Project Proposal (Brian)

Introduction:  

Imagine you are a coffee enthusiast, but at the same time, you are a GRED (Gastroesophageal reflux disease) patient or simply saying acid reflux. There are many causes of acid reflux in the stomach. Producing too much acid by the gastric wall is a common reason. So, your doctor suggests you get rid of acidic food, including coffee¹. You would probably struggle a lot when facing this dilemma.

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The Science Behind Coffee: Acidity and Bitterness?

You may wonder why coffee, which mostly tastes bitter, is acidic? In the scientific aspect, a pH scale is used to describe the tendency of hydrogen ion concentration from 0-14. A substance is considered to be acidic when its pH value drops below 7 due to a relatively high concentration of hydrogen ion. Coffee is slightly acidic with a pH value of around 5 while the major contributors of coffee acidity are different organic compounds like chlorogenic acid, citric acid, and acetic acid².

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However, these acids may not contribute to the bitter taste. The sensation of bitterness is created when these organic compounds, which are thermally decomposed to a range of aromatic compounds like furan and pyrazines, could perfectly fit into the binding site of bitter taste receptor in our tongue³.

Back to the beginning, so what should we do if we want to enjoy a cup of coffee without worrying about our stomach?

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Well, there are a lot of ways to reduce the acidity of coffee through, for example, adjusting the water temperature, brewing method and time, grinding size of coffee beans, etc. But these are hard to investigate when we lack professional equipment at home.

Alternatively, some suggest simply adding some substances with higher pH such as salt, eggshell, or baking soda into the coffee before extraction^4,5. The concept behind is just simple acid-alkaline neutralization, but does it really work? If so, which is the most effective? Let’s check them out in this project!  

Attached is a video explaining the factor affecting the acidity of coffee and how it can be reduced through different methods. Go and check this out if you are interested!

Compare the effect of eggshell, salt and baking soda on lowering the acidity of pour-over coffee

Trial Experimental Design

Please click on the recipe released in the previous post for more details.

Hypothesis

• Baking soda is the most effective agent to reduce the acidity of coffee

Independent Variables:

• Type of alkali: eggshell, salt, and baking soda (They are added respectively before brewing coffee)
• Amount of alkali used (trial experiment): 0g (control), 5g

Dependent Variable: pH value of the coffee

• Measurement: pH paper / pH meter (if possible)

Controlled Variables:

• Water temperature⁶: 93˚C (according to National Coffee Association of U.S.A.)
• Volume of water⁶: 0.18L (according to National Coffee Association of U.S.A.)
• Amount of ground coffee⁶: 15g (according to National Coffee Association of U.S.A.)
• Brewing time

I would upload the record of my trial experiment soon, please keep following my posts!

By Brian TSE Chun Hei
UID: 3035470955   

References:

1. Roman, S., & Kahrilas, P. J. (2013, February 25). Overview of Gastroesophageal Reflux Disease Treatments. Practical Manual of Gastroesophageal Reflux Disease. (pp. 53-68). Oxford: John Wiley & Sons. https://doi.org/doi:10.1002/9781118444788.ch4
2. Farah, A., & Galvan de Lima, Â. (2019). CHAPTER 22 Organic Acids. In Coffee: Production, Quality and Chemistry (pp. 517–542). The Royal Society of Chemistry. https://doi.org/10.1039/9781782622437-00517
3. Seo, H.-S., Finley, J. W., & deMan, J. M. (2018). Flavor In Principles of Food Chemistry. In J. M. deMan, J. W. Finley, W. J. Hurst, &C. Y. Lee (Eds.) (pp. 285–328). Cham: Springer International Publishing. https://doi.org/10.1007/978-3-319-63607-8_7
4. Rodrigo. (2018, December 22). Can Coffee Cause Acid Reflux? Yes! 7 Ways to Avoid It. Retrieved March 2, 2020, from https://www.littlecoffeeplace.com/coffee-acid-reflux
5. JayArr Coffee. (2019, July 25). Reducing Acidity in Coffee: A Helpful Guide to Low Acid Coffee. Retrieved March 2, 2020, from https://jayarrcoffee.com/blogs/news/reducing-acidity-in-coffee-a-helpful-guide-to-low-acid-coffee
6. National Coffee Association of U.S.A. (n.d.). How to Brew Coffee: The NCA Guide to Brewing Essentials. Retrieved March 2, 2020, from https://www.ncausa.org/About-Coffee/How-to-Brew-Coffee