Editing Milk (section)

==Varieties and brands== <!-- This section is linked to -->
{{main|Dairy product}}
[[File:Dairy Crest Semi Skimmed Milk Bottle.jpg|thumb|upright|Glass milk bottle used for home delivery service in the UK]]
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)
* {{anchor|Hay milk}}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 [[Ultra-high-temperature processing|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.

=== Fat content ===
{{Main|Fat content of milk}}
The fat content of whole milk varies, and is adjusted to make different varieties by separating [[skim milk]] from [[cream]], and then using either to mix different ratios, potentially even from the whole milk base. Thereby the different fat content categories are created, like 1%, 2%, and "half and half".

===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 [[ultrafiltered milk|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.<ref name=Peterson2015>{{cite web |last=Peterson |first=Hayley |url=http://www.businessinsider.com/coca-cola-fairlife-milk-review-2015-2#ixzz3Xn6oKt23 |title=We tried Coca-Cola's new milk that costs twice as much as regular{{nbsp}}– here's the verdict|work=Business Insider|date=February 3, 2015|access-date=April 19, 2015|archive-url=https://web.archive.org/web/20150424050647/http://www.businessinsider.com/coca-cola-fairlife-milk-review-2015-2#ixzz3Xn6oKt23|archive-date=April 24, 2015|url-status=live}}</ref> 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]].<ref>{{cite web |url=http://www.nationaldairycouncil.org/nationaldairycouncil/nutrition/products/product_yogurt.pdf |archive-url=https://web.archive.org/web/20051026104232/http://www.nationaldairycouncil.org/nationaldairycouncil/nutrition/products/product_yogurt.pdf |archive-date=October 26, 2005 |title=Yogurt and Other Cultured Dairy Products |publisher=National Dairy Council |date=2000}}</ref> Another milk with ''[[Lactococcus lactis]]'' bacteria cultures ("[[buttermilk|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.<ref>{{Cite book |author=[[Irma S. Rombauer|Rombauer, Irma S.]] and Marion Rombauer Becker |title=The Joy of Cooking |publisher=Bobbs Merrill |year=1975 |page=533 |isbn=978-0-672-51831-7|title-link=The Joy of Cooking |edition=Revised}}</ref>

===Additives and flavoring===
Commercially sold milk commonly has [[vitamin D]] added to it to make up for lack of exposure to [[Ultraviolet|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.<ref>[http://www.ams.usda.gov/howtobuy/dairy.htm "How to Buy Dairy Products"] {{webarchive|url=https://web.archive.org/web/20071202121113/http://www.ams.usda.gov/howtobuy/dairy.htm |date=December 2, 2007 }}, ''Home and Garden Bulletin 255'', [[USDA]], February 1995. Retrieved May 16, 2007.</ref> 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.<ref>{{cite web |last=Main |first=Emily |url=http://www.rodale.com/flavored-milk-and-school-lunch-programs |title=Chocolate Milk Debate Rages On |work=Rodale News |date=November 30, 2009 |access-date=August 28, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100815032450/http://www.rodale.com/flavored-milk-and-school-lunch-programs |archive-date=August 15, 2010}}</ref>

===Distribution===
[[File:Glass milk bottles.jpg|thumb|upright|Returning reusable glass [[milk bottle]]s, used for home delivery service in the UK]]
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{{nbsp}}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{{nbsp}}mL bottles would result in a 13.6% drop in milk consumption; hence, all pint bottles were recalled and replaced by 600{{nbsp}}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.<ref name=wwwa>[https://web.archive.org/web/20080721052114/http://www.zerowastewa.com.au/documents/liquidpboard_fs.pdf Milk and Juice Cartons Fact Sheet], Waste Wise WA, zerowastewa.com.au. Retrieved June 21, 2009.</ref>

Milk is now available in a variety of sizes in paperboard [[milk carton]]s (250&nbsp;mL, 375&nbsp;mL, 600&nbsp;mL, 1 liter and 1.5 liters) and [[plastic bottle]]s (1, 2 and 3 liters). A significant addition to the marketplace has been "long-life" milk ([[Ultra-high-temperature processing|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]].<ref>{{Cite web |title=AdelaideAZ |url=https://adelaideaz.com/articles/iced-coffee-a-south--australian-global--oddity-that-even--outsold-coca-cola- |access-date=January 4, 2021 |website=adelaideaz.com |archive-date=January 10, 2021 |archive-url=https://web.archive.org/web/20210110235719/https://adelaideaz.com/articles/iced-coffee-a-south--australian-global--oddity-that-even--outsold-coca-cola- |url-status=live }}</ref>

====India====
[[File:Milk vender with typical traditional brass containers , Gagar ,used in Majha Region of Punjab 02.jpg|thumb|Vendors in [[Amritsar]], India transporting milk in [[gagar]], 2019]]

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.<ref>{{cite web |title=Adulterated milk is what Indians are drinking |url=http://cseindia.org/content/adulterated-milk-what-indians-are-drinking |work=Centre for Science and Environment |access-date=June 28, 2015 |archive-url=https://web.archive.org/web/20150625083639/http://cseindia.org/content/adulterated-milk-what-indians-are-drinking |archive-date=June 25, 2015 |url-status=dead}}</ref>

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.<ref>{{cite web |title=Milk quality in India |url=http://www.milkproduction.com/Library/Editorial-articles/Milk-quality-in-India/ |url-status=dead |archive-url=https://web.archive.org/web/20150630141724/http://www.milkproduction.com/Library/Editorial-articles/Milk-quality-in-India/ |archive-date=June 30, 2015 |access-date=June 3, 2015 |publisher=milkproduction.com}}</ref>

====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 (transport)|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.<ref>{{cite news |last=Coughlan |first=Sean |url=http://news.bbc.co.uk/1/hi/magazine/4850336.stm |title=Milk's online top-up |work=BBC News |date=March 28, 2006 |access-date=August 28, 2010 |archive-url=https://web.archive.org/web/20070901025635/http://news.bbc.co.uk/1/hi/magazine/4850336.stm |archive-date=September 1, 2007 |url-status=live}}</ref> By 2010, the estimated number of milkmen had dropped to 6,000.<ref>{{cite web |title=Find me a Milkman{{nbsp}}– I want doorstep deliveries! |url=http://www.dairyuk.org/for-consumers-mainmenu-278/find-me-a-milkman-mainmenu-290 |publisher=Dairy UK |access-date=February 8, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20101031090238/http://www.dairyuk.org/for-consumers-mainmenu-278/find-me-a-milkman-mainmenu-290 |archive-date=October 31, 2010 }}</ref> 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).<ref>{{cite web |url=http://archive.defra.gov.uk/environment/business/products/roadmaps/milk.htm |title="Milk product roadmaps", The Department for Environment, Food and Rural Affairs |publisher=Defra.gov.uk |access-date=August 28, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20120405054121/http://archive.defra.gov.uk/environment/business/products/roadmaps/milk.htm |archive-date=April 5, 2012}}</ref>

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 carton]]s. 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 carton]]s 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" ({{convert|{{Rnd|236.5882365}}|mL|imppt|disp=comma|frac=12|abbr=on}}) 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===
{{more citations needed|section|date=August 2018}}

[[File:Milk in different packets.jpg|thumb|Milk in different packets]]
[[File:Four litre bagged milk, Quebec.jpg|thumb|Four liter bagged milk in [[Quebec]], Canada]]

[[File:Mejeriprodukter i Skånsk butik.jpg|thumb|right|upright|The milk section in a Swedish grocery store]]
[[File:Milk bottle and two doughnuts.jpg|thumb|285x285px|Milk bottle and two doughnuts.]]
[[File:Milk-bottle.jpg|thumb|upright|A glass [[milk bottle|bottle]] of non-homogenized, organic, local milk from the US state of California. American milk bottles are generally rectangular in shape.{{citation needed|date=May 2014}}]]
[[File:Kirkland Milk Jug.JPG|thumb|upright|A [[Square milk jug|rectangular milk jug]] design used by [[Costco]] and [[Sam's Club]] stores in the United States which allows for stacking and display of filled containers rather than being shipped to the store in [[milk crate]]s and manual loading into a freezer display rack]]
Glass milk bottles are now rare. Most people purchase milk in bags, plastic bottles, or plastic-coated 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 and translucency|transparent]] or highly [[translucent]] containers are now using thicker materials that block the UV light.
Milk comes in a variety of [[carton|containers]] with local variants:
;Argentina
: Commonly 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 Zealand
: Distributed in a variety of sizes, most commonly in [[Aseptic processing|aseptic]] cartons for up to 1.5 liters, and plastic screw-top bottles beyond that with the following volumes; 1.1&nbsp;L, 2&nbsp;L, and 3&nbsp;L. 1-liter [[milk bag]]s 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.<ref name=wwwa/>
;Brazil
: Used 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.

;Canada
: 1.33 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&nbsp;mL aseptic cartons and 500&nbsp;mL plastic jugs.
;Chile
: Distributed most commonly in [[Aseptic processing|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.
;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 [[Hong Kong-style milk tea|milk tea]].
;Colombia
:Sells milk in 1-liter plastic bags.
;Croatia, Bosnia and Herzegovina, Serbia, Montenegro
: UHT milk (''trajno mlijeko/trajno mleko/''трајно млеко) is sold in 500&nbsp;mL and 1&nbsp;L (sometimes also 200 mL) aseptic cartons. Non-UHT pasteurized milk (''svježe mlijeko/sveže mleko/''свеже млеко) is most commonly sold in 1&nbsp;L and 1.5&nbsp;L PET bottles, though in Serbia one can still find milk in plastic bags.
;Estonia
: Commonly sold in 1 L bags or 0.33 L, 0.5 L, 1 L or 1.5 L cartons.
; Parts of Europe
: Sizes of 500 mL, 1 liter (the most common), 1.5 liters, 2 liters and 3 liters are commonplace.
;Finland
: Commonly sold in 1 L or 1.5 L cartons, in some places also in 2&nbsp;dl and 5&nbsp;dl cartons.
;Germany
: Commonly sold in 1-liter cartons. Sale in 1-liter plastic bags (common in the 1980s) is now rare.
;Hong Kong
: Milk is sold in glass bottles (220 mL), cartons (236 mL and 1&nbsp;L), plastic jugs (2 liters) and aseptic cartons (250&nbsp;mL).
;India
: Commonly sold in 500 mL plastic bags and in bottles in some parts like in the [[Western world|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.
;Indonesia
: Usually sold in 1-liter cartons, but smaller, snack-sized cartons are available.
;Italy
: Commonly 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.
;Japan
: Commonly sold in 1-liter waxed paperboard cartons. 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 commonly seen in [[vending machine]]s.
;Kenya
:Milk 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.<ref name="Tracing the origin of Mursik"/><ref>{{cite web |last1=Neondo |first1=Henry |title=More Kenyans Consume Raw Milk Due to Poverty |url=http://www.cityfarmer.org/milkKenya.html |website=City Farmer |access-date=November 8, 2016 |archive-url=https://web.archive.org/web/20161113231714/http://www.cityfarmer.org/milkKenya.html |archive-date=November 13, 2016 |url-status=live}}</ref> The standard unit of measuring milk quantity in [[Kenya]] is a liter.
;Pakistan
: Milk is supplied in 500 mL plastic bags and carried in jugs from rural to cities for selling
;Philippines
: Milk is supplied in 1000 mL plastic bottles and delivered from factories to cities for selling.
;Poland
: UHT milk is mostly sold in aseptic cartons (500&nbsp;mL, 1&nbsp;L, 2&nbsp;L), and non-UHT in 1&nbsp;L plastic bags or plastic bottles. Milk, UHT is commonly boiled, despite being pasteurized.
;South Africa
: Commonly 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 Korea
: Sold in cartons (180&nbsp;mL, 200&nbsp;mL, 500&nbsp;mL 900&nbsp;mL, 1&nbsp;L, 1.8&nbsp;L, 2.3&nbsp;L), plastic jugs (1&nbsp;L and 1.8&nbsp;L), aseptic cartons (180 mL and 200 mL) and plastic bags (1 L).
;Sweden

: Commonly sold in 0.3&nbsp;L, 1&nbsp;L or 1.5&nbsp;L cartons and sometimes as plastic or glass milk bottles.
;Turkey
: Commonly 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 Kingdom
: Most stores stock [[Imperial units|imperial]] sizes: 1 pint (568&nbsp;mL), 2 pints (1.136&nbsp;L), 4 pints (2.273&nbsp;L), 6 pints (3.408&nbsp;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 States

: Commonly sold in [[gallon]] (3.78&nbsp;L), half-gallon (1.89&nbsp;L) and [[quart]] (0.94&nbsp;L) containers of natural-colored HDPE resin, or, for sizes less than one gallon, cartons of waxed paperboard. Bottles made of opaque [[Polyethylene terephthalate|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 [[Square milk jug|rectangular cube gallon container design]] used for easy stacking in shipping and displaying is used by [[warehouse club]]s such as [[Costco]] and [[Sam's Club]], along with some [[Walmart]] stores.<ref>{{cite news |url=https://www.nytimes.com/2008/06/30/business/30milk.html?ex=1372564800&en=4b8e1de115184001&ei=5124&partner=permalink&exprod=permalink |work=The New York Times |first=Stephanie |last=Rosenbloom |title=Solution, or Mess? A Milk Jug for a Green Earth |date=June 30, 2008 |access-date=February 22, 2017 |archive-url=https://web.archive.org/web/20161018111823/http://www.nytimes.com/2008/06/30/business/30milk.html?ex=1372564800&en=4b8e1de115184001&ei=5124&partner=permalink&exprod=permalink |archive-date=October 18, 2016 |url-status=live}}</ref>
;Uruguay
: Pasteurized milk is commonly sold in 1-liter bags and ultra-pasteurized milk is sold in cardboard boxes called [[Tetra Brik]]s. 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&nbsp;mL paper containers and 100 and 200&nbsp;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}}
[[File:Yakult_drink.jpg|thumb|upright|[[Yakult]], a [[probiotic]] milk-like product made by [[Fermentation (food)|fermenting]] a mixture of [[skimmed milk]] with a special strain of the bacterium ''[[Lactobacillus casei]] Shirota'']]
[[File:Kipsigis_Gourd.jpg|thumb|upright|Gourd used by [[Kalenjin people|Kalenjins]] to prepare a local version of fermented milk called ''[[mursik]]''<ref name="Tracing the origin of Mursik">{{cite web |last1=Kibor |first1=Fred |title=Tracing the origin of Mursik |url=http://www.standardmedia.co.ke/lifestyle/article/2000194283/tracing-the-origin-of-mursik |website=The Standard |date=March 9, 2016 |access-date=November 8, 2016 |archive-url=https://web.archive.org/web/20161109022256/http://www.standardmedia.co.ke/lifestyle/article/2000194283/tracing-the-origin-of-mursik |archive-date=November 9, 2016 |url-status=live}}</ref> ]]

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]] 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,<ref>{{Cite book |title=Culinary nutrition : the science and practice of healthy cooking |last=B. |first=Marcus, Jacqueline |date=2013 |publisher=Elsevier/Academic Press |isbn=978-0-12-391882-6 |location=Amsterdam |oclc=806291270}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=8tlEAgAAQBAJ&q=Pasteurization+of+cow%27s+milk+initially+destroys+any+potential+pathogens+and+increases+the+shelf+life&pg=PA127 |title=Detailed Project Profiles on Dairy & Dairy Products (2nd Edn.) |last=board |first=NPCS |year=2012 |publisher=Niir Project Consultancy Services |isbn=978-93-81039-10-6 |access-date=October 19, 2020 |archive-date=January 25, 2021 |archive-url=https://web.archive.org/web/20210125182629/https://books.google.com/books?id=8tlEAgAAQBAJ&q=Pasteurization+of+cow%27s+milk+initially+destroys+any+potential+pathogens+and+increases+the+shelf+life&pg=PA127 |url-status=live }}</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 [[acid]]ity 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 {{convert|1|and|4|C}} in [[bulk tank]]s. Most milk is pasteurized by heating briefly and then refrigerated to allow transport from [[factory farming|factory farms]] to local markets. The spoilage of milk can be forestalled by using ultra-high temperature ([[Ultra-high-temperature processing|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.<ref name=hui2006>{{cite book |title=Handbook of Food Science, Technology, and Engineering, Volume 2 |author=Yiu H. Hui |publisher=CRC Press |year=2006 |isbn=978-0-8493-9848-3}} [https://books.google.com/books?id=brdM8-ahRg4C&pg=SA58 p. 58]</ref> It can change the taste by destruction of milk-fat globule membranes, releasing oxidized flavors.<ref name=hui2006/>