Coffee tastes sour? 8 reasons and their solutions

It is important to know that coffee is naturally acidic. And acidity is a desirable characteristic of coffee. A pleasant acidity is responsible for the bright and lively taste of coffee from East Africa, for example. Without acid, the coffee tastes flat or bland. However, it is important not to confuse acidity with sourness.

In many cases, the reason why coffee tastes sour is simple and easy to fix. But why does coffee taste sour? Let's look at these possible causes and their respective solutions.

Why does coffee taste sour?

The sour taste of coffee is usually attributed to two main factors: improper brewing techniques, the coffee beans themselves, or a combination of both.

Coffee tastes sour: reasons & solutions

Coffee beans can actually contribute to the sour taste of your coffee. Here are some of the causes of acidic coffee that can be attributed to coffee beans.

1. Under-roasted or shock-roasted coffee tastes sour

Roasting coffee beans in a short period of time at excessively high temperatures results in under-roasted or shock-roasted beans. This roasting process often results in the outer shell of the bean appearing normal or even burnt in some cases. On the other hand, the acids inside the bean have little chance of decomposing and the flavors in the bean are underdeveloped. When the coffee is brewed, the acids dominate the flavor, resulting in a sour and grassy cup. It is therefore important to buy a gently roasted coffee to avoid acidic coffee.

2. Old, stale coffee beans

Green coffee beans have a long shelf life, but once roasted, they lose their flavor and aroma over time, eventually leading to stale coffee. The subtle nuances and complexity that define the flavor profile begin to fade. The aromatic oils in the coffee beans evaporate, the sugar begins to break down, and the once pleasant natural acids turn into sour and bitter flavors.
Typically, coffee beans lose their freshness and begin to taste unbalanced within 5 to 6 weeks of roasting, although this time period can vary depending on how the coffee is stored . Ideally, you should store your coffee beans in an airtight container made of ceramic or another material that does not absorb odors. This means the freshness and quality of the coffee is preserved.

But how do you know if your coffee beans are stale?

If your cup of coffee tastes very spicy and lemony, it's a clear sign that the beans are old and stale.

3. The coffee was roasted too light

Another factor that can contribute to coffee being perceived as sour is the consumption of lighter roasted and fruitier coffees. Some green Arabica coffees have more natural fruit acids. When the coffee is roasted more lightly (lightly roasted), the citrus and floral notes of the coffee are highlighted. Although a light roast makes the coffee taste fruitier, it is not suitable for everyone. Especially if you're used to dark roast coffee, the sharpness of the fruity flavor of light roast Yirgacheffe, for example, can be overwhelming.

You can try to adjust for this by grinding your coffee finer. This increases extraction and results in a more balanced cup. If it still tastes sour, try a milder coffee like Anderacha or Limu coffee . Limu and Anderacha beans are known for their low acidity and balanced body with hints of wine and dark chocolate flavors.

If you use high-quality coffee beans and are careful not to spoil them, the most likely cause of a sour cup of coffee is under-extraction. This means you'll need to make some changes to your brewing process.

Underextraction

Coffee beans contain various aromatic substances such as acids, oils, sugar and plant fibers. As soon as the water comes into contact with the coffee, it begins to extract these aromatics. Regardless of the brewing method, the water extracts the different aromatics in a specific order:

  • Acids and oils are first extracted,
  • followed by the sugars,
  • and finally the plant fibers.

The taste of your coffee depends on the balance of these extracted components. The acids and oils are the first components to be extracted. The acids in coffee are responsible for the crisp and bright flavor profile. However, without other ingredients to balance the acidity, your cup of coffee can become overly acidic and oily.

Next, the sugars are extracted, which balance the acidity by providing sweetness. Eventually the water begins to break down the plant fibers, allowing the bitter substances to be extracted.

If your coffee tastes sour or spicy, it is probably under-extracted. In other words, the water hasn't had enough time to break down enough sugar and introduce a slight bitterness to balance the acidity.

Here are the most common reasons for under-extraction:

4. Short brewing time

Why does coffee taste sour if the brewing time is too short? As we already mentioned, the components of coffee are extracted at different rates during the brewing process. Acids and oils are quickly extracted and dissolved, followed by the sugars. If the brew time is too short, you'll end up with an under-extracted, sour cup. The brewing time should be long enough to bring out the sweeter flavors and balance the acids.

For each coffee brewing method, there is a rough estimate of brewing time. Here is a quick overview of the most common brewing methods and their duration:

Brewing method

Time (approx.)

Pour over

3-4 minutes

French press

4-5 minutes

Aeropress

1-2 minutes

espresso

25-30 seconds

Moka pot

5-7 minutes

Cold brew

12-24 hours

Please note that the brewing times shown in the table are estimates only and may vary depending on personal preference, coffee grind size and brewing device.

There is a " sweet spot " where the coffee just tastes good, but if you brew it too short, only the acids and oils will be extracted, not the additional flavors. With a French press, for example, you may have dipped the filter in too early. If you use a pour-over, you may have filled the water in too quickly and it ran out too quickly.

5. Coarsely ground coffee

The art of brewing coffee is finding the right coffee grind for each bean, roast level and region. If your coffee tastes sour, the grind may be too coarse for the brewing technique you are using. This simply means that the individual particles do not get the time they need for a balanced extraction. This is because coarser coffee particles have a smaller surface area, resulting in flavors and organic compounds being extracted slowly over a period of time, resulting in an under-extracted acidic coffee.

6. Low water temperature

Water temperature is a crucial factor when making coffee as it can significantly affect the extraction rate. According to the Specialty Coffee Association, the ideal water temperature for brewing is between 92 and 96 degrees Celsius. If the water temperature falls below this value, the coffee may not be sufficiently extracted and taste sour. In particular, if the water temperature is less than 85 degrees Celsius, you will end up with under-extracted, sour-tasting coffee - or it will be watery. If the temperature is far above the ideal point, the coffee will be burnt and bitter .

This ideal temperature is just below boiling point. This is the point at which most of the coffee's desired flavors dissolve easily in the water. So if your kettle doesn't have a thermometer, you can bring the water to boiling point and wait about 40 seconds before pouring it over your coffee.

7. Not enough water is used

The ratio of coffee to water is another important factor that should not be ignored. If you use less water to increase the strength of your coffee, it will be difficult for the water to extract all the flavors you want and create a balanced brew. The result can be a sour tasting cup because too little water has been extracted.

It is important to know that a specific ratio of coffee to water is recommended for each brewing method, although this can be easily adjusted depending on your taste preferences.

Brewing method

Coffee-water ratio

Pour over

1:15 - 1:18

French press

1:15 - 1:17

AeroPress

1:15 - 1:17

espresso

1:1 - 1:2

Moka pot

1:10 - 1:12

Cold brew

1:5 - 1:8

Please note that these proportions are general guidelines and personal preferences may vary. It's always a good idea to experiment and adjust the proportions to suit your taste.

8. Note on acidic water

If the pH of the water is below 7, the water used for brewing is acidic and the coffee tastes sour. Using a water filter can help avoid low pH water.

What to do if coffee tastes sour?:Ways to eliminate sour coffee

There are several simple methods to eliminate acidic coffee that are easy to implement. These simple tips can help solve the problem of sour coffee, no matter what brewing method you use.

Use fresh, gently roasted beans

Be sure to use freshly roasted coffee beans and store them properly to preserve their freshness. Do not use old, stale, or shock-roasted (underdeveloped) beans as these can contribute to a sour taste in your coffee.

Use a medium roast coffee

If the coffee was roasted too light and tastes more fruity and sour, try a medium roast coffee. Lightly roasted coffee is not for everyone.

Use a finer grind

The size of the coffee grounds directly affects the extraction process and the resulting flavor profile. Finely ground coffee extracts flavors more quickly, allowing for balanced flavor extraction. Simply grinding your beans finer can significantly improve the taste of your coffee, even if you don't make any other changes. In addition, smaller coffee grounds slow down the water drainage when poured over, which extends the brewing time and ultimately leads to a more harmonious and well-rounded cup of coffee.

Extend brewing time

Another way to avoid sour coffee in your cup is to increase the brewing time. Increasing the brewing time allows the water to properly extract the flavors.

There are different ways to achieve this. For example, if you use an immersion brewer like a French press, you can extend the brewing time by steeping the coffee beans for 30 to 40 seconds longer.

With pour-over coffee, you can adjust the brewing time by pouring the hot water more slowly to allow for gradual extraction.

Experiment with the coffee to water ratio

If you use less water to increase the strength of your coffee, it will be difficult for the water to extract all the flavors you want and create a balanced brew. The result can be a sour taste caused by under-extraction.

Measure the water temperature

If you don't use enough hot water, the coffee beans won't be adequately extracted, resulting in a sour taste in your cup. Be sure to stick to the ideal brewing temperature of 92-96 degrees Celsius.