Coffee Tastes Sour? Why It Happens & How to Fix It

One of the main reasons your cup of joe might not be as delicious as you want is because your coffee tastes sour. It’s a common problem, and there’s a good chance you’ve come across it before. Fortunately, coffee sourness is fixable, so read on to learn why it happens and how to make your coffee taste good!

Why does your coffee taste sour?

There’s quite a bit of science involved in brewing the perfect cup of coffee, with plenty of variables to worry about, like grind size, brew time, and coffee-to-water ratio. Several factors can ruin your coffee drink, from inconsistently ground coffee beans to the wrong water temperature.

Due to the complexity of coffee, even the most committed home barista can end up with a pot of unpalatable coffee. However, patiently examining the many factors can help you fix the problem.

coffee tastes sour

1. Under extraction

Extraction is the fundamental basis of coffee brewing. It refers to how flavor compounds are drawn out of the coffee grounds when steeping them in water. Extraction is a scientific way of saying “making coffee.”

Not giving yourself a long enough extraction time when you brew coffee is a prime suspect for causing sourness. There is a whole range of flavor compounds in coffee beans; not all are extracted at the same rate during the brewing process. The first chemical components drawn out of the coffee beans are fats and acids responsible for the sour coffee taste.

Coffee also contains natural sugars that help to create a balanced taste. However, they take longer to be extracted. Under-extracted coffee tastes sour because all the oils and acids have been pulled out into the water in the early stages of brewing. Still, the sugars haven’t had enough time to seep into the water. You can prevent this problem by steeping coffee for longer to get a balanced range of flavors.

2. Under-roasted coffee beans

Coffee beans must go through a roasting process before being used to brew the delicious coffee that we all know and love. Before they get roasted, green coffee beans contain bitter components and flavors you wouldn’t want in your morning cup.

To turn those unwelcome compounds into a coffee with a decent palate, they need to undergo a chemical reaction known as the Maillard reaction. The actual chemistry of the Maillard reactions is pretty complex and involves astonishing chemical components. Therefore, roasting coffee beans just the right amount is important to get those rich aromatic notes in the final brew. You can choose from light to dark roasts, but even professional coffee roasters sometimes make mistakes.

Roast the beans too much, and the coffee will become burned and bitter. Too little roasting, on the other hand, too little roasting will result in under-roasted coffee beans because they won’t have enough time to undergo the Maillard reaction properly.

Light roast coffee is less roasted than dark roast coffee, which is known to be more acidic than dark roast coffee. While acidity is not the same as sourness, those flavor properties can be confused, especially if you are still calibrating your taste buds.

When trying to rule out what in your brewing process is making your coffee sour, you could switch to darker roasts, at least temporarily. Light roast coffee is a key component of the third-wave coffee movement, which encourages the coffee roaster to take a thoughtful and unique approach to the beans. However, its sour notes are not necessarily everyone’s favorite.

under roasted coffee beans

3. Wrong water temperature

Making a good cup of coffee isn’t just about boiling the kettle and dumping hot water over the grounds. Another factor that affects coffee sourness levels and flavor balance is water temperature.

There are several ways your water temperature can affect whether your coffee tastes sour. Overly hot water risks burning or scalding the grounds before they can steep, creating an acrid, bitter taste that might sometimes stray into sourness and acidity. Though you naturally want hot coffee to enjoy rather than a tepid mug of brown, it’s important not to overdo it.

On the other hand, a water temperature that is too low might result in the appearance of our old enemy under-extraction. The colder your water, the fewer flavors it will be able to draw out of the coffee.

Remember that the first things extracted during brewing are fats and acids that result in a sour flavor. When your water is too cold, you are unlikely to get past that stage of brewing, meaning that sugars will remain locked up in the coffee grounds and not in your cup.

It’s also worth mentioning that coffee tastes weak and watery when brewed with underheated water. It will not be fully extracted, so you won’t get all the vibrant coffee flavor you crave and sour coffee aftertaste.

4. Stale coffee

No matter how you consume your coffee, quality coffee beans are the essence of a delectable coffee cup. Whether you are a fan of more acidic light roast or more bitter dark roast beans, freshness and proper storage will help you enjoy your preferred coffee without a sour taste.

Several factors can influence the quality of coffee beans. They include the storage method, the temperature at which the coffee is kept, and how fresh the beans are. The best way to ensure you get quality beans is to purchase freshly roasted specialty coffee.

Understanding how to store your coffee at home is also very important. Even the best quality coffee can go bad when stored in a moist environment or in an unsealed package or container.

The aromatic flavor compounds that make the coffee enjoyable will evaporate when stored in temperatures above 75 °F (24 °C). As a result, you may end up with a sour brew. Ensuring you source quality coffee beans and store them properly could save your coffee and your day.

smelling ground coffee

5 ways to fix sour coffee

Now that we’ve established why your coffee might taste sour, it’s time to look at some solutions to this coffee-tasting nightmare. From the French press and Aeropress to cold brew and beyond, under-extracted, sour coffee can rear its head across any brewing method.

Thankfully, there are many ways to combat sourness and acidity in coffee, so you’ll be sure to find a technique that suits your tastes and brewing style.

1. Grind the beans more finely

For those who prefer grinding their own beans over buying bags of ground coffee, there is a very simple solution to the problem of sour coffee: go for a fine grind size. Of course, it is much easier to control if your coffee gear includes a burr coffee grinder. However, if you are willing to spend a little time finding the right supplier of preground coffee, grinding beans yourself is not strictly necessary.

It is also worth mentioning that different types of specialty coffee beans taste better when using different grind size, brewing time, and method. For example, while coarsely ground coffee brewed with a French press will produce a nice cup of coffee, espresso with the same grounds will taste sour.

Arguably, the main reason most people suffer from sour coffee is under-extraction. Several things can lead to this problem, including a lack of surface area in your coffee grounds.

With an overly coarse grind, the water won’t be able to pull nearly enough out of the grounds, and you will end up with sour, under-extracted coffee. Therefore, the easiest solution to this problem is to grind your coffee finer.

The finer the grind size, the higher the surface area of your grounds and the more exposed coffee there is for the water to interact with during brewing. As a result, more fats, acids, sugars, and flavors can be released into the water.

Perfect extraction, it turns out, isn’t just about brew time and water temperature. It’s also about finer grinds.

ground coffee spoon

2. Increase the brewing time

The length of time you let grounds steep results in how sour, acidic, or sweet a coffee directly may taste. More time equals more flavor-bearing molecules and different compounds being pulled out of the grounds.

With that in mind, let’s discuss why brewing time might make coffee taste sour. The first substances to be pulled out of coffee are oils and acids, such as citric acid. These are not necessarily bad for the taste of the coffee. After all, a nice citrus zing can be appealing. However, if these sour compounds are all there because the brewing time is too short, things start to get less enjoyable.

It takes some time for more sugars and other complex flavors to come out of steeped coffee. These components will offset that sour taste and make your coffee taste sweeter and more complex. Therefore, it’s essential to let your coffee steep for a decent amount of time before enjoying it at the sweet spot of well-rounded coffee goodness.

However, don’t leave it too long either. Once the fats, acids, sugars, and other flavor molecules have been extracted from the coffee, if the brewing is continued, the water will start to break down the plant fibers in the grounds.

This is why over-extraction is just as bad as under-extraction. The acids in under-extracted coffee might taste sour. Still, the plant fibers in over-extracted coffee release an incredibly bitter taste that will ruin your drinking experience.

To achieve balance and avoid a sugarless, sour cup and a bitter, grassy brew, you’ll want to brew your coffee for at least 4 minutes. Of course, this is somewhat down to taste, but somewhere in the 4-6 minute region will usually give you the best results.

brewing coffee in french press

3. Adjust coffee to water ratio

Sour coffee might also signal the need to adjust your coffee-to-water ratio. The right amounts of water and ground coffee may vary based on the coffee pot or brewing method. However, the bitter coffee flavor of over-extraction or the sour coffee caused by under-extraction can show a mismatch.

If the previous steps to fix sour coffee have not worked for you, you may need to add more water when you brew your coffee. While using a finer grind size can get you more surface area. The increased surface area won’t help you get more extraction if there’s insufficient water to process it properly. However, more water can get the most flavor out of your coffee within reasonable limits.

Ensuring you’re using enough water for your preferred brewing technique will help create a more balanced brew and counteract the acid that ruins your coffee. Conversely, bitterness may be a sign that you are not using enough coffee, as each bean has to work harder when there aren’t enough of them.

water to coffee ratio brewing with chemex

4. Increase water temperature

Finding a happy medium for water temperature can be challenging, but it’s another important place to look if other factors haven’t accounted for what’s making your coffee sour. While you probably want hot coffee, you shouldn’t pour water over your coffee right after it reaches the boiling point because that can lead to bitterness.

However, if the water goes too cold, it won’t benefit the coffee either. Brewing coffee with too cold water will result in under-extraction and thus sour flavors. Think about cold brew: it steeps in cool water, so sour cold brew coffee is a very common problem.

The National Coffee Association recommends a brewing temperature of 195 °F to 205 °F (90 °C to 96 °C). This is below the boiling point, 212 °F (100 °C). Some kettles have built-in thermometers, but you can use a simple cooking thermometer to measure water temperature if you suspect this is causing your sour coffee. While you’ll probably need to let the water boil if you’re brewing manually, let it cool before you pour it over your grounds.

pouring hot water over coffee

5. Add salt to your coffee

Salt is arguably one of the most important foodstuffs in the world. For centuries, it has been prized for its ability to bring out the best flavors in food, even in sweets like chocolate or caramel. Meanwhile, it’s an essential part of a healthy, balanced diet.

When salt is added to coffee, it brings out the drink’s sweetness while dampening bitterness and sourness. It can even help to elevate stale-tasting coffee, with research showing that salt is a better fix for bitterness than sugar!

When the salty and bitter flavor receptors on your taste buds are activated simultaneously, it can trigger a “cross-modal perception” phenomenon. In short, this process reduces your perception of bitterness. It allows other flavors to come through more strongly, such as sweetness. This is why you can use salt to suppress overly sour or bitter notes from a coffee, replacing them with a hint of sweetness that can rescue your cup.

Experiment with salt, and find out if it works for you! Salt is used in coffee worldwide, so you’ll certainly not be alone if you start to add it to your daily brew.

Sourness in coffee is one of those unfortunate facts of life. Unfortunately, it will sometimes happen, perhaps even in a coffee shop. However, knowing how to look for what went wrong in the first place will help you enjoy well-balanced coffee going forward. You might even learn a lot about coffee in the process!

These fixes for sour coffee may need to be adjusted depending on your brewing equipment, coffee type, roast level, water ratio, brew time, filter types, and personal preferences. Timings and grinds may be slightly different for a French press or filter coffee maker vs. a cold brew or an AeroPress. For example, medium-roast coffee beans may need a shorter brew cycle than light roasts to reach your desired strength.

From supermarket coffee blends to single-origin coffees roasted to perfection, brewing coffee is a labor of love. Unfortunately, no single coffee brewing method or secret recipe will guarantee the perfect brew and help avoid sour coffee. However, these tips should get you closer to the sweet spot between sourness and bitterness.

Whether you’re a professional barista or just a coffee enthusiast passionate about good coffee, there is no reason you should suffer while drinking sour coffee.

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