Hello everyone! I am Audrey, a Year 3 student majoring in Chemistry.

I am sure most of us here love our food, especially all the “good food” we constantly share with others on our Instagram, but what exactly makes these “good food” good?  Why does the same dish taste different when prepared by different people? Is there any science behind the preparation of good tasting food? Through this module, I hope to learn a little bit more about the science behind the food we consume on a day to day basis.

Workshop

In week 1, we attended a coffee workshop held by Mr Swee Heng, the founder of The Coffee Roaster, a cafe which can be found in the Faculty of Arts and Social Sciences in our very own campus.

To start off the workshop, we were handed two different cups of coffee and were told to try both of them. After tasting both, we should try to describe their taste and smell to the best of our abilities, taking note of any noticable differences between the two.

I am not too much of a coffee person actually. I rarely drink coffee because my body is relatively sensitive to caffeine so unsurprising, I am neither great at describing the taste of the coffee nor good at telling different types of coffees apart.

With these two cups of coffee, it took me some time to think about how they smelled and tasted, and what kind of words were suitable to describe them. Smell wise, for the coffee labelled C, it was relatively more bitter as compared to the coffee in the cup labelled E, which smelled more sour. For lack of a better description, I thought the coffee in E actually smelled like kimchi. Taste wise, it was the opposite. Coffee in cup C tasted more sour and acidic while coffee in cup E tasted more bitter.

During the discussion, we learnt that there are only three different species of coffee beans in the world (Robusta, Arabica and Liberica), and we tasted two of out these three. The coffee in cup C was actually brewed from Robusta, a cheaper species of coffee bean since it is more resistant to pests and is more commonly found in our local Singaporean kopis – with a more earthy and slight burnt rubber taste. The coffee in cup E was brewed from Arabica, a slightly more expensive species typically served in cafes – with a more complex flavor of fruit, chocolate and hazelnut. With this piece of information, maybe it can serve as justification as to why a cup of black coffee from Starbucks costs $2.10 whereas Kopi O costs $1.00??

Mr Swee Heng then went on to share many interesting facts about different types of coffee, such as long black, americano, latte, cappucino and macchiato etc.

Here’s a list of some of the things he shared that intrigued me the most:

  • Coffee from different parts of the world tastes really different (I’ve always thought coffee was just coffee)
  • Espresso needs to be brewed under very high pressure (at least 9 bars)
  • Americano and long black are basically the same thing, just that long black has more crema (golden layer above coffee) because for americano, hot water is added after the espresso shot, disrupting its crema but for long black, espresso is extracted directly into the hot water. (I never knew adding the water/espresso shot first could actually make a difference. Who knows maybe the addition of milk/cereal first might also lead to a difference?)
  • Flat white, latte and cappucino are basically almost the same thing too, they just have different ratios of espresso to milk to foam.
  • Macchiatos does not involve any special ingredients. As long as there is “staining” on the tea (by things like foam/drizzle), it is considered a macchiato.
  • Kopi O is bitter because of over-extraction. (More does not equal better)

Many different factors could affect the quality of a cup of coffee. This is where the science behind brewing of coffee kicks in. We learnt that factors such as brew ratio, grind size, brew time and hardness of water are what affects the taste of the coffee as it affects the extraction efficiency.

Brew ratio is the mass of coffee grounds to the mass of liquid espresso in a cup. A 1:1 ratio gives us a ristretto, 1:2 ratio gives us a normale, 1:3 gives us a lungo while ratios from 1:14 to 1:17 gives us a pourover. As the brew ratio increases, the espresso may be less heavy and less viscous. The taste of the espresso would thus differ and may seem clearer.

Grind size of the coffee beans is probably the most important factor that can be controlled through brewing methods. Different preparation methods may call for different grind sizes but generally the coffee beans should not be too coarse but also should not be too fine. If it is too coarse, extraction efficiency may be low but if it is too fine, too much of the coffee bean content may be extracted and that may not necessarily be a good thing.

Brew time affects the taste of the coffee because the extraction of the coffee bean follows the sequence of caffeine, acids, lipids & fats, sugars, carbohydrate and lastly plant fiber. Since carbohydrates and plant fiber are bitter, the optimal stop for the extraction is after sugars have been extracted. An under-extracted coffee would be sour due to the presence of the acids and absence of sugars to balance the sourness out. An over-extracted coffee would be bitter due to the extracted plant fibers and would taste hollow.

Hardness of the water refers to the amount of ions and minerals present in the water. Essential ions required for extraction of coffee include calcium ions and magnesium ions, which means that distilled water containing no ions are not suitable to be used for coffee extraction. Surprisingly, the hardness of the water is a factor that has a great impact on the taste of the coffee. Baristas make their own water (by adding specific ions/minerals to pure water) when taking part in international competitions because hardness of water differs across different countries. Interesting!

It can be seen that there are plenty of factors that could affect the quality and taste of a cup of coffee. All of these ultimately point to one thing – A great deal of science lie behind the creation of a good cup of coffee since the scientific knowledge of the extraction process would allow the barista to fine-tune his/her coffee brewing process to switch up the taste of the coffee he/she creates.

Overall, this coffee workshop was definitely eye-opening to me. Since I do not consume coffee that often, I never knew how complex a cup of coffee may be. The fact that such a common drink could actually have such diverse preparation methods and how much science goes behind the preparation amazes me. Even though we learnt about some technical things in the workshop, it was not boring at all as I could feel how much passion Mr Swee Heng actually has for coffee. In turn it makes me excited to share about the random interesting facts that I learnt from this workshop to my other friends who actually consume coffee on a daily basis.

That is all for this chapter. Thank you for reading!