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Coffee Tips

Why Does My Coffee Taste Sour?

Coffee is the number one choice of beverage for many people in the world, thanks to its rich caffeine content, antioxidants, and numerous health benefits. Many people love coffee to tea, while some prefer decaf. Most notably, coffee is loved for its stimulating effects in the body. Studies show that caffeine is a natural stimulant. Although too much caffeine consumption has side effects, it is among the best beverages when consumed moderately.

girl holding coffee mug with dull face expression

Generally, a good-tasting cup of coffee, for example, offers several different tasting notes and aroma, such as roasted nuts, cranberry, chocolate, fruity acidity, and caramel among others. However, sourness does not represent a good cup of coffee for all coffee lovers. If you notice any sourness in your coffee cup, you cannot describe it as something tasty.

Unfortunately, you might mess up your morning coffee for one reason or another. Messing your cup of joe can be extremely annoying. It is not the kind of drink you would want after waking up. You could end up feeling embarrassed, especially if you are hosting guests. One of the most common ways that coffee gets messed up is tasting sour. In worst-case scenarios, extreme sourness can make your brew undrinkable.

So what makes coffee taste sour? How can you prevent sour coffee taste? In this article, we will answer these questions by explaining the reasons that make coffee sour and effective solutions to avoid this problem.


How is Sour Coffee Different from Bitter Coffee?

Although some coffees have fruity flavors that make them tasty, sometimes, you might make mistakes that will introduce unwanted bitterness or sourness.

However, bitterness and sourness are not the same things. While they both describe bad coffee, they have a major difference. Generally, both bitterness and sourness result from poor roasting. Essentially, bitter coffee tastes acerbic while sour coffee tastes grassy.


Reasons for Sour Coffee

There are many causes of sour taste in coffee. The most common causes of a sour brew include:

    1. Under Extraction

Although there are several fixes for sour coffee, one of the main causes of the sour taste is all about extraction. Upon mixing hot water with coffee grounds, the hot water extracts several different compounds from the ground coffee. They include sugars, acids, plant fibers, and oils. These compounds find their way into a ready coffee during the brewing process.

Extraction when brewing with any coffee machine starts with acids and fats. These two compounds are responsible for the strong sourness in coffee. Next, extraction brings out sugar that is responsible for sweetness. Sugars help in creating a balanced taste by neutralizing acidity. Plant fibers are extracted last. It is these plant fibers that cause a bitter taste. Bitterness also helps in smoothing out acidity. However, too many plant fibers cause excessive bitterness and bad aftertaste in coffee.

Essentially, the sour taste in coffee results from stopping the extraction process earlier than required, depending on the brewing method. When you end the brewing process too early, you cause under extraction. Under-extraction means that the sugars that give coffee some sweetness and the plant fibers that add bitterness are not fully extracted. Hence, the acidity will not be balanced. As a result, you will end up with a sour brew.

When brewing, you should allow for enough extraction time to bring out the coffee flavors that balance acids. That way, you will hit the sweet spot that coffee offers. For instance, if you plunge a French press plunger too early, you will under extract the flavors. Similarly, if you are using the drip coffee method or pour-over brewing technique and you pour water at a fast rate down the cone, the water will drain too quickly, thereby causing under extraction. Thus, different coffee makers differ in the brewing time needed.


    2. Under Roasted Coffee Beans

Another culprit for your coffee tasting sour is brewing with under roasted beans. When roasting coffee beans with a coffee roaster, you start with green beans. Getting a perfectly roasted bean is a matter of balancing heat, rotation speed, and air among other factors. During the process of coffee roasting, you transform green beans into roasted beans that are ready for grinding and brewing.

A reaction known as the Maillard Reaction occurs during the coffee roasting process. The reaction causes browning in food. It is a chemical reaction that occurs during processes such as toasting bread, frying bacon, and roasting coffee beans.

When roasting beans, the Maillard Reaction turns raw organic compounds present in green beans into tasty flavors. It also caramelizes coffee sugars. Without this chemical reaction, coffee will taste earthy and sour.

If you roast coffee beans too light, there is a chance that you may fail to reach the Maillard Reaction stage. Hence, your brew will taste sour.

If you notice sourness in coffee, it is likely you under roasted the beans. Under roasted beans are also referred to as underdeveloped beans.

If you are new to coffee roasting, you are more likely to under roast the beans. However, you will perfect the roasting process over time and find it easier to roast them to the preferred roast levels.

Sometimes, sour coffee taste is a result of some people mistaking the taste of light roast coffee for sourness. In this case, you may feel the flavor tastes grassy. Light roasts are best prepared with beans that have fruity notes, which add to the sourness.

Some coffee drinkers confuse light roasts with sourness as a result of having underdeveloped palates. Regardless, not every coffee lover has an exceptional palate with the ability to notice any subtle variation in various roasts. You can gain more tasting experience by trying out different roasts and coffee beans. All in all, if you brew with under-roasted beans, you will end up with a grassy brew.


    3. Brewing with Stale Coffee Beans

Coffee breaks down slowly over time. With passing time, the aromatic oils in the beans evaporate while coffee sugars break down. The delicious natural acids also turn sour over time. Regardless of how aromatic your beans or grounds are, their shelf life is not infinite. Upon roasting beans, they start losing their freshness immediately. They lose their freshness due to oxidation.

While proper storage of coffee beans in an airtight container helps in slowing down the oxidation process, you should use stored beans within 4 to 5 weeks after roasting. If you brew with stale beans, they will taste off and sour. If you notice lemon citrus notes (citric acid), chances are that the beans are completely stale. In that case, your only option is to get a new supply of fresh beans, be it Arabica variety, Robusta, or a combination of different blends.


    4. Brewing with Excessively Coarse Grounds

There is no single grind size that applies to all coffee brewing techniques. Essentially, the brewing method in question determines the grind size. Fine grounds are more ideal for brewing methods that require fast extraction due to their smaller surface area.

On the other hand, coarser grounds require more time to extract flavors from each particle. If the grounds are excessively coarse, each particle will not get sufficient time for balanced flavor extraction due to less contact of the particles with water. Hence, there will be under extraction and sourness in your brew. Thus, if the brewing method you are using results in sour coffee due to coarse grounds, try using a finer grind size to fix sour coffee. The idea is to make adjustments to the grind size setting on your grinder until you find a perfect one for your brewing equipment.


    5. Improper Water Temperature

Just like with under extraction, using a lower water temperature than needed will cause poor extraction. As a result, your brew will taste sour. So why does well prepared cold brew lack a sour taste yet it uses cold water to steep the grounds?

To answer this question, you need to understand that the cold brew process takes at least 10 hours to extract sufficient coffee flavors. The longer coffee steep time allows for sufficient extraction with cold water. However, fast brewing methods such as the espresso and French press require brewing with very hot water.

The purpose of using hot water is to allow the coffee to bloom and for sufficient extraction. That is why you also mix instant coffee with hot milk for it to dissolve. Else, it will not dissolve easily in cold water, not unless you are making whipped cream.


    6. Excessively Fresh Beans

You can also end up with a sour morning coffee due to brewing with very freshly roasted coffee beans. If you brew with beans roasted within the last 1 to 3 days on average, your brew will taste sour, which is a common mistake among inexperienced brewers. Essentially, freshly roasted beans require a few days to de-gas. Insufficient degassing can cause sourness. Here, the solution is to give the beans a week to de-gas before brewing.


How to Prevent and Fix Sour Taste in Coffee

Fortunately, brewing coffee at home gives you the freedom for experimentation. In case your brew tastes sour, there are possible fixes you can try including:

    1. Increase the Brewing Time

If you are someone who prefers buying ground coffee instead of whole beans from roasters or anywhere else on the market, you will need to choose finer grounds for fast brewing techniques. If you happen to buy coarse grounds but are using fast coffee brewers such as an espresso machine, you will need to increase the brewing time for proper extraction.

Sour coffee often occurs due to a shorter brewing time than required. Shorter brewing time causes under extraction of flavors. Increase the brewing time to allow for sufficient extraction. That way, all important flavor compounds will end up in your favorite caffeine drink.

If you are using an AeroPress system or French press to brew, wait a little longer before plunging the grounds. Also, plunge slowly. If you are using the pour-over coffee maker, pour over the water a bit slower to increase the overall time that the grounds interact with water. However, avoid over-extraction as it may cause bitterness.


    2. Use Finer Grounds

As mentioned earlier, under extraction is among the main reasons for sour coffee. Under extraction can occur if the particle size of the ground coffee is too large. It takes longer for water to saturate larger grinds. Consequently, there is insufficient extraction as water passes through the grounds on the filter. In this case, grind your beans to a finer size. You can adjust the grinder speed for finer grounds. Experiment with finer grounds for a couple of times with your favorite recipe for more extraction until you perfect and get a tasty cup of coffee.


    3. Increase the Coffee to Water Ratio

Coffee recipes differ in terms of the coffee to water ratio. The traditional ratio is 2 tablespoons of ground coffee to 8 ounces of water. However, note that this ratio does not work for all coffees. For instance, single-origin coffees, specialty coffee, and some coffee blends taste more sour than regular coffees, even with common recipes. That is why you should utilize your taste buds.

If you use less water than needed, you will risk having a more concentrated and dark coffee beverage. A more potent brew often results in a stronger sourness, and nothing tastes as bad as bitter and sour coffee.

Generally, acidity in coffee comes out as the pleasant flavors you feel in coffee and is balanced out by sweet notes. If your brew is sour, consider increasing the amount of water. With increased water, there is more extraction of all flavors for a balanced cup of coffee with sweet notes and softer acidity level.


    4. Check the Water Temperature

If you are making hot coffee, you need to ensure you are using the right water temperature. Essentially, brewing a well-balanced cup of coffee requires using hot water at a temperature of about 195 to 205 degrees Fahrenheit.

You can use a thermometer to get the temperature right. If you do not have one, just boil enough water. Once it boils, remove it from the heating source and it will have gained the optimum brewing temperature. However, use the boiled water right off the boil to prevent it from cooling.

Some brewing methods use steam pressure which requires boiling water, such as a type of espresso maker known as a steam espresso machine. Also, the moka pot features a design that uses steam, which rises in the direction of the ground coffee to steep it.


    5. Check the Freshness of the Beans

As stated earlier, brewing with stale beans causes a sour taste in coffee. Thus, always brew with fresh beans that have not been stored beyond five weeks after roasting. Also, overly fresh beans cause sourness. Thus, give them some time to de-gas. Brew with beans that have degassed for at least 1 day to avoid any issues with sourness.

Also, always store beans in an airtight container to maintain their freshness by preventing oxygen and moisture from getting into the beans. Store the container at a location away from sunlight. There is a wide range of great storage options and locations, such as inside kitchen cabinets or pantry cabinets.



Pointing out variations in how your coffee tastes is all about the taste buds on your tongue. If your brew tastes sour after taking a sip, it will help to know the cause and possible fixes. Use your taste buds when trying the aforementioned fixes until you get a brew that tastes well balanced according to your preferences. Also, you can try different types of coffee bean such as Ethiopian, Colombian, Kenyan, Indonesia coffee, and Brazil coffee among others. With this guide and tips in mind, we hope that brewing sour coffee will be a thing of the past. After all, no one wants a sour-tasting coffee.


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