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About

Milk



From Wikipedia, the free encyclopedia














A glass of pasteurized cow's milk



Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for infant mammals (including humans who breastfeed) before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to its young and can reduce the risk of many diseases. It contains many other nutrients[1] including protein and lactose.


As an agricultural product, milk is extracted from non-human mammals during or soon after pregnancy. Dairy farms produced about 730 million tonnes of milk in 2011,[2] from 260 million dairy cows.[3] India
is the world's largest producer of milk, and is the leading exporter of
skimmed milk powder, yet it exports few other milk products.[4][5]
The ever increasing rise in domestic demand for dairy products and a
large demand-supply gap could lead to India being a net importer of
dairy products in the future.[6] The United States, India, China and Brazil are the world's largest exporters of milk and milk products.[7]
China and Russia were the world's largest importers of milk and milk
products until 2016 when both countries became self-sufficient,
contributing to a worldwide glut of milk.[8]


Throughout the world, more than six billion people consume milk and
milk products. Over 750 million people live in dairy farming households.[9]



Contents



Etymology


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


Types of consumption


Milk consumption occurs in two distinct overall types: a natural
source of nutrition for all infant mammals and a food product obtained
from other mammals for consumption by humans of all ages.


Nutrition for infant mammals












Breastfeeding to provide a mother's milk












A goat kid feeding on its mother's milk



In almost all mammals, milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later. The early milk from mammals is called colostrum. Colostrum contains antibodies that provide protection to the newborn baby as well as nutrients and growth factors.[11] The makeup of the colostrum and the period of secretion varies from species to species.[12]


For humans, the World Health Organization recommends exclusive breastfeeding for six months and breastfeeding in addition to other food for at least two years.[13] In some cultures it is common to breastfeed children for three to five years, and the period may be longer.[14]


Fresh goats' milk is sometimes substituted for breast milk, which introduces the risk of the child developing electrolyte imbalances, metabolic acidosis, megaloblastic anemia, and a host of allergic reactions.[15]


Food product for humans











The Holstein Friesian cattle is the dominant breed in industrialized dairy farms today



In many cultures, especially in the West, humans continue to consume
milk beyond infancy, using the milk of other mammals (especially cattle,
goats and sheep) as a food product. Initially, the ability to digest
milk was limited to children as adults did not produce lactase, an enzyme necessary for digesting the lactose in milk. People therefore converted milk to curd,
cheese and other products to reduce the levels of lactose. Thousands of
years ago, a chance mutation spread in human populations in Europe that
enabled the production of lactase in adulthood.
This mutation allowed milk to be used as a new source of nutrition
which could sustain populations when other food sources failed.[16] People process milk into a variety of products such as cream, butter, yogurt, kefir, ice cream, and cheese. Modern industrial processes use milk to produce casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additives and industrial products.


Whole milk, butter and cream have high levels of saturated fat.[17][18] 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 human small
intestine after birth and then begins a slow decline unless milk is
consumed regularly.[19] Those groups who do continue to tolerate milk, however, often have exercised great creativity in using the milk of domesticated ungulates, not only of cattle, but also sheep, goats, yaks, water buffalo, horses, reindeer and camels. India is the largest producer and consumer of cattle and buffalo milk in the world. [20]

Per capita consumption of milk and milk products in selected countries in 2011[21]

Country
Milk (liters)
Cheese (kg)
Butter (kg)

 Ireland
135.6
6.7
2.4

 Finland
127.0
22.5
4.1

 United Kingdom
105.9
10.9
3.0

 Australia
105.3
11.7
4.0

 Sweden
90.1
19.1
1.7

 Canada
78.4
12.3
2.5

 United States
75.8
15.1
2.8

 Europe
62.8
17.1
3.6

 Brazil
55.7
3.6
0.4

 France
55.5
26.3
7.5

 Italy
54.2
21.8
2.3

 Germany
51.8
22.9
5.9

 Greece
49.1
23.4
0.7

 Netherlands
47.5
19.4
3.3

 India
39.5
-
3.5

 China
9.1
-
0.1

Terminology


In food use, the term milk is defined under Codex Alimentarius
standards as: "the normal mammary secretion of milking animals obtained
from one or more milkings without either addition to it or extraction
from it, intended for consumption as liquid milk or for further
processing."[22] This definition thereby precludes non-animal products which may resemble milk in color and texture (milk substitutes) such as soy milk, rice milk, almond milk, and coconut milk. The correct name for such products are 'soy beverage', 'rice beverage', etc.


Dairy relates to milk and milk production, e.g. dairy products.


In addition, a substance secreted by pigeons to feed their young is called "crop milk" and bears some resemblance to mammalian milk, although it is not consumed as a milk substitute.[23]


Evolution of lactation


The mammary gland is thought to have derived from apocrine skin glands.[24]
It has been suggested that the original function of lactation (milk
production) was keeping eggs moist. Much of the argument is based on monotremes (egg-laying mammals).[24][25][26] The original adaptive significance of milk secretions may have been nutrition[27] or immunological protection.[28][29] This secretion gradually became more copious and accrued nutritional complexity over evolutionary time.[24]


Tritylodontid cynodonts seem to have displayed lactation, based on their dental replacement patterns.[30]


History











Drinking milk in Germany in 1932



Humans first learned to consume the milk of other mammals regularly following the domestication of animals during the Neolithic Revolution
or the development of agriculture. This development occurred
independently in several global locations from as early as 9000–7000 BC
in Mesopotamia[31] to 3500–3000 BC in the Americas.[32]
People first domesticated the most important dairy animals—cattle,
sheep and goats—in Southwest Asia, although domestic cattle had been
independently derived from wild aurochs populations several times since.[33] Initially animals were kept for meat, and archaeologist Andrew Sherratt
has suggested that dairying, along with the exploitation of domestic
animals for hair and labor, began much later in a separate secondary products revolution in the fourth millennium BC.[34] Sherratt's model is not supported by recent findings, based on the analysis of lipid
residue in prehistoric pottery, that shows that dairying was practiced
in the early phases of agriculture in Southwest Asia, by at least the
seventh millennium BC.[35][36]


From Southwest Asia domestic dairy animals spread to Europe
(beginning around 7000 BC but did not reach Britain and Scandinavia
until after 4000 BC),[37] and South Asia (7000–5500 BC).[38] The first farmers in central Europe[39] and Britain[40] milked their animals. Pastoral and pastoral nomadic
economies, which rely predominantly or exclusively on domestic animals
and their products rather than crop farming, were developed as European
farmers moved into the Pontic-Caspian steppe in the fourth millennium BC, and subsequently spread across much of the Eurasian steppe.[41]
Sheep and goats were introduced to Africa from Southwest Asia, but
African cattle may have been independently domesticated around 7000–6000
BC.[42]
Camels, domesticated in central Arabia in the fourth millennium BC,
have also been used as dairy animals in North Africa and the Arabian
Peninsula.[43] The earliest Egyptian records of burn treatments describe burn dressings using milk from mothers of male babies.[44]
In the rest of the world (i.e., East and Southeast Asia, the Americas
and Australia) milk and dairy products were historically not a large
part of the diet, either because they remained populated by hunter-gatherers
who did not keep animals or the local agricultural economies did not
include domesticated dairy species. Milk consumption became common in
these regions comparatively recently, as a consequence of European colonialism and political domination over much of the world in the last 500 years.


In the Middle Ages, milk was called the "virtuous white liquor" because alcoholic beverages were safer to consume than water.[45]


Industrialization











Preserved Express Dairies three-axle milk tank wagon at the Didcot Railway Centre, based on an SR chassis



The growth in urban population, coupled with the expansion of the
railway network in the mid-19th century, brought about a revolution in
milk production and supply. Individual railway firms began transporting
milk from rural areas to London from the 1840s and 1850s. Possibly the
first such instance was in 1846, when St Thomas's Hospital in Southwark contracted with milk suppliers outside London to ship milk by rail.[46] The Great Western Railway was an early and enthusiastic adopter, and began to transport milk into London from Maidenhead in 1860, despite much criticism. By 1900, the company was transporting over 25 million gallons annually.[47] The milk trade grew slowly through the 1860s, but went through a period of extensive, structural change in the 1870s and 1880s.











Milk transportation in Salem, Tamil Nadu



Urban demand began to grow, as consumer purchasing power increased
and milk became regarded as a required daily commodity. Over the last
three decades of the 19th century, demand for milk in most parts of the
country doubled, or in some cases, tripled. Legislation in 1875
made the adulteration of milk illegal - this combined with a marketing
campaign to change the image of milk. The proportion of rural imports by
rail as a percentage of total milk consumption in London grew from
under 5% in the 1860s to over 96% by the early 20th century. By that
point, the supply system for milk was the most highly organized and
integrated of any food product.[46]











1959 milk supply in Oberlech, Vorarlberg, Austria



The first glass bottle packaging for milk was used in the 1870s. The
first company to do so may have been the New York Dairy Company in 1877.
The Express Dairy Company
in England began glass bottle production in 1880. In 1884, Hervey
Thatcher, an American inventor from New York, invented a glass milk bottle, called 'Thatcher's Common Sense Milk Jar', which was sealed with a waxed paper disk.[48] Later, in 1932, plastic-coated paper milk cartons were introduced commercially.[48]


In 1863, French chemist and biologist Louis Pasteur invented pasteurization, a method of killing harmful bacteria in beverages and food products.[48] He developed this method while on summer vacation in Arbois, to remedy the frequent acidity of the local wines.[49]
He found out experimentally that it is sufficient to heat a young wine
to only about 50–60 °C (122–140 °F) for a brief time to kill the
microbes, and that the wine could be nevertheless properly aged without sacrificing the final quality.[49]
In honor of Pasteur, the process became known as "pasteurization".
Pasteurization was originally used as a way of preventing wine and beer
from souring.[50] Commercial pasteurizing equipment was produced in Germany in the 1880s, and producers adopted the process in Copenhagen and Stockholm by 1885.[51][52]


Overproduction


Continued improvements in the efficiency for the production of milk
led to a worldwide glut of milk by 2016. Russia and China became
self-sufficient and stopped importing milk. Canada has tried to restrict
milk production by forcing new farmers/increased capacity to "buy in"
at CN$24,000 per cow. Importing milk is prohibited. The European Union
theoretically stopped subsidizing dairy farming in 2015. Direct
subsidies were replaced by "environmental incentives" which results in
the government buying milk when the price falls to €200 per 1,000 litres
(220 imp gal; 260 US gal). The United States has a voluntary insurance
program that pays farmers depending upon the price of milk and the cost
of feed.[8]


Sources











Modern dairy farm in Norway



The females of all mammal species can by definition produce milk, but
cow's milk dominates commercial production. In 2011, FAO estimates 85%
of all milk worldwide was produced from cows.[53] Human milk is not produced or distributed industrially or commercially; however, human milk banks collect donated human breastmilk and redistribute it to infants who may benefit from human milk for various reasons (premature neonates, babies with allergies, metabolic diseases, etc.) but who cannot breastfeed.[54]


In the Western world, cow's milk is produced on an industrial scale
and is by far the most commonly consumed form of milk. Commercial dairy
farming using automated milking equipment produces the vast majority of milk in developed countries. Dairy cattle such as the Holstein have been bred selectively for increased milk production. About 90% of the dairy cows in the United States and 85% in Great Britain are Holsteins.[19] Other dairy cows in the United States include Ayrshire, Brown Swiss, Guernsey, Jersey and Milking Shorthorn (Dairy Shorthorn).


Sources aside from cows




Other significant sources of milk



Goats (2% of world's milk)




Buffaloes (11%)



Aside from cattle, many kinds of livestock provide milk used by humans for dairy products. These animals include buffalo, goat, sheep, camel, donkey, horse, reindeer and yak. The first four respectively produced about 11%, 2%, 1.4% and 0.2% of all milk worldwide in 2011.[53]


In Russia and Sweden, small moose dairies also exist.[55]


According to the US National Bison Association, American bison (also called American buffalo) are not milked commercially;[56]
however, various sources report cows resulting from cross-breeding
bison and domestic cattle are good milk producers, and have been used
both during the European settlement of North America[57] and during the development of commercial Beefalo in the 1970s and 1980s.[58]


Production worldwide



Top ten cow milk producers

in 2013[59]

Rank
Country
Production

(metric

tonnes)

1
 United States
91,271,058

2
 India
60,600,000

3
 China
35,310,000

4
 Brazil
34,255,236

5
 Germany
31,122,000

6
 Russia
30,285,969

7
 France
23,714,357

8
 New Zealand
18,883,000

9
 Turkey
16,655,009

10
 United Kingdom
13,941,000


Top ten sheep milk producers

in 2013[60]

Rank
Country
Production

(metric

tonnes)

1
 China
1,540,000

2
 Turkey
1,101,013

3
 Greece
705,000

4
 Syria
684,578

5
 Romania
632,582

6
 Spain
600,568

7
 Sudan
540,000

8
 Somalia
505,000

9
 Iran
470,000

10
 Italy
383,837


Top ten goat milk producers

in 2013[61]

Rank
Country
Production

(metric

tonnes)

1
 India
5,000,000

2
 Bangladesh
2,616,000

3
 Sudan
1,532,000

4
 Pakistan
801,000

5
 Mali
720,000

6
 France
580,694

7
 Spain
471,999

8
 Turkey
415,743

9
 Somalia
400,000

10
 Greece
340,000


Top ten buffalo milk producers

in 2013[62]

Rank
Country
Production

(metric

tonnes)

1
 India
70,000,000

2
 Pakistan
24,370,000

3
 China
3,050,000

4
 Egypt
2,614,500

5
   Nepal
1,188,433

6
 Myanmar
309,000

7
 Italy
194,893

8
 Sri Lanka
65,000

9
 Iran
65,000

10
 Turkey
51,947

In 2012, the largest producer of milk and milk products was India
followed by the United States of America, China, Pakistan and Brazil.[63] All 28 European Union members together produced 153.8 million tonnes of milk in 2013, the largest by any politico-economic union.[64]


Increasing affluence in developing countries, as well as increased
promotion of milk and milk products, has led to a rise in milk
consumption in developing countries in recent years. In turn, the
opportunities presented by these growing markets have attracted
investments by multinational
dairy firms. Nevertheless, in many countries production remains on a
small scale and presents significant opportunities for diversification
of income sources by small farms.[65]
Local milk collection centers, where milk is collected and chilled
prior to being transferred to urban dairies, are a good example of where
farmers have been able to work on a cooperative basis, particularly in countries such as India.[66]


Production yields











Child milking a cow by hand



FAO reports[53]
Israel dairy farms are the most productive in the world, with a yield
of 12,546 kilograms (27,659 lb) milk per cow per year. This survey over
2001 and 2007 was conducted by ICAR (International Committee for Animal
Recording[67])
across 17 developed countries. The survey found that the average herd
size in these developed countries increased from 74 to 99 cows per herd
between 2001 and 2007. A dairy farm had an average of 19 cows per herd
in Norway, and 337 in New Zealand. Annual milk production in the same
period increased from 7,726 to 8,550 kg (17,033 to 18,850 lb) per cow in
these developed countries. The lowest average production was in New
Zealand at 3,974 kg (8,761 lb) per cow. The milk yield per cow depended
on production systems, nutrition of the cows, and only to a minor extent
different genetic potential of the animals. What the cow ate made the
most impact on the production obtained. New Zealand cows with the lowest
yield per year grazed all year, in contrast to Israel with the highest
yield where the cows ate in barns with an energy-rich mixed diet.


The milk yield per cow in the United States, the world's largest cow
milk producer, was 9,954 kg (21,945 lb) per year in 2010. In contrast,
the milk yields per cow in India and China – the second and third
largest producers – were respectively 1,154 kg (2,544 lb) and 2,282 kg
(5,031 lb) per year.[68]


Price


It was reported in 2007 that with increased worldwide prosperity and
the competition of bio-fuel production for feed stocks, both the demand
for and the price of milk had substantially increased worldwide.
Particularly notable was the rapid increase of consumption of milk in
China and the rise of the price of milk in the United States above the
government subsidized price.[69] In 2010 the Department of Agriculture
predicted farmers would receive an average of $1.35 per US gallon of
cow's milk (35 cents per liter), which is down 30 cents per gallon from
2007 and below the break-even point for many cattle farmers.[70]


Grading



In the United States, there are two grades of milk, with grade A
primarily used for direct sales and consumption in stores, and grade B
used for indirect consumption, such as in cheese making or other
processing.


The differences between the two grades are defined in the Wisconsin
administrative code for Agriculture, Trade, and Consumer Protection,
chapter 60.[71]
Grade B generally refers to milk that is cooled in milk cans, which are
immersed in a bath of cold flowing water that typically is drawn up
from an underground water well rather than using mechanical
refrigeration.


Physical and chemical properties











Butterfat is a triglyceride (fat) formed from fatty acids such as myristic, palmitic, and oleic acids.



Milk is an emulsion or colloid of butterfat globules within a water-based fluid that contains dissolved carbohydrates and protein aggregates with minerals.[72]
Because it is produced as a food source for the young, all of its
contents provide benefits for growth. The principal requirements are
energy (lipids, lactose, and protein), biosynthesis of non-essential
amino acids supplied by proteins (essential amino acids and amino
groups), essential fatty acids, vitamins and inorganic elements, and
water.[73]


pH


The pH of milk ranges from 6.4 to 6.8[74] and it changes over time. Milk from other bovines and non-bovine mammals varies in composition, but has a similar pH.


Lipids



Initially milk fat is secreted in the form of a fat globule surrounded by a membrane.[75]
Each fat globule is composed almost entirely of triacylglycerols and is
surrounded by a membrane consisting of complex lipids such as phospholipids, along with proteins. These act as emulsifiers which keep the individual globules from coalescing and protect the contents of these globules from various enzymes
in the fluid portion of the milk. Although 97–98% of lipids are
triacylglycrols, small amounts of di- and monoacylglycerols, free
cholesterol and cholesterol esters, free fatty acids, and phospholipids
are also present. Unlike protein and carbohydrates, fat composition in
milk varies widely in the composition due to genetic, lactational, and
nutritional factor difference between different species.[75]


Like composition, fat globules vary in size from less than 0.2 to about 15 micrometers
in diameter between different species. Diameter may also vary between
animals within a species and at different times within a milking of a
single animal. In unhomogenized cow's milk, the fat globules have an
average diameter of two to four micrometers and with homogenization,
average around 0.4 micrometers.[75] The fat-soluble vitamins A, D, E, and K along with essential fatty acids such as linoleic and linolenic acid are found within the milk fat portion of the milk.[19]


Proteins


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


Caseins



The largest structures in the fluid portion of the milk are "casein micelles": aggregates of several thousand protein molecules with superficial resemblance to a surfactant micelle, bonded with the help of nanometer-scale particles of calcium phosphate.
Each casein micelle is roughly spherical and about a tenth of a
micrometer across. There are four different types of casein proteins:
αs1-, αs2-, β-, and κ-caseins. Collectively, they make up around 76–86%[73]
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,
k-casein, reaching out from the body of the micelle into the surrounding fluid. These kappa-casein molecules all have a negative electrical charge and therefore repel each other, keeping the micelles separated under normal conditions and in a stable colloidal suspension in the water-based surrounding fluid.[19][76]


Milk contains dozens of other types of proteins beside caseins and
including enzymes. These other proteins are more water-soluble than
caseins and do not form larger structures. Because the proteins remain
suspended in whey remaining when caseins coagulate into curds, they are collectively known as whey proteins. Whey proteins make up approximately 20% of the protein in milk by weight. Lactoglobulin is the most common whey protein by a large margin.[19]



Salts, minerals, and vitamins


Minerals or milk salts, are traditional names for a variety of
cations and anions within bovine milk. Calcium, phosphate, magnesium,
sodium, potassium, citrate, and chlorine are all included as minerals
and they typically occur at concentration of 5–40 mM.
The milk salts strongly interact with casein, most notably calcium
phosphate. It is present in excess and often, much greater excess of
solubility of solid calcium phosphate.[73]
In addition to calcium, milk is a good source of many other vitamins.
Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin, riboflavin,
folates, and pantothenic acid are all present in milk.


Calcium phosphate structure


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


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


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


Some sources indicate that the trapped calcium phosphate is in the
form of Ca9(PO4)6; whereas, others say it is similar to the structure of
the mineral brushite CaHPO4 -2H2O.[77]


Carbohydrates and miscellaneous contents











A simplified representation of a lactose molecule being broken down into glucose (2) and galactose (1)



Milk contains several different carbohydrate
including lactose, glucose, galactose, and other oligosaccharides. The
lactose gives milk its sweet taste and contributes approximately 40% of
whole cow's milk's calories. Lactose is a disaccharide composite of two simple sugars, glucose and galactose.
Bovine milk averages 4.8% anhydrous lactose, which amounts to about 50%
of the total solids of skimmed milk. Levels of lactose are dependent
upon the type of milk as other carbohydrates can be present at higher
concentrations that lactose in milks.[73]


Other components found in raw cow's milk are living white blood cells, mammary gland cells, various bacteria, and a large number of active enzymes.[19]


Appearance


Both the fat globules and the smaller casein micelles, which are just
large enough to deflect light, contribute to the opaque white color of
milk. The fat globules contain some yellow-orange carotene, enough in
some breeds (such as Guernsey and Jersey cattle) to impart a golden or
"creamy" hue to a glass of milk. The riboflavin in the whey portion of milk has a greenish color, which sometimes can be discerned in skimmed milk or whey products.[19]
Fat-free skimmed milk has only the casein micelles to scatter light,
and they tend to scatter shorter-wavelength blue light more than they do
red, giving skimmed milk a bluish tint.[76]


Processing











Milk products and productions relationships (click to enlarge)



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


Pasteurization



Pasteurization is used to kill harmful Pathogenic bacteria
by heating the milk for a short time and then immediately cooling it.
Types of pasteurized milk include full cream, reduced fat, skim milk,
calcium enriched, flavoured, and UHT.[78] The standard high temperature short time (HTST) process of 72 °C for 15 seconds completely kills pathogenic bacteria in milk,[79] rendering it safe to drink for up to three weeks if continually refrigerated.[80] Dairies print best before dates on each container, after which stores remove any unsold milk from their shelves.


A side effect of the heating of pasteurization is that some vitamin
and mineral content is lost. Soluble calcium and phosphorus decrease by
5%, thiamin and vitamin B12 by 10%, and vitamin C by 20%.[81]
Because losses are small in comparison to the large amount of the two
B-vitamins present, milk continues to provide significant amounts of
thiamin and vitamin B12. The loss of vitamin C is not nutritionally
significant, as milk is not an important dietary source of vitamin C.


Microfiltration


Microfiltration
is a process that partially replaces pasteurization and produces milk
with fewer microorganisms and longer shelf life without a change in the
taste of the milk. In this process, cream is separated from the whey and
is pasteurized in the usual way, but the whey is forced through ceramic
microfilters that trap 99.9% of microorganisms in the milk[82] (as compared to 99.999% killing of microorganisms in standard HTST pasteurization).[83] The whey then is recombined with the pasteurized cream to reconstitute the original milk composition.


Creaming and homogenization











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 often is sold as a separate product with its own uses.
Today the separation of the cream from the milk usually is accomplished
rapidly in centrifugal cream separators.
The fat globules rise to the top of a container of milk because fat is
less dense than water. The smaller the globules, the more other
molecular-level forces prevent this from happening. In fact, the cream
rises in cow's milk much more quickly than a simple model would predict:
rather than isolated globules, the fat in the milk tends to form into
clusters containing about a million globules, held together by a number
of minor whey proteins.[19]
These clusters rise faster than individual globules can. The fat
globules in milk from goats, sheep, and water buffalo do not form
clusters as readily and are smaller to begin with, resulting in a slower
separation of cream from these milks.[19]


Milk often is homogenized,
a treatment that prevents a cream layer from separating out of the
milk. The milk is pumped at high pressures through very narrow tubes,
breaking up the fat globules through turbulence and cavitation.[84] A greater number of smaller particles possess more total surface area
than a smaller number of larger ones, and the original fat globule
membranes cannot completely cover them. Casein micelles are attracted to
the newly exposed fat surfaces. Nearly one-third of the micelles in the
milk end up participating in this new membrane structure. The casein
weighs down the globules and interferes with the clustering that
accelerated separation. The exposed fat globules are vulnerable to
certain enzymes present in milk, which could break down the fats and
produce rancid flavors. To prevent this, the enzymes are inactivated by pasteurizing the milk immediately before or during homogenization.


Homogenized milk tastes blander but feels creamier in the mouth than
unhomogenized. It is whiter and more resistant to developing off
flavors.[19]
Creamline (or cream-top) milk is unhomogenized. It may or may not have
been pasteurized. Milk that has undergone high-pressure homogenization,
sometimes labeled as "ultra-homogenized", has a longer shelf life than milk that has undergone ordinary homogenization at lower pressures.[85]


The homogenization process increases the shelf life of milk because
it decreases the radius of fat globules and other particles (per stokes' law) thus delaying the rate of agglomeration.[citation needed]


UHT


Ultra Heat Treatment (UHT), is a type of milk processing where all
bacteria are destroyed with high heat to extend its shelf life for up to
6 months, as long as the package is not opened. Milk is firstly
homogenized and then is heated to 138 degrees Celsius for 1–3 seconds.
The milk is immediately cooled down and packed into a sterile container.
As a result of this treatment, all the pathogenic bacteria within the
milk are destroyed, unlike when the milk is just pasteurised. The milk
will now keep for up for 6 months if unopened. UHT milk does not need to
be refrigerated until the package is opened, which makes it easier to
ship and store. But in this process there is a loss of vitamin B1 and
vitamin C and there is also a slight change in the taste of the milk.[86]


Nutrition and health



The composition of milk differs widely among species. Factors such as
the type of protein; the proportion of protein, fat, and sugar; the
levels of various vitamins and minerals; and the size of the butterfat
globules, and the strength of the curd are among those that may vary.[21] For example:




  • Human milk contains, on average, 1.1% protein, 4.2% fat, 7.0% lactose (a sugar), and supplies 72 kcal of energy per 100 grams.

  • Cow's milk contains, on average, 3.4% protein, 3.6% fat, and 4.6% lactose, 0.7% minerals[87] and supplies 66 kcal of energy per 100 grams. See also Nutritional value further on


Donkey and horse milk have the lowest fat content, while the milk of seals and whales may contain more than 50% fat.[88][89]

Milk composition analysis, per 100 grams[90][91]

Constituents
Unit
Cow
Goat
Sheep
Water

buffalo

Water
g
87.8
88.9
83.0
81.1

Protein
g
3.2
3.1
5.4
4.5

Fat
g
3.9
3.5
6.0
8.0

----Saturated fatty acids
g
2.4
2.3
3.8
4.2

----Monounsaturated fatty acids
g
1.1
0.8
1.5
1.7

----Polyunsaturated fatty acids
g
0.1
0.1
0.3
0.2

Carbohydrate (i.e. the sugar form of lactose)
g
4.8
4.4
5.1
4.9

Cholesterol
mg
14
10
11
8

Calcium
mg
120
100
170
195

Energy
kcal
66
60
95
110

kJ
275
253
396
463


Cow's milk


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

Milk fat percentages

Cow breed
Approximate percentage

Jersey
5.2

Zebu
4.7

Brown Swiss
4.0

Holstein-Friesian
3.6

The protein range for these four breeds is 3.3% to 3.9%, while the lactose range is 4.7% to 4.9%.[19]


Milk fat percentages may be manipulated by dairy farmers' stock diet
formulation strategies. Mastitis infection can cause fat levels to
decline.[92]


Nutritional value

Nutrient contents in %DV of common foods (raw, uncooked) per 100 g

[show]
Protein
Fiber
Vitamins
Minerals

Ch. = Choline; Ca = Calcium; Fe = Iron; Mg = Magnesium; P =
Phosphorus; K = Potassium; Na = Sodium; Zn = Zinc; Cu = Copper; Mn =
Manganese; Se = Selenium; %DV = % daily value i.e. % of DRI (Dietary Reference Intake)
Note: All nutrient values including protein and fiber are in %DV per
100 grams of the food item. Significant values are highlighted in light
Gray color and bold letters. [93][94] Cooking reduction = % Maximum typical reduction in nutrients due to boiling without draining for ovo-lacto-vegetables group[95][96] Q = Quality of Protein in terms of completeness without adjusting for digestability.[96]

Cow's milk (whole)

Nutritional value per 100 g (3.5 oz)

Energy
252 kJ (60 kcal)


5.26 g

Sugars

5.26 g

5.26 g


3.25 g

Saturated
1.865 g

Monounsaturated
0.812 g

Polyunsaturated
0.195 g


3.22 g

Tryptophan
0.075 g

Threonine
0.143 g

Isoleucine
0.165 g

Leucine
0.265 g

Lysine
0.140 g

Methionine
0.075 g

Cystine
0.017 g

Phenylalanine
0.147 g

Tyrosine
0.152 g

Valine
0.192 g

Arginine
0.075 g

Histidine
0.075 g

Alanine
0.103 g

Aspartic acid
0.237 g

Glutamic acid
0.648 g

Glycine
0.075 g

Proline
0.342 g

Serine
0.107 g


Vitamins

Vitamin A equiv.

(6%)

46 μg

Thiamine (B1)

(4%)

0.044 mg

Riboflavin (B2)

(15%)

0.183 mg

Vitamin B12

(19%)

0.45 μg

Choline

(3%)

14.3 mg

Vitamin D

(0%)

2 IU


Minerals

Calcium

(11%)

113 mg

Magnesium

(3%)

10 mg

Potassium

(3%)

132 mg

Sodium

(3%)

43 mg


Other constituents

Water
88.32 g



100 mL corresponds to 103 g.[97]



Percentages are roughly approximated using US recommendations for adults.

Source: USDA Nutrient Database

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



The amount of calcium from milk that is absorbed by the human body is disputed.[98] Calcium from dairy products has a greater bioavailability than calcium from certain vegetables, such as spinach, that contain high levels of calcium-chelating agents,[99]
but a similar or lesser bioavailability than calcium from low-oxalate
vegetables such as kale, broccoli, or other vegetables in the Brassica genus.[100][101]


Milk as a calcium source has been questioned in media, but scientific
research is lacking to support the hypothesis of acidosis induced by
milk. The hypothesis in question being that acidosis would lead to
leeching of calcium storages in bones to neutralize pH levels (also
known as acid-ash hypothesis). Research has found no link between metabolic acidosis and consumption of milk.[102][103][104]


Recommended consumption


The U.S. federal government document Dietary Guidelines for Americans, 2010[105]
recommends consumption of three glasses of fat-free or low-fat milk for
adults and children 9 and older (less for younger children) per day.
This recommendation is disputed by some health researchers who call for
more study of the issue, given that there are other sources for calcium
and vitamin D. The researchers also claim that the recommendations have
been unduly influenced by the American dairy industry,[106] and that whole milk may be better for health due to its increased ability to satiate hunger.


Medical research


A 2008 review found evidence suggesting that consumption of milk is effective at promoting muscle growth.[107] Some studies have suggested that conjugated linoleic acid, which can be found in dairy products, is an effective supplement for reducing body fat.[108]
With regards to the claim of milk promoting stronger bones, there has
been no association between milk consumption or excess calcium intake[109] and a reduced risk of bone fractures.


In 2011, The Journal of Bone and Mineral Research published a
meta-analysis examining whether milk consumption might protect against
hip fracture in middle-aged and older adults. Studies could find no
association between drinking milk and lower rates of fractures.[110] In 2014, JAMA Pediatrics
published a report after monitoring almost 100,000 men and women for
more than two decades. Subjects were asked to report on how much milk
they had consumed as teenagers, and were followed to see if there is any
association with a reduced chance of hip fractures later in life, it
found there was not any.[111][112] A study published in The BMJ
that followed more than 45,000 men and 61,000 women in Sweden age 39
and older had similar results. Milk consumption in adults was associated
with no protection for men, and an increased risk of fractures in
women. The risk of any bone fracture increased 16 percent in women who
drank three or more glasses daily, and the risk of a broken hip
increased 60 percent. It was also associated with an increased risk of
death in both sexes.[112]


Milk and dairy products have the potential for causing serious
infection in newborn infants. Unpasteurized milk and cheeses can promote
the growth of Listeria bacteria. Listeria monocytogenes can also cause serious infection in an infant and pregnant woman and can be transmitted to her infant in utero or after birth. The infection has the potential of seriously harming or even causing the death of a preterm infant, an infant of low or very low birth weight, or an infant with an immune system defect or a congenital defect of the immune system. The presence of this pathogen can sometimes be determined by the symptoms that appear as a gastrointestinal illness in the mother. The mother can also acquire infection from ingesting food that contains other animal products such as, hot dogs, delicatessen meats, and cheese.[113]


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. Lactose intolerance is a condition in which people have
symptoms due to not enough of the enzyme lactase in the small intestines.[114] Those affected vary in the amount of lactose they can tolerate before symptoms develop. These may include abdominal pain, bloating, diarrhea, gas, and nausea. Severity depends on the amount a person eats or drinks.[115]
Those affected are usually able to drink at least one cup of milk
without developing significant symptoms, with greater amounts tolerated
if drunk with a meal or throughout the day.[115][116]


Lactose intolerance does not cause damage to the gastrointestinal tract.[117]
There are four types: primary, secondary, developmental, and
congenital. Primary lactose intolerance is when the amount of lactase
decline as people age. Secondary lactose intolerance is due to injury to
the small intestine such as from infection, celiac disease, inflammatory bowel disease, or other diseases.[115][118] Developmental lactose intolerance may occur in premature babies and usually improves over a short period of time. Congenital lactose intolerance is an extremely rare genetic disorder in which little or no lactase is made from birth.[115]
When lactose intolerance is due to secondary lactase deficiency,
treatment of the underlying disease allows lactase activity to return to
normal levels.[119] Lactose intolerance is different from a milk allergy.[115]


The number of people with lactose intolerance is unknown.[120] Some human populations have developed lactase persistence,
in which lactase production continues into adulthood probably as a
response to the benefits of being able to digest milk from farm animals.[114]
The percentage of the population that has a decrease in lactase as they
age is less than 10% in Northern Europe and as high as 95% in parts of
Asia and Africa.[114]


Possible harms



Some studies suggest that milk consumption may increase the risk of suffering from certain health problems. Cow's milk allergy (CMA) is an immunologically mediated adverse reaction, rarely fatal, to one or more cow's milk proteins.[121] Milk from any mammal contains amino acids and microRNA which influence the drinker's metabolism and growth;[122]
this "programming" is beneficial for milk's natural consumers, namely
infants of the same species as the milk producer, but post-infancy and
trans-species milk consumption affects the mTORC1 metabolic pathway and may promote diseases of civilization such as obesity and diabetes.[122][123]


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 spectrum disorders,[124][125] and casein-free diets
are widely promoted. Studies supporting these claims have had
significant flaws, and the data are inadequate to guide autism treatment
recommendations.[125][126]


The most recent assessment by the World Cancer Research Fund and the American Institute for Cancer Research found that most individual epidemiological studies showed increased risk of prostate cancer with increased intake of milk or dairy products.[127]
"Meta-analysis of cohort data produced evidence of a clear
dose-response relationship between advanced/aggressive cancer risk with
milk intake, and between all prostate cancer risk and milk and dairy
products." Possible mechanisms proposed included inhibition of the
conversion of vitamin D
to its active metabolite, 1,25- dihydroxy vitamin D3 by calcium (which
some evidence suggests increases cell proliferation in the prostate),
and elevation of levels of insulin-like growth factor-1 (IGF-1).[127] Several sources suggest a correlation between high calcium intake from milk, in particular, and prostate cancer,[128][129][130]
consistent with a calcium/vitamin D based mechanism. Overall, the
WCRF/AICR panel concluded that "The evidence is inconsistent from both
cohort and case-control studies. There is limited evidence suggesting
that milk and dairy products are a cause of prostate cancer."[127]


Medical studies also have shown a possible link between milk consumption and the exacerbation of diseases such as Crohn's disease,[131] Hirschsprung's disease–mimicking symptoms in babies with existing cow's milk allergies,[132] and the aggravation of Behçet's disease.[133]


Flavored milk in US schools


Milk must be offered at every meal if a United States school district wishes to get reimbursement from the federal government.[134]
A quarter of the largest school districts in the US offer rice or soy
milk and almost 17% of all US school districts offer lactose-free milk.
Seventy-one percent of the milk served in US school cafeterias is
flavored, causing some school districts to propose a ban because
flavored milk has added sugars. (Though some flavored milk products use
artificial sweeteners instead.) The Boulder, Colorado, school district
banned flavored milk in 2009 and instead installed a dispenser that
keeps the milk colder.[134]


Bovine growth hormone supplementation


Since November 1993, recombinant bovine somatotropin (rbST),
also called rBGH, has been sold to dairy farmers with FDA approval.
Cows produce bovine growth hormone naturally, but some producers
administer an additional recombinant version of BGH which is produced
through genetically engineered E. coli to increase milk production. Bovine growth hormone also stimulates liver production of insulin-like growth factor 1 (IGF1). The US Food and Drug Administration,[135] the National Institutes of Health[136] and the World Health Organization[137] have reported that both of these compounds are safe for human consumption at the amounts present.


On June 9, 2006, the largest milk processor in the world and the two largest supermarkets in the United States – Dean Foods, Wal-Mart, and Kroger – announced that they are "on a nationwide search for rBGH-free milk."[138]
Milk from cows given rBST may be sold in the United States, and the FDA
stated that no significant difference has been shown between milk
derived from rBST-treated and that from non-rBST-treated cows.[139] Milk that advertises that it comes from cows not treated with rBST, is required to state this finding on its label.


Cows receiving rBGH supplements may more frequently contract an udder infection known as mastitis.[140]
Problems with mastitis have led to Canada, Australia, New Zealand, and
Japan banning milk from rBST treated cows. Mastitis, among other
diseases, may be responsible for the fact that levels of white blood cells in milk vary naturally.[141][142]


rBGH is also banned in the European Union.[143]


Criticism



Vegans and some other vegetarians do not consume milk for reasons mostly related to animal rights and environmental concerns.
They may object to features of dairy farming including the necessity of
keeping dairy cows pregnant, the killing of almost all the male
offspring of dairy cows (either by disposal soon after birth, for veal production, or for beef), the routine separation of mother and calf soon after birth, other perceived inhumane treatment of dairy cattle, and culling of cows after their productive lives.[144]


Some have criticized the American government's promotion of milk
consumption. Their main concern is the financial interest that the
American government has taken in the dairy industry, promoting milk as
the best source of calcium.[citation needed] All United States schools that are a part of the federally funded National School Lunch Act
are required by the federal government to provide milk for all
students. The Office of Dietary Supplements recommends that healthy
adults between ages 19 and 50 get about 1,000 mg of calcium per day.[145]


Milk production is also resource intensive. On a global weighted
average, for the production of a given volume of milk, a thousand times
as much water has to be used.[146]


Varieties and brands












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, flavourings)

  • age (e.g. cheddar, old cheddar)

  • coagulation (e.g. cottage cheese)

  • farming method (e.g. organic, grass-fed)

  • 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)


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


Reduction or elimination of lactose


Lactose-free milk can be produced by passing milk over lactase enzyme
bound to an inert carrier. Once the molecule is cleaved, there are no
lactose ill effects. Forms are available with reduced amounts of lactose
(typically 30% of normal), and alternatively with nearly 0%. The only
noticeable difference from regular milk is a slightly sweeter taste due
to the generation of glucose by lactose cleavage. It does not, however,
contain more glucose, and is nutritionally identical to regular milk.


Finland, where approximately 17% of the Finnish-speaking population has hypolactasia,[147] has had "HYLA" (acronym for hydrolysed lactose)
products available for many years. Lactose of low-lactose level cow's
milk products, ranging from ice cream to cheese, is enzymatically
hydrolysed into glucose and galactose. The ultra-pasteurization process,
combined with aseptic packaging, ensures a long shelf life. In 2001, Valio
launched a lactose-free milk drink that is not sweet like HYLA milk but
has the fresh taste of ordinary milk. Valio patented the chromatographic separation method to remove lactose. Valio also markets these products in Sweden, Estonia, Belgium,[148] and the United States, where the company says ultrafiltration is used.[149]


In the UK, where an estimated 4.7% of the population are affected by lactose intolerance,[150] Lactofree produces milk, cheese, and yogurt products that contain only 0.03% lactose.


To aid digestion in those with lactose intolerance, milk with added bacterial cultures such as Lactobacillus acidophilus ("acidophilus milk") and bifidobacteria ("a/B milk") is available in some areas.[151] Another milk with Lactococcus lactis bacteria cultures ("cultured buttermilk") often is used in cooking to replace the traditional use of naturally soured milk, which has become rare due to the ubiquity of pasteurization, which also kills the naturally occurring Lactococcus bacteria.[152]


Additives and flavoring


In areas 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 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.[153]


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.[154]


Distribution











Returning reusable glass milk bottles, used for home delivery service in the UK












A glass bottle
of non-homogenized, organic, local milk from the US state of
California. American milk bottles are generally rectangular in shape[citation needed]












A 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 crates and manual loading into a freezer display rack



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 (568ml) 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 were concerned that the replacement of the pint bottles with
500ml bottles would result in a 13.6% drop in milk consumption; hence,
all pint bottles were recalled and replaced by 600 mL bottles. With
time, due to the steadily increasing cost of collecting, transporting,
storing and cleaning glass bottles, they were replaced by cardboard
cartons. A number of designs were used, including a tetrahedron which
could be close-packed without waste space, and could not be knocked over
accidentally. (slogan: No more crying over spilt milk.) However, the
industry eventually settled on a design similar to that used in the
United States.[155]


Milk is now available in a variety of sizes in cardboard cartons (250 mL, 375 mL, 600 mL, 1 liter and 1.5 liters) and plastic bottles (1, 2 and 3 liters). A significant addition to the marketplace has been "long-life" milk (UHT),
generally available in 1 and 2 liter rectangular cardboard cartons. In
urban and suburban areas where there is sufficient demand, home delivery
is still available, though in suburban areas this is often 3 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.[citation needed]


India


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


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


A 2011 survey by the Food Safety and Standards Authority of India
found that nearly 70 per cent 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 eight per cent of samples in the survey were found to
have detergents, which are hazardous to health.[156]


Pakistan


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


United Kingdom


Since the late 1990s, milk-buying patterns have changed drastically in the UK. The classic milkman, who travels his local milk round (route) using a milk float (often battery powered) during the early hours and delivers milk in 1 pint glass bottles with aluminium 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.[157] By 2010, the estimated number of milkmen had dropped to 6,000.[158]
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).[159]


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


United States











Getting milk at the back door ~ 1940



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


The "half pint" .5 US pints (0.24 l; 0.42 imp pt) milk carton is the
traditional unit as a component of school lunches, though some companies
have replaced that unit size with a plastic bottle, which is also
available at retail in 6- and 12-pack size.


Packaging


Glass milk bottles are now rare. Most people purchase milk in bags, plastic bottles, or plastic-coated paper cartons. Ultraviolet (UV) light from fluorescent lighting can alter the flavor of milk, so many companies that once distributed milk in transparent or highly translucent containers are now using thicker materials that block the UV light. Milk comes in a variety of containers with local variants:


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
cartons for up to 1.5 liters, and plastic screw-top bottles beyond that
with the following volumes; 1.1 L, 2 L, and 3 L. 1 liter milk bags
are starting to appear in supermarkets, but have not yet proved
popular. Most UHT-milk is packed in 1 or 2 liter paper containers with a
sealed plastic spout.[155]

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 mL aseptic cartons and 500 mL
plastic jugs.

Chile

Distributed most commonly in aseptic
cartons for up to 1 liter, but smaller, snack-sized cartons are also
popular. The most common flavors, besides the natural presentation, are
chocolate, strawberry and vanilla.

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.

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 mL and 1 L (sometimes also 200 mL) aseptic cartons. Non-UHT pasteurized milk (svježe mlijeko/sveže mleko/свеже млеко) is most commonly sold in 1 L and 1.5 L PET bottles, though in Serbia one can still find milk in plastic bags.

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 dl and 5 dl cartons.

Germany

Commonly sold in 1-liter cartons. Sale in 1-liter plastic bags (common in the 1980s) now rare.

Hong Kong

Milk is sold in glass bottles (220 mL), cartons (236 mL and 1 L), plastic jugs (2 liters) and aseptic cartons (250 mL).

India

Commonly sold in 500 mL plastic bags and in bottles in some parts
like in 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 different sizes, usually in aseptic cartons.

Indonesia

Usually sold in 1 liter cartons, but smaller, snack-sized cartons are available.

Israel











A plastic bag of milk in Israel.




Non-UHT milk is most commonly sold in 1 liter waxed cardboard boxes
and 1 liter plastic bags. It may also be found in 1.5 L and 2 L waxed
cardboard boxes, 2 L plastic jugs and 1 L plastic bottles. UHT milk is
available in 1 liter (and less commonly also in 0.5 L) carton "bricks".

Japan

Commonly sold in 1 liter waxed paperboard cartons. In most city centers there is also home delivery of milk in glass jugs. As seen in China, sweetened and flavored milk drinks are commonly seen in vending machines.

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.[160][161] 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 mL, 1 L, 2 L), and
non-UHT in 1 L plastic bags or plastic bottles. Milk, UHT is commonly
boiled, despite being pasteurized.

South 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 mL, 200 mL, 500 mL 900 mL, 1 L, 1.8 L, 2.3 L),
plastic jugs (1 L and 1.8 L), aseptic cartons (180 mL and 200 mL) and
plastic bags (1 L).

Sweden











The milk section in a Swedish grocery store.




Commonly sold in 0.3 L, 1 L or 1.5 L cartons and sometimes as plastic or glass milk bottles.

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 stock imperial
sizes: 1 pint (568 mL), 2 pints (1.136 L), 4 pints (2.273 L), 6 pints
(3.408 L) or a combination including both metric and imperial sizes.
Glass milk bottles delivered to the doorstep by the milkman are
typically pint-sized and are returned empty by the householder for
repeated reuse.
Milk is sold at supermarkets in either aseptic cartons or HDPE bottles.
Supermarkets have also now begun to introduce milk in bags, to be
poured from a proprietary jug and nozzle.

United States

Commonly sold in gallon (3.78 L), half-gallon (1.89 L) and quart
(0.94 L) containers of natural-colored HDPE resin, or, for sizes less
than one gallon, cartons of waxed paperboard. Bottles made of opaque PET
are also becoming commonplace for smaller, particularly metric, sizes
such as one liter. The US single-serving size is usually the half-pint
(about 240 mL). Less frequently, dairies deliver milk directly to
consumers, from coolers filled with glass bottles which are typically
half-gallon sized and returned for reuse. Some convenience store chains
in the United States (such as Kwik Trip in the Midwest) sell milk in half-gallon bags, while another rectangular cube gallon container design used for easy stacking in shipping and displaying is used by warehouse clubs such as Costco and Sam's Club, along with some Wal-Mart stores.[162]

Uruguay

Pasteurized milk is commonly sold in 1 liter bags and ultra-pasteurized milk is sold in cardboard boxes called Tetra Briks. Non-pasteurized milk is forbidden. Until the 1960s no treatment was applied; milk was sold in bottles. As of 2017, plastic jugs used for pouring the bags, or "sachets", are in common use.


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


Spoilage and fermented milk products












Yakult, a probiotic milk-like product made by fermenting a mixture of skimmed milk with a special strain of the bacterium Lactobacillus casei Shirota












Gourd used by Kalenjins to prepare a local version of fermented milk called mursik[160]



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


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


In order to prevent spoilage, milk can be kept refrigerated and stored between 1 and 4 °C (34 and 39 °F) in bulk tanks. Most milk is pasteurized by heating briefly and then refrigerated to allow transport from factory farms to local markets. The spoilage of milk can be forestalled by using ultra-high temperature (UHT)
treatment. Milk so treated can be stored unrefrigerated for several
months until opened but has a characteristic "cooked" taste. Condensed milk, made by removing most of the water, can be stored in cans for many years, unrefrigerated, as can evaporated milk. 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.[163] It can change the taste by destruction of milk-fat globule membranes, releasing oxidized flavors.[163]


Use in other food products











Steamed milk is used in a variety of espresso-based coffee beverages.



Milk is used to make yogurt, cheese, ice milk, pudding, hot chocolate and french toast. Milk is often added to dry breakfast cereal, porridge and granola. Milk is often served in coffee and tea. Steamed milk is used to prepare espresso-based drinks such as cafe latte.


Language and culture











Hindu Abhisheka ritual in Agara, Bangalore Rural District, Karnataka



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", the expression "there's no use crying over spilt
milk" (which means don't "be unhappy about what cannot be undone"),
"don't milk the ram" (this means "to do or attempt something futile")
and "Why buy a cow when you can get milk for free?" (which means "why
pay for something that you can get for free otherwise.").[164] In ancient Greek mythology, the goddess Hera spilled her breast milk after refusing to feed Heracles, resulting in the Milky Way in the sky.


In many African and Asian countries, butter is traditionally made
from fermented milk rather than cream. It can take several hours of
churning to produce workable butter grains from fermented milk.[165]


Holy books have also mentioned milk. The Bible contains references to the 'Land of Milk and Honey'. In the Qur'an,
there is a request to wonder on milk as follows: 'And surely in the
livestock there is a lesson for you, We give you to drink of that which
is in their bellies from the midst of digested food and blood, pure milk
palatable for the drinkers.'(16-The Honeybee, 66). The Ramadan fast is traditionally broken with a glass of milk and dates.


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


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


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


Other uses


Besides serving as a beverage or source of food, milk has been described as used by farmers and gardeners as an organic fungicide and fertilizer,[168][169][170]
however, its effectiveness is debated. Diluted milk solutions have been
demonstrated to provide an effective method of preventing powdery
mildew on grape vines, while showing it is unlikely to harm the plant.[171][172]


See also



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