1. Introduction

1.1 Background Research

Scientific information about coffee 

Coffee comes from the simple extraction of solutes (coffee solids) with a solvent (water) from a matrix (coffee grounds) to produce a solution (coffee beverage) (Steiman, 2016). The compounds of coffee include but is not limited to Caffeine, chlorogenic acid, caffeic acid, trigonelline etc. Coffee is made from the cherries of the coffee arabica plant, which is thought to be indigenous to Eastern Africa. Although the coffee cherry is a fruit, it is more commonly referred as a “coffee bean”, due to its aesthetic similarities with an actual bean. There are two types of coffee beans, Arabica and Robusta, of which Arabica is more common with 70% usage in the industry. However, the Robusta bean has more caffeine and is more bitter. It is slightly acidic and has a stimulating effect on the human brain due to its caffeine content. From the perspective of a nerve cell, the caffeine in coffee is seen as adenosine, which is a neurotransmitter responsible for the basic nervous system communication. Adenosine transmissions are found to be linked to regulating the brain’s sleep cycle and affect the quality of sleep. Adenosine accumulates in one’s bloodstream when one is awake, and eventually will make one drowsy. Regulation of non-REM sleep occurs when an enzyme, adenosine deaminase breaks down adenosine molecules, causing adenosine levels to drop, and thus inducing sleepiness. When drinking caffeine, it achieves its stimulating effects by blocking the brains adenosine processing. 

History of coffee

The first credible signs of coffee came from Yemen in southern Arabia in the middle of the 15 century in the Sufi shrines (Weinberg et al., 2001), although it was first discovered around the 9th century when Islamic Shepherds discovered that it has a stimulating effect on their sheep. Arabia is where the first coffee beans were roasted and brewed. Since then, the world’s first coffeehouses were introduced in present-day Saudi Arabia. Now, more than 70 countries including Brazil, Vietnam, Colombia, Indonesia and Ethiopia export coffee. It is a major export commodity; and is among the world’s largest agricultural exports (Oder, 2015). The United States, the largest consumer of coffee, drank 587 million cups of coffee in 2013, which equals to an average of three cups a day per person. Although coffee is now a famous drink around the world, there have been several attempts to ban it during the 15th to 17th century. In 1511, coffee was believed to cause radicalism in Mecca, Saudi Arabia. The then governor also thought that coffee would cause people to hang out, which would lead them to unite his opposition, coffee was thus banned. When coffee was first brought to Christian Europe in the 15-16th century, it was greeted by suspicion as people thought that it was the drink of the Islamic infidels that they have been at war with for centuries. The name of “Satan’s Beverage” was then brought up. However, it was inevitable that the drink was brought to the Vatican, palace and official residence of the Pope in Rome. Then advisors of Pope Clement VIII clamoured for the Pope to ban the drink, but he refused to do so without trying the drink himself. After that, he was brought a mug of coffee or otherwise then known as java, and took a sip. He was immediately delighted by the taste of coffee, and according to legend, he declared, “This devil’s drink is delicious. We should cheat the devil by baptising it.” Due to the papal blessing, coffee quickly spread through Europe and gained fame. 

Health benefits

Coffee has been suggested to help protect against gout (by lowering uric acid levels), tooth decay and gallstones (Davies, 2011). There is also strong evidence for coffee providing some protection against type 2 diabetes (Davies, 2011). Recent studies show that coffee assuages asthma bouts and allergies, prevents tooth decay, activates burning of fats in the body, replenishes potassium deficit and contributes to the improvement of the cardiovascular function. Coffee is a source of vitamin P needed to strengthen blood vessels. A cup of coffee contains 20% of the daily requirement in vitamin P. 

Fun fact

The drink also has the unusual ability of being able to retain its aroma through a person's sweat glands. (Thorn, Segal, 2007). In the days where bathing was not common, this deodorant effect must have been greatly appreciated (Thorn, Segal, 2007).] 

Ways of preparing coffee

Coffee can be prepared in a lot of ways, of which the most common are espresso, latte, cappuccino, americano and french press. Different types of coffee also have different caffeine concentrations, of which espresso has the highest. Caffeine concentration in the coffee can be controlled by varying the coffee grind size and the type of coffee. 

1.2 Research Questions

The following are our research questions: 

    1. What are the chemicals in coffee? 

    2. How do we measure the caffeine levels in coffee? 

    3. What determines the caffeine concentration in coffee? 

1.3 Hypothesis 

Our hypothesis is that as the time taken increases, the caffeine concentration in the coffee will be higher. 

Independent variable

    - Exposure of coffee beans in the hot water 

Dependent variable

    - Caffeine concentration in coffee 

Controlled variables 

    - Temperature of water 

    - Amount of water 

    - Use of de-ionised water 

    - Size of beakers 

    - Amount of grounded coffee beans

    - Size of grounded coffee beans 

    - Duration & interval of measurement 

    - Absence of wind 

    - Use of the same equipment (Other than disposable ones)