How Does Butter Get Its Texture, Flavor, and Color?

Turning cream into a stick of butter involves some complex chemistry, crystallization, and (traditionally) fermentation. Learn more -- plus the difference between sweet cream, cultured, and European butters -- in today's episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to BrainStuff, a production of iHeartRadio. Hey BrainStuff, Lauren
Vogelbaum here. Butter has been a source of nutrition, pleasure, disagreement,
and fascination for millennia. It was probably invented by accident
in many Neolithic or late Stone Age societies that were

(00:22):
starting to herd and domesticate grazing mammals like goats, sheep, camels,
and cattle around 7,000 BCE. We know that people were
making butter on purpose by at least 2500 BCE because
of Sumerian tablets that recorded info about the technology and
ritual use of butter. It's been used in religious and

(00:44):
spiritual practices from around Africa to India to Northern Europe
and beyond, and was reviled by some olive oil-steep cultures
around the Mediterranean. We've gotta admit that butter is a
little magical, scientifically speaking. Today, let's talk about the science
of butter. Butter is a concentration of the fatty and

(01:07):
fat-soluble parts of milk, or cream, really. In its solid form,
it's actually a crystallization of those fats. Forget gemstones, I'd
like to submit butter as the most beautiful type of crystal.
But in explaining butter, let's start with milk and cream.
Milk is mostly water, but about 5-12% of it is

(01:29):
little globules of fats suspended throughout that water in an emulsion.
An emulsion is a mixture of two things that don't
like to be mixed together, and more on how milk
accomplishes that in a second. A cream is a greater
concentration of those fat globules emulsified in water, about 15-25%. Butter, meanwhile,

(01:51):
has had almost all of that water taken out. It's
about 80-90% fats. Of course, there are also water-soluble and
fat-soluble things mixed in with the water and fats here,
proteins and sugars and minerals, but today we're mostly concerned
with the fat. And now, just filtering the water out
of cream won't get you butter. You have to agitate it.

(02:15):
By agitate, I don't mean you're sending it links to
inflammatory opinion pieces. You're physically shaking it up. This is
necessary because in order to get the fats in there
to clump together, you've got to invert the emulsion of cream. Okay,
cream is, again, an emulsion, an even mixture of fats

(02:35):
and water, which do not usually like to mix, because
cream also contains these protein chains called caseins that are
made up of both hydrophilic, or water-loving, and lipophilic, or fat-loving, particles.
When presented with both water and fats, caseins will grab
bits of fat and cluster up into globules called micelles,

(02:58):
with the fat safely stored on the inside and the
water-loving bits on the outside. These water-loving particles grab onto
electrons in the water, meaning that each micelle winds up
having a negative charge. And since negatively charged particles repel
each other, the globules suspend themselves throughout the water in
order to keep their distance. Thus, an emulsion is created.

(03:23):
And to make butter, you have to invert that emulsion.
The way you do that is you agitate it so
that the micelles slam into each other, physically breaking up
the bonds that hold them together. The fats that used
to be cuddled safe inside the micelles are freaking out.
Water is everywhere. Thrashing out for safety, they'll cling first

(03:44):
to air bubbles in the mixture. And this is how
you get whipped cream. But if you keep shaking the
mixture up, breaking apart more micelles, eventually you expose enough
fats that they can clump together and push the water out. Begone,
foul beast. This is inverting the emulsion. It's also called
the churning process. When you're done, you're left with clumps

(04:08):
of butterfat surrounded by buttermilk. That is, that water and
water-soluble milk stuff. you then work or knead the clumps
together to press out more liquid. So that's your concentrated
butter fat, but remember how I mentioned that butter is crystallized? Okay,
the physics of this part get a little complicated, and

(04:29):
I was an English major, but here's how I understand it. Basically,
the wee particles of fats that start out wrapped up
cozy inside their micelles can be either liquid or crystalline
in structure, depending on their temperature. There's a wide range
of freezing transformation points for fats, but again, basically, butter

(04:50):
fats start crystallizing at around 50 degrees Fahrenheit, or 10 Celsius. So,
in cream that has been cooled before churning, you've got
a mixture of both liquid and crystal fat particles. Those
microstructures interact with each other, especially as the butter is
churned and worked, and the liquids will stick to the crystals.

(05:11):
To get the consistency of your final butter just right,
neither melty and greasy nor stiff and flaky, you want
to get your mix of liquid and crystal fats just right.
The exact way that you cool the cream is important,
and the way that you cool the butter after churning
is important. Before the advent of machinery and gauges to

(05:32):
achieve these factors precisely, butter probably did feel a lot
like magic. There's actually been a bunch of super in-depth
physics research into exactly how these butter microstructures work, which
is fabulous. But okay, that is the basic process for
making butter. Churning, working, and simultaneous cooling all the while.

(05:54):
But there are a bunch of different types of butter available.
On grocery shelves in the U.S., you can usually find
varieties including sweet cream, salted or unsalted, cultured, and European.
Sweet cream unsalted butter is the type that a lot
of American cooks and bakers will reach for when they're
looking for a light, slightly sweet buttery flavor, and if

(06:15):
they prefer to add their own salt to recipes to taste.
But this is a newfangled invention, born of the industrial
age of pasteurization, refrigeration, and the speedy mechanical separation of
cream from milk. Prior to the 1880s, all butter would
have been either salted or cultured or both. Butter is

(06:37):
traditionally a cultured, that is, fermented, product. Like other common foods,
like yogurt, cheese, sourdough bread, and pickles, some of butter's
characteristics originally came from fermentation with friendly lactic acid bacteria.
This category of bacteria eat some of the sugars in

(06:57):
milk and excrete acids. Those acids help out in a
few ways. At first, they can make the milk or
cream an unwelcome environment for unfriendly microbes that might make
you sick. Also, the acids help break up the globules
in the cream, making churning easier, and give a slight
tangy flavor to the finished butter. Lactic acid bacteria live

(07:22):
all around us, so prior to pasteurization and refrigeration, they
would have naturally gone to work on milk and cream
before it was made into butter. These days, cultured butter
is usually made from cream that's been pasteurized to peel
off any potentially harmful microbes, and then specific strains of
lactic acid bacteria are added on purpose to culture it.

(07:43):
Sweet cream butter is made without culturing. Most of what
we consider butter flavor actually comes from lactic acid bacteria.
They also excrete diacetyl, which is the compound that tastes buttery.
Diacetyl is sometimes added to sweet cream butter to make
it taste like butter. This compound is also at work

(08:04):
in other products of fermentation. It's what makes some chardonnays
taste buttery, for example. Salt was traditionally not as much
a flavoring as another way to preserve butter before refrigeration.
Just like us, the microbes that spoil food need water
to live, so salt can really muck them around. But

(08:25):
because most butter today is made from pasteurized cream, salt
is added as an optional flavoring. These days, butter may
also be colored during manufacturing. The yellow of butter comes
from fresh grass in cows' diets. And I know, grass
is green, not yellow, but it contains beta-carotene, you know,

(08:46):
that useful compound that our bodies convert to vitamin A
and that gives a lot of orangey plants like pumpkins
and carrots their rich color. It's locked up in grass
so you can't see it, but it does get transferred
to cow's milk. And I know cow's milk is white,
but beta-carotene is a fat-soluble compound. In milk, it's locked

(09:09):
up in the fat molecules, which are themselves locked up
in micelles. Or rather, they are, until you start messing
with those micelles during the churning process. So milk from
cows fed on more fresh grass, which is only available
in the summer, is will create yellower butter. This is
also what makes some cheeses yellow or orange in color.

(09:31):
When cows are given less fresh grass, maybe because they
aren't allowed to pasture graze, or maybe because it's winter,
that butter will be whiter. So, for consistency or preference,
or to fib about their quality in feeding practices, some
brands color their butter. The same thing happens with some cheeses, too. Okay.

(09:54):
But what about European butter? Folks outside of Europe might
have seen fancy-looking and often fancy-priced packages of foil-wrapped butter
in your grocery store or on your favorite cooking show
and wondered what the hubbub is about. Different governments regulate
foods differently, which is perhaps obvious, but those details can
and do impact a finished product. The European Union's rules

(10:18):
for butter include that it must contain at least 82% butterfat. U.S.
regulations require only 80% butterfat. It sounds small, but it
can absolutely make a difference in a dish. European butters,
and particularly ones that get exported and sold in specialty stores,
are also more likely to be cultured and tangy, and

(10:39):
to have more noticeable grassy or pasture flavors. Of course,
producers outside of Europe, like in the States, can make
higher-fat and more flavorful butters, too. Check your labels if
you're looking for something special for a particular use. If
you want to, you can even make your own butter
at home. You don't even need a churn. You can

(10:59):
just shake a cup of heavy cream in a quart-sized
mason jar for about 15 minutes, or until the butter
forms up. Then rinse it with cold water a couple
of times and knead it until the pockets of air
and water work themselves out. Some parents report that this
is a good way to get a kid involved in
the kitchen. This is also a micro-scale version of the

(11:20):
traditional industrial process, which goes something like this. First, cream
is separated out from whole milk and pasteurized, then cooled.
Then it is time for churning. Churns these days are
huge aluminum drums spun on the horizontal axis by motors,
like a clothes dryer. A clothes dryer that fits thousands

(11:42):
of gallons of stuff inside. the cream is piped in
and you start spinning the churn. There's often a porthole
on one end of the cylinder, so you can keep
an eye on things. Within an hour, the fats come
together and the liquids separate out. You then drain off
the buttermilk and sometimes rinse the butter with cold water.
After that, you start the butterfat spinning again to work

(12:04):
it further and to mix in any flavorings or colorings.
The butter clumps together into a huge mass, which you
then pull or spin out of the drum and weigh
out into batches, and mold and package for industry and
consumer use. Industrial producers may be handling between 1,500 to
5,000 pounds of butter per batch, which is about 700

(12:28):
to 2,300 kilos, which is a lot. By the way,
going back to buttermilk. Although any liquid that comes off
of butter during the butter-making process is technically buttermilk, the
term refers specifically to soured, that is, cultured butter liquids.
And because most American butter is not cultured, generally, the

(12:50):
buttermilk that's sold in the U.S. is not a byproduct
of the butter-making process. It's just milk that's been soured
by adding lactic acid and maybe a thickener to change
the consistency. And finally, if you came here wondering about
the nutritional science of butter... Nutrition is always complicated, and

(13:10):
the story of how our bodies process different fats, and
why there's so much confusion about that, is nuanced enough
that it deserves its own episode. And that's on my list.
But very basically, butter is a calorie-dense food. It's just
fine to eat unless a healthcare professional has told you otherwise.
Just don't overdo it. Today's episode was written by me,

(13:37):
Lauren Vogelbaum. BrainStuff is a production of iHeart Podcasts in
partnership with HowStuffWorks.com and is produced by Tyler Klang. For
more shows from iHeart Podcasts, visit the iHeart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.