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你最爱的油炸食品的科学 – 译学馆
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你最爱的油炸食品的科学

The Chemistry of Fried Food

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.
而且非常好吃
And it’s delicious.
是不是因为这个原因我们才去集市呢?
I mean, isn’t that why we all go to fairs?
除了能够满足我们的味蕾 酥炸的食物里面根据你所用的油和面糊
Besides making our tastebuds happy, deep-fried foods also involve some really cool chemistry
也会含有一些非常酷的化学物质-这些是从烹饪过程中产生的
– from the cooking process itself, to the kind of oil and batter you’re using.
当你把食物放进热油锅中 一连串的化学反应就开始了
When you submerge a piece of food in really hot oil, a bunch of chemical reactions start
你的食物也有了酥脆的外皮
happening, cooking your food and giving it a crisp outer layer.
通常 你会想把油温控制在180度左右
Typically, you’ll want the temperature of the oil to be around 180 degrees Celsius,
但是油温也视菜品而定
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.
实际上是食物表面的水分挥发走了 因为此时油温差不多是
It’s actually moisture boiling off the surface of the food, since the oil’s temperature
水的沸点的2倍
is nearly twice the boiling point of water.
随着食物水分流失 两件事正在发生
As the water leaves the food, two things are happening:
首先是食物表面脱水 酥脆外表开始形成
First, the food’s surface dehydrates and a crispy crust begins to form!
同时水分子的流失让油分子趁机进入食物填补空隙
But also, the escaping water molecules leave gaps that let oil molecules enter the food,
这个现象研究人员称之为油量吸收
which is what researchers call the oil uptake.
事实上 有些研究表面油量的吸收和水分的流失
In fact, some studies have shown that the amount of oil uptake is directly proportional
是直接成正比的
to the amount of water that’s lost.
油量增多会导致食物脂肪含量的增加 同时能量值(卡路里)
More oil increases the food’s fat content, and therefore its energy content, also known
也会增加
as the calories.
如果吸收过多的油 你吃的这一顿可能比较油腻
And if too much oil gets absorbed, you might be left with a greasy mess of a meal.
但是你也不想让食物里的油流失太快
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.
其原理在于烹饪就是热传递
That’s because cooking is all about heat transfer!
当食物在油炸过程中 因为热油产生的气流四处流动
When food is in a deep fryer, the outside layer of molecules is heated up thanks to
产生对流 从而加热了分子外部
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.
食物内部因为热传导受热
So, the inside is heated because of conduction.
所以这是炸东西的基本步骤 但是要做成一个美味的玉米热狗
So those are the basics of deep frying food, but there’s a lot more that goes into making
还有很多步
a tasty corn dog.
就好比 如果你把面团油炸或者是包裹了面包屑的面团油炸
Like, what happens when you add batter or a breading to the outside of your soon-to-be-fried
会发生什么
food?
那么面团主要是 在食物和热油之间所附加的一层
Well, batter is basically an extra layer between the food and the hot oil, so the batter is
所以面团脱水最厉害
mostly what’s getting dehydrated.
此时热传递仍然在进行
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!
因为啤酒中由二氧化碳形成的气泡 使整个面团变得松软
That’s because the carbon dioxide in the beer forms bubbles that fluff up the batter,
同时啤酒中的某种蛋白质–起泡剂 使那些气泡产生的速度
and foaming agents, which are certain proteins found in beer, keep those bubbles from bursting
比平常要快
as fast as they normally would.
同时啤酒中的酒精挥发得比水要快 那是因为乙醇分子
Plus, the ethanol in beer evaporates faster than water, because alcohol molecules aren’t
彼此的吸引力没有水分子那么强
as strongly attracted to each other as water molecules are.
这意味着面团会更快变干 所以要生成酥脆的外皮
This means the batter will dry out faster, so the food doesn’t have to be in the fryer
不用炸很久
as long to get a crispy crust.
但是一项研究表明 啤酒油炸面团比水稻或者小麦炸面团更吸油
But one study did show that beer batters do have more oil uptake than water-based rice
所以你吃这个 卡路里计数器就会“报警”
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.
不同的油由不同种类的脂肪分子或者脂类组成
Different oils are made up of different kinds of fat molecules, or lipids, and have different
而且有不同的营养价值
nutritional benefits.
他们同时可以影响食物的口感 因为他们会不同形式地分解
They can also affect the flavor of your food, because they break down differently.
看吧 每种油都有发烟点-达到这个温度它就开始产生烟
See, every oil has something called a smoke point – a temperature where it starts to
这样烹饪出来的食物口感不好
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
这些化学物质很容易就转化为气体
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
影响它的口感
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.
同时它能在较低的温度下分解
And it tends to break down more easily, at lower temperatures.
因为多元不饱和脂肪酸中的碳氢键不够牢固
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.
所以当你在油炸食物时 你要寻找一种有高发烟点
So, when you’re deep-frying something, you’ll probably want to look for an oil that has
的油
a high smoke point.
大多数的植物油都符合~~
And most vegetable oils fit that bill!
油炸食品比你预想的更加科学严谨
Deep-frying food is a lot more scientific than you’d expect.
你一定要把所有那些热传递和脂肪含量的知识都运用进去
You have to apply all kinds of knowledge about heat transfer and fat content, so that your
这样你的食物才能吃喔
food is actually edible.
把这期视频当作一次精神食粮 下一次你会吃到美味的
So, treat this as some food for thought the next time you’re eating some delicious,
热热的薯条
hot french fries.
感谢观看这期的科学秀
Thanks for watching this episode of SciShow!
感恩节快要到来 还有其他的节日也接踵而至
So Thanksgiving is coming up, along with a bunch of other holidays.
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And we’ve got just the thing!
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If you want to look really snazzy in the kitchen, or for any messy task, head over to dftba.com/scishow
去看看一些棒棒哒科学秀主题的新围裙
to check out these awesome new SciShow aprons.
像往常一样 去youtube.com/scishow
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