Milk
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[[Image:Milk glass.jpg|thumb|200px|A glass of [[pasteurized]] [[cow]] milk.]]
'''Milk''' is an opaque white liquid produced by the [[mammary gland]]s of female [[mammal]]s (including [[monotreme]]s). It provides the primary source of nutrition for newborn mammals before they are able to [[digestion|digest]] other types of food. The early [[lactation]] milk is known as [[colostrum]], and carries the mother's [[antibody|antibodies]] to the baby. It can reduce the risk of many diseases in the baby. The exact components of raw milk varies by species, but it contains significant amounts of [[saturated fat]], [[protein]] and [[calcium]] as well as [[vitamin C]].
==Types of consumption==
There are two distinct types of milk consumption: a natural source of nutrition for all infant mammals; and a food product for humans of all ages derived from other animals.
===Nutrition for infant mammals===
[[Image:Kid feeding on mothers milk.jpg|thumb|250px|A goat kid feeding on its mother's milk.]]
In almost all mammals, milk is fed to [[infant]]s through [[breastfeeding]], either directly or, for humans, by [[breastfeeding#expression|expressing]] the milk to be stored and consumed later. Some cultures, historically or currently, continue to use breast milk to feed their children until as old as seven years.<ref>[http://www.timesonline.co.uk/tol/life_and_style/health/features/article388488.ece . . . or just go with the flow?]. [[The Times]], [[May 5]], [[2005]].</ref>
===Food product for humans===
In many cultures of the world, especially the Western world, humans continue to consume milk beyond infancy, using the milk of other animals (in particular, cows) as a food product. For millennia, cow milk has been processed into dairy products such as [[cream]], [[butter]], [[yogurt]], [[ice cream]], and especially the more durable and easily transportable product, [[cheese]]. Industrial science has brought us [[casein]], [[whey protein]], [[lactose]], [[condensed milk]], [[powdered milk]], and many other food-additive and industrial products.
{|class="wikitable" align=left style="clear:left"
! colspan=4|Top Ten Milk Consumers — 2006 Per Capita Consumption
|-
| Country || Liters || Cheese (kg) || Butter(kg)
|-
| {{FIN}} || 183.9 || 19.1 || 5.3
|-
| {{SWE}} || 145.5 || 18.5 || 1.0
|-
| {{IRL}} || 129.8 || 10.5 || 2.9
|-
| {{NED}} || 122.9 || 20.4 || 3.3
|-
| {{NOR}} || 116.7 || 16.0 || 4.3
|-
| {{ESP}} || 119.1 || 9.6 || 1.0
|-
| {{SUI}} || 112.5 || 22.2 || 5.6
|-
| {{GBR}} || 111.2 || 12.2 || 3.7
|-
| {{AUS}} || 106.3 || 11.7 || 3.7
|-
| {{CAN}} || 94.7 || 12.2 || 3.3
|-
|colspan=4 style="font-size:.7em"|Source: [http://www.foodsci.uoguelph.ca/dairyedu/intro.html Introduction to Dairy Science and Technology: Milk History, Consumption, Production, and Composition]
|}
Humans are an exception in the natural world for consuming milk past infancy. Even those humans who drink milk after eating solid foods are uncommon within the whole of humanity.{{Fact|date=March 2008}} Most humans lose the ability to fully digest milk after childhood (that is, they become [[lactose intolerant]]). The sugar [[lactose]] is found only in milk, [[forsythia]] flowers, and a few tropical shrubs. The enzyme needed to digest lactose, [[lactase]], reaches its highest levels in the small intestines after birth and then begins a slow decline unless milk is consumed regularly. <ref name="On Food and Cooking">{{cite book
| last = McGee
| first = Harold
| authorlink = Harold McGee
| title = On Food and Cooking: The Science and Lore of the Kitchen
| year = 1984
| publisher = Charles Scribner's Sons
| location = New York
| language = English
| isbn = 0-684-18132-0
| pages = 3-53
| chapter = Milk and Dairy Products
}}</ref> On the other hand, those groups that do continue to tolerate milk often have exercised great creativity in using the milk of [[domestication|domesticated]] [[ungulates]], not only of [[cow]]s, but also [[sheep]], [[goat]]s, [[yak]]s, [[Domestic buffalo|water buffalo]], [[horse]]s, and [[camel]]s.
The term ''milk'' is also used for whitish non-animal substitutes such as [[soy milk]], [[rice milk]], [[almond milk]], and [[coconut milk]]. Even the regurgitated substance secreted by glands in the mucosa of their upper digestive tract which [[Columbidae|pigeons]] feed their young is called [[crop milk]] though it bears little resemblance to mammalian milk.
==History==
[[Image:Holstein cows large.jpg|right|thumb|200px|[[Holstein (cattle)|Holstein]] cattle, the dominant breed in industrialized dairying today.]]
Milking has its advent in the very evolution of [[placental mammal]]s. While the exact time of its appearance is not known, the immediate ancestors of modern mammals were much like [[monotreme]]s, including the [[platypus]]. Such animals today produce a milk-like substance from glands on the surface of their skin, but without the nipple, for their offspring to drink after hatching from their eggs. Likewise, [[marsupial]]s, the closest cousin to placental mammals, produce a milk-like substance from a teat-like organ in their pouches. The earliest immediate ancestor of placental mammals known seems to be [[eomaia]], a small creature superficially resembling rodents, that is thought to have lived 125 million years ago, during the [[Cretaceous]] era. It almost certainly produced what would be considered milk, in the same way as modern placental mammals.
Animal milk is first known to have been used as human food at the beginning of animal domestication. [[Cow]] milk was first used as human food in the [[Middle East]]. [[Goats]] and [[sheep]] were [[domesticated]] in the [[Middle East]] between 9000 and 8000 BC{{Fact|date=February 2007}}. Goats and sheep are [[ruminant]]s: [[mammals]] adapted to survive on a diet of dry [[grass]], a food source otherwise useless to humans, and one that is easily stockpiled. The animals were probably first kept for [[meat]] and [[hides]]{{Fact|date=March 2007}}, but dairying proved to be a more efficient way of turning uncultivated [[grasslands]] into sustenance: the food value of an animal killed for [[meat]] can be matched by perhaps one year's worth of milk from the same animal, which will keep producing milk — in convenient daily portions — for years.<ref>McGee, 8-10</ref>
Around 7000 BC, [[cattle]] were being herded in parts of [[Turkey]]. There is evidence from DNA extraction of skeletons from the [[Neolithic period]] that people in the northern [[Europe]] could not consume milk as they were missing the necessary genes to process lactose. Scientists claim it is more likely that the genetic mutation allowing the digestion of milk arose at some point after dairy farming began.<ref>http://news.bbc.co.uk/2/hi/health/6397001.stm Early man 'couldn't stomach milk</ref> The use of [[cheese]] and [[butter]] spread in [[Europe]], parts of [[Asia]] and parts of [[Africa]]. Domestic cows, which previously existed throughout much of [[Eurasia]], were then introduced to the colonies of Europe during the [[Age of exploration]]. {{Fact|date=February 2007}}
Milk was first delivered in [[Milk bottle|bottles]] on [[January 11]], [[1878]]. The day is now remembered as '''Milk Day''' and is celebrated annually. The town of [[Harvard, Illinois]] also celebrates milk in the summer with a festival known as Milk Days. Theirs is a different tradition meant to celebrate dairy farmers in the "Milk Capital of the World."<ref>[http://www.milkdays.com/ Harvard Milk Days<!-- Bot generated title -->]</ref>
==Other animal sources==
[[Image:Goat in melking stall 20050429-593.jpg|thumb|Goat milk can be used for other applications such as cheese and other dairy products.]]
In addition to [[cows]], the following animals provide milk used by humans for dairy products:
*[[Buffalo]]
*[[Camel]]s (including the South American [[camelid]]s)
*[[Donkey]]s
*[[Goat]]s (the nanny)
*[[Horse]]s (the mare)
*[[Reindeer]]
*[[Sheep]] (the ewe)
*[[Domestic buffalo|Water buffalo]]
*[[Yak]]s
In [[Russia]] and [[Sweden]], small [[moose milk|moose dairies]] also exist.<ref>{{cite news|url=http://www.theglobeandmail.com/servlet/ArticleNews/TPStory/LAC/20040626/MOOSE26/TPEntertainment/Style|date=[[26 June]] [[2004]]|accessdate=2007-08-27|title=Moose milk makes for unusual cheese|publisher=The Globe and Mail}}</ref> Donkey and horse milk have the lowest fat content, while the milk of [[pinniped|seal]]s contains more than 50% fat.<ref>[http://www.havemilk.com/article.asp?id=1485#contentbyspecies Milk From Cows and Other Animals, web page by Washington Dairy Products Commission]</ref>
[[Whale]] milk, not used for human consumption, is one of the highest-fat milks, containing up to 50% fat.<ref>[http://encarta.msn.com/encyclopedia_761565254_3/Whale.html MSN encarta]</ref> <ref>[http://www.livescience.com/animals/top10_amazing_animals-1.html livescience.com]</ref> The high fat content of whale milk is not a product of [[cetacean]]'s great size, as [[guinea pig]] milk has an average fat content of 46%.<ref>{{cite book | last = Morales | first = Edmundo | title = The Guinea Pig : Healing, Food, and Ritual in the Andes | publisher = University of Arizona Press |date=1995 | id = ISBN 0-8165-1558-1 }}</ref>
Human milk is not produced or distributed industrially or commercially; however, milk banks exist that allow for the collection of donated human milk and its redistribution to infants who may benefit from human milk for various reasons (premature neonates, babies with allergies or [[Metabolic disorder|metabolic diseases]], etc.).
All other female mammals do produce milk, but are rarely or never used to produce dairy products for human consumption.
==Modern production==
{{main|Dairy farming}}
{| class="wikitable" align=left style="clear:left"
! colspan=2|Top Ten Milk Producers — 2005<br>(1000 tonnes)
|-
| {{IND}} || style="padding-left:10px" | 91,940
|-
| {{USA}} || style="padding-left:10px" | 80,264
|-
| {{CHN}} || style="padding-left:10px" | 32,179
|-
| {{RUS}} || style="padding-left:10px" | 31,144
|-
| {{PAK}} || style="padding-left:10px" | 29,672
|-
| {{GER}} || style="padding-left:10px" | 28,487
|-
| {{FRA}}|| style="padding-left:10px" | 26,133
|-
| {{BRA}} || style="padding-left:10px" | 23,455
|-
| {{UK}} || style="padding-left:10px" | 14,577
|-
| {{NZL}} || style="padding-left:10px" | 14,500
|-
|'''World Total''' || style="padding-left:10px" | '''372,353'''
|-
|colspan=2 style="font-size:.7em"|Source: [http://faostat.fao.org/site/340/default.aspx UN Food & Agriculture Organisation]
|}
[[Image:Milk.PNG|thumb|right|Milk output in 2005. Click the image for the details.]]
In the Western world today, [[cow]] milk is produced on an industrial scale. It is by far the most commonly consumed form of milk in the western world. Commercial [[dairy farming]] using [[automatic milking|automated milking]] equipment produces the vast majority of milk in [[Developed country|developed countries]]. Types of [[cattle]] such as the [[Holstein (cattle)|Holstein]] have been specially bred for increased milk production. According to McGee, 90% of the dairy cows in the [[United States]] and 85% in [[Great Britain]] are Holsteins (McGee 12). Other milk cows in the United States include [[Ayrshire cattle|Ayrshire]], [[Brown Swiss]], [[Guernsey cattle|Guernsey]], [[Jersey cattle|Jersey]], and [[Milking Shorthorn]]. The largest producers of dairy products and milk today are [[India]] followed by the [[United States]]<ref>[http://www.fao.org/docrep/009/j7927e/j7927e09.htm FAO Food outlook: International dairy product prices are turning down: how far, how fast? FAO online publication, 1 June 2006]</ref> and China. In India, [[Amul]], a cooperative owned jointly by 2.6 million small farmers was the engine behind the success of [[Operation Flood]].{{Fact|date=December 2007}}
==Price==
It was reported in 2007 that with increased world-wide prosperity and the competition of biofuel production for feedstocks, both the demand for and the price of milk had substantially increased world wide. 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.<ref>"A Thirst for Milk Bred by New Wealth Sends Prices Soaring" article by Wayne Arnold in the [[New York Times]] September 4, 2007</ref>
<br style="clear:left" />
==Physical and chemical structure==
[[Image:MicelleSchematic.png|thumb|left|140px|Schematic of a [[micelle]].]]
Milk is an [[emulsion]] or [[colloid]] of [[butterfat]] [[globules]] within a water-based fluid. Each fat globule is surrounded by a membrane consisting of [[phospholipids]] and proteins; these [[emulsifier]]s keep the individual globules from joining together into noticeable grains of butterfat and also protect the globules from the fat-digesting activity of [[enzymes]] found in the fluid portion of the milk. In unhomogenized cow milk, the fat globules average about four [[micrometre|micrometer]]s across. The [[fat-soluble]] vitamins [[vitamin A|A]], [[vitamin D|D]], [[vitamin E|E]], and [[vitamin K|K]] are found within the milkfat portion of the milk (McGee 18).
The largest structures in the fluid portion of the milk are [[casein]] protein [[micelles]]: aggregates of several thousand protein molecules, bonded with the help of nanometer-scale particles of [[calcium phosphate]]. Each micelle is roughly spherical and about a tenth of a micrometer across. There are four different types of casein proteins, and collectively they make up around 80 percent of the protein in milk, by weight. 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, [[kappa-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 [[colloid]]al [[suspension (chemistry)|suspension]] in the water-based surrounding fluid<ref>[http://www.foodsci.uoguelph.ca/dairyedu/chem.html#protein3 Dairy Chemistry and Physics, webpage of University of Guelph]</ref> (McGee 19–20).
[[Image:Lactose color.png|right|thumb|220px|A simplified representation of a [[lactose]] molecule being broken down into [[glucose]] and [[galactose]].]]
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. Skimmed milk, however, appears slightly blue because casein micelles scatter the shorter wavelengths (blue compared to red).
The fat globules contain some yellow-orange carotene, enough in some breeds — [[Guernsey cattle|Guernsey]] and [[Jersey cattle|Jersey]] cows, for instance — 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 can sometimes be discerned in skim milk or whey products (McGee 17). Fat-free skim milk has only the casein micelles to scatter light, and they tend to scatter shorter-wavelength blue light more than they do red, giving skim milk a bluish tint.<ref>[http://www.foodsci.uoguelph.ca/dairyedu/chem.html#optical Dairy Chemistry and Physics, webpage of University of Guelph]</ref>
Milk contains dozens of other types of proteins besides the caseins. They are more water-soluble than the caseins and do not form larger structures. Because these proteins remain suspended in the [[whey]] left behind when the caseins coagulate into curds, they are collectively known as ''whey proteins''. Whey proteins make up around twenty percent of the protein in milk, by weight. [[Lactoglobulin]] is the most common whey protein by a large margin (McGee 20–21).
The [[carbohydrate]] [[lactose]] gives milk its sweet taste and contributes about 40% of whole cow milk's calories. Lactose is a composite of two [[Monosaccharide|simple sugars]], [[glucose]] and [[galactose]]. In nature, lactose is found only in milk and a small number of plants (McGee 17). Other components found in raw cow milk are living [[white blood cell]]s. Mammary-gland cells, various [[bacteria]], and a large number of active [[enzyme]]s are some other components in milk (McGee 16).
==Processing==
[[Image:Milkproducts.svg|thumb|left|350px|Milk products and productions relationships (Click for details)]]
In most [[western world|Western]] countries, a centralised [[dairy]] facility processes milk and products obtained from milk ([[dairy products]]), such as [[cream]], [[butter]], and [[cheese]]. In the United States, these dairies are usually local companies, while in the [[southern hemisphere]] facilities may be run by very large nationwide or trans-national corporations (such as [[Fonterra]]).
===Pasteurization===
[[Pasteurization]] is used to kill harmful [[microorganisms]] by heating the milk for a short time and then cooling it for storage and transportation. Pasteurized milk is still perishable and must be stored cold by both suppliers and consumers. Dairies print [[Distressed inventory|expiration date]]s on each container, after which stores will remove any unsold milk from their shelves. In many countries it is illegal to sell milk that is not pasteurized.
Milk may also be further heated to extend its [[shelf life]] through ultra-high temperature treatment ([[UHT]]), which allows it to be stored unrefrigerated, or an even longer lasting [[Sterilization (microbiology)|sterilization]] process.
===Creaming and homogenization===
[[Image:Cow milking machine in action DSC04132.jpg|thumb|200px|A milking machine in action.]]
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 is often sold as a separate product with its own uses; today the separation of the cream from the milk is usually accomplished rapidly in [[centrifuge|centrifugal]] cream separators. The fat globules rise to the top of a container of milk because fat is less dense than water. The smaller the globules, the more other molecular-level forces prevent this from happening. In fact, the cream rises in cow 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 (McGee 19). These clusters rise faster than individual globules can. The fat globules in milk from goats, sheep, and water buffalo do not form clusters so readily and are smaller to begin with; cream is very slow to separate from these milks (McGee 19). Milk is often [[homogenization|homogenized]], a treatment which 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]].<ref>[http://www.foodsci.uoguelph.ca/dairyedu/homogenization.html Homogenization of Milk and Milk Products, webpage of University of Guelph]</ref> 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 briefly vulnerable to certain [[enzyme]]s present in milk, which could break down the fats and produce [[rancidity|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 (McGee 23). Creamline, or cream-top, milk is unhomogenized; it may or may not have been pasteurized. Unlike pasteurization, homogenization confers no health or safety benefits to the milk, only the convenience of not needing to shake the bottle oneself. {{Fact|date=August 2007}}
==Nutrition and health==
The composition of milk differs widely between 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]] [[globule]]s and the strength of the [[curd]] are among those than can vary.<ref>[http://www.foodsci.uoguelph.ca/dairyedu/intro.html Introduction to Dairy Science and Technology, webpage of University of Guelph]</ref> For example:
*[[breast milk|Human milk]] contains, on average, 1.1% protein, 4.2% fat, 7.0% lactose (a sugar), and supplies 72 kcal of energy per 100 [[gram]]s.
*[[Cow]] milk contains, on average, 3.4% protein, 3.6% fat, and 4.6% lactose, 0.7% [[Dietary_mineral|minerals]]<ref>[http://www.hindu.com/seta/2008/07/10/stories/2008071050201800.htm Milk contains traces of ash]</ref> and supplies 66 kcal of energy per 100 grams. See also [[Milk#Nutritional benefits|Nutritional benefits]] further on.
Aquatic mammals, such as [[pinniped|seals]] and [[whales]], produce milk that is very rich in fats and other solid nutrients when compared with land mammals' milk.
===Nutritional value=== <!-- This section is linked from [[Milk]] -->
{{nutritionalvalue | name=Cow milk (whole) | water=88 g | kJ=250 | protein=3.2 g | fat=3.25 g | carbs=5.2 g | sugars=5.2 g | lactose=5.2 g | calcium_mg=113 | satfat=1.9 g | monofat=0.8 g | polyfat=0.2 g | vitA_ug=28 |thiamin_mg=0.04 | riboflavin_mg=0.18 | vitB12_ug=0.44 | vitD_iu=40 | potassium_mg=143 | magnesium_mg=10 | right=1 | source_usda=1 | note=100 ml corresponds to 103 g.<ref>{{cite web|url=http://hypertextbook.com/facts/2002/AliciaNoelleJones.shtml|title=Density of Milk|last=Jones|first=Alicia Noelle|work=The Physics Factbook|year=2002}}</ref>}}
Processed milk began containing differing amounts of fat during the 1950s. A serving (1 cup or 250 ml) of 2%-fat milk contains 285 mg of [[calcium]], which represents 22% to 29% of the [[daily recommended intake]] (DRI) of calcium for an adult. Depending on the age, 8 [[gram]]s of [[protein]], and a number of other nutrients (either naturally or through fortification):
*[[Biotin]] and [[pantothenic acid]] are [[B vitamins]] important for energy production.
*[[Iodine]] is a mineral essential for [[thyroid]] function.
*[[Potassium]] and [[magnesium]] are for cardiovascular health.
*[[Selenium]] is a cancer-preventive [[Micromineral|trace mineral]].
*[[Thiamine]] is a B-vitamin important for [[Cognition|cognitive function]], especially memory.
*[[Vitamin A]] is critical for [[Immune system|immune function]].
*[[Vitamin B12]] and [[riboflavin]] are necessary for cardiovascular health and energy production.
*[[Vitamin D|Vitamins D]] and [[vitamin K|K]] are essential for bone health.
The amount of [[calcium]] from milk that is absorbed by the human body is disputed.<ref>[http://www.thehealthierlife.co.uk/article/3097/calcium-rich-foods.html Calcium Rich Foods: Get All The Calcium You Need Without Milk]</ref><ref>Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. Am J Public Health 1997; 87:992-7.</ref> Calcium from dairy products has a greater [[bioavailability]] than calcium from certain vegetables, such a spinach, that contain high levels of calcium-[[chelating]] agents,<ref> Brody T. Calcium and phosphate. In: Nutritional biochemistry. 2nd ed. Boston: Academic Press, 1999:761–94 </ref> but a similar or lesser bioavailability than calcium from low-oxalate vegetables such as kale, broccoli, or other vegetables in the Brassica genus.<ref>American Journal of Clinical Nutrition, Heaney and Weaver, 51 (4): 656.</ref>
===Medical research===
Studies show possible links between low-fat milk consumption and reduced risk of [[arterial hypertension]], [[coronary heart disease]], colorectal cancer and [[obesity]]. Overweight individuals who drink milk may benefit from decreased risk of [[insulin resistance]] and type 2 [[Diabetes mellitus|diabetes]].<ref>[http://www.nationaldairycouncil.org/NationalDairyCouncil/Nutrition/Reducing/DairysRoleManagingBP.htm Dairy's Role in Managing Blood Pressure, web page of the US National Dairy Council]</ref> One study has shown that for women desiring to have a child, those who consume full fat dairy products may actually slightly increase their fertility, while those consuming low fat dairy products may slightly reduce their fertility due to interference with ovulation. However, studies in this area are still inconsistent.<ref>[http://english.pravda.ru/news/science/01-03-2007/87904-ice_cream-0 Fat ice cream and milk may help woman shoot for pregnancy - Pravda.Ru<!-- Bot generated title -->]</ref> Milk is a source of [[Conjugated linoleic acid]], a [[fatty acid]] that inhibits several types of cancer in mice. It has been shown to kill human [[skin cancer]], [[colorectal cancer]] and [[breast cancer]] cells ''in vitro'' studies, and may help lower cholesterol and prevent atherosclerosis; only available in milk from [[Cattle feeding|grass-fed]] cows.{{Fact|date=March 2008}}
Other studies suggest that milk consumption may increase the risk of suffering from certain health problems. Milk contains [[casein]], a substance that breaks down in the human stomach to produce [[casomorphin]], an [[opioid peptide]]. In the early 1990s it was hypothesized that casomorphin can cause or aggravate [[autism]],<ref>{{cite journal |author= Reichelt KL, Knivsberg A-M, Lind G, Nødland M |title= Probable etiology and possible treatment of childhood autism |journal= Brain Dysfunct |year=1991 |volume=4 |pages=308–19}}</ref><ref>{{cite journal |journal= J Dev Behav Pediatr |date=2006 |volume=27 |issue=2 Suppl 2 | pages = S162 |title= Elimination diets in autism spectrum disorders: any wheat amidst the chaff? |author= Christison GW, Ivany K |pmid=16685183 | doi = 10.1097/00004703-200604002-00015 <!--Retrieved from CrossRef by DOI bot-->}}</ref> and [[Gluten-free, casein-free diet|casein-free diets]] are widely promoted. Studies supporting these claims have had significant flaws, and the data are inadequate to guide autism treatment recommendations.<ref>{{cite journal |journal= J Dev Behav Pediatr |date=2006 |volume=27 |issue=2 Suppl 2 | pages = S162 |title= Elimination diets in autism spectrum disorders: any wheat amidst the chaff? |author= Christison GW, Ivany K |pmid=16685183 | doi = 10.1097/00004703-200604002-00015 <!--Retrieved from CrossRef by DOI bot-->}}</ref> [[Milk allergy|Cow milk allergy]] (CMA) is as an immunologically mediated adverse reaction to one or more cow milk proteins. Rarely is it severe enough to cause death.<ref>[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&uid=7704117&cmd=showdetailview&indexed=google Cow's milk protein allergy and intolerance in infa...[Pediatr Allergy Immunol. 1994] - PubMed Result<!-- Bot generated title -->]</ref>
Studies described in the book [[The China Study]] note a correlation between casein intake and the promotion of cancer cell growth when exposed to carcinogens. However other studies have shown whey protein offers a protective effect against colon cancer. <ref>Hakkak, et al., "Dietary Whey Protein Protects against Azoxymethane-induced Colon Tumors in Male Rats," Cancer Epidemiology Biomarkers & Prevention, Vol. 10, 555-558, May 2001.</ref>
A study demonstrated that men, and to some degree women, who drink a large amount of milk and consume dairy products were at a slightly increased risk of developing [[Parkinson's disease]].<ref>[http://aje.oxfordjournals.org/cgi/content/abstract/165/9/998 H. Chen et al., Consumption of Dairy Products and Risk of Parkinson's Disease], American Journal of Epidemiology. 2007 May;165(9):998-1006</ref> The reason behind this is not fully understood, and it also remains unclear why there is less of a risk for women.<ref>[http://aje.oxfordjournals.org/cgi/content/abstract/165/9/998 H. Chen et al., Consumption of Dairy Products and Risk of Parkinson's Disease], American Journal of Epidemiology. 2007 May;165(9):998-1006</ref><ref>{{cite news | url = http://news.bbc.co.uk/1/hi/health/4419477.stm | publisher = [[BBC News]] | title = Milk linked to Parkinson's risk }}</ref> Several sources suggest a correlation between high calcium intake (2000 mg per day, or twice the US [[recommended daily allowance]], equivalent to six or more glasses of milk per day) and [[prostate cancer]].<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9458087 Giovannucci, E. et al., Calcium and fructose intake in relation to risk of prostate cancer., Cancer Res. 1998 Feb 1;58(3):442-7.]</ref> A large study specifically implicates dairy.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Abstract&list_uids=11566656 Chan, J.M., Dairy products, calcium, and prostate cancer risk in the Physicians' Health Study. Am J Clin Nutr. 2001 Oct;74(4):549-54. (disputed publication)]</ref> A review published by the [[World Cancer Research Fund]] and the [[American Institute for Cancer Research]] states that at least eleven human population studies have linked excessive dairy product consumption and prostate cancer,<ref>{{cite journal |journal= Food, nutrition and the prevention of cancer: a global perspective |date=1997|title= Food, nutrition and the prevention of cancer: a global perspective |author= The World Cancer Research Fund and American Institute for Cancer Research}}</ref> however [[Randomized controlled trial|randomized clinical trial]] data with appropriate controls only exists for calcium, not dairy produce, where there was no correlation.<ref>Chan JM et al., (2005) Role of diet in prostate cancer development and progression. J Clin Oncol 23:8152-60.</ref> Medical studies have also shown a possible link between milk consumption and the exacerbation of diseases such as Crohn’s Disease,<ref>[http://www.sciencedaily.com/releases/2007/12/071210104002.htm How Bacteria In Cows' Milk May Cause Crohn's Disease]</ref> Hirschsprung's disease–mimicking symptoms in babies with existing cow milk allergies,<ref>[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WKP-4MHHXD1-X&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=760c097c4357bff51dd6ede9bb7ef633 Cow milk protein allergy presenting with Hirschsprung's disease–mimicking symptoms. ]</ref> severe gastroesophageal reflux disease in infants and children hypersenstitive to milk,{{Fact|date=March 2008}} and the aggravation of Behçet's disease.<ref>[http://ard.bmj.com/cgi/content/abstract/61/5/459 Humoral and cell mediated immune response to cow's milk proteins in Behçet's disease]</ref>
Since November 1993, with FDA approval, [[Monsanto]] has been selling [[Bovine Somatotropin|recombinant bovine somatotropin (rbST)]]--or rBGH--to dairy farmers. Additional bovine growth hormone is administered to cattle in order to increase their milk production, though the hormone also naturally fosters liver production of [[Insulin-like growth factor 1|insulin-like growth factor 1 (IGF1)]]. The deposit thereof in the milk of rBGH-affected cattle has been the source of concern; however, all milk contains IGF1 since all milking cows produce bovine growth hormone naturally. The IGF1 in milk from rBGH-affected cattle does not vary from the range normally found in a non-supplemented cow.<ref>[http://www.idfa.org/reg/biotech/talking2.cfm IDFA - Biotechnology and Bovine Somatotropin (BST or BGH)<!-- Bot generated title -->]</ref> Elevated levels of IGF1 in human blood has been linked to increased rates of breast, colon, and prostate cancer by stimulating their growth,<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16773200 Kahan, Z et al., Elevated levels of circulating insulin-like growth factor-I, IGF-binding globulin-3 and testosterone predict hormone-dependent breast cancer in postmenopausal women: a case-control study. Int J Oncol. 2006 Jul;29(1):193-200.]</ref><ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16774935 Pacher, M. et al., Impact of constitutive IGF1/IGF2 stimulation on the transcriptional program of human breast cancer cells. Carcinogenesis. 2006 Jun 14]</ref> though this has not been linked to milk consumption. [[European Union|The EU]] has recommended against Monsanto milk.<ref>[http://www.preventcancer.com/press/releases/march21_99.htm International Scientific Committee Warns of Serious Risks of Breast and Prostate Cancer from Monsanto's Hormonal Milk. Press release of the Cancer Prevention Coalition.]</ref> In addition, the cows receiving rBGH supplements may more frequently contract an udder infection known as [[mastitis]].<ref>[http://www.preventcancer.com/consumers/general/milk.htm Milk: Epstein, S., America's Health Problem. Web page of the Cancer Prevention Coalition.]</ref> Milk from rBGH-affected cattle is banned in [[Canada]], [[Australia]], [[New Zealand]], and [[Japan]] due to the mastitis problems. On [[June 2006#9 June 2006|June 9, 2006]] the largest milk processor in the world and the two largest [[supermarket]]s in the United States--[[Dean Foods]], [[Wal-Mart]], and [[Kroger]]--announced that they are "on a nationwide search for rBGH-free milk."<ref>[http://www.organicconsumers.org/2006/article_747.cfm Oca News Articles<!-- Bot generated title -->]</ref> No study has indicated that consumption of rBST-produced milk increases IGF1 levels, nor has any study demonstrated an increased risk of any disease between those consuming rBST and non-rBST produced milk. In 1994, the FDA stated that no significant difference has been shown between milk derived from rBST-treated and non-rBST-treated cows, and that no test exists which can differentiate between milk from rBST-treated and non-rBST treated cows.<ref>[http://www.fda.gov/bbs/topics/ANSWERS/ANS00564.html Dietary IGF-I and rbST<!-- Bot generated title -->]</ref>
Milk may contain varying levels of [[white blood cells]] depending upon the health of the source animals, according to guidelines set up by the [[Food and Drug Administration]] and statistics reported by the dairy industry.<ref>[http://www.ag.ndsu.edu/pubs/ansci/dairy/as1131w.htm Mastitis Control Programs: Milk Quality Evaluation Tools for Dairy Farmers<!-- Bot generated title -->]</ref><ref>[http://www.veganoutreach.org/health/gotmilk.html Greger, Michael. Paratuberculosis and Crohn's Disease: Got Milk? Pro-vegan online publication, January 2001]</ref> Although not considered a human health issue by most authorities, elevated white blood cell levels indicate an immune response by cattle, due in part to [[mastitis]].<ref>[http://www.ag.ndsu.edu/pubs/ansci/dairy/as1131w.htm Mastitis Control Programs: Milk Quality Evaluation Tools for Dairy Farmers<!-- Bot generated title -->]</ref> There are concerns regarding the transmission of bovine paratubeculosis through somatic cells to humans,<ref>[http://www.veganoutreach.org/health/gotmilk.html Paratuberculosis and Crohn's Disease: Got Milk? (Vegan Outreach)<!-- Bot generated title -->]</ref> but the evidence is largely inconclusive.
===Lactose intolerance===<!-- This section is linked from [[Milk]] -->
{{main|lactose intolerance}}
[[Lactose]], the [[disaccharide]] sugar component of all milk must be cleaved in the small intestine by the [[enzyme]] [[lactase]] in order for its constituents ([[galactose]] and [[glucose]]) to be absorbed. The production of this enzyme declines significantly after [[weaning]] in all mammals including humans(except for most northern westerners and a few other ethnic groups, lactase decline occurs after weaning, sometime between the ages of two and five). Once lactase levels have decreased sufficiently, consumption of small amounts of lactose can cause [[diarrhea]], [[Flatulence|intestinal gas]], [[cramps]] and [[bloating]], as the undigested lactose travels through the [[gastrointestinal tract]] and serves as nourishment for intestinal [[microflora]] who [[excrete]] gas. <ref>http://en.wikipedia.org/wiki/Anaerobic_respiration</ref>
===Nutrition - comparison by animal source===
'''Milk Composition Analysis''', per 100 grams
{| class="wikitable" style="text-align:center"
|-
! Constituents
! unit
! [[Cow]]
! [[Goat]]
! [[Sheep]]
! [[Domestic buffalo|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
|-
| Carbohydrate
| g
| 4.8
| 4.4
| 5.1
| 4.9
|-
| Energy
| kcal
| 66
| 60
| 95
| 110
|-
|
| kJ
| 275
| 253
| 396
| 463
|-
| Sugars (Lactose)
| g
| 4.8
| 4.4
| 5.1
| 4.9
|-
| Fatty Acids:
|-
| Saturated
| g
| 2.4
| 2.3
| 3.8
| 4.2
|-
| Mono-unsaturated
| g
| 1.1
| 0.8
| 1.5
| 1.7
|-
| Polyunsaturated
| g
| 0.1
| 0.1
| 0.3
| 0.2
|-
| Cholesterol
| mg
| 14
| 10
| 11
| 8
|-
| Calcium
| IU
| 120
| 100
| 170
| 195
|}
Source: McCane, Widdowson, Scherz, Kloos.[http://www.northwalesbuffalo.co.uk/milk_analysis.htm]
These compositions vary by breed, animal, and point in the lactation period. [[Jersey cattle|Jersey]] cows produce milk of about 5.2% fat, [[Zebu]] cows produce milk of about 4.7% fat, [[Brown Swiss]] cows produce milk of about 4.0% fat, and [[Holstein (cattle)|Holstein-Friesian]] cows produce milk of about 3.6% fat. The protein range for these four breeds is 3.3% to 3.9%, while the lactose range is 4.7% to 4.9%. <ref>{{cite book | last = McGee | first = Harold | authorlink = Harold McGee | title = On Food and Cooking: The Science and Lore of the Kitchen, Completely Revised and Updated | publisher = Scribner |date=2004 | location = New York, NY | pages = 13 | isbn = 9780684800011}}</ref>
Milk fat percentages in all [[Dairy cattle|dairy breeds]] vary according to digestible fibre, starch and oil intakes<ref>http://www.kt.iger.bbsrc.ac.uk/FACT%20sheet%20PDF%20files/kt21.pdf</ref>, and can therefore be manipulated by dairy farmers' diet formulation strategies. Mastitis infection can cause fat levels to decline.<ref>[http://books.google.com/books?id=qJgdAEhQvnMC&pg=PA226&lpg=PA226&dq=mastitis+and+milk+fat+levels&source=web&ots=PrguNhnHdm&sig=W_MS2A7FWTBksmBYvZZk38dRh4A Google Books - Designing Foods: Animal Product Options in the Marketplace]</ref>
==Varieties and brands== <!-- This section is linked to -->
{{seealso|Fat content of milk|Milk bottle top}}
Milk products are sold in a number of varieties based on types/degrees of
*age (e.g., cheddar),
*additives (e.g., vitamins),
*coagulation (e.g., cottage cheese),
*farming method (e.g., organic, grass-fed).
*fat content (e.g., half and half),
*fermentation (e.g., buttermilk),
*flavoring (e.g., chocolate),
*homogenization (e.g., raw milk),
*mammal (e.g., cow, goat, sheep),
*packaging (e.g., bottle),
*sterilization (e.g., pasteurization),
*water content (e.g., dry milk),
Organic Milk (in the United States) or Bio-Milk & Biologique Milk (in Europe) is milk produced without the use of chemical herbicides or pesticides, and generally with more natural fertilizers and higher standards for the animals{{Fact|date=September 2007}}, and is now easy to find on the shelves in many areas. [[Demeter International|Demeter]] certified milk is produced with [[biodynamic agriculture]] methods and is similar in standards to organic milk and biological milk, with a few special farm procedures added that are biodynamic-specific.
Cow milk is generally available in several varieties according to approximate [[butterfat]] content. See ''[[fat content of milk]]''.
===Additives and flavoring===
In countries where the cattle (and often the people) live indoors, commercially sold milk commonly has [[vitamin D]] added to it to make up for lack of exposure to [[Ultraviolet light|UVB]] radiation.
Reduced fat milks often have added [[vitamin A]] 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.<ref> [http://www.ams.usda.gov/howtobuy/dairy.htm "How to Buy Dairy Products"], ''Home and Garden Bulletin 255'', [[USDA]], February 1995. Retrieved 16 May 2007.</ref>
To aid digestion in those with [[lactose intolerance]], milk is available in some areas with added bacterial cultures such as ''[[Lactobacillus acidophilus]]'' ("[[acidophilus milk]]") and [[bifidobacteria]] ("[[a/B milk]]").<ref>[http://www.nationaldairycouncil.org/nationaldairycouncil/nutrition/products/product_yogurt.pdf "Yogurt and Other Cultured Dairy Products"], [[National Dairy Council]], 2000.</ref> Another milk with ''[[Lactococcus lactis]]'' bacteria cultures ("[[buttermilk|cultured buttermilk]]") is often used in cooking to replace the traditional use of naturally [[soured milk]], which has become rare due to the ubiquity of pasteurization which kills the naturally occurring lactococcus bacteria.<ref>{{cite book | author=[[Irma Rombauer|Rombauer, Irma S.]] and [[Marion Rombauer Becker]] | title=[[Joy of Cooking]] (Revised Edition) | publisher=Bobbs Merrill | year=1975 | pages=533 | isbn=0-672-51831-7}}</ref>
Milk often has [[flavoring]] added to it for better taste or as a means of improving sales. [[Chocolate]] [[Flavoured milk|flavored milk]] has been sold for many years and has been followed more recently by such other flavors as strawberry and banana.
[[South Australia]] has the highest consumption of flavored milk per person in the world, where [[Farmers Union Iced Coffee]] outsells [[Coca-Cola]], a success shared only by [[Inca Kola]] in [[Peru]] and [[Irn-Bru]] in [[Scotland]].
[[Switzerland]] has a soft drink based on milk that tastes and looks much like SevenUp. This popular "milk-cola", named [[Rivella]], is in fact the national soft drink and even comes complete in low calorie & low sugar varieties. In spite of what might be expected, it does not taste like milk.
===Distribution===
Because milk spoils so easily, it should, ideally, be distributed as quickly as possible. In many countries milk used to be delivered to households daily, but economic pressure has made milk delivery much less popular, and in many areas daily delivery is no longer available. People buy it chilled at grocery or convenience stores or similar retail outlets. Prior to the widespread use of [[plastic]]s, milk was sold in wax-coated paper containers; prior to that milk was often distributed to consumers in [[glass]] bottles; and before glass bottles, in bulk that was ladled into the customer's container.
[[Image:Glass milk bottles.jpg|thumb|150px|Glass milk bottles used for home delivery service]]
In the [[United Kingdom|UK]], milk can be delivered daily by a [[milkman]] who travels his local [[milk round]] (route) using a battery-powered [[milk float]] during the early hours. Milk is delivered in 1 [[pint glass]] bottles with [[aluminium foil]] tops. Silver top denotes full cream unhomogenized; red top full cream homogenized; red/silver top semi-skimmed; blue/silver check top skimmed; and gold top channel island.
Empty bottles are rinsed before being left outside for the milkman to collect and take back to the dairy for washing and reuse. Currently many milkmen operate franchises as opposed to being employed by the dairy and payment is made at regular intervals, by leaving a check; by cash collection; or [[direct debit]].
Although there was a steep decline in doorstep delivery sales throughout the 1990s, the service is still prominent, as dairies have diversified and the service is becoming more popular again. The doorstep delivery of milk is seen as part of the UK's heritage, and is relied upon by people up and down the country.
In [[New Zealand]], milk is no longer distributed in glass bottles. In rural [[India]], milk is delivered daily by a local milkman carrying bulk quantities in a metal container, usually on a bicycle; and in other parts of metropolitan India, milk is usually bought or delivered in a plastic bags or cartons via-shops or supermarkets.
In the United States bottles were replaced with [[milk carton]]s, which are tall paper boxes with a square cross-section and a peaked top that can be folded outward upon opening to form a spout. Now milk is increasingly sold in plastic bottles. First the gallon and half-gallon sizes were sold in plastic jugs while the smaller sizes were sold in milk cartons. Recently milk has been sold in smaller resealable bottles made to fit in [[automobile]] [[cup holder]]s.
[[Image:Dry skim milk.jpg|thumb|150px|right|Dry skim milk]]
The half-pint milk carton is the traditional unit as a component of school lunches. In the U.S., pictures of [[Child abduction|missing children]] were printed on the larger milk cartons as a public service until it was determined that this was disturbing to children.
[[Image:Brique lait dsc04430.jpg|thumb|right|A brick of [[France|French]] [[Ultra-high-temperature processing|UHT]] milk]]
Milk preserved by the [[Ultra-high-temperature processing|UHT]] process is sold in cartons often called a brick that lack the peak of the traditional milk carton. Milk preserved in this fashion does not need to be refrigerated before opening and has a longer shelf life than milk in ordinary packaging. It is more typically sold unrefrigerated on the shelves in Europe than in America.
Glass milk containers are now rare. Most people purchase milk in bags, plastic jugs or waxed-paper cartons. [[Ultraviolet]] (UV) light from [[fluorescent lamp|fluorescent lighting]] can alter the flavor of milk, so many companies that once distributed milk in [[Transparency (optics)|transparent]] or highly [[translucent]] containers are now using thicker materials that block the UV light. Many people feel that such "UV protected" milk tastes better.
Milk comes in a variety of containers with local variants:
*[[Australia]] and [[New Zealand]]: Distributed in a variety of sizes, most commonly in [[Aseptic processing|aseptic]] cartons for up to 1 litres, and plastic screw-top bottles beyond that with the following volumes; 1.1L, 2L, and 3L. 1 litre Bags are starting to appear in supermarkets, but have not yet proved popular. Most UHT-milk is packed in 1 or 2 litre paper containers with a sealed plastic spout.
*[[Brazil]]: Used to be sold in cooled 1 litre bags, just like in [[South Africa]]. Nowadays the most common form is 1 litre aseptic cartons containing UHT skimmed, semi-skimmed or whole milk, although the plastic bags are still in use.
*[[Canada]]: 1.33 litre plastic bags (sold as 4 litres in 3 bags) are widely available in some areas (especially [[Ontario]] and [[Québec]]), although the 4 litre plastic jug has supplanted them in [[western Canada]]. Other common packaging sizes are 2 litre, 1 litre, 500 [[millilitre]], and 250 millilitre cartons, as well as 4 litre, 1 litre, 250 mL aseptic cartons and 500 [[millilitre]] plastic jugs.
*[[China]]: Sweetened 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]].
* Parts of [[Europe]]: Sizes of 500 millilitres, 1 litre (the most common), 2 litres and 3 litres are commonplace.
*[[Hong Kong]] - milk is sold in glass bottles (220 mL), cartons (236 mL and 1L), plastic jugs (2 litres) and aseptic cartons (250 mL).
*[[India]]: Commonly sold in 500 mL plastic bags. 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 different sizes, usually in aseptic cartons.
*[[Indonesia]]: Usually sold in 1 litre cartons, but smaller, snack-sized cartons are available.
*[[Israel]]: Non-UHT milk is most commonly sold in 1 litre waxed cardboard boxes and 1 litre plastic bags. It may also be found in 0.5L and 2L waxed cardboard boxes, 2L plastic jugs and 1L plastic bottles. UHT milk is available in 1 litre (and less commonly also in 0.25L) carton "bricks".
*[[Japan]]: Commonly sold in 1 litre waxed cardboard boxes. In most city centers there is also [[Delivery (commerce)|home delivery]] of milk in glass jugs. As seen in [[China]], sweetened and flavored milk drinks are very popular to see in [[vending machine]]s.
*[[South Africa]]: Commonly sold in 1 litre bags. The bag is then placed in a plastic jug and the corner cut off before the milk is poured.
*[[South Korea]]: sold in cartons (180mL, 200mL, 500mL 900mL, 1L, 1.8L, 2.3L), plastic jugs (100Ml and 1.8L), aseptic cartons (180mL and 200mL) and plastic bags (100mL).
*[[Poland]]: UHT milk is mostly sold in aseptic cartons (500mL, 1L, 2L), and non-UHT in 1L plastic bags or plastic bottles. Milk, UHT is commonly boiled, despite being pasteurized.
*[[Turkey]]: Commonly sold in 500 mL or 1L cartons or special plastic bottles. UHT milk is more popular. Milkmen also serve in smaller towns and villages.
*[[United Kingdom]]: Most stores still stock [[Imperial unit|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 also sold at supermarkets in either aseptic cartons or HDPE bottles. Milk can still be legally sold by the Imperial pint in [[reuse|reusable]] bottles in the UK under EU regulations (a distinction only shared with beer and cider), whilst a growing number of manufacturers such as [[Northern Foods]] now sell milk in 1 and 2 litre bottles.
*[[United States]]: Commonly sold in [[gallon]], half-gallon and [[quart]] containers ([[U.S. customary units#Liquid volume|U.S. customary units]]) of rigid plastic or, occasionally for sizes less than a gallon, waxed cardboard, although bottles made of opaque [[Polyethylene terephthalate|PET]] are starting to become more commonplace in all smaller sizes. The US single-serving size is usually the half-pint (about 240 ml). Occasionally dairies will deliver milk straight to customers in coolers filled with glass bottles (usually half-gallon). Some [[convenience store]] chains in the United States (such as [[Kwik Trip]] in the [[Midwest]]) sell milk in 1/2 gallon bags.
*[[Uruguay]]: Commonly sold in 1 litre bags. The bag is then placed in a plastic jug and the corner cut off before the milk is poured.
Practically everywhere, [[condensed milk]] and evaporated milk is 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.
[[Image:Yakult brazil.jpg|thumb|Brazilian [[Yakult]], an example of the use of milk.]]
===Spoilage and fermented milk products===
When [[raw milk]] is left standing for a while, it turns "[[sour]]". This is the result of [[fermentation (food)|fermentation]], where [[lactic acid bacteria]] ferment the [[lactose]] inside 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 caused 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]], [[yoghurt]], [[cheese]], [[buttermilk]], [[viili]], [[kefir]] and [[kumis]]. ''See [[Dairy product]]'' for more information.
[[Pasteurized|Pasteurization]] of cow milk initially destroys any potential pathogens and increases the shelf-life <ref>[http://www.fda.gov/fdac/features/2004/504_milk.html Got Milk? Make Sure It's Pasteurized<!-- Bot generated title -->]</ref><ref>http://jds.fass.org/cgi/reprint/65/12/2233.pdf</ref>, 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 [[refrigerator|refrigerated]] and stored between 1 and 4 [[Celsius|degrees Celsius]] in [[bulk tank]]s. Most milk is [[pasteurized]] by heating briefly and then [[refrigerator|refrigerated]] to allow transport from [[factory farming|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. Sterilized milk, which is heated for a much longer period of time, will last even longer, but also loses more nutrients and assume a different taste.{{Fact|date=November 2007}} [[Condensed milk]], made by removing most of the water, can be stored in cans for many years, unrefrigerated, as can [[evaporated milk]]. The most durable form of milk is [[milk powder]], which is produced from milk by removing almost all [[water]]. The [[moisture content]] is usually less than five percent in both drum and spray dried [[milk powder]].
==Language and culture==
{{wikisourcepar|Littell's Living Age/Volume 144/Issue 1861/Chinese Prohibition of the Consumption of Cow's Milk|an account (1880) of a Chinese prohibition against drinking cow's milk.}}
The importance of milk in human culture is attested to by the numerous expressions embedded in our languages, for example "the milk of human kindness". In ancient [[Greek mythology]], the [[goddess]] [[Hera]] spilled her [[breast]] milk after refusing to feed [[Heracles]], resulting in the [[Milky Way]].
In [[Africa]]n and [[Asia]]n [[developing country|developing nations]], [[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.<ref>Crawford ''et al'', part B, section III, ch. 1: [http://www.fao.org/docrep/003/t0251e/T0251E15.htm#ch1 Butter]. Retrieved 28 November 2005.</ref>
Holy books have also mentioned milk; the Bible contains references to the Land of Milk and Honey. In the [[Quran]], 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 Ramadhan fast is traditionally broken with a glass of milk and dates.
The verb, "to milk" something is often used in the vernacular of many English-speaking countries as a synonym for extortion or, in less loaded terms, taking advantage of a situation where one has another person at a disadvantage,
==See also==
{{portal|Food}}
{{col-begin}}{{col-2}}
*[[Babcock test]] (determines the butterfat content of milk)
*[[Bovine somatotropin]]
*[[Fat content of milk]]
*[[Got Milk?]] (US [[Advertising campaign|ad campaign]] encouraging the consumption of milk)
*[[Grain milk]]
*[[Milk bottle]]
*[[Powdered milk]]
*[[Raw milk]]
{{col-break}}
*[[Breast]]
*[[Breastfeeding]]
*[[Cheese]]
*[[Lactation]]
*[[Mammary gland]]
*[[Milk line]]
*[[Nipple]]
*[[Operation Flood]]
{{col-end}}
==Notes==
{{reflist|2}}
==References==
*{{cite book | author=McGee, Harold | title=On Food and Cooking (Revised Edition) | publisher=Scribner | year=2004 | id=ISBN 0-684-80001-2}}
*[http://www.parmalat.com.au/information/information.cfm?/section/3/subsection/22/ Information on milk by Parmalat]
*[http://www.foodsci.uoguelph.ca/dairyedu/intro.html Introduction to Dairy Science and Technology: Milk History, Consumption, Production, and Composition]
*[http://www.madehow.com/Volume-4/Milk.html Milk]
*[http://www.sciencebyjones.com/MILK_NOTES.HTM Milk Notes]
==External links==
{{cookbook}}
{{wiktionary|milk}}
{{commons}}
*[http://www.hsph.harvard.edu/nutritionsource/calcium.html Harvard School of Public Health: Calcium and Milk]: describes claims of milk supporters and critics
[[Category:Milk| ]]
[[Category:Symbols of Vermont]]
[[Category:Symbols of Oregon]]
[[Category:Symbols of Wisconsin]]
{{Link FA|es}}
[[af:Melk]]
[[am:ወተት]]
[[ar:حليب]]
[[ast:Lleche]]
[[gn:Kamby]]
[[ay:Millk'i]]
[[bm:Nɔnɔ]]
[[zh-min-nan:Leng]]
[[ba:Һөт]]
[[be-x-old:Малако]]
[[bar:Muich]]
[[bs:Mlijeko]]
[[br:Laezh]]
[[bg:Мляко]]
[[ca:Llet]]
[[cv:Сĕт]]
[[cs:Mléko]]
[[cy:Llaeth]]
[[da:Mælk]]
[[pdc:Millich]]
[[de:Milch]]
[[nv:Abeʼ]]
[[et:Piim]]
[[el:Γάλα]]
[[es:Leche]]
[[eo:Lakto]]
[[eu:Esne]]
[[fa:شیر (لبنیات)]]
[[fr:Lait]]
[[fur:Lat]]
[[ga:Bainne]]
[[gd:Bainne]]
[[gl:Leite]]
[[ko:젖]]
[[hy:Կաթ]]
[[hi:दूध]]
[[hr:Mlijeko]]
[[io:Lakto]]
[[id:Susu]]
[[ia:Lacte]]
[[is:Mjólk]]
[[it:Latte]]
[[he:חלב]]
[[jv:Susu]]
[[ka:რძე]]
[[rw:Amata]]
[[sw:Maziwa]]
[[la:Lac]]
[[lv:Piens]]
[[lt:Pienas]]
[[li:Mèlk]]
[[ln:Míliki]]
[[hu:Tej]]
[[mk:Млеко]]
[[ml:പാല്]]
[[mn:Сүү]]
[[nah:Chichihualātl]]
[[nl:Melk (drank)]]
[[nds-nl:Mölk]]
[[cr:ᒎᒎᔑᓈᐴ]]
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[[ja:乳]]
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[[oc:Lach]]
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[[ksh:Milesch]]
[[ro:Lapte]]
[[qu:Lichi]]
[[ru:Молоко]]
[[sq:Qumështi]]
[[simple:Milk]]
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[[sr:Млеко]]
[[fi:Maito]]
[[sv:Mjölk]]
[[tl:Gatas]]
[[ta:பால்]]
[[tt:Söt]]
[[te:పాలు]]
[[th:นม]]
[[vi:Sữa]]
[[tr:Süt]]
[[uk:Молоко]]
[[wa:Laecea]]
[[yi:מילך]]
[[zh-yue:奶]]
[[bat-smg:Pėins]]
[[zh:牛奶]]