Name: The Chemistry of Fried Food
Uploaded: 2017-09-18T14:49:15.000Z
Duration: 4 min 50 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Whether it’s doughnuts, french fries, chicken,
or Oreos – fried food is everywhere.

I mean, isn’t that why we all go to fairs?

Besides making our tastebuds happy, deep-fried foods also involve some really cool chemistry

– from the cooking process itself, to the
kind of oil and batter you’re using.

When you submerge a piece of food in really
hot oil, a bunch of chemical reactions start

happening, cooking your food and giving it a crisp outer layer.

Typically, you’ll want the temperature of
the oil to be around 180 degrees Celsius,

You’ll know the oil is hot enough when you drop some food in and it starts bubbling.

Now, some people might think that’s the
oil boiling, but it’s not.

It’s actually moisture boiling off the surface of the food, since the oil’s temperature

is nearly twice the boiling point of water.

As the water leaves the food, two things are happening:

First, the food’s surface dehydrates and
a crispy crust begins to form!

But also, the escaping water molecules leave
gaps that let oil molecules enter the food,

which is what researchers call the oil uptake.

In fact, some studies have shown that the
amount of oil uptake is directly proportional

More oil increases the food’s fat content,
and therefore its energy content, also known

And if too much oil gets absorbed, you might
be left with a greasy mess of a meal.

But you don’t want to take your food out
of the oil too soon, either.

Otherwise, the outside won’t be hot enough,
for long enough, to cook it all the way through.

That’s because cooking is all about heat
transfer!

When food is in a deep fryer, the outside
layer of molecules is heated up thanks to

convection, from the currents of hot oil flowing around.

Then, all of those food molecules start bumping into each other and transferring heat energy.

So, the inside is heated because of conduction.

So those are the basics of deep frying food, but there’s a lot more that goes into making

Like, what happens when you add batter or a breading to the outside of your soon-to-be-fried

Well, batter is basically an extra layer between the food and the hot oil, so the batter is

All that heat transfer is still happening.

Only this way, the food at the center holds
onto more moisture and doesn’t get too dry.

As fish and chips, fried chicken, and tempura lovers will know, a little batter can also

let you add more flavor to the food and give it a crunchy, textured crust.

You can even add beer to your batter to make the crust softer and crispier!

That’s because the carbon dioxide in the
beer forms bubbles that fluff up the batter,

and foaming agents, which are certain proteins found in beer, keep those bubbles from bursting

Plus, the ethanol in beer evaporates faster
than water, because alcohol molecules aren’t

as strongly attracted to each other as water molecules are.

This means the batter will dry out faster,
so the food doesn’t have to be in the fryer

But one study did show that beer batters do have more oil uptake than water-based rice

or wheat batters – so calorie-counters be
warned!

You might also have heard that some oils are better to use than others when frying food.

Different oils are made up of different kinds of fat molecules, or lipids, and have different

They can also affect the flavor of your food, because they break down differently.

See, every oil has something called a smoke point – a temperature where it starts to

create smoke, which can give the food a bad taste.

Basically, the heat causes the lipids in the
oil to break down and produce some volatile

compounds, which are chemicals that can easily become gases.

Some of these leave the oil and enter the
nearby atmosphere as smoke, but others can

Corn oil, for example, is made up of lipids with lots of double bonds, also known as polyunsaturated fats.

And it tends to break down more easily, at
lower temperatures.

That’s because polyunsaturated fats have
some weak carbon-hydrogen bonds, which break

and set off a chain of chemical reactions
that eventually produce volatile compounds.

So, when you’re deep-frying something, you’ll probably want to look for an oil that has

Deep-frying food is a lot more scientific
than you’d expect.

You have to apply all kinds of knowledge about heat transfer and fat content, so that your

So, treat this as some food for thought the next time you’re eating some delicious,

Thanks for watching this episode of SciShow!

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