Project Proposal (Agnes)

Project title

Does waiting make the better or bitterer coffee?

 

Introduction

The popularity of cold brew coffee has been rising in recent years, providing coffee lovers an alternative choice. This smooth and refreshing coffee is originated from Kyoto in the 1600s, the idea was from Dutch traders who invented this method so coffee can be stored long enough to be carried on their ships1. There are different recipes of cold brew coffee around the world, the most common use method is easy to make and more affordable than buying from a coffee shop. But how can we modify the recipe to make the perfect cold brew for yourself? In this experiment, the effect of the time of brewing on acidity and taste of cold brew will be investigated.

The 5W’s

Who?

Yeung Tsz Ying, Agnes

What?

To investigate the effect of steeping time on the pH/ bitterness of cold brew coffee.

When?

Trial experiments will be done during mid-March to April.

Where?

Home/ coffee shop

Why?

Try to suggest the perfect steeping time for coffee lovers to make their own cold brew at home.

How?

Prepare four pot of cold brew coffee according to the recipe. By adjusting the steeping time (4, 8, 12, 24hours), the pH of coffee will be measured by pH paper or bitterness will be evaluated and compared. Hence, the effect of steeping time on the chemical change or taste can be investigated.

Materials needed

120g of coffee beans

480ml of water

4 jars

Filter paper

Timer

pH paper

The three variables

Independent variable	Dependent variables	Controlled variables
-       The time for the coffee to brew (4, 8, 12, 24hours)	-       The pH of coffee -       The bitterness of coffee	-       The grind size of coffee beans -       The amount of ground coffee -       The amount of water -       The temperature of water -       The surrounding temperature during steeping

The science behind

For traditional hot-brewed coffee, acids, sugars, and caffeine are extracted from coffee grounds when hot water is added. The process of extraction is very fast as the heat speeds up the chemical reaction. However, the brew also degrades and oxidizes in a very short time. Sourness and bitterness are generated from the oxidized oils and degraded acids².

  In order to reduce these undesirable flavors, cold brew can be an alternative method for coffee brewing. Cold water is used instead of hot water, although the brewing process takes much longer time than hot-brewed coffee, it oxidizes and degrades much slower. For cold brew with longer steeping time, it is expected to taste more bitter as it allows more time for acids to degrade which generates the taste of bitterness³.  

By Yeung Tsz Ying, Agnes
UID: 3035565413

Reference

1. The Cool Chemistry Behind the Flavor of Cold-Brew Coffee. (n.d.). Retrieved from https://curiosity.com/topics/the-cool-chemistry-behind-the-flavor-of-cold-brew-coffee-curiosity/

2. The History of Cold Brew. (2019, June 18). Retrieved from https://driftaway.coffee/the-history-of-cold-brew/

3. Kate, Diana, Kate, Kristin, Matthew, Kenzie, … Jackson. (2019, July 4). Cold Brew Coffee (Recipe & Tips!). Retrieved from https://cookieandkate.com/cold-brew-coffee-recipe/