- Oh, hello.
I'm glad you could meet me here today
in my large, empty warehouse
with my cheese.
(upbeat, playful music)
Cheese is milk that's been spoiled on purpose
to prevent it from spoiling accidentally.
This preserves milk's lifespan,
allows for the existence of all of my favorite foods,
and means that cheese contains some
pretty weird stuff.
Here are five examples.
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Okay, if you're going to make milk into cheese,
the first thing you need to do is remove the liquids
called the whey, leaving the solids, called the curds.
You may know this process by the name curdling.
Yeah, the same thing that makes a forgotten
quart of milk go all lumpy in your fridge
is the first step in cheese making.
And most cheeses use the same type
of curdling agent at work in your fridge.
Bacteria.
A few types of bacteria eat lactose,
the sugar that occurs naturally in milk,
and excrete lactic acid.
As they do so,
the acidity level of the milk increases,
which changes the charge of some of milk's molecules,
which in turn allows some of the solids
that were previously repellent to begin to coagulate.
But don't worry, these bacteria aren't dangerous.
They actually help fight off hazardous germs,
and they're excrement as flavor.
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Many cheeses receive a second coagulation agent.
Rennet.
Natural rennet comes from the fourth
stomach lining of young cows, goats, and sheep.
There it helps the animal digest its mother's milk
by separating out the whey from the curds.
Traditionally it's added to cheese by soaking
pieces of dried stomach in water,
then straining and adding that water to the curdling milk.
But hey, animals aren't killed just to make rennet.
It's a by-product of the meat industry,
and most rennet these days comes from
bacteria that either naturally produce similar enzymes
or have been genetically modified to do so.
Some plants, like fig leaves and thistle,
make rennet-like enzymes, too.
By the way, if you're curious about about all
the coagulation chemistry that I keep
kind of glossing over,
or even if you have a question about another edible,
let me know in the comments.
I did way too much research for this episode
and I love talking about food
and eating food.
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Milk isn't yellow,
so cheese that's yellow or orange
contains some kind of coloring.
Naturally that's beta-carotene.
You know, the stuff that makes carrots orange.
It also occurs in grass.
When cows eat lots of fresh grass,
the beta-carotene winds up in their milk's fat molecules.
There the color is concealed within protein structures,
but during the cheese making process,
the beta-carotene is released,
making the cheese yellow.
If it's aged a long time,
that color can deepen to a natural orange.
But the practice of dying cheese
is artificially originated in 17th century lies.
Yes, some cheese makers began cheating
their customers by skimming cream
off of their cow's milk,
but the resulting cheese was less deliciously fatty
and much less yellow since the fatty parts
contain the beta-carotene.
They tricked customers into buying this
cheaper cheese by adding food coloring.
Today dyes help large manufacturers
keep their product consistent,
especially if they sometimes feed their cows
grains and dried grasses,
which contain less beta-carotene than fresh grass.
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Molds in the penicillium genus love to eat cheese
as much as we do.
Normally you'd want to remove any fungus
growing on your cheese,
but two particular species,
p. roqueforti and p. glaucum
are encouraged in blue cheeses.
As a by-product of existing,
they give those cheeses their characteristic textures
and flavors by accelerating the breakdown
of proteins and fats in the curd,
making the cheese creamier and giving it that tangy flavor.
But mold isn't only for blue cheeses.
Other species of penicillium,
specifically subspecies of p. camemberti
are sprayed on the outside of soft,
ripened cheeses like brie as they age.
These molds also break down proteins in the curds,
but in this case the result is that
white semi-firm rind around the runny curd within.
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You may have noticed that your favorite
bright orange, shelf stable nacho ingredients
declares itself pasteurized, processed cheese food
or spread or product.
This is science cheese configured in laboratories
to melt better, cost less, stay fresh longer,
and be perfectly consistent from batch to batch.
Here in the U.S. the FDA only requires these
products to consist of 51% cheese by final weight.
The other 49% can be lots of stuff,
including but not limited to,
emulsifiers to keep the product smooth when heated,
acidifying agents to speed up production,
mold inhibitors which are pretty self-explanatory,
moisture-binding gums or hydrocolloids
to make the product more spreadable,
and sweeteners and other flavor enhancers.
Of course, these are not the only weird ingredients
that have ever been put into cheese.
Like, ah, worms, anyone?
You can hear that story in this video
right here.
And if you want to learn lots more about
everything from cheese to chili peppers,
check out howstuffworks.com.
(piano music)