The science of milk – Jonathan J. O’Sullivan

Why do humans drink so much milk? And given that all mammals lactate, why do we favor certain types of milk
over others? Milk is the first thing we drink, and thanks to developments in the
production and variety of dairy products, it can take on countless forms for our
dietary and sensory well-being. Milk’s primary function is as a complete
source of nutrition for newborns. In fact, since it has all of the vital
nutrients for development and growth, proteins, carbohydrates, fats, vitamins and minerals, and water, milk is the only thing a baby
even needs to ingest for the first six months of life. The unique makeup of milk can vary
depending on factors like species, diet, and location. Reindeer of the Arctic Circle,
for example, make energy-dense milk
that’s about 20% fat, roughly five times more than human
or cow’s milk, to help their young survive the harsh,
freezing climate. So how is milk made? In the uniquely mammalian process
of lactation, a special class of milk-secreting cells
known as mammocytes line up in a single layer around
pear-shaped alveoli. Those cells absorb all of the building
blocks of milk, then synthesize tiny droplets of fat on structures called
smooth endoplasmic reticula. The droplets combine with each other
and other molecules and are then expelled and stored
in spaces between cells. Mammary glands eventually secrete the milk
through the breasts, udders, or, in the rare case of the platypus,
through ducts in the abdomen. Although this process is typically
reserved for females, in some species, like dayak fruit bats, goats, and even cats, males can also lactate. Milk drinkers worldwide consume
dairy from buffalo, goats, sheeps, camels, yaks, horses, and cows. Almost all of these species are ruminants, a type of mammal with
four-chambered stomachs that yield large quantities of milk. Of these, cows were the most
easily domesticated and produce a milk that is both
easily separated into cream and liquid and has a similar fat content
to human milk. In their natural environment, mammals secrete milk on call
for immediate consumption by their young. But with the demands of thirsty consumers, the dairy industry has enlisted methods
to step up production, enhance shelf life, and provide a variety of milk products. In the dairy, centrifugation machines
spin milk at high speeds, forcing less dense fats to separate
from the liquid and float up. After being skimmed off, this fat, known as butterfat,
can be used in dairy products like butter, cream, and cheese. Or it can be later added back to
the liquid in varying proportions to yield different fat content milks. Full fat milk, sometimes referred to
as whole milk, has 3.25% butterfat added compared to 1-2% for low
and reduced fat milk, and less than half a percent
for skim milk. To stop reseparation of the fat
from the water, or creaming, the mixture undergoes the high-energy
pressurized process of homogenization. Before milk hits the shelves, it’s also
typically heat treated to reduce its level of microbes, a government-sanctioned process that raw milk enthusiasts argue
may reduce milk’s nutritional worth. Milk spoilage is started by microbes, which consume and break down
the nutrients in milk. That process causes butterfat
to clump together, leading to a visually unpleasant product. And the byproducts of
the microbes’ consumption are compounds that taste
and smell nasty. But there’s a bigger problem. Raw milk can carry microbes that are
the sources of deadly diseases, so in order to kill as many of those
microbes as possible, and keep milk fresh longer, we use a technique called pasteurization. One version of this process involves
exposing milk to about 30 seconds of high heat. Another version,
called ultra-high temperature processing, or ultra pasteurization, blasts the milk with considerably higher
temperatures over just a few seconds. UHT milk boasts a much longer shelf life, up to twelve months unrefrigerated, compared to pasteurized milk’s
two weeks in the fridge. That’s because the higher temperatures
of UHT processing inactivate far more microbes. Yet the higher processing temperatures may adversely affect the nutritional
and sensory properties of the milk. Ultimately, that choice lies
in the consumer’s taste and need for convenience. Fortunately, there are many
choices available in an industry that produces in excess
of 840 million tons of products each year.


  1. Ahmad Nasser

    August 1, 2018 at 7:05 pm

    If this video gets a view added, and it becomes "661,*666*", then I'LL BE DEAD.

  2. Emmy Blonde

    August 2, 2018 at 9:05 pm

    Milk that can sit out on the counter for a year?? WHAT

  3. Ella Smith

    August 5, 2018 at 4:38 pm

    what about the animal cruelty of the milk industry 🙁

  4. ceefe

    August 6, 2018 at 6:45 pm

    In other words, theres no good reason for adults to drink milk from other animals.

  5. issa princess

    August 16, 2018 at 10:31 pm

    i dont like milk.

  6. Charlemagne Evangelista

    August 19, 2018 at 12:02 am

    Why some people are lactose intolerant

  7. Ray Day

    August 21, 2018 at 2:39 pm


  8. Davineo

    August 21, 2018 at 10:19 pm

    I tought this was gonna be a vegan safe video.

    I was disappointed.

  9. Kian Siong

    August 22, 2018 at 2:45 am

    They didn't touch on the bad side of most diary farms 🙁

  10. Alveera Rahman

    August 23, 2018 at 5:48 pm

    Respect your mother 🙂

  11. A. J. R. Wilde

    August 25, 2018 at 11:26 pm

    why show a bottle of formula when talking about breastfeeding, idiots

  12. febriandri suharto

    August 28, 2018 at 1:12 pm

    I love uht milk and greenfield milk☺

  13. iActivateMC

    September 2, 2018 at 6:17 am

    I just got a 57-minute non-skippable ad…a like for surviving?! 😂😂😂

    It was supposed to go the other way 😅

  14. Suga Kookiez

    September 3, 2018 at 9:07 pm

    Alveoli? More like ravioli!

  15. Ionut

    September 23, 2018 at 10:28 am

    Milk causes the body to lose calcium since it's very concentrated the body can't process it very good, detects a lot of calcium being eaten, but cannot process it.
    Water may help, but no so much, green vegetables and other products like tomatoes, almonds are rich in calcium.

  16. Bakugou Katsuki

    September 30, 2018 at 12:02 am

    I just realozed that those sucker bottles were designed to be like nipples

  17. Annie Boom Fannie

    October 5, 2018 at 10:33 pm

    Cows milk is

  18. Arun Sooknarine

    October 13, 2018 at 1:01 am

    Omg he said "sheeps"😱

  19. El Hombre de oro

    October 17, 2018 at 3:00 am

    I love buffalo milk

  20. Hero Number Two

    October 31, 2018 at 1:04 pm

    You need sum milk

  21. erio milk

    November 10, 2018 at 4:19 am

    0:50 THEY'RE SO CUTE



  22. Rafael Marzall

    November 15, 2018 at 12:22 pm

    Horses are not ruminants. They are strictly herbivore non ruminant.

  23. Professor Slime

    November 21, 2018 at 2:28 am

    I hate milk

  24. Taczpat

    November 21, 2018 at 8:14 pm

    Jonathan J.

    Is this a jojo refrence?

  25. Ale GilMen

    November 22, 2018 at 3:31 am

    I thought this was going to go into more science, specifically around breastmilk and breastfeeding.

  26. Noah Aubrey Linus Sorensen

    December 1, 2018 at 1:36 am


  27. SpectreSeven1138

    December 1, 2018 at 10:00 am


  28. Lisa M

    December 8, 2018 at 10:53 am

    Why do humans drink so much milk?
    Drinks a sip of milk once a month

  29. LD

    December 22, 2018 at 11:57 am

    watches as is eating cereal

  30. Test1 test2

    December 22, 2018 at 10:38 pm

    Platypuses are so frickin’ weird!

  31. black wolf spirit

    December 25, 2018 at 11:35 pm

    …but horses aren't ruminants

  32. Kaj'Or Reinholdt

    December 31, 2018 at 5:33 pm

    Human males can also lactate. It's rare, but it happens.

  33. AxolotlMilk

    January 2, 2019 at 2:31 am

    Calcium should be called milk on the element table

  34. Moët 111

    January 5, 2019 at 4:26 pm

    I need some milk!

  35. Alice Deathbelle

    January 6, 2019 at 3:09 am

    I've always hated milk but I love cheese and yoghurt, I don't get it

  36. SuperPowerGames

    January 7, 2019 at 7:35 pm

    plant milk isn't milk just swallow this

  37. eliza bongiovi

    January 10, 2019 at 12:37 pm

    triggered vegans, homosexuals, feminists have left the chat

  38. talia maloof

    January 12, 2019 at 4:22 pm

    Baby bunnies nurse on their backs.

  39. Tran Khai

    January 13, 2019 at 1:29 pm

    It's so satisfying when you say "milk":))))

  40. via lactea

    January 14, 2019 at 3:17 am

    dont judge people who drink milk not everyone could grow up in 1st world countries with a big variety of food.

  41. Bung Scrung

    January 23, 2019 at 2:14 pm


    Tiddy joos.

  42. Felipe Emos

    January 24, 2019 at 9:30 am

    What about the amount of cruelty in this product? This is a blood product

  43. Катя Барковская

    January 27, 2019 at 6:16 pm

    Nowadays milk isn't the healthiest product, also meat and vegetables – they are all chemically/ hormonally treated. In substance these product are all healthy, but due to big rates of consumption such treatments are inevitable. Diet is a combination of all products in special proportions, if you are concerned about your diet you can go to a nutritionist and he'll make a right menu for you, and you can take a truthful advice from him, an educated in this sphere of knowledge person, not from the comment section on YouTube

  44. Tiny Dinosaur

    February 2, 2019 at 11:12 pm

    I only dribk Milk and Water and very rarley I will drink juice or soda. Thats how I am healthy.

  45. Lillian Swaim

    February 5, 2019 at 3:15 am

    Gods, how I love dairy, but why is eggs included in "dairy"?

  46. Cassy Studios

    February 7, 2019 at 11:41 pm

    Why m I watching this when I'm Lactose Intolerant??😑😐

    Still worth it

  47. B1tsNpieces

    February 15, 2019 at 12:10 pm


  48. swapertxking

    March 5, 2019 at 4:44 am

    Shame that a large majority of people will never experience the delicious taste and texture of a fine cheese or milk liquor.

  49. Jung Chang

    March 13, 2019 at 11:03 pm

    The science of milf

  50. Vanilla Flexagon

    March 15, 2019 at 9:59 pm

    Anyone 2019?

  51. Vanilla Flexagon

    March 15, 2019 at 9:59 pm

    Btw the animation is so adorable!

  52. The Almighty Loaf

    March 22, 2019 at 12:34 am

    So almonds are mammals?

  53. I’m watching u UwU

    March 22, 2019 at 2:01 am


  54. mMm Borgers

    March 23, 2019 at 7:02 am

    I wonder what a Cow feels when getting milked 🤔

  55. Odett Martinez

    March 24, 2019 at 4:28 am

    I want milk now

  56. Mint Diz

    March 24, 2019 at 8:17 am

    thirsty consumers

  57. חגי נוימן

    March 25, 2019 at 9:34 pm

    Yap, milk. Enjoy

  58. Virdian Sefrizal

    March 26, 2019 at 8:57 am


  59. dingaring

    March 30, 2019 at 5:02 pm

    Did anyone else see milkr

  60. Ellie McMurray

    April 8, 2019 at 11:06 pm

    Males can lactate? Learn something new every day…….

  61. Kevin Besa

    April 13, 2019 at 2:25 pm

    Watching this while drinking milk. Awesome

  62. Alive Zero

    April 16, 2019 at 6:58 am


  63. Daniel Bendl

    May 23, 2019 at 11:48 am

    I'm just curious…
    Why are we so persistant with trying to drink other mammals' milk, even though so many people even nowadays aren't able to digest it properly?

  64. Abbieq11

    May 26, 2019 at 3:01 am

    Why is that kid in the beginning drinking straight from the carton?

  65. Lindamorena

    May 26, 2019 at 5:43 am

    Sheeps is not a word its sheep. Dont @me

  66. Alexander Andersen

    June 7, 2019 at 9:52 pm

    I NEVER Really liked milk But…..

    I still dont

  67. igobivo

    June 12, 2019 at 2:37 pm

    Rare ted video i disliked 🙁

  68. Indiematic

    June 13, 2019 at 8:20 pm

    T I T T Y J U I C E

  69. DramaticDraggo

    June 14, 2019 at 2:14 am

    Milk is just filtered blood.

  70. Mandar Rane

    June 16, 2019 at 5:51 pm

    Can I use the parts of these videos to demonstrate & training purpose?

  71. Rabiah Pascall

    June 30, 2019 at 2:20 am


  72. Leema

    June 30, 2019 at 3:05 am

    Lactose intolerants left the chat

  73. Mendez Incorporation

    July 2, 2019 at 1:26 pm

    Unless your lactose intolerant

  74. Peroroncino

    July 4, 2019 at 7:21 am

    I thought Jonathan was an archaeologist

  75. Tricus pidbard

    July 6, 2019 at 1:14 am

    Where are my Oreos 🅱️

  76. Neelima Goturi

    July 8, 2019 at 7:06 pm

    I’m lactose intolerant why am I here??

  77. Andrew&Olga

    July 17, 2019 at 6:20 am

    So Gaylord Focker from Meet the parents wasn’t lying.

  78. Delta Squad

    July 24, 2019 at 3:03 am

    The science of YEET

  79. Dont touch my food

    July 24, 2019 at 10:14 pm

    You need some milk

  80. mafarmerga

    July 31, 2019 at 5:56 pm

    Milk is actually a type of sweat, originally produced not to feed young but as a way of distributing anti-microbial peptides over the surface of the animal.

  81. Sprout Does Stuff

    August 4, 2019 at 3:17 am

    I saw the thumbnail I was like educational tiddy 👀

  82. Corn Storm

    August 9, 2019 at 3:00 am

    The title is a seed for a jungle in minecraft.

    The science of milk -Jonathan J.

    I cut out a space so the . would fit.

  83. Russell from Up

    August 10, 2019 at 4:48 am

    Wait so first 6 months of life a baby doesn’t need food but just need milk? Interesting taking notes

  84. Rosalind Kincannon

    August 11, 2019 at 3:20 am

    Do brown cows give chocolate milk ?

  85. Mikal Madsen

    August 12, 2019 at 10:45 am

    I wanted to know more about the effects of human milk vs formula on babies' development. The bit about cells was interesting, but otherwise I feel like you wasted my time.

  86. Tinka Like AngelOK

    August 12, 2019 at 11:53 am

    I rather milk my oats 🤷🏼‍♀️


    August 13, 2019 at 1:30 pm

    I hate milk.

  88. BmnGameBoy

    August 14, 2019 at 3:55 pm

    Reindeer of the arctic circle🎶 sounds like a line in a song

  89. • Jen Dog •

    August 17, 2019 at 4:28 am

    “Why do humans drink so much milk”
    Me: I don’t

  90. mexicano soy

    August 17, 2019 at 6:32 pm


  91. Huitzilli

    August 18, 2019 at 4:11 am

    I don't Drink cows milk. 🐄 🍼 I'm not a cow. Lol

  92. Chad Patterson

    August 25, 2019 at 5:16 am

    I ❤️whole milk

  93. Dream Cardigan

    August 26, 2019 at 3:06 pm

    Male cats?!?

  94. Theodore Bugsby

    August 27, 2019 at 11:13 pm

    Then, if milk supposedly supplies most of the needed calcium the more one drinks milk more chances there are to get osteoporosis?

  95. aidan harrison

    August 28, 2019 at 2:56 am

    From sheeps ?

  96. aidan harrison

    August 28, 2019 at 2:59 am

    The fats in milk are not " added "

  97. True Sagittarius

    September 3, 2019 at 4:35 am

    Not gonna lie, I thought the video would be talking about the tits, disappointed.

  98. Josue Alejandro

    September 16, 2019 at 9:20 pm

    This is not cience, this its the market of milk…

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