When you boil potatoes on the stove top, it can take half an hour to cook them till tender.
如果使用灶台上烹煮土豆，要半小时才能煮软。
But, when you boil them in a pressure cooker, instead presto,they're ready in about five minutes.
但高压锅只需短短5分钟就可以做好。
What's the difference?
两者有何区别呢？
What makes pressure cookers cook so quickly?
为何高压锅烹饪如此迅速？
Let's start with the potatoes boiling on the stove top.
首先让我们从炉子上的土豆烹饪说起。
The temperature of the boiling water won't go above 212 degrees Fahrenheit, no matter how high you turn up the burner or how long you leave the pot on the stove.
无论你将煤气灶调至多大，抑或是烹饪时间多长，水的沸点都不会超过华氏212度。
That's because, at normal air pressure, water boils at 212 degrees and escapes as steam.
这是由于在标准大气压下，水一达到华氏212度就会沸腾形成水蒸气挥发掉。
In a pressure cooker, on the other hand, the steam can't make such an easy get away.
而在高压锅内，水蒸气并不会如此容易挥发出去。
These a led lid keeps the steam inside, raising the pressure inside the cooker to about twice normal air pressure.
密封盖将水蒸气封存在锅里，致使锅内压强升至标准大气压的两倍。
Now here's the secret of speedy pressure cooking.
这就是高压锅烹饪快速的秘诀。
As pressure rises, so does the boiling point of water.
随着锅内压强上升，水的沸点也逐渐升高。
At the higher pressure inside the cooker, the boiling point of water goes up to about 252 degrees.
锅内压维持在较高水平，水的沸点会上升至华氏252度左右。
So, food cooks at a much higher temperature in a pressure cooker, and that`s why it cooks more quickly.
因此，在高压锅中烹饪食物的温度更高，烹饪时间明显缩短。
Pressure cookers control cooking temperature by maintaining a certain pressure.
高压锅通过维持一定的压力来调节烹饪温度。
A vent on the lid releases steam when the right pressure, and therefore the right cooking temperature is reached.
而借由密封盖上的排气孔释放水蒸气达到合适的压力，烹饪温度也能达到理想值。
And to prevent disasters like boiled potatoes exploding onto the ceiling, modern pressure cookers also have a safety valve to release steam, just in case the vent gets stuck.
为了避免发生诸如煮熟的土豆炸飞到天花板的意外情况，现代高压锅还设计了安全阀门释放水蒸气，以防排气孔堵塞。
