Project proposal (Michael)

https://foodal.com/drinks-2/coffee/guides-coffee/in-hot-water-optimizing-your-h2o/

Introduction:

Water is King! Water plays a critical role either to human or to coffee. It helps human to control their blood pressure, electrolyte concentration…, similarly, it affects the taste, texture and various aspects of a cup of coffee.

As recommend by National Coffee Association of U.S.A., the optimised water temperature for making a cup of perfect coffee is about 200˚F (=93˚C). However, have you ever wondered about that why it is 93˚C? Without doubt, the water temperature is an important parameter in coffee-making chemistry.

In order to explore the effects of water temperature on coffee, an experiment is going to be conducted.

Experimental:

Independent variable:

Water temperature 

0˚C (ice water), 35˚C, 70˚C and 100˚C (boiling water)

Dependent variables: 

pH value (at 25˚C/RT) and caffeine content (if possible)

Controlled variables: 

Amount of water, amount of ground coffee and brewing time

Who?

Lee Ki Wai (Michael)

What: 

Investigate the effects of water temperature on the pH value/ caffeine content of coffee

Where?

Home/ Laboratory

When?

March-April

Why?

Try to figure the correlation of the water temperature and the taste of coffee, and the science behind

How?

Several identical ground coffee (with same mass) will be brewed with fixed amount of water with various temperature under same brewing time. 

The resulting coffee will be tested by pH paper to determine their pH value. After that, they will be treated with different chemicals so as to extract the caffeine out. (please see reference 1)

https://www.grainger.com/product/MICRO-ESSENTIAL-pH-Paper-1-EA-Testing-Parameter-3UUT4

The science behind:

The nature of brewing itself is dissolution, which can be considered as a chemical reaction. The kinetic (rate of reaction) is strongly affected by the temperature. Therefore, the temperature of water will affect the extraction efficiency of the brewing step resulting in a different taste of caffeine.

By Lee Ki Wai Michael (3035374450)

Reference:

1. Extraction of caffeine (experiment). Chemistry LibreTexts. 

https://chem.libretexts.org/Bookshelves/Ancillary_Materials/Laboratory_Experiments/Wet_Lab_Experiments/Organic_Chemistry_Labs/Experiments/3%3A_Extraction_of_Caffeine_(Experiment)

2. How to brew coffee. National Coffee Association USA. https://www.ncausa.org/About-Coffee/How-to-Brew-Coffee

3. Chemical kinetic (Summary). Chemistry LibreTexts.

 https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/14%3A_Chemical_Kinetics/14.S%3A_Chemical_Kinetics_(Summary)