Can Espresso Be Under-Extracted Due to the Type of Bean?

Espresso can indeed be under-extracted, and this often has a lot to do with the type of bean used. Under-extraction occurs when the coffee grounds fail to release sufficient quantities of soluble compounds during the brewing process, leading to a sour or weak flavor. Let's dive into the factors related to bean type and how they can influence extraction.

Bean Origin

Different regions have unique flavor profiles and solubility characteristics. For instance, beans from East Africa, often lighter roasted, may require distinct brewing parameters compared to darker roasts. These lighter roasts tend to be more acidic, and thus, may need a finer grind and longer extraction time to balance their flavors properly. Misusing these beans in an espresso machine can lead to under-extraction.

Roast Level

Roast levels play a significant role in espresso characteristics. Lighter roasts are more acidic and delicate. Therefore, they often require a finer grind and a longer extraction time to achieve optimal flavor. Conversely, if the grind is too coarse or the extraction time is too short, it can result in under-extraction. To correct this, one can reduce both the dose and yield, keeping the grind size finer to maintain an extraction time around 25-30 seconds.

Bean Freshness

Freshness is a critical factor in espresso extraction. Freshly roasted beans contain higher levels of carbon dioxide, which can affect the extraction process. If the beans aren’t allowed to rest adequately after roasting, they may retain trapped gases, resulting in a sour taste. Properly rested beans can lead to smoother and more flavorful espresso.

Bean Density

Density impacts extraction as well. Denser beans require more pressure and time to extract properly. Conversely, less dense beans might extract too quickly, leading to a thin or sour shot. Adjusting the grind size and brew time can help strike the right balance.

Processing Method

The method used to process coffee beans (washed, natural, etc.) can significantly influence their solubility and extraction characteristics. For example, natural-processed beans often have more fruity and complex flavors, and if not brewed correctly, they can be under-extracted, leading to a less satisfying taste profile.

Advice for Achieving Optimal Extraction

To achieve optimal extraction, it's essential to adjust grind size, brewing time, and other variables based on the specific type of bean being used. Experimenting with these parameters can help you find the best balance for any given bean variety.

Note: High-grown Single-Harvest (SHB) beans are a bit harder to extract. Both the dose and yield need to be lower, while the grind size should be finer to maintain an extraction time around the 25-30 seconds range.

It's important to remember that the only situation where espresso might taste under-extracted due to the bean is if mistakenly using a bean roasted for a different brew method in an espresso machine. Espresso beans need to be roasted to specific parameters, unlike filter coffee, which is lighter roasted and ideal for other brewing methods. Using espresso-roasted beans improperly will result in a sour and hollow taste.