Sour Vs. Bitter Coffee (Why Does It Taste Like This)

Last Updated on September 22, 2023 by Barry Gray

Bitter or sour-tasting coffee can result from a few things, including beans that have gone bad, brewing methods, storing methods, and water temperature, to name a few. The best-tasting coffee, for most, is mellow and flavorful. Perhaps robust, nutty, and aromatic, anything but bitter!

This article will cover the following topics to help you to avoid sour or bitter coffee:

  • The importance of using freshly ground beans and why it matters 
  • Using the correct water temperatures to prevent your coffee from under or over-extracting the oil and flavor of the bean
  • Understanding brew time and how it impacts flavor 
  • Learning why it is essential that coffee is stored correctly and what happens if it is not 
  • Why not cleaning your coffee equipment can result in sour-tasting coffee or even just making coffee taste ‘Ik’. 

Let’s Agree To Disagree. 

Years ago, I went on holiday to South Africa, and it is truly one of the most beautiful places I’ve ever been. There are coffee shops galore and absolutely no shortage of delicious coffee. It is available in bucket loads. 

You will find no supply shortage if you love wine or coffee. 

We decided to travel up to the Eastern Cape, renowned for its beautiful little dorpes, known to us as towns, on our way to Durban. Dorpes can vary in size from tiny, as in a shop, a petrol station, and a church, to relatively large and bustling. 

what makes coffee sour or bitter

Sometimes Coffee Doesn’t Work Out

On one of these travels, I stopped in a quaint little town I shall not name to protect the innocent. It was beautifully furnished, and I ordered a cappuccino

The waiter served us, and the coffee looked terrific. It even smelled fantastic. A thick, golden crema and a dash of nutmeg finished the beverage nicely. 

It had been a tough, long day; we had driven some 12 hours to the North Coast, so I was looking forward to this. One big sip later, and I had to spit it out. It was as though it was drenched in lemons. It was so sour. Underneath that crema was a dark and horrible coffee. 

At that moment, the waiter asked me how the coffee was. ‘A bit bitter,’ I said as politely as I could. 

‘Bitter?’ he said. ‘But we serve the best coffee in town!’. 

Sometimes Coffee Is Just Bitter 

what makes coffee bitter

So there you go. The town liked it; the waiter was proud of it, but it couldn’t have tasted more unpleasant to me. Was it bitter or a matter of taste? The verdict on that one is still out. 

I’ve had the same the world over. You’ve probably been to a well-known coffee shop a bit late in the day, and they have allowed the coffee to be over-extracted, and you get that cup before they replenish the coffee machine. It isn’t enjoyable. 

Some coffee shops in Europe are famous for their coffee, but perhaps you ordered some that tasted sour while everyone else was quite content with it. It can also boil down to personal preference. 

There Are Times When Coffee Is Bitter 

how to stop coffee from tasting bitter

Let’s be honest. We have probably occasionally produced some sour-tasting coffee at home, so here are a few pointers on how to avoid this. 

When things go wrong, these could be the issues you are facing:

  • Roast level: Lighter roasts are more sour, while darker roasts are more bitter because the roasting process breaks down the coffee beans’ acids, resulting in a more balanced flavor.
  • Grind size: A finer grind will extract more flavor compounds from the coffee beans faster, which can lead to a more bitter cup of coffee. A coarser grind will extract less flavor, producing a more sour cup of coffee.
  • Water temperature: The ideal temperature for brewing coffee is between 195 and 205 degrees Fahrenheit. If the water is too hot, it will extract too many bitter flavor compounds from the beans, resulting in a bitter cup of coffee. If the water is too cold, it will not remove enough flavor, resulting in a sour cup of coffee.
  • Brewing time: The longer the coffee is brewed, the more flavor compounds will be extracted. If the brew time is too long, this can lead to a bitter cup of coffee, and this is where, in coffee shops, the coffee has been left too long in the coffee machine. 
  • Stale coffee beans: Stale coffee beans will taste sour and flat because the volatile flavor compounds in the beans have evaporated over time.
  • Coffee brewing equipment: If your coffee brewing equipment is not clean, it can impart off-flavors to your coffee, making it taste sour or bitter. I know, for example, if I don’t clean my Moka pot correctly, I will get bitter-tasting coffee, mainly if small grounds are trapped in the filter. 

My Key Tips on Avoiding Sour or Bitter Coffee

use freshly roasted and ground beans to avoid bitter coffee

Here are some tips to avoid sour or bitter coffee.

  • Use freshly roasted coffee beans.
  • Grind your coffee beans just before brewing.
  • Use the correct water temperature.
  • Brew your coffee for the right amount of time.
  • Store your coffee beans in an airtight container in a cool, dark place.
  • Clean your coffee brewing equipment regularly.

Using Freshly Roasted Coffee Beans 

When coffee beans are roasted, they release volatile flavor compounds. These compounds are responsible for the aroma and flavor of coffee. However, these compounds are also volatile, meaning they can quickly evaporate. 

Grinding your coffee just before you drink it is the way to go.

Nothing beats the smell and taste of freshly ground coffee beans. 

Freshly ground coffee also contains fewer acids, which can give off that sour taste. So, while stored ground coffee can taste bad, you can avoid this if you grind it just before use. 

Use The Correct Grind Size 

If you grind your beans into a fine powder, more flavor can be extracted. So, to avoid that, a coarser grind will taste better, but if you over-extract, it can also taste sour. If you use finely ground beans, do not over-brew them. Four minutes should be the maximum, but all beans are different so you might need some practice. Trial and error is often the best teacher. 

This is where you need to understand the perfect grind size for the brewing method you will use. It’s different for your Moka pot compared to a French Press.

Don’t Use Very Hot Water 

The ideal water temperature for brewing coffee is between 195 and 205 degrees Fahrenheit. If the water is too hot, it will extract too many bitter flavor compounds from the beans. If the water is too cold, it will not remove enough flavor, resulting in a sour cup of coffee.

Using water at a perfect temperature will avoid these pitfalls in making coffee, resulting in bitter and sour coffee. 

Store Coffee Correctly 

Coffee is an investment. It is not the cheapest beverage, mainly if you buy different blends. So storage becomes very important. Inadequate storage can turn good beans into bad-tasting beans. 

The First Steps To Storing Coffee Beans Correctly 

It would help if you avoided heat, sunlight, and oxygen when storing coffee beans. For example, light and oxygen will rob your precious coffee beans of flavor by breaking down the molecular structure of your beans and taking oils away from the coffee beans. To learn more about storing coffee beans, check out our article here

All you need is a completely airtight container in a dark cupboard. Check that the closet is cool and doesn’t draw humidity to it, and you are good to go. 

Some recommend using the fridge or freezer. You can have some success with freezer and fridge storage, but I prefer not to. Mildew and mold can become issues for beans stored in a moist environment. 

I also recommend buying beans as you need them and not overstocking them. I know it can be tempting to over-buy if the beans are on sale, but often, they are on sale because they are nearing their sell-by date. So buy as you need. You can become a dab hand at how long a particular coffee will last in your home over time. 

Finally Clean Your Coffee Equipment Often 

I love a Moka pot, amongst other great coffee makers, but cleaning and airing it is crucial. I’ve often cleaned it and put the pot back together only to see water in the base, which stinks. That is one thing that can cause awful-tasting coffee, but not checking that all of the old grounds are cleaned away is another culprit. 

I use two little OXO brushes to clean my Moka, and I don’t use soap, only occasionally. I scrub it well, dry it out, and let it air dry overnight. 

Make sure you are doing maintenance on your machines. If not, you will have coffee that could taste bitter. 

To Conclude

There are several reasons why your coffee could be sour or bitter. From equipment not being clean, to coffee beans going stale, exposing the coffee to water that’s too hot, and having the wrong grind size for the brewing method all play a role.

Basically, your coffee can taste different if you fail to extract the coffee correctly. It won’t always result in it tasting disgusting and to the point where you cannot drink it, but understanding the extraction process should make life easier.