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I was watching Iron Chef America, and one of the contestants used liquid nitrogen to prepare part of their meal; how does liquid nitrogen work, and is it safe for consumption?
Question Date: 2010-06-04
Answer 1:

Liquid nitrogen is a very cold liquid. Its boiling point is 77K, which is -196 C or -321 F. So, when you see it in its liquid form, it is at that temperature. It works by bringing things that it touches down to that temperature, as it consumes heat in order to boil. For an analogy: Imagine if the world was normally really hot (150 C, or 302 F), and you had water sitting around. It boils at 100 C, or 212 F, so it would pull heat away from its surroundings in order to boil - A pot in the stove is like this "hot world".

When you cook with liquid nitrogen, it freezes any water that is in the food ingredients. Typically, the nitrogen boils away and you don't end up eating any. Since the atmosphere is 70% nitrogen, we don't really notice it around us as a gas either. If you were to consume liquid nitrogen (as a liquid), it would cause severe injury or death. It would cause freezing of the tissue around your mouth or esophagus, which would be severely painful and dangerous - therefore I do not recommend eating liquid nitrogen! Great care must be taken when cooking with liquid nitrogen to make sure that things don't get too cold, as you can cause internal or external frostbite. In the lab, we always handle liquid nitrogen with safety glasses, gloves, and long sleeves/pants and closed-toe shoes, since we do not want topical frostbite or blindness.

In conclusion, direct consumption of liquid nitrogen is not safe. Consumption of foods prepared with liquid nitrogen are safe, if it is not too cold.

Hope that is what you are looking for!

Answer 2:

At room temperature nitrogen is a gas. In fact, about 78% of the air we breathe is nitrogen gas. However, at very low temperatures nitrogen undergoes a phase change from gas to liquid. This happens at 77 Kelvin, which is about -321 degree Fahrenheit! This is so cold that is will freeze just about anything instantly. This makes liquid nitrogen great for making ice cream, but it also means that you should always be very careful when handling liquid nitrogen because it can give you frostbite if a large amount of it comes in contact with your skin. Liquid nitrogen is safe to use in food because it immediately boils and just goes into the air as harmless nitrogen gas, but you have to be very careful with it while it is still in liquid form.

Answer 3:

Liquid nitrogen is just N2, the same molecule that constitutes about 3/4of our atmosphere, but in liquid form. The only difference is it's much colder. It's temperature is 77 degrees Kelvin, or 77 degrees above absolute zero. To put that in perspective, room temperature (around 70 or75 degrees F) is about 295 degrees Kelvin.

Another comparison to make is to water. Water freezes at 273 degrees Kelvin (32 degrees F) and boils at 383 degrees Kelvin (212 degrees F). Although liquid nitrogen is very cold, it is actually boiling! When it boils it just becomes gaseous N2 and is entirely safe to inhale. The only danger is the low temperature can burn people if freezes their skin cells.

Answer 4:

Nitrogen comes from the air. About 79% of the air we breathe in and out is nitrogen. Although the important part of the air for us is oxygen, the nitrogen doesn't do anything because it's inert, so it just goes in and out of our lungs.

Liquid nitrogen is just nitrogen from the air. The air is cooled down enough so that it turns into liquid, then the nitrogen can be separated from the other parts of the air. The boiling point of nitrogen is -320 Fahrenheit Degrees, so when it's a liquid, it's at or below this temperature. You definitely shouldn't consume liquid nitrogen, because it's so cold that it could damage your body. But if it's just used in preparation of the food, the food should be safe to eat, as long as the food has been given time to reach normal temperatures again. Whatever liquid nitrogen remaining with the food, it will have evaporated by then.

Answer 5:

Nitrogen has a boiling temperature of 77 Kelvin, or -196 Celsius. Causing liquid nitrogen to boil into gas takes energy, and that means that it will cool off whatever it is in contact with until it is at the boiling temperature or the liquid entirely evaporates into gas. This means that anything containing water (including most food) will be very, very frozen.Liquid nitrogen is dangerous only because it is cold. Once it evaporates and becomes nitrogen gas, it's just like any other nitrogen in the atmosphere, and roughly 80% of the atmosphere is nitrogen gas. Used in a closed space, this can still be dangerous because it can lower the concentration of oxygen. However, with proper ventilation (or outside), nitrogen gas is harmless, and liquid nitrogen becomes gas very quickly.

Answer 6:

There is nothing especially magical about liquid N2. At 1 bar pressure or the typical pressure at the Earth's surface near sea level, Nitrogen is a diatomic molecule N2. It boils at one bar at 77 K..... Thats 77 Kelvin or 77 degrees above absolute zero.

The conversion from K to centigrade is to subtract 273. So deg C= deg K -273. Hence diatomic nitrogen boils (or liquefies from a gas, its the same thing!) at a chilly -196 deg C. the temp rite now in SB is about 20 deg C!!!

Recall that about 80% of the AIR we breathe is diatomic nitrogen! Its quite inert chemically at least at earth surface temperatures; it does not react too readily in the gas state. When oxidized we can get nitrates and nitrites. Nitrate is an important food for plants.

So, while nitrogen is safe as far as toxic effect, liquid N2 is VERY COLD and if you handle it improperly it can 'burn' you.

At any rate the main use of liquid N2 in cooking is to chill something very fast!

Here is what some top chefs do

Answer 7:

Thank you so much for your question.

Nitrogen gas composes about 77% of the air that we breathe - liquid nitrogen is just the nitrogen taken from the air under pressure to put it in its liquid state. The boiling point of nitrogen is -186 degrees Celsius, meaning that it is very, very cold as a liquid and is boiling at room temperature. Any steam that you see is a result of the condensation of water from the air. Using it in cooking is becoming more common to rapidly cool/freeze items - one of my favorites is using liquid nitrogen to make ice cream, and I know there is a shop in the Denver, CO area known for making their ice cream to order using liquid N2. So in the aspect of using the element nitrogen for cooking - it is safe for consumption as it just boils away and makes the food very cold.

However, there are always some safety concerns. Due to the risk of frostbite you should wear appropriate gloves for handling liquid nitrogen, never stick your hands into the liquid, and be careful of eating and handling solid foods that have just become frozen with it. Also, the Dewar (like a thermos for containing liquid nitrogen) should be clean - so as not to transfer any dust/dirt to the food.

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