EXTRACT THE ETERNAL
FROM THE EPHEMERAL
CHARLES BAUDELAIRE
Extract from the ephemeral – the eternal.
In the book The Espresso Quest, by the Australian restorer, the passionate coffee expert recounts the “divine” explosion of taste during a successful espresso shot: “I saw God in my espresso cup”.
The very wording suggests that this experience isn't so easy to achieve. Preparing a truly successful shot is indeed no simple task. Besides personal taste preferences, several important parameters are required. The equipment used also plays a significant role: especially the grinder and espresso machine.
Let's delve a little deeper.
Water: Water plays a central role as a solvent and medium for coffee. For the aspect of acid extraction, the terms carbonate hardness and alkalinity are important. Carbonate hardness indicates the amount of dissolved calcium carbonate and magnesium carbonate (both are forms of limescale) in the water. Alkalinity describes the water's capacity to buffer acids, i.e., to counteract acidification. During coffee extraction, several acids are extracted from the coffee grounds, such as citric, malic, and phosphoric acid. Depending on the water's alkalinity, this acidification is buffered. This influences our perception of "sourness." Calcium and especially magnesium are important extract boosters. They increase the extract content in the cup. Conversely, soft water leads to a "sour" and "weak" coffee taste. Water that is too hard causes limescale buildup in the machines and masks the valuable aromas.
Recommended: Carbonate hardness 4-6 dH°, total hardness 7-9 dH°, pH value 7.
The extraction ratio (brew ratio): A rule of thumb for espresso is 1:2: 20g of ground coffee yields 40g of coffee in the cup after 25 seconds. Why? Coffee brewing is a solid-liquid extraction process. Extraction: the components are drawn out of the coffee grounds into the cup using water. Caffeine, organic acids (e.g., citric acid), and other easily soluble flavor compounds like sweet, malty notes (methylbutanal) are present in the first drops of espresso at an extraction temperature of approximately 92°C. The bitter components (breakdown products of chlorogenic acids) and roasted pyrazines are less soluble and dissolve later and at higher temperatures. For a well-rounded espresso, we need the full spectrum of flavors. If the espresso flows too quickly and therefore for too short a time, it results in under-extraction. The result is a weak, acidic coffee. If the espresso flows too slowly and therefore for too long, it results in over-extraction. The result is a predominance of bitter and astringent sensations on the tongue. Furthermore, the caffeine content is also increased due to the long extraction time.
Extraction temperature also plays a crucial role in this context: lower temperatures result in more acidic coffees, while excessively high temperatures bring out the bitterness. Determining the correct extraction temperature for a particular coffee is essential, and this is directly related to the roast level. Darker roasts tend to require lower temperatures, and vice versa.
To achieve this 1:2 ratio, the balance between coffee grounds quantity, grind size, tamping, and pressure setting is crucial. A slightly tricky aspect is that each bean requires a different grind setting due to its varying structure, roast level, and age (roast date).
By adjusting these parameters, you can bring out the characteristic flavor profile of each coffee and emphasize it more strongly according to your preference. On the one hand, this is an exciting experiment with the raw material of coffee, and on the other hand, it allows us to gradually work our way towards the optimal result in the cup.
And so the circle closes: finding "God in an espresso cup" is a challenge. But if you find him, it's definitely worth the effort. Good luck!