Getting the perfect tasting Espresso is an art which requires optimal extraction which is a range between over extraction and under extraction.
Causes Of Under Extracted Sour Tasting Espresso
The first thing to look at is the extraction time if the water is pulled through the coffee beans to quickly under extraction will occur and your Espresso will be sour and salty. Your extraction time should be between 20 and 30 seconds depending on your bean. You should experiment with different extraction times between 20-30 seconds to eliminate any sour taste.
If you’re having difficulty getting the targeted extraction time you need to pay attention to your grinding and the coarseness of your grind. If the beans are too coarse, they will naturally speed up the water flow resulting in under extraction, if this is the case try grinding your beans a little finer. Again experimentation is key, and through trial and error, you will determine the perfect grind for your chosen bean.
Finally, check your water temperature which should be between 90-95 degrees Celsius. If you want to get technical slightly higher temperatures can be used to optimize lower solubility roasts while marginally lower temperatures can be used to optimise higher solubility roasts.
Utilising these three principles will help you eliminate Sour tasting Espresso.