Milk
Mammals produce a white liquid called milk from mammary glands. This substance serves as the primary nutrition source for young mammals before they can digest solid food. The first milk produced after birth is known as colostrum. Colostrum contains antibodies and immune-modulating components that strengthen an infant's immune system against many diseases. In humans, the World Health Organization recommends exclusive breastfeeding for six months. Breastfeeding continues in addition to other foods for up to two years or more. Some cultures breastfeed children for three to five years. Fresh goats' milk sometimes substitutes for breast milk but introduces risks like electrolyte imbalances and metabolic acidosis. Lactase is an enzyme needed to break down lactose found in milk. Without this enzyme, individuals experience difficulty digesting milk sugars.
Humans began consuming milk from other mammals following animal domestication during the Neolithic Revolution. Dairying developed independently in multiple global locations starting around 9000, 7000 BC in Mesopotamia. Archaeologist Andrew Sherratt suggested dairying began later in a secondary products revolution during the fourth millennium BC. Recent findings analyzing lipid residue in prehistoric pottery show dairying occurred by at least the seventh millennium BC. Dairy animals spread from Southwest Asia to Europe beginning around 7000 BC. They reached Britain and Scandinavia only after 4000 BC. Pastoral economies relying on domestic animals developed as farmers moved into the Pontic, Caspian steppe in the fourth millennium BC. Camels were domesticated in central Arabia in the fourth millennium BC for use in North Africa. The earliest Egyptian records describe burn dressings using milk from mothers of male babies. In the Middle Ages, milk was called the virtuous white liquor because alcoholic beverages were safer than water. Cows were imported to New England in 1624. Journalist Avery Yale Kamila noted that George Weymouth's 1605 voyage report misinterpreted evidence about Wabanaki people milking deer.
The growth in urban population coupled with railway expansion brought a revolution in milk production during the mid-19th century. St Thomas's Hospital in Southwark contracted with suppliers outside London to ship milk by rail possibly in 1846. The Great Western Railway began transporting milk into London from Maidenhead in 1860. Legislation in 1875 made the adulteration of milk illegal. By 1900, the Great Western Railway transported over 30 million gallons annually. Pasteurization was invented by French chemist Louis Pasteur in 1863 while on summer vacation in Arbois. He developed this method to kill harmful bacteria in beverages and food products. Commercial pasteurizing equipment was produced in Germany in the 1880s. Homogenization distributes milk fat evenly throughout the rest of the milk. Auguste Gaulin exhibited homogenization at the 1900 World's Fair in Paris. The first glass bottle packaging for milk appeared in the 1870s. Hervey Thatcher invented a glass milk jar sealed with a waxed paper disk in 1884. Plastic-coated paper milk cartons were introduced commercially in 1932.
In 2011, dairy farms produced around 600 billion liters of milk from 260 million dairy cows worldwide. India is the world's largest producer of milk and leading exporter of skimmed milk powder. New Zealand, Germany, and the Netherlands are the largest exporters of milk products. Between 750 and 900 million people live in dairy-farming households. FAO estimates 85% of all milk worldwide came from cows in 2011. Israel dairy farms are the most productive in the world with yields reaching 10,000 kilograms per cow annually. Average herd sizes increased from 74 to 99 cows between 2001 and 2007 across developed countries. Norway had an average of 19 cows per herd while New Zealand averaged 337. Heat stress reduces daily milk yield by 0.2 kg when temperatures reach 20 degrees Celsius. Research in humid tropical climates shows every unit of heat stress reduces yield by 2.13%. In China, production may decline up to 50% by 2070 due to climate change. Milk prices rose substantially worldwide in 2007 due to increased prosperity and biofuel competition.
Milk contains many nutrients including calcium protein lactose and saturated fat. Whole milk has about 33 grams of fat per liter including 19 grams of saturated fat. Bovine milk averages 4.8% anhydrous lactose which amounts to about 50% of total solids in skimmed milk. Human milk contains on average 1.1% protein 4.2% fat and 7.0% lactose. Cow's milk supplies 66 kcal of energy per 100 grams. Lactose intolerance occurs when people lack the enzyme lactase in their small intestine. Symptoms include abdominal pain bloating diarrhea gas and nausea. Milk allergy affects between 2% and 3% of babies and young children. The US Food and Drug Administration states that no significant difference exists between milk from rBST-treated cows and non-rBST-treated cows. Canada Australia New Zealand and Japan ban milk from rBST-treated cows for animal welfare reasons. Mastitis is an udder infection that may occur more frequently in cows receiving rBGH supplements.
Glass milk bottles used for home delivery services remain common in parts of the United Kingdom. In rural India, local milkmen carry bulk quantities in metal containers usually on bicycles. Pakistan supplies milk in jugs as a staple food among pastoral tribes. Australia and New Zealand distributed milk in 1-pint glass bottles prior to metrication. A government funded free milk program existed for school children in Australia and Ireland. Plastic-coated paper cartons replaced glass bottles due to collection and cleaning costs. Argentina commonly sells milk in 1-liter bags placed inside plastic jugs. China distributes sweetened milk drinks popular with students in small plastic bags complete with straws. Kenya uses plastic-coated aseptic paper cartons supplied in 300 mL or 500 mL volumes. South Africa sells milk in 1-liter bags cut at the corner before pouring. The UK classic milkman route using battery-powered floats has almost disappeared since the late 1990s. By 2010 only 6% to 7% of all milk consumed by UK households came from milkmen deliveries.
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Common questions
What is milk and how do mammals produce it?
Mammals produce a white liquid called milk from mammary glands. This substance serves as the primary nutrition source for young mammals before they can digest solid food.
When did humans begin consuming milk from other mammals?
Humans began consuming milk from other mammals following animal domestication during the Neolithic Revolution. Dairying developed independently in multiple global locations starting around 9000 BC or 7000 BC in Mesopotamia.
Who invented pasteurization and when was it created?
Pasteurization was invented by French chemist Louis Pasteur in 1863 while on summer vacation in Arbois. He developed this method to kill harmful bacteria in beverages and food products.
Which country produces the most milk globally in recent years?
India is the world's largest producer of milk and leading exporter of skimmed milk powder. In 2011, dairy farms produced around 600 billion liters of milk from 260 million dairy cows worldwide.
Why does lactose intolerance occur in some people?
Lactose intolerance occurs when people lack the enzyme lactase in their small intestine. Without this enzyme, individuals experience difficulty digesting milk sugars.