At this event, I was in charge of coffee, and we shared two types of coffee at this event: pre-made cold brew and espresso using a siphon coffee maker. To make coffee, you only need two ingredients: coffee and water. However, temperature, pressure, and time are key factors in making your perfect brew.
To make cold brew, it is a much easier process that trades time for temperature, and it yields a much stronger and less acidic brew. 

Cold Brew Recipe:  Yields: 1 gallon | Time: 12-18 hours

  • 1 pound of coarse coffee grounds 
  • 1 gallon of water
  1. To make the cold brew, all you need is to do is mix the coffee grounds with the water and let it sit for at least 12 hours at room temperature or in the fridge. 
  • Coarse coffee grounds must be used. Coarse coffee grounds allow for an even extraction that produces a smooth coffee that is not too bitter. Fine coffee grounds will yield an over-extracted coffee that is very bitter. 

Espresso/Siphon Coffee Maker: 

On the other hand, espresso is a much quicker process that involves hot water and pressure. At this event, we used a siphon coffee maker to brew some coffee. Espresso usually uses high pressure to extract a much more concentrated brew. The siphon coffee maker uses 200ml of water and 2 tablespoons of fine coffee grounds. The siphon coffee maker brews coffee by using gas laws to create vacuums in the reservoir. 

There are two main parts to the siphon coffee maker: one chamber filled with water and another filled with coffee grounds.

  • As the water heats up, there is an increase in vapor pressure causing the water to move to the chamber with the coffee grounds; the water will steep the coffee. 
  • As the chamber with water becomes empty, there is a vacuum created due to gravity and as it cools down. The vacuum in the empty chamber pulls the filtered coffee into the chamber. 

Overall, this was my first Atlanta Science Festival event, and I am so glad I got to share it with such a wonderful group of people! Being able to share my love of coffee and science with others in the community is a fantastic feeling, and it would not have been possible without the help of all my fellow STEMCommers. At the beginning of the event, I was pretty nervous presenting my drinks and the science behind them, but I knew that Dr. Leavey, Dr. Evans, and Dr. Greco were all there walking around and helping out. I am so glad this was successful, and it would not have been possible without such a tremendous STEMComm team!

Sources:

Bilow, R. (2018, May 30). Cold Brew Common Mistakes You Would Never Make. Retrieved from https://www.bonappetit.com/test-kitchen/common-mistakes/article/cold-brew-coffee-common-mistakes

Malina is a second-year neuroscience and industrial engineering student at Georgia Institute of Technology. Her passions include baking, sleeping, and drinking copious amounts of coffee.