Coffee Tastes Sour? 8 Reasons & Their Solutions

It is important to note that coffee naturally contains acidity. And acidity is a desirable quality in coffee. For example, a pleasant acidity is responsible for the bright and vibrant tasting coffee from East Africa. Without acidity, coffee tastes flat or dull. However, it is important not to confuse acidity with sourness.

 In many cases, the reason for coffee’s sourness is something simple and easy to fix.  But why does coffee taste sour? Let's explore these possible causes and their respective solutions.

Why Coffee Tastes Sour?

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

Coffee beans can indeed be a contributing factor to the sour taste in your coffee. Here are some of the causes of sour coffee that can be traced back to coffee beans.

1. Under roasted or Shock roasted coffee test sour

When coffee beans are roasted at excessively high temperatures within a short period of time, it leads to underdeveloped or shock-roasted beans. This roasting process often causes the bean's outer shell to appear normal or even burnt in some cases. On the other hand, the acids inside hardly have an opportunity to undergo the necessary breakdown process and the flavours present within the bean will be underdeveloped. When brewing such coffee, the acids dominate the flavour leading to sour and grassy cup. Therefore, buying a gently roasted coffee is important to avoid a sour coffee.

2. Old, Stale Coffee Beans

While green coffee beans have a long shelf life, once they have been roasted, their flavours and aromas begin to deteriorate over time, eventually resulting in stale coffee. The intricate nuances and complexities that define the flavour profile begin to fade. The aromatic oils in the coffee beans evaporate, the sugars begin to break down and the once delightful natural acids turn into sour and harsh flavours.

Typically, coffee beans lose their freshness and start to taste less balanced within 5 to 6 weeks of roasting, although this can vary depending on how you store your coffee. Ideally, you should store your coffee beans in an airtight container made of ceramic or another material that doesn't retain odours. This will help to preserve the freshness and quality of the coffee.

Read our guide about how to properly store your beans: Coffee Bean Storage Guide

But how do you know when your coffee beans have gone stale?

If your cup of coffee tastes a rather very sharp lemony flavour, it is a clear indication the beans are old and stale.

3. The coffee was roasted too light

Another factor that can contribute to the perception of coffee tastes sour is drinking the lighter roasted and fruitier coffees. Some green Arabica coffees have more natural fruit acids. If roasted lighter  the coffee's citrus and floral notes will be highlighted. Although light roast makes the coffee taste fruitier - it may not appeal to everyone. Particularly if you’re used to a dark roasted coffee, the sharpness of the fruity flavor of light roasted Yirgacheffee, For example can be overwhelming.

You can try to adjust by grind your coffee finer. This will help to increase the extraction and leading to a better-balanced cup. But if it still tastes sour try a milder coffee like Anderacha coffee or Limu coffee. Limu and Anderacha beans are known for their low acidity, and a well-balanced body with hints of winey and dark chocolate flavours notes. 

If you're using high-quality coffee beans and making sure none of them go stale, the most likely cause of a sour cup of coffee is under-extraction. That is, you will need to make a few changes to your brewing process.

Under-extraction

coffee beans contain different flavour compounds like acids, oils, sugars and plant fibers. Once water comes into contact with the coffee, it starts to extract these flavor compounds. Regardless of the brewing method, the water extracts the different flavor compounds in a specific sequence:

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

The taste of your coffee depends on the balance of these extracted compounds. Acids and oils are the first components to be extracted. Coffee acids are responsible for the crisp and bright flavor profile. However, without other compounds to counterbalance the acidity, your cup of coffee may become overly sour and oily.

Sugars are extracted next, which serve to balance out the acidity by providing sweetness. Eventually, the water will start to break down the plant fibers, allowing the extraction of bitter elements.

If your coffee tastes sour or sharp chances are it is under extracted. In other words, the water hasn't had sufficient time to break down enough sugars and incorporate a slight bitterness to balance the acidity.

Here are common reasons under-extraction tend to happen:

4. Short brewing time

Why does coffee taste sour if the brewing time is too short? As we already pointed out the compounds in coffee are extracted at different rates during the brewing process. Acids and oils, are extracted and dissolved quickly, followed by sugars. If the brewing time is too short, you’d get an under-extracted sour cup.  You want to brew long enough to bring out the sweeter flavors to balances the acids.

Every coffee brewing method has a rough estimate of brewing time. Here’s a quick overview of the most common methods and how long they take:

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 keep in mind that the brewing times listed in the table are only estimates and may vary depending on personal preference and coffee grind size.

There is a "sweet spot" where the coffee tastes just good, but if you brew it too shorts, only the acids and oils are extracted, not the additional flavors. With a French press, for example, you may have dipped the filter down too soon. If you are using a pour-over cone, you may have poured the water in too quickly and it has drained too quickly.

5. Coarsely ground coffee

Getting the coffee grinds just right for each bean, roast level, and region is part of the art of brewing coffee. If your coffee tastes sour, your grind size could be too coarse for the brewing technique you are using. It simply mean that each particle isn't getting the time it needs for a balanced extraction.This is because coarser coffee particles have a smaller surface area, leading flavours and organic compounds to be extracted slowly a given period of time, leading to under extracted sour coffee.

6. Low water temperature

Water temperature is a crucial factor in coffee preparation 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 threshold, you may end up with an under-extracted coffee that tastes sour. In particular, if the water temperature is below 85 degrees Celsius, you will get a rather under-extracted, sour-tasting coffee - or it will become watery. If the temperature is well above the ideal point, you will end up with a  bitter coffee .

This ideal temperature is just below the boiling point. It is the point where most desirable flavours in coffee dissolve easily in the water. So if your kettle does not have a thermometer, you can bring the water to the boiling point and wait for approximately 40 seconds before pouring it over your coffee.

7. Not enough water is used

The coffee-to-water ratio is another important factor that should not be overlooked. If you use less water in an attempt to increase the strength of your coffee, it becomes challenging for the water to extract all the desired flavors and achieve a well-balanced brew. Consequently, you may end up with a sour taste caused by under-extraction.

It is important to note that each brewing method has a recommended ratio of coffee to water ration, although slight adjustments can be made to suit individual taste preferences. It's always a good idea to experiment and adjust the proportions to suit your taste.

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

 

8. Note on acidic water

If the pH value of the water is below 7 the water used for brewing is acidic and will result in a sour tasting coffee. Using a water filter can help prevent low pH values in the water.

What to do if coffee tastes sour?: Ways to Fix Sour Coffee

There are several straightforward methods to fix sour coffee, which can be easily implemented. These simple tips can help resolve the issue of sour coffee regardless of the brewing method you use.

Use fresh, gently roasted beans

Make sure to use freshly roasted coffee beans and store them properly to maintain their freshness. Avoid using old, stale, or shock roasted (underdeveloped) beans, as they can contribute to a sour taste in your coffee.

Use a medium roast coffee

If the coffee was roasted too light and is tasting fruitier and sour try a medium roasted coffee. Light roasted coffee does not appeal to everyone.

Use a finer grind

The size of the coffee grounds directly impacts the extraction process and the resulting flavor profile. Finer grounds extract flavors more quickly, facilitating a balanced flavor extraction. Simply grinding your beans finer can significantly improve the taste of your coffee, even if no other changes are made. Moreover, in pour-over brewing methods, smaller grounds slow down the water drainage, prolonging the brewing time and ultimately leading to a more harmonious and well-rounded cup of coffee.

Increase brewing time

Another way to avoid having sour coffee in your cup is to increase the brewing time. Increasing the overall brewing time will allow the water to properly extract the flavours.

There are several approaches to achieve this. For example, if you are using immersion brewer like French press, you can extend the brewing time by steeping the coffee beans for additional 30 – 40 seconds.

In the case of pour-over coffee, you can adjust the brewing time by pouring the hot water more slowly, allowing for a more gradual extraction process.

Experiment with your Coffee to Water Ratio

If you use less water in an attempt to increase the strength of your coffee, it will be difficult for the water to extract all the desired flavours and create a well-balanced brew. As a result, you may end up with a sour taste caused by under-extraction.

Measure water temperature

If you use water that is not sufficiently hot, it will lead to under-extraction of the coffee beans, resulting in a sour taste in your cup. It is essential to adhere to the ideal brewing temperature range of 92-96 degrees Celsius.