Why Does Coffee Taste Sour?

Have you ever had a cup of sour coffee?

It’s a pretty common problem, right up there with coffee tasting too bitter. In fact, the two problems are actually related!

So why does coffee taste sour?

In this article, I want to address the problem of sour (and bitter) coffee, and what options you have to eliminate these unwelcome flavors.

What Makes Coffee Sour?

Sour coffee is a symptom of under-extraction during the brewing process.

The good news is that this leaves the solution in your hands, as all you’ll need to do is make minor adjustments to how you’re brewing your coffee.

Sour vs 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. To put it simply, “Extraction is everything that the water takes from the coffee.

Different compounds are extracted at different points of the brewing process, and in the same order every time.

  • First, the fats and acids are extracted, producing that oily, sour flavor
  • Next come 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.

So, as you can imagine, the length of brew time is the major deciding factor here, with the two unwanted options — sour and bitter — on opposite ends of the brewing spectrum.

If you steep your coffee too quickly, not enough sugars will be 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.

Here’s a good visual of what under-extracted and over-extracted coffee can look like when using an espresso machine.

How to Fix Sour Coffee Depending on your Brewing Method

If you’re wondering what you can do to get rid of that awful taste in your coffee, it’s time to change up your grind size and brewing timeRyan from Bean Box lays out a few great tips tailored to some of the most common brewing methods.

Note: Coincidentally, Bean Box also has one of our favorite coffee subscriptions, too! 

If you’re getting sour French press coffee, consider letting the grounds steep longer. You don’t want to venture far from that ideal coarse grind so that you end up getting sediment in your cup, but experimenting with brew timing can make a huge difference. Make sure you’re giving the coffee at least 3-4 minutes of brew time.

You can brew even longer than this, but eventually you’re going to start getting that bitter flavor. It’s easy to over-extract coffee with a French press, so if you have leftover coffee after filling your cup(s), decanting is usually recommended.

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. However, if you have sour cold brew coffee, chances are you’re not using a fine enough grind or enough coffee grounds in general. As a rule of thumb, you usually want between a 1:5 and 1:4 grounds-to-water ratio for cold brew.

If you’re getting sour drip coffee you may be using too coarse of a grind. This can also lead to sour pour over coffee or cause a sour taste to your coffee maker pot. Carefully increase the fineness of the grind until you achieve a nicer flavor. Just don’t get too fine or you’ll clog your filter and start introducing that bitterness!

If your Aeropress coffee tastes sour or you keep pulling a sour espresso, again, try a finer grind size. Particularly with these kinds of methods, the extraction time can be mere seconds, which means the grind has to be fine enough to allow the extraction at a rapid pace.

Note: If you’re feeling confident and have the equipment to closely monitor your water temperature, you can also experiment with different levels of heat. The SCAA sets the official brewing temperature at 200°F ± 2°F (92.2 – 94.4°C). Try to track the temperature you’re brewing at and alter it ever so slightly. This can have a significant effect on the sourness of a cup of coffee!

One Last Note: On Sour Arabica Coffee

Another factor that can contribute to the perception of sourness is drinking lighter roasted, fruitier coffees – especially of the Arabica variety.

If you are used to darker roasts but try a light coffee, such as an Ethiopian or Kenyan single origin, the sharpness of the fruity flavors can be overwhelming.

Not only that, but the fruity flavors can actually come across as sour, when really you are simply not used to fruitiness in coffee.

Note: If your coffee smells sour rather than tastes sour, it’s a good sign the oils in the beans are going bad, and therefore the beans themselves are going bad.

So, Why Does Coffee Taste Sour?

Extraction, extraction, extraction. If your coffee is under-extracted, it’s going to taste sour.

Fortunately, it’s an easy problem to fix. Just tinker with your brewing method a bit and see if you can’t dial things in to get that perfect cup a joe!

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!

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