What are the characteristics of coffee extraction? What should be noted when extracting light-roast Yirgacheffe coffee?

Coffee extraction is a complex chemical process. Different parameters such as roast level, bean-to-powder ratio, extraction amount, and water quantity all become factors that alter coffee's aroma. To brew a cup of coffee, the fusion of grounds and water is essential, and perfect extraction helps enhance the taster's palate experience. Therefore, the process of water penetrating coffee grounds becomes the key action affecting coffee extraction.

In FrontStreet Coffee's bean selection, the extraction principles for coffee beans from Ethiopia's Yirgacheffe region are adjusted according to these beans' characteristics. The basic water temperature is between 90 to 92 degrees Celsius, with a grinding sieve rate of 80%. Of course, many other details require slight adjustments based on these beans' origin, estate, and roast level.

The Changes in Coffee Extraction

In coffee extraction, aroma and acidity are the first to be released, while mid-to-late notes bring sweetness and bitterness. If over-extracted (exceeding the time for extracting late notes), it will result in excessive bitterness and astringency, causing the final flavor to become overly dense yet hollow.

Additionally, if coffee particles are too fine, they are more prone to over-extraction (because coffee particles are extracted quickly, and if water hasn't penetrated yet, it becomes soaking). Conversely, if coffee particles are too coarse, under-extraction occurs (because before complete contact with water, it has already fully penetrated). Therefore, matching appropriate coffee grind size and various parameters for different brewing methods is essential to perfectly interpret coffee extraction.

Important Parameters Affecting Coffee Extraction

Golden Cup Theory

According to the Golden Cup Theory from the Specialty Coffee Association (SCA), coffee concentration between 1.15-1.45% and extraction rate between 18-22% are essential data conditions for good-tasting coffee.

Coffee Concentration

Below 1.15%: Tastes overly diluted with weak flavor

Above 1.45%: Tastes overly concentrated with too intense flavor

Extraction Rate

Below 18%: Too much acidity, excessive sharp and uncomfortable sourness

Above 22%: Obvious bitterness, dry and negative mouthfeel

Following the data mentioned above, we can find that the balance between coffee concentration and extracted substances is very important. If one aspect is too light, it will increase the proportion of the other, causing poor tasting experiences such as excessive acidity or bitterness. Therefore, the water-to-coffee ratio also becomes an important factor affecting extraction.

About Extraction

The longer the extraction time, the more suitable for coarsely ground coffee particles; conversely, the shorter the extraction time, the more fine grinding will be chosen. Precisely standardizing extraction time can showcase coffee's unique flavor, making the final tasting experience approach perfection.

Longer extraction time: Suitable for coarser grind, taste tends toward refreshing sweetness and acidity

Medium extraction time: Suitable for medium grind, taste tends toward balanced sweetness

Shorter extraction time: Suitable for finer grind, taste is rich, pure, and slightly bitter