Sour Coffee And Extraction (and How To Fix It) - HomeGrounds

Sour Coffee: Ways To Fix It Using Pro Extraction Tips

Have you ever had a sour cup of coffee? It’s a pretty common problem, right up there with coffee tasting too bitter.

So why does coffee taste sour? Hint: it has something to do with extraction. In this article, I want to address the possible causes of sour coffee and offer a range of solutions to eliminate these unwelcome flavors.

What Makes Coffee Taste Sour?

Sour coffee is most often a symptom of under-extraction of the coffee grounds during the brewing process. When under-extraction occurs, the coffee bean’s sweeter flavors don’t make it into the cup. There is nothing to balance the acidity, and a sip of coffee may taste grassy and sour (1).

“Under-extracted coffee won’t have the sweetness and slight bitterness needed for balance and will have a sour taste…You can create coffee that is balanced to your taste by controlling the extraction.”

The good news is that the solution is in your hands. All you need to do is make minor adjustments to how you’re brewing your coffee to avoid those unpleasantly sharp flavors (2).

Fresh Coffee Is The Best Coffee

One thing you can’t fix, no matter how much you tweak your coffee recipe, is old beans. As coffee loses freshness, its oils evaporate, its natural sugars break down, and its lovely balance of organic acids is thrown off. This can lead to a sour taste in your coffee.

Fortunately, this problem is easy to solve. Buy freshly roasted coffee beans directly from the roaster whenever possible, and don’t buy more than you can drink in a month.

Sour Or Bitter Coffee: The Two Sides Of The Extraction Coin

Coffee extraction occurs when the flavor compounds of the ground coffee beans are extracted with hot water. Different components are extracted at different points of the brewing process, always in the same order (​3​​​).

First, the fats and acids are extracted, producing that oily, sour flavor. Next comes the sugars, which serve to balance things out with their sweetness. And finally, if you overdo it, the plant fibers will extract, allowing the bitter elements to come out to play.

The length of brew time is the primary deciding factor, with the two unwanted options (sour and bitter) at opposite ends of the brewing spectrum. If you brew too fast, not enough sugars will be fully extracted from the beans. On the flip side, if you let the coffee steep for too long, it can over-extract and lead to bitter coffee.

Ways To Fix Sour Coffee (No Matter The Brew Method)

Assuming you’ve got fresh, high-quality coffee beans, preventing sour coffee at home is a matter of adjusting your brewing variables to nail the perfect extraction.

Check out this video with Steven Holms from Home Grounds for a great demonstration:

The four primary brew variables are:

1. Brewing time: A longer brewing time increases extraction. Note that finer grinds in drip and pour over coffee methods will also lengthen the brew time, essentially doubling the effect.
2. Grind size: With a finer grind size, you’ll extract more flavor because the coffee grounds have more surface area in contact with the hot water. Getting the grind size right for each type of bean and brew method is part of the art of coffee. Download our coffee grind chart here.
3. Water temperature: Chemical reactions double for every increase of 10 degrees Celsius, which means raising the water temperature increases extraction (4). Be careful, though – too high a water temperature results in bitter or burned tasting coffee. The Specialty Coffee Association advises a brew temperature between 195 and 205 F (​5​​​).
4. Coffee-to-water ratio: The coffee-to-water ratio mainly controls how much flavor is in the cup (whether it tastes weak or strong). But in some infusion methods, like a French press or Aeropress, the amount of coffee and water can affect the sour/bitter balance.

Here are our recommended solutions for fixing the sour flavor in several popular brewing methods. Where we offer multiple solutions, the most likely culprit (and the easiest fix!) is listed first.

Problem: Sour French Press Coffee

Here’s what to do if your french-press coffee tastes sour:

SOLUTION 1: Increase The Brew Time

Make sure you give the coffee at least 4 minutes of brew time. You can brew even longer than this (we’ve found some coffees brew a perfect cup after six minutes of steeping), but eventually, you’ll start getting a bitter flavor. It’s easy to over-extract coffee with a French press, so if you have leftover coffee after filling your cup(s), we recommend decanting.

SOLUTION 2: Use A Finer Grind

This is tricky with the French press, because grounds that are too fine will clog the mesh filter or, worse, fill your coffee cup with mud from the tiny particles the mesh doesn’t capture. You may need to experiment to find a “sweet spot” where the grinds are fine enough to produce a balanced brew but coarse enough that you don’t end up chewing your morning mug.

SOLUTION 3: Try A Different Type Of Coffee

Many French press lovers prefer the flavor of a dark roast, which tends to feature more sweet and bitter tastes. If you’re using a light roast coffee and coarse coffee grounds, you run the risk of under-extracting and a cup of coffee that tastes sour. Talk to your coffee roaster for suggestions.

Problem: Sour Cold Brew Coffee

Here’s what to do if your cold brew tastes sour:

SOLUTION 1: Use A Finer Grind

Cold brew coffee is made similarly to French press (you can even make it in a French press!) and is steeped so long that it generally doesn’t have under-extraction issues. If you have sour cold brew coffee, you’re probably not using fine enough grounds.

SOLUTION 2: Use A Higher Coffee-to-Water Ratio

You might simply not be using enough coffee grounds. As a rule of thumb, you usually want a 1:5 or 1:4 weight ratio of coffee to water for cold brew.

Problem: Sour Drip Or Pour Over Coffee

Here’s what to do if your pour-over coffee is sour:

SOLUTION 1: Use A Finer Grind

Sour drip coffee or pour over coffee usually results from an overly coarse grind. Carefully decrease the size of your ground coffee until you achieve the ideal balance of flavor. Remember that finer grounds slow the drawdown, increasing the extraction in two ways. You need to “sneak up on” the grind carefully.

SOLUTION 2: Increase Your Brew Time

This isn’t always feasible with a pour over brewer because the timing is an integral part of the design. If you have something like a Clever Dripper or Hario Switch, try increasing your brew time in small increments – 15 to 30 seconds – and note the resulting flavor. If you have an automatic drip coffee machine with a “Bold” setting, use that.

Problem: Sour Aeropress Coffee

Here’s what to do if you make a sour Aeropress coffee:

SOLUTION 1: Use A Finer Grind

​If your Aeropress coffee tastes sour, a smaller grind size is the first thing to try. Because the extraction time with an Aeropress coffee maker can be so fast, the grounds need to be fine enough for rapid extraction. This is also true of sour espresso.

SOLUTION 2: Use The Aeropress Inverted Method

​What does turning the Aeropress upside down have to do with sour coffee? Using the traditional technique, a small amount of under-extracted coffee dribbles from the brew chamber into your cup. To solve this, Aeropress fans developed a way of steeping coffee with the Aeropress upside down. When the steep time is over, you put your mug on top of the brew chamber and flip the whole thing over.

NOTE: If you feel confident and have the equipment to closely monitor your water temperature, you can experiment with different heat levels. Track your brew temperature and alter it slightly, staying within the recommended range between 195 and 205 F. This can have a significant effect on the sourness of a cup of coffee!

A Final Note On Sour Arabica Coffee

Another factor contributing to the perception of sourness may simply be the combination of the coffee and your taste buds. Many light roast specialty coffee beans are praised for their bright acidity and fruit flavors. But if you are used to dark roast coffee beans, this may taste sour to your palate.

Related: Download the Coffee Flavor Wheel

The easiest solution for this: Turn your coffee grinder a few clicks towards the finer end of the grind scale when brewing a more acidic coffee. This will increase the extraction, making the coffee taste sweeter. Be sure to make notes on the setting you like best so you can repeat it next time.

NOTE: If your coffee smells sour, it’s a good sign the oils in the beans are going rancid. The best solution is to get a good coffee container that protects your beans from heat, light, oxygen, and moisture.

So, Why Is My Coffee Sour?

Extraction! If your coffee is under-extracted, it will result in sour coffee. Fortunately, it’s an easy problem to fix. Just tinker with your brewing method to dial in that perfect cup of joe! Try grinding finer, using a longer brew time, or increasing the coffee-to-water ratio.

If you’re dealing with or have conquered this problem in the past, comment with your experience. Also, please consider sharing the post so that we can save as many innocent sour coffee-drinking victims as possible.

FAQs

What is the difference between sour and acidic?

The difference between sour and acidic is that acidity is a neutral term that doesn’t necessarily refer to an unpleasant flavor. In fact, all coffee is acidic because it has a pH below 7. However, when properly extracted, that acidity is balanced by sweet and bitter notes. A sour-tasting coffee can have the same pH value as a sweet coffee despite its undesirable flavor.

Why does coffee turn sour as it cools?

Coffee turns sour as it cools because its chemical composition is changing. A component of coffee called quinine (a bitter compound also found in tonic water) converts to quinic acid, which has a much sharper, more sour taste (6).

Can sour coffee make you sick?

No, sour coffee can’t make you sick. When coffee goes bad, it may start to taste bland, sour, or otherwise unpleasant. But it doesn’t cause illness like some expired foods. On the other hand, if your coffee tastes sour because you’ve put sour milk in it, you could be in trouble!

References

1. Fernando. (2018, December 02). Understanding Coffee Extraction For Your Perfect Cup. Retrieved From https://www.perfectdailygrind.com/2018/11/understanding-coffee-extraction-for-your-perfect-cup/
2. Rayner, J. (2014, June 07). Hot shot: The story behind the great global coffee revolution. Retrieved from https://www.theguardian.com/lifeandstyle/2014/jun/08/the-coffee-revolution-jay-rayner
3. How Coffee Extraction Works. (n.d.). Retrieved from https://clivecoffee.com/blogs/learn/how-coffee-extraction-works
4. Petrucci et al. (2016). The Effect of Temperature on Reaction Rates. General Chemistry. Retrieved from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_General_Chemistry_(Petrucci_et_al.)/14%3A_Chemical_Kinetics/14.09%3A_The_Effect_of_Temperature_on_Reaction_Rates#title
5. Coffee Standards. (n.d.). Retrieved From https://sca.coffee/research/coffee-standards/
6. Fine Sense Coffee. (2016, February 2). The Academics of Acid in Coffee. Retrieved from https://fivesenses.com.au/blogs/news/academics-acid-coffee/