无论是甜甜圈 薯条 炸鸡 或者炸奥利奥 油炸食品到处都是
Whether it’s doughnuts, french fries, chicken, or Oreos – fried food is everywhere.
And it’s delicious.
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,
but that varies depending on the recipe.
当你把东西放到油锅里 油锅开始冒泡泡 你就知道油足够热了
You’ll know the oil is hot enough when you drop some food in and it starts bubbling.
现在 有些人可能会认为那是油沸腾了 然而并非如此
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
to the amount of water that’s lost.
More oil increases the food’s fat content, and therefore its energy content, also known
as the calories.
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.
如果油流失太快 它外表温度不够 无法在油锅里长时间油炸
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.
然后 所有的食物中的分子开始相互碰撞 转换成热能
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
a tasty corn dog.
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
mostly what’s getting dehydrated.
All that heat transfer is still happening.
只有这样做 在处在中间的食物才能锁住更多水分 不会太干
Only this way, the food at the center holds onto more moisture and doesn’t get too dry.
作为炸鱼和薯条 炸鸡 和天妇罗的爱好者会知道
As fish and chips, fried chicken, and tempura lovers will know, a little batter can also
一点点的面团会让你增加食物的口感 让食物表皮变的脆脆的 有质感
let you add more flavor to the food and give it a crunchy, textured crust.
你甚至可以在你的面团里加些啤酒 让表皮变的更加柔软 更脆
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
as fast as they normally would.
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
as long to get a crispy crust.
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!
你可能也听说过 用有些油来炸东西 比其他的油要好些
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.
通常来说 油中的油脂受热分解 产生一些挥发性的化合物
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.
他们中的一些离开了油 进入到附近空气中变成烟 但是其他会进入到食物中
Some of these leave the oil and enter the nearby atmosphere as smoke, but others can
enter the food and change its flavor.
举个例子吧 玉米油是由油脂（多元不饱和脂肪酸）组成 油脂中含有大量双键
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
此键断裂后 会发生一连串的化学反应 最后产生挥发性化合物
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
a high smoke point.
And most vegetable oils fit that bill!
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
food is actually edible.
So, treat this as some food for thought the next time you’re eating some delicious,
hot french fries.
Thanks for watching this episode of SciShow!
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无论是甜甜圈 薯条 炸鸡 或者炸奥利奥 油炸食品到处都是