Liquid Nitrogen, the Leidenfrost Effect, and Food?

Liquid nitrogen is extremely cold and allows the long term storage of cells when they are not being grown or used in an experiment. Liquid nitrogen seems very dangerous and should be treated with caution, but can be used safely in and outside of the lab. Wait, did I just say outside of the lab? You read correctly, some people use liquid nitrogen to do cool tricks - do not try these at home, but you can watch some examples below.

Someone even did the ALS Ice Bucket Challenge with liquid nitrogen instead, which had to have been so incredibly cold.

Others use liquid nitrogen for molecular gastronomy, which is essentially using principles of chemistry and physics to make interesting food and drinks. A very common dish is ice cream that is flash frozen by liquid nitrogen. Once the ingredients are mixed, liquid nitrogen is applied and the ice cream is ready in under a minute.

Liquid nitrogen has even made it to the bar, as a visual appealing addition to standard drinks.

While liquid nitrogen can be safe even when included in mixed alcoholic drinks, the liquid nitrogen must be completely evaporated off of the drink - just as the fire must be gone before something that has undergone flambé is consumed. If not, there can be immediate and severe effects, such as the degradation of the stomach.  

How can liquid nitrogen be used safely though, if it can also cause severe burns? Liquid nitrogen's boiling point is −195.8 °C, whereas room temperature is right around 20 °C, which is over a 200 degree difference. Because of this large difference, liquid nitrogen evaporates at a very high rate when exposed to room temperature, and will form droplets surrounded by its own vapor. This process is known as the Leidenfrost Effect. 

Figure 1. An example of what evaporating liquid nitrogen would
look like as it hits a room temperature surface (Walker, n.d.). 

References:

BBC News. 2015. Liquid nitrogen cocktail: Lancaster's Oscar's Wine Bar fined £100k. <http://www.bbc.com/news/uk-england-lancashire-34277429>.

Darryl's Wood Fire Grill. 2012. Liquid Nitrogen Mixed Drinks! <https://www.youtube.com/watch?v=T4GfdM9cKU8>.

Grant Thompson - "The King of Random." 2016. What does Liquid Nitrogen do to Your Face? <https://www.youtube.com/watch?v=l1XRspReAvI>.

Helmenstine, A. M. 2016. Liquid Nitrogen Facts.<http://chemistry.about.com/od/moleculescompounds/a/liquidnitrogen.htm>.

Helmenstine, A. M. 2016. Room Temperature Definition. <http://chemistry.about.com/od/chemistryglossary/g/Room-Temperature-Definition.htm>.

ImaginationStationOH. 2014. Liquid nitrogen ice cream. <https://www.youtube.com/watch?v=dNmMW4E54lI>.

MolecularRecipes.com. n.d. What is Molecular Gastronomy? <http://www.molecularrecipes.com/molecular-gastronomy/>.

NurdRage. 2014. ALS Liquid Nitrogen "Ice Bucket Challenge" (Ft. Muhammad Qureshi). <https://www.youtube.com/watch?v=Xj-prpHfyEY>.

NurdRage. 2010. Hand vs. Liquid Nitrogen - Revisited. <https://www.youtube.com/watch?v=wV7g8L633Sg&t=14s>.

Walker, J. n.d. Boiling and the Leidenfrost Effect. Cleveland State University. [PDF].