When making espresso at home, you may encounter a shot that tastes sour. It’s easy to blame the coffee or the roaster in that instance, but it is usually going to be in the building of the espresso. So there are a few reasons for this, and in this article, we will discuss some easy tips to fix a sour espresso.
Why is my coffee sour?
Coffee can have a sour taste, but it is not inherently sour. The taste of coffee depends on many factors, including the type of coffee bean, roast level, brewing method, and extraction time. When coffee is extracted, there are three main phases of flavour perception that occur, namely sour, sweet, and bitter. Early on in the extraction, the compounds that taste sour are heightened, while later in the extraction, the compounds that taste bitter are heightened.
The Three Phases of Coffee Flavour Perception
When coffee is extracted, there are three main phases of flavour perception that occur: sour, sweet, and bitter. Early in the extraction, the compounds that taste sour are heightened. If the shot is stopped too early, it will be sour. If the shot is pushed too far, it will become bitter and dry, if the shot is unevenly extracted it will be a mixture of both, with the sourness coming through particularly strong.
How Under Extraction Causes Sour Espresso
The main cause of sour espresso is under-extraction, which occurs when the coffee does not extract enough compounds from the grounds during the brewing process. When coffee is extracted, there are three phases of flavour perception: sour, sweet, and bitter. Early in the extraction process, the compounds that taste sour are heightened, so if you stop your shot short, it will taste sour.
How to fix under extracted espresso
One of the biggest culprits for sour espresso is grinding the coffee too coarsely, which results in a shorter extraction time and under-extraction. In this case, tightening the grind and allowing more contact time with the same yield can improve extraction and balance the flavours. Some grinders fall short exactly here and either can't grind fine enough or can't grind consistently fine enough, take a look at our best grinders guide if you want to upgrade.
How Over Extraction Causes Sour Espresso
On the other hand, over-extraction can also result in a sour espresso. Over-extraction occurs when the coffee extracts too much from the grounds, resulting in a drying feeling on the tongue. It's important to understand that there's a distinction between the bitterness that can occur from under-extraction and the bitterness that can occur from over-extraction.
Alternatively, over-extraction can also occur when the coffee is ground too finely, resulting in a longer extraction time and under-extraction in certain areas of the puck. In this case, coarsening the grind and shortening the extraction time will allow for a more even flow of water through the puck, resulting in a better-tasting espresso.
How a Small Yield Causes Sour Espresso
Another easy fix is to simply run the shot longer. If the yield is too small for the amount of coffee in the portafilter, increasing the yield by pulling a longer shot may balance the flavours.
(It's probably not the beans causing sour espresso)
It's important to note that while coffee can be acidic, a sour espresso is not usually due to the bean, but rather the extraction. Therefore, blaming the coffee itself for a sour espresso is not accurate. Especially if you follow our guide how to choose coffee beans, then the roastery you are likely trusting is producing high quality beans. Don't confuse an acidic medium roast with being sour, sometimes medium roasts are harder to extract properly, but the end result will probably be high acidity in the palette but not sourness.
In summary, if your espresso tastes sour, there are a few easy fixes you can try. These include adjusting the grind size, extraction time, and yield. With some experimentation, you can create a perfectly balanced and delicious shot of espresso.
Sour Espresso Brewing FAQ
What causes sour espresso?
Sour espresso is usually caused by under-extraction, which occurs when the coffee does not extract enough compounds from the grounds during the brewing process. Over-extraction can also result in a sour espresso, but is less common.
How can I fix under-extracted espresso?
One of the easiest fixes for under-extracted espresso is to grind the coffee finer to increase the extraction time. Another option is to increase the yield by pulling a longer shot.
How can I fix over-extracted espresso?
To fix over-extracted espresso, try grinding the coffee coarser to decrease the extraction time. Alternatively, you can shorten the shot by reducing the yield to allow for a more even flow of water through the puck.
Is a sour espresso caused by the coffee beans?
No, a sour espresso is not caused by the coffee beans themselves, but rather the extraction process.