk, Old High German miluh, German Milch, Gothic miluks)”.^[10]

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.”^[11] 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

Further information: Breastfeeding and Lactation

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.^[12] The makeup of the colostrum and the period of secretion varies from species to species.^[13]

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.^[14] In some cultures it is common to breastfeed children for three to five years, and the period may be longer.^[15]

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.^[16]

Food product for humans

In many cultures, especially in the West, humans continue to consume milk beyond infancy, using the milk of other mammals (especially cattle, goats and sheep) 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.^[17] 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.^[18][19] The sugar lactose is found only in milk, and possibly in forsythia flowers and a few tropical shrubs.^[20] 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.^[21] 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.^[22]

Country	Milk (liters)	Cheese (kg)	Butter (kg)
Ireland	135.6	6.7	2.4
Finland	127.0	22.5	4.1
United Kingdom	105.9	10.9	3.0
Australia	105.3	11.7	4.0
Sweden	90.1	19.1	1.7
Canada	78.4	12.3	2.5
United States	75.8	15.1	2.8
Europe	62.8	17.1	3.6
Brazil	55.7	3.6	0.4
France	55.5	26.3	7.5
Italy	54.2	21.8	2.3
Germany	51.8	22.9	5.9
Greece	49.1	23.4	0.7
Netherlands	47.5	19.4	3.3
India	39.5	–	3.5
China	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 9000–7000 BC in Mesopotamia^[24] to 3500–3000 BC in the Americas.^[25] 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.^[26] 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.^[27] 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.^[28][29]

From Southwest Asia domestic dairy animals spread to Europe (beginning around 7000 BC but did not reach Britain and Scandinavia until after 4000 BC),^[30] and South Asia (7000–5500 BC).^[31] The first farmers in central Europe^[32] and Britain^[33] 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.^[34] Sheep and goats were introduced to Africa from Southwest Asia, but African cattle may have been independently domesticated around 7000–6000 BC.^[35] Camels, domesticated in central Arabia in the fourth millennium BC, have also been used as dairy animals in North Africa and the Arabian Peninsula.^[36] The earliest Egyptian records of burn treatments describe burn dressings using milk from mothers of male babies.^[37] In the rest of the world (i.e., East and Southeast Asia, the Americas and Australia), 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.^[38] 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.^[39]

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.^[40][41] The tribes of the northern woodlands have historically been making nut milk.^[42] Cows were imported to New England in 1624.^[43]

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.^[44] 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 25 million imperial gallons (110 million litres; 30 million US gallons) annually.^[45] 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.^[44] Milk was analyzed for infection with tuberculosis. In 1907 180 samples were tested in Birmingham and 13.3% were found to be infected.^[46]

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.^[47] In 1932, plastic-coated paper milk cartons were introduced commercially.^[47]

In 1863, French chemist and biologist Louis Pasteur invented pasteurization, a method of killing harmful bacteria in beverages and food products.^[47] He developed this method while on summer vacation in Arbois, to remedy the frequent acidity of the local wines.^[48] He found out experimentally that it is sufficient to heat a young wine to only about 50–60 °C (122–140 °F) for a brief time to kill the microbes, and that the wine could be nevertheless properly aged without sacrificing the final quality.^[48] In honor of Pasteur, the process became known as “pasteurization”. Pasteurization was originally used as a way of preventing wine and beer from souring.^[49] Commercial pasteurizing equipment was produced in Germany in the 1880s, and producers adopted the process in Copenhagen and Stockholm by 1885.^[50][51]

Sources

All mammal species have females who can produce milk for some time after giving birth. Cow milk dominates the amount of milk produced. In 2011, FAO estimates 85% of all milk worldwide was produced from cows.^[52] Human milk is not produced or distributed industrially or commercially; however, human milk banks collect donated human breastmilk and redistribute it to infants who may benefit from human milk for various reasons (premature neonates, babies with allergies, metabolic diseases, etc.) but who cannot breastfeed.^[53] Actual inability to produce enough milk is rare, with studies showing that mothers from malnourished regions still produce amounts of milk of similar quality to that of mothers in developed countries.^[54][55][56] There are many reasons a mother may not produce enough breast milk.^[57][58][59] The amount of milk produced depends on how often the mother is nursing and/or pumping: the more the mother nurses her baby or pumps, the more milk is produced.^{[60][61][62][63]}

In the Western world, cow’s 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 bred selectively for increased milk production. About 90% of the dairy cows in the United States and 85% in Great Britain are Holsteins.^[21] Other dairy cows in the United States include Ayrshire, Brown Swiss, Guernsey, Jersey and Milking Shorthorn (Dairy Shorthorn).

Other animal-based sources

Other significant sources of milk

Goats (2% of world’s milk)

Buffaloes (11%)

Aside from cattle, many kinds of livestock provide milk used by humans for dairy products. These animals include water buffalo, goat, sheep, camel, donkey, horse, reindeer and yak. The first four respectively produced about 11%, 2%, 1.4% and 0.2% of all milk worldwide in 2011.^[52]

In Russia and Sweden, small moose dairies also exist.^[64]

According to the US National Bison Association, American bison (also called American buffalo) are not milked commercially;^[65] however, various sources report cows resulting from cross-breeding bison and domestic cattle are good milk producers, and have been used both during the European settlement of North America^[66] and during the development of commercial Beefalo in the 1970s and 1980s.^[67]

Swine are almost never milked, even though their milk is similar to cow’s milk and perfectly suitable for human consumption. The main reasons for this are that milking a sow’s numerous small teats is very cumbersome, and that sows cannot store their milk as cows can.^[68] A few pig farms do sell pig cheese as a novelty item; these cheeses are exceedingly expensive.^[69]

Production worldwide

Main articles: List of countries by milk production and Dairy farming

Rank	Country	Production (metric tons)
1	India	186,143,000
–	European Union	167,256,000
2	United States	98,646,000
3	Pakistan	45,623,000
4	Brazil	35,539,000
5	China	31,592,000
6	Russia	31,527,000
7	Turkey	22,791,000
8	New Zealand	21,372,000
World		842,989,000

Rank	Country	Production (metric tons)
1	United States	101,251,009
2	India	87,822,387
3	Brazil	36,508,411
4	China	34,400,000
5	Germany	33,164,910
6	Russia	31,959,801
7	France	25,147,310
8	Pakistan	22,508,000
9	New Zealand	21,871,305
10	Turkey	20,000,000

Rank	Country	Production (metric tons)
1	China	1,211,831
2	Turkey	1,207,427
3	Greece	945,430
4	Syria	705,582
5	Algeria	592,293
6	Spain	556,250
7	Italy	481,970
8	Romania	426,000
9	Sudan	416,002
10	Somalia	406,541

Rank	Country	Production (metric tons)
1	India	5,888,077
2	Bangladesh	2,671,911
3	Sudan	1,165,043
4	Pakistan	965,000
5	France	679,300
6	Turkey	554,143
7	Spain	523,900
8	South Sudan	467,148
9	Niger	407,346
10	Netherlands	407,000

Rank	Country	Production (metric tons)
1	India	90,026,273
2	Pakistan	37,256,000
3	China	2,919,966
4	Egypt	1,747,641
5	Nepal	1,380,600
6	Italy	253,830
7	Myanmar	205,102
8	Iran	128,000
9	Mongolia	104,645
10	Indonesia	89,983

In 2012, the largest producer of milk and milk products was India, followed by the United States of America, China, Pakistan and Brazil.^[75] All 28 European Union members together produced 153.8 million tonnes (169.5 million short tons) of milk in 2013, the largest by any politico–economic union.^[76]

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 investments 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 farms.^[77] 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.^[78]

Production yields

FAO reports^[52] Israel dairy farms are the most productive in the world, with a yield of 12,546 kilograms (27,659 lb) milk per cow per year. This survey over 2001 and 2007 was conducted by ICAR (International Committee for Animal Recording)^[79] across 17 developed countries. The survey found that the average herd size in these developed countries increased from 74 to 99 cows per herd between 2001 and 2007. A dairy farm had an average of 19 cows per herd in Norway, and 337 in New Zealand. Annual milk production in the same period increased from 7,726 to 8,550 kg (17,033 to 18,850 lb) per cow in these developed countries. The lowest average production was in New Zealand at 3,974 kg (8,761 lb) per cow. The milk yield per cow depended on production systems, nutrition of the cows, and only to a minor extent different genetic potential of the animals. What the cow ate made the most impact on the production obtained. New Zealand cows with the lowest yield per year grazed all year, in contrast to Israel with the highest yield where the cows ate in barns with an energy-rich mixed diet.

The milk yield per cow in the United States was 9,954 kg (21,945 lb) per year in 2010. In contrast, the milk yields per cow in India and China – the second and third largest producers – were respectively 1,154 kg (2,544 lb) and 2,282 kg (5,031 lb) per year.^[80]

The IPCC Sixth Assessment Report mentions the possibility that the already recorded stagnation of dairy production in both China and West Africa can be attributed to persistent increases in heat stress caused by climate change.^[81]: 747 This is a plausible hypothesis, because even mild heat stress can reduce daily yields: research in Sweden found that average daily temperatures of 20–25 °C (68–77 °F) reduce daily milk yield per cow by 0.2 kg, with the loss reaching 0.54 kg for 25–30 °C (77–86 °F).^[82] Research in a humid tropical climate describes a more linear relationship, with every unit of heat stress reducing yield by 2.13%.^[83] In the intensive farming systems, daily milk yield per cow declines by 1.8 kg during severe heat stress. In organic farming systems, the effect of heat stress on milk yields is limited, but milk quality suffers substantially, with lower fat and protein content.^[84] In China, daily milk production per cow is already lower than the average by between 0.7 and 4 kg in July (the hottest month of the year), and by 2070, it may decline by up to 50% (or 7.2 kg) due to climate change.^[85] Heatwaves can also reduce milk yield, with particularly acute impacts if the heatwave lasts for four or more days, as at that point the cow’s thermoregulation capacity is usually exhausted, and its core body temperature starts to increase.^[86]

Price

It was reported in 2007 that with increased worldwide prosperity and the competition of bio-fuel production for feed stocks, both the demand for and the price of milk had substantially increased worldwide. Particularly notable was the rapid increase of consumption of milk in China and the rise of the price of milk in the United States above the government subsidized price.^[87] In 2010 the Department of Agriculture predicted farmers would receive an average of $1.35 per US gallon ($0.36/L; $1.62/imp gal) of cow’s milk, which is down 30 cents per US gallon (7.9 ¢/L; 36 ¢/imp gal) from 2007 and below the break-even point for many cattle farmers.^[88]

Composition

Milk is an emulsion or colloid of butterfat globules within a water-based fluid that contains dissolved carbohydrates and protein aggregates with minerals.^[89] Because it is produced as a food source for the young, all of its contents provide benefits for growth. The principal requirements are energy (lipids, lactose, and protein), biosynthesis of non-essential amino acids supplied by proteins (essential amino acids and amino groups), essential fatty acids, vitamins and inorganic elements, and water.^[90]

pH

The pH of cow’s milk, ranging from 6.7 to 6.9, is similar to other bovines and non-bovine mammals.^[91]

Lipids

Main article: Butterfat

Full fat milk contains about 33 grams of fat per liter, including about 19 grams of saturated fat, 1.2 grams of omega 6 fatty acids, and 0.75 grams of omega 3 fatty acids per liter. The amount of fat varies for products where (some of) the fat has been removed, such as in skimmed milk.^[92]

Initially milk fat is secreted in the form of a fat globule surrounded by a membrane.^[93] Each fat globule is composed almost entirely of triacylglycerols and is surrounded by a membrane consisting of complex lipids such as phospholipids, along with proteins. These act as emulsifiers which keep the individual globules from coalescing and protect the contents of these globules from various enzymes in the fluid portion of the milk. Although 97–98% of lipids are triacylglycerols, small amounts of di- and monoacylglycerols, free cholesterol and cholesterol esters, free fatty acids, and phospholipids are also present. Unlike protein and carbohydrates, fat composition in milk varies widely due to genetic, lactational, and nutritional factor difference between different species.^[93]

Fat globules vary in size from less than 0.2 to about 15 micrometers in diameter between different species. Diameter may also vary between animals within a species and at different times within a milking of a single animal. In unhomogenized cow’s milk, the fat globules have an average diameter of two to four micrometers and with homogenization, average around 0.4 micrometers.^[93] The fat-soluble vitamins A, D, E, and K along with essential fatty acids such as linoleic and linolenic acid are found within the milk fat portion of the milk.^[21]

Fatty acid	length	mol% (rounded)
Butyryl	C4	12
Myristyl	C14	11
Palmityl	C16	24
Oleyl	C18:1	24

Proteins

Normal bovine milk contains 30–35 grams of protein per liter, of which about 80% is arranged in casein micelles. Total proteins in milk represent 3.2% of its composition (nutrition table).

Caseins

Main article: Casein

The largest structures in the fluid portion of the milk are “casein micelles”: aggregates of several thousand protein molecules with superficial resemblance to a surfactant micelle, bonded with the help of nanometer-scale particles of calcium phosphate. Each casein micelle is roughly spherical and about a tenth of a micrometer across. There are four different types of casein proteins: αs1-, αs2-, β-, and κ-caseins. Most of the casein proteins are bound into the micelles. There are several competing theories regarding the precise structure of the micelles, but they share one important feature: the outermost layer consists of strands of one type of protein, k-casein, reaching out from the body of the micelle into the surrounding fluid. These kappa-casein molecules all have a negative electrical charge and therefore repel each other, keeping the micelles separated under normal conditions and in a stable colloidal suspension in the water-based surrounding fluid.^[21][95]

Milk contains dozens of other types of proteins beside caseins and including enzymes. These other proteins are more water-soluble than caseins and do not form larger structures. Because the proteins remain suspended in whey, remaining when caseins coagulate into curds, they are collectively known as whey proteins. Lactoglobulin is the most common whey protein by a large margin.^[21] The ratio of caseins to whey proteins varies greatly between species; for example, it is 82:18 in cows and around 32:68 in humans.^[96]

Species	Ratio
Human	29.7:70.3 – 33.7:66.3
Bovine	82:18
Caprine	78:22
Ovine	76:24
Buffalo	82:18
Equine	52:48
Camel	73:27 – 76:24
Yak	82:18
Reindeer	80:20 – 83:17

Salts, minerals, and vitamins

Bovine milk contains a variety of cations and anions traditionally referred to as “minerals” or “milk salts”. Calcium, phosphate, magnesium, sodium, potassium, citrate, and chloride are all included and they typically occur at concentrations of 5–40 mM. The milk salts strongly interact with casein, most notably calcium phosphate. It is present in excess and often, much greater excess of solubility of solid calcium phosphate.^[90] In addition to calcium, milk is a source of many vitamins: Vitamins A, B1, B2, B5 B6, B7, B12, and D.

Calcium phosphate structure

For many years the most widely accepted theory of the structure of a micelle was that it was composed of spherical casein aggregates, called submicelles, that were held together by calcium phosphate linkages. However, there are two recent models of the casein micelle that refute the distinct micellular structures within the micelle.

The first theory, attributed to de Kruif and Holt, proposes that nanoclusters of calcium phosphate and the phosphopeptide fraction of beta-casein are the centerpiece to micellar structure. Specifically in this view unstructured proteins organize around the calcium phosphate, giving rise to their structure, and thus no specific structure is formed.

Under the second theory, proposed by Horne, the growth of calcium phosphate nanoclusters begins the process of micelle formation, but is limited by binding phosphopeptide loop regions of the caseins. Once bound, protein-protein interactions are formed and polymerization occurs, in which K-casein is used as an end cap to form micelles with trapped calcium phosphate nanoclusters.

Some sources indicate that the trapped calcium phosphate is in the form of Ca₉(PO₄)₆; whereas others say it is similar to the structure of the mineral brushite, CaHPO₄·2H₂O.^[97]

Sugars and carbohydrates

Milk contains several different carbohydrates, including lactose, glucose, galactose, and other oligosaccharides. The lactose gives milk its sweet taste and contributes approximately 40% of the calories in whole cow’s milk’s. Lactose is a disaccharide composite of two simple sugars, glucose and galactose. Bovine milk averages 4.8% anhydrous lactose, which amounts to about 50% of the total solids of skimmed milk. Levels of lactose are dependent upon the type of milk as other carbohydrates can be present at higher concentrations than lactose in milks.^[90]

Miscellaneous contents

Other components found in raw cow’s milk are living white blood cells, mammary gland cells, various bacteria, vitamin C, and a large number of active enzymes.^[21]

Appearance

Both the fat globules and the smaller casein micelles, which are just large enough to deflect light, contribute to the opaque white color of milk. The fat globules contain some yellow-orange carotene, enough in some breeds (such as Guernsey and Jersey cattle) to impart a golden or “creamy” hue to a glass of milk. The riboflavin in the whey portion of milk has a greenish color, which sometimes can be discerned in skimmed milk or whey products.^[21] Fat-free skimmed milk has only the casein micelles to scatter light, and they tend to scatter shorter-wavelength blue light more than they do red, giving skimmed milk a bluish tint.^[95]

Processing

In most Western countries, centralized dairy facilities process milk and products obtained from milk, such as cream, butter, and cheese. In the US, these dairies usually are local companies, while in the Southern Hemisphere facilities may be run by large multi-national corporations such as Fonterra.

Pasteurization

Main article: Pasteurization § Milk

Pasteurization is used to kill harmful pathogenic bacteria such as M. paratuberculosis and E. coli 0157:H7 by heating the milk for a short time and then immediately cooling it.^[98] Types of pasteurized milk include full cream, reduced fat, skim milk, calcium enriched, flavored, and UHT.^[99] The standard high temperature short time (HTST) process of 72 °C (162 °F) for 15 seconds completely kills pathogenic bacteria in milk,^[100] rendering it safe to drink for up to three weeks if continually refrigerated.^[101] Dairies print best before dates on each container, after which stores remove any unsold milk from their shelves.

A side effect of the heating of pasteurization is that some vitamin and mineral content is lost. Soluble calcium and phosphorus decrease by 5%, thiamin and vitamin B12 by 10%, and vitamin C by 20% or greater (even to complete loss).^[102] Because losses are small in comparison to the large amount of the two B-vitamins present, milk continues to provide significant amounts of thiamin and vitamin B12. The loss of vitamin C is not nutritionally significant in a well-balanced diet, as milk is not an important dietary source of vitamin C.

Filtration

Microfiltration is a process that partially replaces pasteurization and produces milk with fewer microorganisms and longer shelf life without a change in the taste of the milk. In this process, cream is separated from the skimmed milk and is pasteurized in the usual way, but the skimmed milk is forced through ceramic microfilters that trap 99.9% of microorganisms in the milk^[103] (as compared to 99.999% killing of microorganisms in standard HTST pasteurization).^[104] The skimmed milk then is recombined with the pasteurized cream to reconstitute the original milk composition.

Ultrafiltration uses finer filters than microfiltration, which allow lactose and water to pass through while retaining fats, calcium and protein.^[105] As with microfiltration, the fat may be removed before filtration and added back in afterwards.^[106] Ultrafiltered milk is used in cheesemaking, since it has reduced volume for a given protein content, and is sold directly to consumers as a higher protein, lower sugar content, and creamier alternative to regular milk.^[107]

Creaming and homogenization

Upon standing for 12 to 24 hours, fresh milk has a tendency to separate into a high-fat cream layer on top of a larger, low-fat milk layer. The cream often is sold as a separate product with its own uses. Today the separation of the cream from the milk usually is accomplished rapidly in centrifugal cream separators. The fat globules rise to the top of a container of milk because fat is less dense than water.^[21]

The smaller the globules, the more other molecular-level forces prevent this from happening. The cream rises in cow’s milk much more quickly than a simple model would predict: rather than isolated globules, the fat in the milk tends to form into clusters containing about a million globules, held together by a number of minor whey proteins.^[21] These clusters rise faster than individual globules can. The fat globules in milk from goats, sheep, and water buffalo do not form clusters as readily and are smaller to begin with, resulting in a slower separation of cream from these milks.^[21]

Milk often is homogenized, a treatment that prevents a cream layer from separating out of the milk. The milk is pumped at high pressures through very narrow tubes, breaking up the fat globules through turbulence and cavitation.^[108] A greater number of smaller particles possess more total surface area than a smaller number of larger ones, and the original fat globule membranes cannot completely cover them. Casein micelles are attracted to the newly exposed fat surfaces.

Nearly one-third of the micelles in the milk end up participating in this new membrane structure. The casein weighs down the globules and interferes with the clustering that accelerated separation. The exposed fat globules are vulnerable to certain enzymes present in milk, which could break down the fats and produce rancid flavors. To prevent this, the enzymes are inactivated by pasteurizing the milk immediately before or during homogenization.

Homogenized milk tastes blander but feels creamier in the mouth than unhomogenized. It is whiter and more resistant to developing off flavors.^[21] Creamline (or cream-top) milk is unhomogenized. It may or may not have been pasteurized. Milk that has undergone high-pressure homogenization, sometimes labeled as “ultra-homogenized”, has a longer shelf life than milk that has undergone ordinary homogenization at lower pressures.^[109]

UHT

Ultra Heat Treatment (UHT) is a type of milk processing where all bacteria are destroyed with high heat to extend its shelf life for up to 6 months, as long as the package is not opened. Milk is firstly homogenized and then is heated to 138 degrees Celsius for 2–4 seconds. The milk is immediately cooled down and packed into a sterile container. As a result of this treatment, all the pathogenic bacteria within the milk are destroyed, unlike when the milk is just pasteurized. The treated milk will keep for up to 6 months if unopened. UHT milk does not need to be refrigerated until the package is opened, which makes it easier to ship and store. However, in this process there is a loss of vitamin B1 and vitamin C, and there is also a slight change in the taste of the milk.^[110]

Nutrition and health

See also: Fat content of milk

The composition of milk differs widely among species. Factors such as the type of protein; the proportion of protein, fat, and sugar; the levels of various vitamins and minerals; and the size of the butterfat globules, and the strength of the curd are among those that may vary.^[23] For example:

• Human milk contains, on average, 1.1% protein, 4.2% fat, 7.0% lactose (a sugar), and supplies 72 kcal of energy per 100 grams.
• Cow’s milk contains, on average, 3.4% protein, 3.6% fat, and 4.6% lactose, 0.7% minerals^[111] and supplies 66 kcal of energy per 100 grams. See also Nutritional value further on in this article and more complete lists at online sources that list values and differences in categories.^[112]

Donkey and horse milk have the lowest fat content, while the milk of seals and whales may contain more than 50% fat.^[113]

Constituents	Unit	Cow	Goat	Sheep	Water buffalo
Water	g	87.8	88.9	83.0	81.1
Protein	g	3.2	3.1	5.4	4.5
Fat	g	3.9	3.5	6.0	8.0
—-Saturated fatty acids	g	2.4	2.3	3.8	4.2
—-Monounsaturated fatty acids	g	1.1	0.8	1.5	1.7
—-Polyunsaturated fatty acids	g	0.1	0.1	0.3	0.2
Carbohydrate (i.e. the sugar form of lactose)	g	4.8	4.4	5.1	4.9
Cholesterol	mg	14	10	11	8
Calcium	mg	120	100	170	195
Energy	kcal	66	60	95	110
	kJ	275	253	396	463

Cow’s milk: variation by breed

These compositions vary by breed, animal, and point in the lactation period.

Cow breed	Approximate percentage
Jersey	5.2
Zebu	4.7
Brown Swiss	4.0
Holstein-Friesian	3.6

The protein range for these four breeds is 3.3% to 3.9%, while the lactose range is 4.7% to 4.9%.^[21]

Milk fat percentages may be manipulated by dairy farmers’ stock diet formulation strategies. The infection known as mastitis, especially in dairy cattle, can cause fat levels to decline.^[114]

Nutritional value

Processed cow’s milk was formulated to contain differing amounts of fat during the 1950s. One cup (250 mL) of 2%-fat cow’s milk contains 285 mg of calcium, which represents 22% to 29% of the daily recommended intake (DRI) of calcium for an adult. Depending on its age, milk contains 8 grams of protein, and a number of other nutrients^[which?] (either naturally or through fortification).

Whole milk has a glycemic index of 39±3.^[115] A food is considered to have a low GI if it is 55 or less.

For protein quality, whole milk has a Digestible Indispensable Amino Acid Score (DIAAS) of 1.43, with the limiting amino acid for those groups being methionine and cysteine.^[116] A DIAAS of 1 or more is considered to be an excellent/high protein quality source.^[117]

Disease

There is mixed evidence that drinking milk increases the risk of cancer in general, and good evidence that milk drinking may have a protective effect specifically against bowel cancer.^[118]

Allergy

Main article: Milk allergy

One of the most common food allergies in infants is to cow’s milk. This is an immunologically mediated adverse reaction, rarely fatal, to one or more cow’s milk proteins.^[119] Milk allergy affects between 2% and 3% of babies and young children.^[120] To reduce risk, recommendations are that babies should be exclusively breastfed for at least four months, preferably six months, before introducing cow’s milk.^[121] The majority of children outgrow milk allergy, but for about 0.4% the condition persists into adulthood.^[122]

Lactose intolerance

Main article: Lactose intolerance

Lactose intolerance is a condition in which people have symptoms due to deficiency or absence of the enzyme lactase in the small intestine, causing poor absorption of milk lactose.^[123][124] People affected vary in the amount of lactose they can tolerate before symptoms develop,^[123] which may include abdominal pain, bloating, diarrhea, gas, and nausea.^[123] Severity depends on the amount of milk consumed.^[123] Those affected are usually able to drink at least one cup of milk without developing significant symptoms, with greater amounts tolerated if drunk with a meal or throughout the day.^[123][125]

Evolution of lactation

Main article: Lactation

The mammary gland is thought to have derived from apocrine skin glands.^[126] It has been suggested that the original function of lactation (milk production) was keeping eggs moist. Much of the argument is based on monotremes (egg-laying mammals).^{[126][127][128]} The original adaptive significance of milk secretions may have been nutrition^[129] and immunological protection.^{[130][131][132][133]}

Tritylodontid cynodonts seem to have displayed lactation, based on their dental replacement patterns.^[134]

Bovine growth hormone supplementation

Since November 1993, recombinant bovine somatotropin (rbST), also called rBGH, has been sold to dairy farmers with FDA approval. Cows produce bovine growth hormone naturally, but some producers administer an additional recombinant version of BGH which is produced through genetically engineered E. coli to increase milk production. Bovine growth hormone also stimulates liver production of insulin-like growth factor 1 (IGF1).

Human health

The US Food and Drug Administration,^[135] the National Institutes of Health^[136] and the World Health Organization^[137] have reported that both of these compounds are safe for human consumption at the amounts present.

Milk from cows given rBST may be sold in the United States, and the FDA stated that no significant difference has been shown between milk derived from rBST-treated and that from non-rBST-treated cows.^[138]

Milk that advertises that it comes from cows not treated with rBST, is required to state this finding on its label.

Animal welfare

Cows receiving rBGH supplements may more frequently contract an udder infection known as mastitis.^[139] Problems with mastitis have led to Canada, Australia, New Zealand, and Japan banning milk from rBST treated cows. Mastitis, among other diseases, may be responsible for the fact that levels of white blood cells in milk vary naturally.^[140][141]

rBGH is also banned in the European Union, for reasons of animal welfare.^[142]

Varieties and brands

Main article: Dairy product

Milk products are sold in a number of varieties based on types/degrees of:

• additives (e.g. vitamins, flavorings)
• age (e.g. cheddar, old cheddar)
• coagulation (e.g. cottage cheese)
• farming method (e.g. organic, grass-fed, haymilk)
• fat content (e.g. half and half, 3% fat milk, 2% milk, 1% milk, skim milk)
• fermentation (e.g. buttermilk)
• flavoring (e.g. chocolate and strawberry)
• homogenization (e.g. cream top)
• packaging (e.g. bottle, carton, bag)
• pasteurization (e.g. raw milk, pasteurized milk)
• reduction or elimination of lactose
• species (e.g. cow, goat, sheep)
• sweetening (e.g., chocolate and strawberry milk)
• water content (e.g. dry milk powder, condensed milk, ultrafiltered milk)

Milk preserved by the UHT process does not need to be refrigerated before opening and has a much longer shelf life (six months) than milk in ordinary packaging. It is typically sold unrefrigerated in the UK, US, Europe, Latin America, and Australia.

Reduction or elimination of lactose

Lactose-free milk can be produced by passing milk over lactase enzyme bound to an inert carrier. Once the molecule is cleaved, there are no lactose ill effects. Forms are available with reduced amounts of lactose (typically 30% of normal), and alternatively with nearly 0%. The only noticeable difference from regular milk is a slightly sweeter taste due to the cleavage of lactose into glucose and galactose. Lactose-reduced milk can also be produced via ultra filtration, which removes smaller molecules such as lactose and water while leaving calcium and proteins behind. Milk produced via these methods has a lower sugar content than regular milk.^[105] To aid digestion in those with lactose intolerance, another alternative is dairy foods, milk and yogurt, with added bacterial cultures such as Lactobacillus acidophilus (“acidophilus milk”) and bifidobacteria.^[143] Another milk with Lactococcus lactis bacteria cultures (“cultured buttermilk“) often is used in cooking to replace the traditional use of naturally soured milk, which has become rare due to the ubiquity of pasteurization, which also kills the naturally occurring Lactococcus bacteria.^[144]

Additives and flavoring

Commercially sold milk commonly has vitamin D added to it to make up for lack of exposure to UVB radiation. Reduced-fat milks often have added vitamin A palmitate to compensate for the loss of the vitamin during fat removal; in the United States this results in reduced fat milks having a higher vitamin A content than whole milk.^[145] Milk often has flavoring added to it for better taste or as a means of improving sales. Chocolate milk has been sold for many years and has been followed more recently by strawberry milk and others. Some nutritionists have criticized flavored milk for adding sugar, usually in the form of high-fructose corn syrup, to the diets of children who are already commonly obese in the US.^[146]

Distribution

Due to the short shelf life of normal milk, it used to be delivered to households daily in many countries; however, improved refrigeration at home, changing food shopping patterns because of supermarkets, and the higher cost of home delivery mean that daily deliveries by a milkman are no longer available in most countries.

Australia and New Zealand

In Australia and New Zealand, prior to metrication, milk was generally distributed in 1 pint (568 mL) glass bottles. In Australia and Ireland there was a government funded “free milk for school children” program, and milk was distributed at morning recess in 1/3 pint bottles. With the conversion to metric measures, the milk industry was concerned that the replacement of the pint bottles with 500 mL bottles would result in a 13.6% drop in milk consumption; hence, all pint bottles were recalled and replaced by 600 mL bottles. With time, due to the steadily increasing cost of collecting, transporting, storing and cleaning glass bottles, they were replaced by cardboard cartons. A number of designs were used, including a tetrahedron which could be close-packed without waste space, and could not be knocked over accidentally (slogan: “No more crying over spilt milk”). However, the industry eventually settled on a design similar to that used in the United States.^[147]

Milk is now available in a variety of sizes in paperboard milk cartons (250 mL, 375 mL, 600 mL, 1 liter and 1.5 liters) and plastic bottles (1, 2 and 3 liters). A significant addition to the marketplace has been “long-life” milk (UHT), generally available in 1 and 2 liter rectangular cardboard cartons. In urban and suburban areas where there is sufficient demand, home delivery is still available, though in suburban areas this is often three times per week rather than daily. Another significant and popular addition to the marketplace has been flavored milks; for example, as mentioned above, Farmers Union Iced Coffee outsells Coca-Cola in South Australia.^[148]

India

In rural India, milk is home delivered, daily, by local milkmen carrying bulk quantities in a metal container, usually on a bicycle. In other parts of metropolitan India, milk is usually bought or delivered in plastic bags or cartons via shops or supermarkets.

The current milk chain flow in India is from milk producer to milk collection agent. Then it is transported to a milk chilling center and bulk transported to the processing plant, then to the sales agent and finally to the consumer.

A 2011 survey by the Food Safety and Standards Authority of India found that nearly 70% of samples had not conformed to the standards set for milk. The study found that due to lack of hygiene and sanitation in milk handling and packaging, detergents (used during cleaning operations) were not washed properly and found their way into the milk. About 8% of samples in the survey were found to have detergents, which are hazardous to health.^[149]

Although India is the world’s largest milk producer and a major exporter, the country’s ever-increasing demand for dairy products could eventually make it a net importer.^[150]

Pakistan

In Pakistan, milk is supplied in jugs. Milk has been a staple food, especially among the pastoral tribes in this country.

United Kingdom

Since the late 1990s, milk-buying patterns have changed drastically in the UK. The classic milkman, who travels his local milk round (route) using a milk float (often battery powered) during the early hours and delivers milk in 1-pint glass bottles with aluminum foil tops directly to households, has almost disappeared. Two of the main reasons for the decline of UK home deliveries by milkmen are household refrigerators (which lessen the need for daily milk deliveries) and private car usage (which has increased supermarket shopping). Another factor is that it is cheaper to purchase milk from a supermarket than from home delivery. In 1996, more than 2.5 billion liters of milk were still being delivered by milkmen, but by 2006 only 637 million liters (13% of milk consumed) was delivered by some 9,500 milkmen.^[151] By 2010, the estimated number of milkmen had dropped to 6,000.^[152] Assuming that delivery per milkman is the same as it was in 2006, this means milkmen deliveries now only account for 6–7% of all milk consumed by UK households (6.7 billion liters in 2008/2009).^[153]

Almost 95% of all milk in the UK is thus sold in shops today, most of it in plastic bottles of various sizes, but some also in milk cartons. Milk is hardly ever sold in glass bottles in UK shops.

United States

In the United States, glass milk bottles have been replaced mostly with milk cartons and plastic jugs. Gallons of milk are almost always sold in jugs, while half gallons and quarts may be found in both paper cartons and plastic jugs, and smaller sizes are almost always in cartons.

The “half pint” (237 mL, ⁵⁄₁₂ imp pt) milk carton is the traditional unit as a component of school lunches, though some companies have replaced that unit size with a plastic bottle, which is also available at retail in 6- and 12-pack size.

Packaging

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Glass milk bottles are now rare. Most people purchase milk in bags, plastic bottles, or plastic-coated paper cartons. Ultraviolet (UV) light from fluorescent lighting can alter the flavor of milk, so many companies that once distributed milk in transparent or highly translucent containers are now using thicker materials that block the UV light. Milk comes in a variety of containers with local variants:ArgentinaCommonly sold in 1-liter bags and cardboard boxes. The bag is then placed in a plastic jug and the corner cut off before the milk is poured.Australia and New ZealandDistributed in a variety of sizes, most commonly in aseptic cartons for up to 1.5 liters, and plastic screw-top bottles beyond that with the following volumes; 1.1 L, 2 L, and 3 L. 1-liter milk bags are starting to appear in supermarkets, but have not yet proved popular. Most UHT-milk is packed in 1 or 2 liter paper containers with a sealed plastic spout.^[147]BrazilUsed to be sold in cooled 1-liter bags, just like in South Africa. Today the most common form is 1-liter aseptic cartons containing UHT skimmed, semi-skimmed or whole milk, although the plastic bags are still in use for pasteurized milk. Higher grades of pasteurized milk can be found in cartons or plastic bottles. Sizes other than 1-liter are rare.Canada1.33 liter plastic bags (sold as 4 liters in 3 bags) are widely available in some areas (especially the Maritimes, Ontario and Quebec), although the 4 liter plastic jug has supplanted them in western Canada. Other common packaging sizes are 2 liter, 1 liter, 500 mL, and 250 mL cartons, as well as 4 liter, 1 liter, 250 mL aseptic cartons and 500 mL plastic jugs.ChileDistributed most commonly in aseptic cartons for up to 1 liter, but smaller, snack-sized cartons are also popular. The most common flavors, besides the natural presentation, are chocolate, strawberry and vanilla.ChinaSweetened milk is a drink popular with students of all ages and is often sold in small plastic bags complete with straw. Adults not wishing to drink at a banquet often drink milk served from cartons or milk tea.ColombiaSells milk in 1-liter plastic bags.Croatia, Bosnia and Herzegovina, Serbia, MontenegroUHT milk (trajno mlijeko/trajno mleko/трајно млеко) is sold in 500 mL and 1 L (sometimes also 200 mL) aseptic cartons. Non-UHT pasteurized milk (svježe mlijeko/sveže mleko/свеже млеко) is most commonly sold in 1 L and 1.5 L PET bottles, though in Serbia one can still find milk in plastic bags.EstoniaCommonly sold in 1 L bags or 0.33 L, 0.5 L, 1 L or 1.5 L cartons.Parts of EuropeSizes of 500 mL, 1 liter (the most common), 1.5 liters, 2 liters and 3 liters are commonplace.FinlandCommonly sold in 1 L or 1.5 L cartons, in some places also in 2 dl and 5 dl cartons.GermanyCommonly sold in 1-liter cartons. Sale in 1-liter plastic bags (common in the 1980s) is now rare.Hong KongMilk is sold in glass bottles (220 mL), cartons (236 mL and 1 L), plastic jugs (2 liters) and aseptic cartons (250 mL).IndiaCommonly sold in 500 mL plastic bags and in bottles in some parts like in the West. It is still customary to serve the milk boiled, despite pasteurization. Milk is often buffalo milk. Flavored milk is sold in most convenience stores in waxed cardboard containers. Convenience stores also sell many varieties of milk (such as flavored and ultra-pasteurized) in various sizes, usually in aseptic cartons.IndonesiaUsually sold in 1-liter cartons, but smaller, snack-sized cartons are available.ItalyCommonly sold in 1-liter cartons or bottles and less commonly in 0.5 or 0.25-liter cartons. Whole milk, semi-skimmed milk, skimmed, lactose-free, and flavored (usually in small packages) milk is available. Milk is sold fresh or UHT. Goat’s milk is also available in small amounts. UHT semi-skimmed milk is the most sold, but cafés use almost exclusively fresh whole milk.JapanCommonly sold in 1-liter waxed paperboard cartons. In most city centers there is also home delivery of milk in glass jugs. As seen in China, sweetened and flavored milk drinks are commonly seen in vending machines.KenyaMilk in Kenya is mostly sold in plastic-coated aseptic paper cartons supplied in 300 mL, 500 mL or 1 liter volumes. In rural areas, milk is stored in plastic bottles or gourds.^[154][155] The standard unit of measuring milk quantity in Kenya is a liter.PakistanMilk is supplied in 500 mL plastic bags and carried in jugs from rural to cities for sellingPhilippinesMilk is supplied in 1000 mL plastic bottles and delivered from factories to cities for selling.PolandUHT milk is mostly sold in aseptic cartons (500 mL, 1 L, 2 L), and non-UHT in 1 L plastic bags or plastic bottles. Milk, UHT is commonly boiled, despite being pasteurized.South AfricaCommonly sold in 1-liter bags. The bag is then placed in a plastic jug and the corner cut off before the milk is poured.South KoreaSold in cartons (180 mL, 200 mL, 500 mL 900 mL, 1 L, 1.8 L, 2.3 L), plastic jugs (1 L and 1.8 L), aseptic cartons (180 mL and 200 mL) and plastic bags (1 L).SwedenCommonly sold in 0.3 L, 1 L or 1.5 L cartons and sometimes as plastic or glass milk bottles.TurkeyCommonly sold in 500 mL or 1 L cartons or special plastic bottles. UHT milk is more popular. Milkmen also serve in smaller towns and villages.United KingdomMost stores stock imperial sizes: 1 pint (568 mL), 2 pints (1.136 L), 4 pints (2.273 L), 6 pints (3.408 L) or a combination including both metric and imperial sizes. Glass milk bottles delivered to the doorstep by the milkman are typically pint-sized and are returned empty by the householder for repeated reuse. Milk is sold at supermarkets in either aseptic cartons or HDPE bottles. Supermarkets have also now begun to introduce milk in bags, to be poured from a proprietary jug and nozzle.United StatesCommonly sold in gallon (3.78 L), half-gallon (1.89 L) and quart (0.94 L) containers of natural-colored HDPE resin, or, for sizes less than one gallon, cartons of waxed paperboard. Bottles made of opaque PET are also becoming commonplace for smaller, particularly metric, sizes such as one liter. The US single-serving size is usually the half-pint (about 240 mL). Less frequently, dairies deliver milk directly to consumers, from coolers filled with glass bottles which are typically half-gallon sized and returned for reuse. Some convenience store chains in the United States (such as Kwik Trip in the Midwest) sell milk in half-gallon bags, while another rectangular cube gallon container design used for easy stacking in shipping and displaying is used by warehouse clubs such as Costco and Sam’s Club, along with some Walmart stores.^[156]UruguayPasteurized milk is commonly sold in 1-liter bags and ultra-pasteurized milk is sold in cardboard boxes called Tetra Briks. Non-pasteurized milk is forbidden. Until the 1960s no treatment was applied; milk was sold in bottles. As of 2017, plastic jugs used for pouring the bags, or “sachets”, are in common use.

Practically everywhere, condensed milk and evaporated milk are distributed in metal cans, 250 and 125 mL paper containers and 100 and 200 mL squeeze tubes, and powdered milk (skim and whole) is distributed in boxes or bags.

Spoilage and fermented milk products

See also: Fermented milk products

When raw milk is left standing for a while, it turns “sour“. This is the result of fermentation, where lactic acid bacteria ferment the lactose in the milk into lactic acid. Prolonged fermentation may render the milk unpleasant to consume. This fermentation process is exploited by the introduction of bacterial cultures (e.g. Lactobacilli sp., Streptococcus sp., Leuconostoc sp., etc.) to produce a variety of fermented milk products. The reduced pH from lactic acid accumulation denatures proteins and causes the milk to undergo a variety of different transformations in appearance and texture, ranging from an aggregate to smooth consistency. Some of these products include sour cream, yogurt, cheese, buttermilk, viili, kefir, and kumis. See Dairy product for more information.

Pasteurization of cow’s milk initially destroys any potential pathogens and increases the shelf life,^[157][158] but eventually results in spoilage that makes it unsuitable for consumption. This causes it to assume an unpleasant odor, and the milk is deemed non-consumable due to unpleasant taste and an increased risk of food poisoning. In raw milk, the presence of lactic acid-producing bacteria, under suitable conditions, ferments the lactose present to lactic acid. The increasing acidity in turn prevents the growth of other organisms, or slows their growth significantly. During pasteurization, however, these lactic acid bacteria are mostly destroyed.

In order to prevent spoilage, milk can be kept refrigerated and stored between 1 and 4 °C (34 and 39 °F) in bulk tanks. Most milk is pasteurized by heating briefly and then refrigerated to allow transport from factory farms to local markets. The spoilage of milk can be forestalled by using ultra-high temperature (UHT) treatment. Milk so treated can be stored unrefrigerated for several months until opened but has a characteristic “cooked” taste. Condensed milk, made by removing most of the water, can be stored in cans for many years, unrefrigerated, as can evaporated milk.

Powdered milk

The most durable form of milk is powdered milk, which is produced from milk by removing almost all water. The moisture content is usually less than 5% in both drum- and spray-dried powdered milk.

Freezing of milk can cause fat globule aggregation upon thawing, resulting in milky layers and butterfat lumps. These can be dispersed again by warming and stirring the milk.^[159] It can change the taste by destruction of milk-fat globule membranes, releasing oxidized flavors.^[159]

Use in other food products

Milk is used to make yogurt, cheese, ice milk, pudding, hot chocolate and french toast, among many other products. Milk is often added to dry breakfast cereal, porridge and granola. Milk is mixed with ice cream and flavored syrups in a blender to make milkshakes. Milk is often served in coffee and tea. Frothy steamed milk is used to prepare espresso-based drinks such as cafe latte.

In language and culture

In Greek mythology, the Milky Way was formed after the trickster god Hermes suckled the infant Heracles at the breast of Hera, the queen of the gods, while she was asleep.^[160][161] When Hera awoke, she tore Heracles away from her breast and splattered her breast milk across the heavens.^[160][161] In another version of the story, Athena, the patron goddess of heroes, tricked Hera into suckling Heracles voluntarily,^[160][161] but he bit her nipple so hard that she flung him away, spraying milk everywhere.^[160][161]

In many African and Asian countries, butter is traditionally made from fermented milk rather than cream. It can take several hours of churning to produce workable butter grains from fermented milk.^[162]

Holy books have also mentioned milk. The Bible contains references to the “Land of Milk and Honey” as a metaphor for the bounty of the Promised Land. In the Qur’an, there is a request to wonder on milk as follows: “And surely in the livestock there is a lesson for you, We give you to drink of that which is in their bellies from the midst of digested food and blood, pure milk palatable for the drinkers” (16-The Honeybee, 66). The Ramadan fast is traditionally broken with a glass of milk and dates. In Jewish religious law, Chalav Yisrael is the term regulating consumption of milk.^{[163][164][165]}

Abhisheka is conducted by Hindu and Jain priests, by pouring libations on the idol of a deity being worshipped, amidst the chanting of mantras. Usually offerings such as milk, yogurt, ghee, honey may be poured among other offerings depending on the type of abhishekam being performed.

A milksop is an “effeminate spiritless man,” an expression which is attested to in the late 14th century.^[10] Milk toast is a dish consisting of milk and toast. Its soft blandness served as inspiration for the name of the timid and ineffectual comic strip character Caspar Milquetoast, drawn by H. T. Webster from 1924 to 1952.^[166] Thus, the term “milquetoast” entered the language as the label for a timid, shrinking, apologetic person. Milk toast also appeared in Disney’s Follow Me Boys as an undesirable breakfast for the aging main character Lem Siddons.

To “milk” someone, in the vernacular of many English-speaking countries, is to take advantage of the person, by analogy to the way a farmer “milks” a cow and takes its milk. The word “milk” has had many slang meanings over time. In the 19th century, milk was used to describe a cheap and very poisonous alcoholic drink made from methylated spirits (methanol) mixed with water. The word was also used to mean defraud, to be idle, to intercept telegrams addressed to someone else, and a weakling or “milksop.” In the mid-1930s, the word was used in Australia to refer to siphoning gas from a car.^[167]

Non-culinary uses

Besides serving as a beverage or source of food, milk has been described as used by farmers and gardeners as an organic fungicide and fertilizer,^[168] however, its effectiveness is debated. Diluted milk solutions have been demonstrated to provide an effective method of preventing powdery mildew on grape vines, while showing it is unlikely to harm the plant.^[169][170]

Milk paint is a nontoxic water-based paint. It can be made from milk and lime, generally with pigments added for color.^[171] In other recipes, borax is mixed with milk’s casein protein in order to activate the casein and as a preservative.^[172]

Milk has been used for centuries as a hair and skin treatment. ^[173] Hairstylist Richard Marin states that some women rinse their hair with milk to add a shiny appearance to their hair.^[173] Cosmetic chemist Ginger King states that milk can “help exfoliate and remove debris [from skin] and make hair softer. Hairstylist Danny Jelaca states that milk’s keratin proteins may “add weight to the hair”.^[173] Some commercial hair products contain milk.^[173]

A milk bath is a bath taken in milk rather than just water. Often additives such as oatmeal, honey, and scents such as rose, daisies and essential oils are mixed in. Milk baths use lactic acid, an alpha hydroxy acid, to dissolve the proteins which hold together dead skin cells.^[174]

Interspecies milk consumption

The consumption of milk between species is not unique to humans. Seagulls, sheathbills, skuas, western gulls and feral cats have been reported to directly pilfer milk from the elephant seals‘ teats.^[175]