Why does my espresso taste bitter?

Bitterness is a common frustration for home baristas, but it is also a clear signal that your extraction process needs refinement. When espresso tastes bitter, it means the water has spent too much time in contact with the coffee or has been forced through grounds that are too fine, resulting in the extraction of undesirable, harsh compounds. Think of it as 'over-cooking' the coffee.

To address bitterness, start by looking at your grind size. If your grind is too fine, the water struggles to pass through the puck, increasing contact time and leading to over-extraction. Try adjusting your grinder to a slightly coarser setting. This will speed up the flow rate and reduce the amount of time the water spends dissolving those bitter compounds.

Water temperature also plays a critical role. If your machine is running too hot, it will extract flavors more aggressively, often pushing the coffee into bitter territory. If your machine allows for temperature control, try lowering it by a few degrees. Additionally, consider your roast level; darker roasts are naturally more soluble and prone to bitterness, so they often require a slightly coarser grind or a lower brew temperature than lighter roasts.

Finally, check your brew ratio. If you are pulling a very long shot, you may be extracting the bitter 'tail' of the coffee. Try stopping the shot earlier to see if the flavor profile improves. In practice, the goal is to find the 'sweet spot' where the acidity, sweetness, and bitterness are in harmony. By making small, incremental changes to your grind size and brew time, you can eliminate the bitterness and reveal the true character of your beans.