Why does your coffee taste sour?

1. Under extraction

The ground coffee has simply been in contact with hot water for too short a time, or the water was not hot enough so that it can extract little or no flavors from the coffee. This results in a weak and often sour coffee. You can often tell directly by the color: which is very light and a little yellowish. 

Coffee beans are ground too coarse.

There is a good chance that the coffee beans have been ground too coarsely with an espresso machine or a fully automatic espresso machine. We, therefore, recommend that you set the built-in coffee grinder to the most refined setting. For example, ground coffee gives more resistance to the water, resulting in a more prolonged extraction.

The water is not hot enough.

You need hot water to extract all the flavors from a coffee bean. The colder the water, the longer the extraction should take. The ideal temperature is between 90 and 96 degrees. Have you set the bean grinder in the most delicate setting? Then check whether the temperature of the water is warm enough. 

Ground coffee is not evenly tamped. 

With a piston machine, you press the ground coffee manually with the tamper. It can happen – especially if you have little experience – that you press the ground coffee harder on one side than on the other. This results in non-uniform extraction, which can also result in sour flavors. 

1. Light Roasted Coffee Beans

Lightly Roasted coffee beans are all the rage these days, but if your coffee beans are roasted too lightly, the coffee bean has had too little time to develop a flavor profile. You should see it this way: the shorter the coffee bean is in the roaster, the sourer it tastes. The longer the coffee bean sits in the roaster, the more bitter the flavors. 

1. Old coffee beans

Coffee beans lose flavor immediately after roasting. This process is prolonged for whole coffee beans but very fast for ground coffee beans. The bean breaks down slowly like everything else in nature. Old coffee beans taste sour when the sugars have broken down. It is best to buy freshly roasted coffee beans and consume them within 8-12 weeks of the roasting date. 

Sour coffee: this is what you can do about it!

When the coffee tastes sour, you first look at the roasting degree of the coffee beans and the freshness. Are they old coffee beans, or are they very lightly roasted? Then it is better to buy new coffee beans. But it can also depend on the settings of your coffee machine or how you have tamped the ground coffee. Do you make the coffee beans yourself? Then don't forget to look at the best coffee grinders.