编辑“︁乳”︁

{{about|动物乳汁|植物分泌的乳汁|乳胶}}
{{about|动物乳汁|油水混合的乳浊液|乳液}}
{{Expand language|1=es|status=yes|time=2022-04-19T09:21:27+00:00}}
[[File:Milk glass.jpg|thumb|200px|[[牛奶]]是人類最普遍的乳品]]
'''乳'''或稱'''乳汁'''，俗称'''奶'''，为乳状物，是一種[[哺乳類]]（包括[[單孔目]]）[[雌性]]動物（有時為雄性）[[乳腺]]的[[分泌物]]，也是哺乳類特有的能力之一<ref name="lechq">{{cite web |url= http://www.quimica.urv.es/~w3siiq/DALUMNES/98/siiq3/leche.html |title= Leche |accessdate= 2008-01-11 |author= Química.urv.es |language= es |deadurl= yes |archiveurl= https://web.archive.org/web/20111222142044/http://www.quimica.urv.es/~w3siiq/DALUMNES/98/siiq3/leche.html |archivedate= 2011-12-22 }} {{Wayback|url=http://www.quimica.urv.es/~w3siiq/DALUMNES/98/siiq3/leche.html |date=20111222142044 }}</ref><ref name="delaval">{{cite web |url= http://www.delaval.com.ar/Dairy_Knowledge/EfficientCooling/Leche.htm |title= Leche |accessdate= 2008-01-11 |author= Delaval.com.ar |language= es |archive-url= https://web.archive.org/web/20080426152812/http://www.delaval.com.ar/Dairy_Knowledge/EfficientCooling/Leche.htm |archive-date= 2008-04-26 |dead-url= yes }} {{Wayback|url=http://www.delaval.com.ar/Dairy_Knowledge/EfficientCooling/Leche.htm |date=20080426152812 }}</ref><ref name="crlnd">{{cite web |url= http://costaricalinda.com/Mamiferos/ |title= Mamíferos de Costa Rica |accessdate= 2008-01-11 |author= Costaricalinda.com |language= es |deadurl= yes |archiveurl= https://web.archive.org/web/20080627023439/http://costaricalinda.com/Mamiferos/ |archivedate= 2008-06-27 }} {{Wayback|url=http://costaricalinda.com/Mamiferos/ |date=20080627023439 }}</ref>。它營養豐富，色白、不透光，主要功能是在幼兒能夠自行消化其他食物（即[[斷奶]]）之前提供哺育。透過調節能量產生的[[代謝]]過程，尤其是[[葡萄糖]]和[[胰島素]]的代謝，乳汁能夠保護幼兒的[[消化道]]，不受[[病原體]]、[[毒素]]和[[炎症|發炎症狀]]的侵害，有益幼兒健康。在現今絕大多數人類文明，[[馴養|家畜]]的乳汁也供人類食用，其中以牛乳為大宗，但也有[[綿羊]]、山羊、[[馬]]和[[駱駝]]等乳源。

動物剛生產後所分泌的乳汁稱為[[初乳|初乳]]，是用於哺育剛出生的幼兒的，含有多種[[抗體]]，可以降低幼兒生病的可能性<ref>{{cite web|url=http://www.angrin.tlri.gov.tw/cow/dfar152/dfar152p18.htm/|title=餵飼小牛高品質代初乳的重要性|accessdate=2014-01-27|author=祥圃實業股份有限公司|language=zh|publisher=台灣畜產種原資訊網}}{{dead link|date=2017年11月 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>。人类乳汁一般用于[[母乳喂养]]。乳汁的成分依动物种类不同而有所差异，但主要成分相同，包括[[水]]、[[離子]]（[[食鹽]]、礦物質和[[鈣質]]）、[[醣類]]（[[乳糖]]）、[[脂肪]]和[[蛋白質]]<ref name="delaval" />。海洋[[哺乳]]動物，例如鯨魚，其乳汁比陸生[[哺乳]]動物含有更高的脂肪和營養物質<ref>Alais, C. 1971. ''Ciencia de la leche'' (乳品科學). Cía. Editorial, México, DF. {{es icon}}</ref>。

[[乳汁]]是許多[[乳製品]]的原料，例如[[鮮奶油|奶油]]、[[乾酪|-{zh-tw:起司;zh-cn:奶酪;zh-hk:芝士;}-]]和[[酸奶]]<ref>{{cite web |url = http://www.ua-cc.org/lacteos.jsp |title = Nutrición y salud - Lácteos (營養與健康 - 乳製品) |accessdate = 2008-01-11 |author = Ua-cc.org |language = es |deadurl = yes |archiveurl = https://web.archive.org/web/20080120081810/http://www.ua-cc.org/lacteos.jsp |archivedate = 2008-01-20 }} {{Wayback|url=http://www.ua-cc.org/lacteos.jsp |date=20080629020147 }}</ref>。它也常用於乳製品加工產業，或製造[[化学工业|化工]]和[[醫藥]]產品，如[[煉乳]]、[[奶粉]]、[[酪蛋白]]和[[乳糖]]等<ref>{{cite web |url = http://www.vanguardia.com.mx/diario/noticia/salud/vidayarte/omnia:_tipos_de_leche/50333 |title = >> Omnia: Tipos de leche |accessdate = 2008-01-11 |author = Vanguardia.com.mx |language = es |archive-date = 2009-05-31 |archive-url = https://web.archive.org/web/20090531080310/http://www.vanguardia.com.mx/diario/noticia/salud/vidayarte/omnia:_tipos_de_leche/50333 |dead-url = no }} {{Wayback|url=http://www.vanguardia.com.mx/diario/noticia/salud/vidayarte/omnia:_tipos_de_leche/50333 |date=20090531080310 }}</ref>。常温下的牛乳的[[pH值]]介于6.5到6.7之间<ref>{{cite web |url=http://www.shilemu.com/1312.html |language=zh |title=乳的pH值与酸度及异常乳的概念和种类 |publisher=石家庄乐牧贸易有限公司 |accessdate=2014-01-27 |deadurl=yes |archiveurl=https://web.archive.org/web/20140203025700/http://www.shilemu.com/1312.html |archivedate=2014-02-03 }} {{Wayback|url=http://www.shilemu.com/1312.html |date=20140203025700 }}</ref>，因此会稍稍带[[酸]]。

== 种类 ==
=== 奶源 ===
{{main|母乳|牛奶|羊奶}}
[[File:Woman breastfeeding an infant.jpg|thumb|母乳餵養]]
幾乎所有的哺乳動物都通過[[哺乳]]行為，即讓幼兒直接吮吸[[乳頭]]或將乳汁儲存在其它容器中以供幼兒飢餓時飲用。產後的動物用自己的乳汁餵養嬰兒的時期稱為哺乳期。人類的哺乳期大約為十個月至一年，[[世界卫生组织]]和[[联合国儿童基金会]]建議純母乳餵六個月，配合其他副食品餵到二歲<ref>{{cite web|url=http://www.cdia.org.cn/newsds.aspx?NID=681&MID=4|language=中文|title=母乳喂养的好处|publisher=中国乳制品工业协会|accessdate=2014-01-27|deadurl=yes|archiveurl=https://web.archive.org/web/20140202112324/http://www.cdia.org.cn/newsds.aspx?NID=681&MID=4|archivedate=2014-02-02}} {{Wayback|url=http://www.cdia.org.cn/newsds.aspx?NID=681&MID=4 |date=20140202112324 }}</ref>，而其他動物的哺乳期則各不相同。

常見的動物乳汁有[[牛奶|牛乳]]、[[羊奶|羊乳]]、[[馬乳]]等。

===定义===
{{see also|初乳|生乳|鲜奶|巴氏奶|保久乳}}
*[[初乳]]：[[哺乳動物]]分娩後短時間內分泌的乳汁，如[[牛初乳]]；初乳以後的乳汁称为[[後奶]]。
*[[生乳]]：奶畜乳房中擠出的未經過巴氏消毒等方式加工的常乳。
*[[巴氏奶]]：採用[[巴斯德消毒法]]加工过的奶。
*[[保久乳]]：用120°C左右高溫短暫加熱過的奶，保質期比巴氏奶長。

==外觀==
乳脂肪球及較小的酪蛋白膠束都大到足以使光偏轉，因此乳汁會呈不透明的白色。有些品種的乳牛（像[[根西牛]]或[[娟珊牛]]）乳脂肪球中會帶有橘黃色的胡蘿蔔素，因此奶水會呈金黃色。乳汁中乳清的[[核黄素]]會使乳汁呈綠色，有時在脫脂乳品或是乳清製品中也會看到類似情形<ref name="On Food and Cooking">{{Cite book|last = McGee|first = Harold|authorlink = Harold McGee|title = On Food and Cooking: The Science and Lore of the Kitchen|origyear = 1984|year = 2004|publisher = Scribner|edition = 2nd|location = New York|isbn = 978-0-684-80001-1|url = http://books.google.com/books?id=bKVCtH4AjwgC&lpg=PP1&pg=PA7|pages = 7–67|chapter = Milk and Dairy Products|access-date = 2014-01-27|archive-date = 2020-08-06|archive-url = https://web.archive.org/web/20200806030259/https://books.google.com/books?id=bKVCtH4AjwgC&lpg=PP1&pg=PA7|dead-url = no}} {{Wayback|url=http://books.google.com/books?id=bKVCtH4AjwgC&lpg=PP1&pg=PA7 |date=20200806030259 }}</ref>。脫脂奶中只有酪蛋白可以使光線散射，酪蛋白對於波長較短的光（如藍光）會有較明顯的散射，因此脫脂奶會略呈藍色<ref name="chem">{{cite web|last=Goff|first=Douglas|title=Dairy Chemistry and Physics|url=http://www.foodsci.uoguelph.ca/dairyedu/chem.html|work=Dairy Science and Technology|publisher=University of Guelph|accessdate=8 February 2011|year=2010|archive-date=2006-06-14|archive-url=https://web.archive.org/web/20060614214133/http://www.foodsci.uoguelph.ca/dairyedu/chem.html|dead-url=no}} {{Wayback|url=http://www.foodsci.uoguelph.ca/dairyedu/chem.html |date=20060614214133 }}</ref>。
==成分==
[[File:TriglycerideDairyButter.svg|thumb|400px|[[乳脂]]是由像[[肉豆蔻酸]]、[[棕櫚酸]]及[[油酸]]等脂肪酸形成的[[三酸甘油脂]]。]]
乳汁是由[[乳脂]]球分散在水中形成的[[膠體]]或[[乳濁液]]，其中也會有溶在水中的[[碳水化合物]]及[[蛋白質]]和礦物質的聚集體<ref>Rolf Jost "Milk and Dairy Products" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. {{DOI|10.1002/14356007.a16_589.pub3}}</ref>。由於乳汁是作為動物新生兒的營養來源，因此其中的成份都是對有益於牠們成長的。動物新生兒的主要需求是能量（脂質，[[乳糖]]和蛋白質）、可以提供必需胺基酸的蛋白質（可以在動物體內合成非必需胺基酸）、必需脂肪酸、維生素、無機礦物質以及水<ref name="autogenerated5">Fox, P. F. Advanced Dairy Chemistry, Vol. 3: Lactose, Water, Salts and Vitamins. 2nd ed. Chapman and Hall: New York, 1995.</ref>。

不同種類的乳汁成分相差很大<ref name="intro">{{cite web|last=Goff|first=Douglas|title=Introduction to Dairy Science and Technology: Milk History, Consumption, Production, and Composition|url=http://www.foodsci.uoguelph.ca/dairyedu/intro.html|work=Dairy Science and Technology|publisher=University of Guelph|accessdate=8 February 2011|year=2010|archive-date=2009-12-25|archive-url=https://web.archive.org/web/20091225063301/http://www.foodsci.uoguelph.ca/dairyedu/intro.html|dead-url=no}} {{Wayback|url=http://www.foodsci.uoguelph.ca/dairyedu/intro.html |date=20091225063301 }}</ref>。例如：

*[[母乳|人類母乳]]平均包含1.1%的蛋白質，4.2%的脂肪，7.0%的乳糖。 100克母乳可提供72千卡能量。
*[[奶牛]]乳汁平均包含3.4%的蛋白质，3.6%的脂肪，4.6%的乳糖，0.7%的[[膳食礦物質|矿物质]]<ref>{{Cite news |url=http://www.hindu.com/seta/2008/07/10/stories/2008071050201800.htm |title=Milk contains traces of ash |publisher=Hindu.com |date=2008-07-10 |accessdate=2010-08-28 |location=Chennai, India |archive-date=2012-01-18 |archive-url=https://web.archive.org/web/20120118000721/http://www.hindu.com/seta/2008/07/10/stories/2008071050201800.htm |dead-url=no }} {{Wayback|url=http://www.hindu.com/seta/2008/07/10/stories/2008071050201800.htm |date=20120118000721 }}</ref>。100克牛奶可提供66千卡的能量。（參見下面的營養表格）
*[[驴]]和[[马]]的乳汁脂肪含量最低，而[[鰭足類|海豹]]和[[鲸]]的乳汁脂肪含量超过50%。<ref>{{cite web |url=http://www.havemilk.com/article.asp?id=1485#contentbyspecies |title=Milk From Cows and Other Animals, web page by Washington Dairy Products Commission |publisher=Havemilk.com |accessdate=2010-08-28 |archive-date=2014-08-26 |archive-url=https://web.archive.org/web/20140826151626/http://www.havemilk.com/article.asp?id=1485#contentbyspecies |dead-url=no }} {{Wayback|url=http://www.havemilk.com/article.asp?id=1485#contentbyspecies |date=20140826151626 }}</ref><ref>{{cite encyclopedia|title=Whale|url=http://encarta.msn.com/encyclopedia_761565254_3/Whale.html|publisher=Encarta|deadurl=yes|archiveurl=https://www.webcitation.org/5kx5gN68d?url=http://encarta.msn.com/encyclopedia_761565254_3/Whale.html|archivedate=2009-11-01|access-date=2017-08-03}}</ref>

{| class="wikitable"
|+ 乳汁成分分析（每100克）<ref>{{cite web |title=Milk analysis |publisher=North Wales Buffalo |url=http://www.northwalesbuffalo.co.uk/milk_analysis.htm |archiveurl=https://web.archive.org/web/20070929071651/http://www.northwalesbuffalo.co.uk/milk_analysis.htm |archivedate=2007-09-29 |accessdate=3 August 2009 |deadurl=yes }} {{Wayback|url=http://www.northwalesbuffalo.co.uk/milk_analysis.htm |date=20070929071651 }} (Citing McCane, Widdowson, Scherz, Kloos, International Laboratory Services.)</ref><ref>{{cite web |url=http://www.ars.usda.gov/nutrientdata |language=en |title=USDA National Nutrient Database for Standard Reference |publisher=Ars.usda.gov |accessdate=2014-01-27 |archive-date=2008-08-21 |archive-url=https://web.archive.org/web/20080821160823/http://www.ars.usda.gov/nutrientdata |dead-url=no }} {{Wayback|url=http://www.ars.usda.gov/nutrientdata |date=20080821160823 }}</ref>
! 成分
! 单位
! [[奶牛]]
! [[山羊]]
! [[绵羊]]
! [[水牛]]
|-
| 水
| g
| 87.8
| 88.9
| 83.0
| 81.1
|-
| 蛋白质
| g
| 3.2
| 3.1
| 5.4
| 4.5
|-
| 脂肪
| g
| 3.9
| 3.5
| 6.0
| 8.0
|-
| ----饱和脂肪酸
| g
| 2.4
| 2.3
| 3.8
| 4.2
|-
| ----[[单元不饱和脂肪酸]]
| g
| 1.1
| 0.8
| 1.5
| 1.7
|-
| ----[[多元不饱和脂肪酸]]
| g
| 0.1
| 0.1
| 0.3
| 0.2

|-
| 碳水化合物（比如[[乳糖]]）
| g
| 4.8
| 4.4
| 5.1
| 4.9
|-
| 胆固醇
| mg
| 14
| 10
| 11
| 8
|-
| 钙
| mg
| 120
| 100
| 170
| 195
|-
|rowspan="2"| 能量
| kcal
| 66
| 60
| 95
| 110
|-
| kJ
| 275
| 253
| 396
| 463
|}

== 乳制品 ==
{{main|乳制品}}
在大多数人类文化中，人类即使在过了哺乳期以后仍然会食用乳汁或奶制品。为了保存以及运输方便，人类将动物乳汁制成各式各样的[[奶制品]]，如[[鮮奶油|奶油]]、[[黄油]]、[[乾酪|奶酪]]、[[酸奶]]、[[克非尔]]等等。到了现代，人们成功从乳汁中提取出各种营养成分，如[[酪蛋白]]、[[乳清蛋白]]、[[乳糖]]、[[奶粉]]、[[炼奶]]等等，作为添加剂或调料。

儘管乳汁和[[乳製品]]是人類常見的食物之一，全世界有一半以上的人特別是九成以上的[[華人]]有[[乳糖不耐症]]。乳糖不耐症的原因是[[小腸]]無法完全吸收乳汁中的[[乳糖]]而導致乳糖在[[大腸]]中分解產氣，從而產生噁心、腹瀉、腹脹等症狀。小腸降解乳糖的主要手段是[[乳糖酶]]<ref>{{cite web|url=http://www.nsc.gov.tw/scitechvista/zh-tw/Video/C/0/10/1/348.htm|language=中文|title=乳糖不耐症|publisher=行政院國家科學委員會|accessdate=2014-01-27|deadurl=yes|archiveurl=https://archive.today/20140126183918/http://www.nsc.gov.tw/scitechvista/zh-tw/Video/C/0/10/1/348.htm|archivedate=2014-01-26}} {{Webarchive|url=https://archive.today/20140126183918/http://www.nsc.gov.tw/scitechvista/zh-tw/Video/C/0/10/1/348.htm |date=2014-01-26 }}</ref>。小肠制造乳糖酶的能力在幼儿时最高，而一般在二、三岁后就开始减退，因此成人对乳汁和乳制品中乳糖的耐受性会比较差。近年來市面上出現了專門針對乳糖不耐人群的無乳糖乳製品（Lactose-Free），以解決此類人群難以消耗乳製品的問題。

==其他用途==
乳類除了當作飲料或是食物外，也有農夫及園丁用乳類作為有機的[[杀菌农药|杀菌剂]]及肥料<ref>{{cite web
 |url          = http://www.abc.net.au/gardening/stories/s948323.htm
 |title        = Fact Sheet: Milk Fungicide
 |publisher    = Australian Broadcasting Corporation
 |last         = Campbell
 |first        = Malcolm
 |date         = September 19, 2003
 |accessdate   = April 1, 2009
 |archive-url  = https://web.archive.org/web/20160818160904/http://www.abc.net.au/gardening/stories/s948323.htm
 |archive-date = 2016-08-18
 |dead-url     = yes
}} {{Wayback|url=http://www.abc.net.au/gardening/stories/s948323.htm |date=20160818160904 }}</ref><ref>{{cite web |last=Hoffelt |first=Jeffrey |title=Milk works as fertilizer, says preliminary study |url=http://m.minnesotafarmguide.com/news/regional/milk-works-as-fertilizer-says-preliminary-study/article_028652ea-849c-11e0-9dcc-001cc4c03286.html |work=Minnesota Farm Guide |accessdate=June 3, 2015 |date=May 25, 2011 |archive-date=2016-09-01 |archive-url=https://archive.today/20160901045602/http://m.minnesotafarmguide.com/news/regional/milk-works-as-fertilizer-says-preliminary-study/article_028652ea-849c-11e0-9dcc-001cc4c03286.html |dead-url=yes }} {{Webarchive|url=https://archive.today/20160901045602/http://m.minnesotafarmguide.com/news/regional/milk-works-as-fertilizer-says-preliminary-study/article_028652ea-849c-11e0-9dcc-001cc4c03286.html |date=2016-09-01 }}</ref><ref>{{cite web |last=Phipps |first=Nikki |title=Milk Fertilizer Benefits: Using Milk Fertilizer On Plants |url=http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/milk-fertilizer.htm |work=www.gardeningknowhow.com |accessdate=June 3, 2015 |archive-date=2015-06-30 |archive-url=https://web.archive.org/web/20150630144851/http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/milk-fertilizer.htm |dead-url=no }} {{Wayback|url=http://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/milk-fertilizer.htm |date=20150630144851 }}</ref>，不過其效果仍有爭議。有一種預防葡萄白粉病的方案中有使用稀釋乳，此方案已確定是有效的，而且不太可能會傷害植物本身<ref>{{cite web
| url = http://www.sciencedaily.com/releases/2002/09/020912071438.htm
| title = Drop of white the right stuff for vines
| publisher = Science Daily
| date = September 12, 2002
| accessdate = April 1, 2009
| archive-date = 2020-10-08
| archive-url = https://web.archive.org/web/20201008155224/https://www.sciencedaily.com/releases/2002/09/020912071438.htm
| dead-url = no
}} {{Wayback|url=http://www.sciencedaily.com/releases/2002/09/020912071438.htm |date=20201008155224 }}</ref><ref>{{cite web|authors=Wagner Bettiol, Brenno Domingues Astiarraga and Alfredo José Barreto Luiz|title=Effectiveness of cow's milk against zucchini squash powdery mildew (Sphaerotheca fuliginea) in greenhouse conditions|url=http://www.agrar.de/agenda/bettiol.htm|work=agrar.de|accessdate=June 3, 2015|archive-date=2015-04-25|archive-url=https://web.archive.org/web/20150425043433/http://www.agrar.de/agenda/bettiol.htm|dead-url=no}} {{Wayback|url=http://www.agrar.de/agenda/bettiol.htm |date=20150425043433 }}</ref>。

==相關條目==
{{col-begin}}{{col-2}}
*[[乳房]]（[[乳腺]]、[[乳頭]]）
*{{link-en|乳房线|Milk line}}
*[[代乳品]]
*{{link-en|A2乳|A2 milk}}
*{{link-en|巴布科克试验|Babcock test}}（檢驗其中乳脂肪的含量）

== 參考資料 ==
{{reflist}}

==外部連結==
{{Sister project links|wikt=milk}}
*{{Dmoz|Business/Food_and_Related_Products/Dairy/Milk|Milk}}
*[http://www.carnamah.com.au/milk-cream-butter.html Virtual Museum Exhibit on Milk, Cream & Butter] {{Wayback|url=http://www.carnamah.com.au/milk-cream-butter.html |date=20130226122225 }}

{{Authority control}}
[[Category:奶|*]]