On 16/1/2020 I had attended my first ever coffee workshop which was hosted by the owner of “The Coffee Roaster”, NUS almunus Swee Heng! (No, he doesn’t own the bakery) Through him, I have learnt about the complexity of the art of coffee brewing and I was even able to taste test 2 different but commonly used brands. Disclaimer: I am a tea-girl so this post would not only be informative, but also biased yay!

Coffee Tasting

The first activity we did was to taste test 2 unknown blends of coffee beans. Due to my apparent lack of interest in coffee and taste-buds, both cups only tasted incredibly sour to me. According to the coffee connoisseurs in the module though, the cup on left had a fruity taste and had less of an aroma, whereas the cup on the right had a stronger aroma and tasted more bitter. Lo and behold, it was revealed that the left cup of coffee was made from an Ethiopian blend, whereas the cup on the right was made from a Colombian blend. Interestingly, Swee Heng had explained that different regions of the world produces coffee of a different taste; and that Asian coffees usually are heavier.

Types of Coffee Beans

I learnt that there were mainly 2 types of coffee beans used commercially- Arabica, Robusta. Arabica coffee beans which are more elongated, are harder to grow and thus usually used for “gourmet coffee”. Robusta beans which carries twice the amount of caffeine are easier to grow and thus used in cheaper instant coffee.

The Art of Brewing

Brewing is the process of extraction into water of desirable substances from the coffee beans, in amounts that produces a balanced drink. In the words of Swee Heng “Extraction is everything that the water takes from the coffee”. This means that brewers have to make sure that only the desired substances are extracted- the science behind it was explained simply to us by Swee Heng. The sequence below is arranged in decreasing solubility and what contributions to the coffee they provide when extracted.

Caffeine (bitter) > Acids (sour and thin) > Lipids and Fats (for good mouthfeel, viscous) > Carbohydrates and plant fibres (bitter)

Caffeine, which is polar and the most soluble in water, would be extracted first, followed by acids. Lipids and carbohydrates are hydrophobic(non-polar) thus are insoluble in water and takes the longest to be extracted. Hence, the flavor, colour and body of the finished drink are determined by the (1) Grind size (2) Brew time(for immersion brewing) (3) Brew temperature (4) Brew Ratio(for expresso) (5) Pressure (6)Water hardness.

The smaller the particles, the harder it is for water to flow all the way through; an analogy would be comparing water flowing through sand or rocks. The higher the temperature (90-93 degree celcius) of the water, the higher the solubility of the solids in water. This is because the molecules gain enough kinetic energy(converted from heat energy) to overcome intermolecular forces of attraction. Water hardness is something I had discussed briefly in the previous post “Welcome to my blog!!”. Hard water contains more minerals and ions such as calcium and magnesium and Singapore’s tap water, which has a hardness of 70ppm, is suitable as it is for coffee brewing. It would be interesting to attend a coffee brewing competition to test each competitors preferred water hardness and how it affects the taste of their coffee!

Types of Coffee Brewing ways

Percolators are like a special electric kettle used to brew coffee repeatedly, but it tends to overextract as it usually operates at a boil. The more commonly used automatic drip brewers nowadays are convenient, but they are not able to dish out near boiling water. This meant that extraction occurs for a long time which causes aroma to be lost and carbohydrates and plant fibres, which further increases the bitterness to coffee, to be extracted. Manual drip cones on the other hand allows some specks of bitter particles to pass through, causing the coffee to taste bitter and not as smooth.

From the coffee workshop, it is evident that many coffee/non-coffee drinkers such as myself, do not know of the complexity of brewing coffee. I am glad that I had attended the workshop!