Last Updated on June 26, 2023 by Barry Gray
I’m sure I’ve told you every now and then throughout this website that I love coffee. It’s fantastic, but I admit that not every cup tastes as good as it perhaps should.
I think there is nothing worse than starting your day with a substandard cup of coffee. Do you know the time when I feel my coffee is at its lowest?
When it’s sour.
Honestly, it’s not a pleasant experience when that happens. But what causes it, and how can you fix it?
Your coffee may be sour because it is under-extracted, or you are using old coffee beans past their best. Look for the best coffee beans around, as some may be sour, and focus on the brewing temperature. Too high a temperature can lead to bitterness and a sour taste.
Basically, you have several reasons why your coffee may not taste as good as you hoped. So, allow me to help you counteract this sour taste and get your coffee back tasting as you expect.
Why Does Under-Extracted Coffee Taste Sour?
I think one of the most common reasons why coffee may taste sour is because of the extraction process. If it’s under-extracted, you will quickly notice your coffee is somewhat lacking in, well, pretty much everything.
Unfortunately, I’ve had some under-extracted coffee, as I’m sure most coffee lovers have, and it’s pretty disgusting. Honestly, it’s just weak coffee.
The problem with under-extracted coffee is that it does mean you have failed to extract enough of the different compounds that create the flavor. You miss the body and density of the coffee, and often the flavor compounds that come through are not quite as pleasant to the taste.
Under-extracted coffee occurs for two main reasons. You failed to brew it long enough, or the grind size was too coarse for the type of coffee you wanted to make.
Either of those issues is problematic, but they are easy to fix even though they involve you making brand-new coffee.
First, check your grind size. You don’t want a rough grind for espresso, for example, and I have a number of articles here on Baristajoy that will take you through grind sizes for different drinks.
Next, don’t rush the brewing process. Some coffee is meant to be brewed slowly to allow the flavors to develop.
Interfering with the coffee and its brew time is not a good idea, so let it do its thing, and you will enjoy the outcome.
Why Do Old Coffee Beans Make Coffee Taste Stale?
Coffee beans have a shelf life regarding the flavor they will produce when turned from beans into that tasty coffee.
This is due to the way coffee beans deteriorate over time, and the roasting process really kickstarts the drop in flavor.
However, it’s not instantaneous.
The problem is old coffee beans begin to lose both their flavor and acidity. That changes everything.
But your coffee tasting sour at this point is not your only problem. It will also taste relatively flat, and that isn’t very pleasant.
Of course, the way to resolve this is to only ever use freshly roasted coffee beans. Grind them yourself, and there will be no opportunity for those beans to taste stale or sour.
Why Low-Quality Beans Can Taste Sour
This kind of follows on from the issue of old beans because I’ve noticed how low-quality coffee beans have a completely different taste to their better counterparts.
What happens is a lack of quality control. The beans have been grown in some incorrect conditions, and the flavor is then lacking.
You see, coffee beans need time to mature on the plant. They need to absorb their growing conditions as they all play a role in the quality of the bean the plant can then produce.
If they are rushed or harvested too early, the quality will diminish, and that spells bad news for your coffee.
Low-quality beans will lack the depth of flavor you want in your coffee. Less care has been taken over them, and this has a tendency to produce beans with more of a sour taste to them.
Also, I tend to find the acidity in low-quality beans to be completely off the charts. I’m not too fond of this about them, and if I do encounter a coffee like this, it’s poured down the sink.
The way to deal with this issue is to try to only ever purchase quality coffee beans. It may be more costly, but you will at least be guaranteed a decent cup of coffee rather than throwing everything away.
How the Brewing Temperature Can Influence Your Coffee
The brewing temperature is integral to producing a good cup of coffee. Ideally, you should aim at something between 195 and 205 degrees Fahrenheit.
But what happens if the temperature is wrong?
Well, it depends on whether the temperature is too hot or too cold, as it will have a different impact according to which way around it all is.
Let’s say the water is too hot. It has the potential to pull too much flavor from the beans leading to that bitterness increasing.
I’ve already stated how bitterness in coffee can make it taste sour, so you can see where this is going if you overboil the water.
But going too cold is also a problem.
If the temperature is too low, fully expect your coffee to be weak and disappointing. Also, getting the full range of flavor extracted from the beans is impossible, and there’s no point in having weak coffee.
How Your Water Can Influence Coffee
If you have hard water, and do nothing about it, then those impurities in your water will have a negative impact on your coffee. In short, the water will change the taste, and not in a good way.
The problem with impure water, which is often high in calcium and other elements, is it pushes the acidity of the water up. That’s not something you want to happen due to the way it affects coffee beans.
If your water is even slightly too acidic, it will result in extremely bitter coffee, and that’s where the sour taste will come into play.
I know people don’t put too much thought into their water and its potential influence, and that’s something I want to change. You need to know if your water is hard or soft because it changes everything.
Also, hard water leads to you having to descale your espresso machine. That alone can produce more of a sour taste to your coffee, and it’s just so easy to avoid.
How Do You Fix Sour Coffee?
I’ve shown the different things that can contribute to sour coffee, but how do you fix it?
Well, you don’t have to completely change everything you are doing, and it won’t take long for you to get back to the sort of coffee you love.
Increase the Brew Time
The first thing I would do is to increase my brew time. That’s because under-extracted coffee is the number one reason why your coffee tastes sour.
So, it makes sense to increase the brew time to counteract all of this.
Now, this does depend on the brewing method you are using. It’s not that easy to slow down an espresso being pulled, but you can certainly increase the brew time quite easily with a French press.
But what if you are making a pour-over? Well, that’s where changing the grind size can play a role, and if you combine having the correct grind size with the perfect brew time, you will have a winning cup of coffee.
Also, you may want to add more water to the brew to increase the time. That alone will help the coffee and bring out more of those sweet and floral notes you need to counteract the sour taste.
The Grind Size
Not all types of coffee will use the same grind size, so having an understanding of what’s required for each brewing method is key.
Take an espresso as an example.
You need a very fine grind for espresso to increase the surface area coming into contact with the water. It then leads to more flavor and an intense coffee experience.
If you used a more coarse grind, the water would fall through the espresso leading to a significantly weaker coffee in the end.
But the same applies to a pour-over, which I’m using as another example here.
A pour-over does not require a fine grind. Actually, that’s something you need to completely avoid.
A finer grind with a pour-over means you will over-extract the coffee leading to an increasingly bitter cup. That is where the sour taste can occur, so getting the correct grind size for your coffee is essential.
Throw Out Old Coffee
If you know your coffee has been sitting around for an extended period, I would throw it out.
I know this sounds horrific, and I agree it’s not something I enjoy doing. Still, it may be essential to get your coffee back to something that resembles a decent cup.
Keep your coffee as fresh as possible. Don’t buy in bulk if you know you won’t drink it over the course of a couple of weeks.
That is a waste of money, and you only increase the chances of producing coffee you simply cannot drink.
My Recap on Why Your Coffee Is Sour
Experiencing those sour notes in your coffee is never a pleasant experience. Yet, I’ve covered some key points that will counteract this problem.
- Use fresh beans. Old beans are more likely to taste sour
- Use the correct grind for your coffee to ensure the correct flavor
- Under-extraction will produce sour coffee, so increase brew time
- Do not use hard water, as it will make the coffee more bitter
- Use the correct brew temperature to ensure the right flavors are extracted
When you look at those points, you can see it’s easy to rectify the problem, which comes as a relief for any coffee lover.
Sour coffee is not nice, but you don’t have to be stuck with it as an option. The tips I’ve mentioned above will certainly help and allow you to enjoy your coffee once again.
Yet, the hardest thing is that coffee may suddenly taste sour, and you only know it after that first sip. However, prevention is the best way to stop this happening, and that was my aim.
Hopefully, you will now know how to cope with that sour coffee and can move forward to producing quality coffee suitable for your tastebuds.