How To Fix Your Sour Cold Brew Now And Forever

You just made a fresh batch of cold brew. You take your first sip and it’s sour and just not nice. What happened and how can you make sure this never happens again? I did some research and found out.

If your cold brew tastes sour, try the following solutions for your next batch;

  • Get fresh beans with a darker roast
  • Grind slightly smaller
  • Let your cold brew steep for longer. Aim for 20 – 24 hours.
  • Make small batches so it doesn’t go bad before you can finish it.

There are a few more things you can do and reasons why your cold brew might be sour. Keep reading below to find out everything you can try.

Sour Cold Brew Reasons

To know how to fix a bad cold brew, we first need to know why it went wrong in the first place. So here are the biggest reasons.

First, let’s clear something up. Acidity is not the same as sour. Acidity can be a great part of the taste of your coffee. Acidity brings a bright, open taste to your coffee. Sour is when it tastes bad.

You can compare it to white wine and vinegar. White wine has a pretty acidic taste but is usually nice to drink. Vinegar is absolutely not nice to drink. And of course, the line of what is too much is different for everyone.

However, there are a few things that are likely to create a bad sour taste and not a good level and type of acidity.

Stale coffee

The first suspect is stale coffee. Coffee gets old pretty quickly. Quicker than most people would expect. Even whole beans are not immune to this. From the moment the roasting process is finished, volatile oils and aromas evaporate out of the beans.

Storing them in an airtight container in a dark, cool place helps extend their life but after a few months, they have had their best life. While they’ll still taste OK for a long time, they’ll become worse and worse.

Stale coffee means that the taste is not balanced like it was before. This leaves flat spots in the taste and can just taste bad in general. Usually, the taste becomes more bitter and sour and can even become rancid.

Good coffee always starts with the right beans. If you don’t use cold brew beans, try that before changing anything else. Cold brew beans are roasted differently so they produce a better taste with cold water (and inversely don’t taste as good when brewed with hot water. This Bizzy Light & Bright cold brew (Amazon link) coffee produces the taste most people like from their cold brew. If you prefer whole beans, these are great (Amazon)

Type of coffee

Next up is the type of coffee you used. People go crazy over wine tasting since there are so many different tastes, notes, and nuances. Coffee is no different. There is such a gigantic variety of coffee beans that you can never taste all of them. And then on top of that, you can combine different beans in a single cup of coffee.

So it could come as no surprise that some coffees are more sour and acidic than others.

The roast of the beans is one part of the equation that I’ll touch on later. But the type and sourcing of the beans is also a very important part


Arabica beans and Robusta beans have pretty different flavor profiles. Generally, Arabica beans are seen as higher quality and better tasting than Robusta beans.

Robusta beans have more chlorogenic acid which adds extra acidity to the taste. That’s why Robusta is often roasted darker since that negates some of the acidity.

But for the least sour cold brew, it’s better to use 100% Arabica beans. Also, there are more and more blends of coffee that are specially formulated to have the least amount of acidity as possible. However, that might cause you to throw away the baby with the bathwater because you’re also limiting the good parts of acidity in coffee.

Medium roasted Arabica ground for cold brew.
Using a medium or light roasted Arabica gives cold brew fruity flavors with almost no bitterness.

Under extracted

Something can also go wrong in the brewing process. When you’re washing clothes, hotter temperatures mean the clothes are easier to get clean. It’s similar to coffee. The hotter the water, the easier it is to extract all the compounds from the coffee grounds.

With cold brew, heat is exactly the thing you’re missing. That can cause the coffee grounds to not be extracted enough. In this case, it’s actually the lack of compounds that balance out the taste that causes your cold brew to be sour.

On the opposite end, there is over-extraction. This happens when you use water that’s too hot and the taste becomes bitter. This is unlikely to be a problem with cold brew since there is no heat involved in the brewing process. That’s exactly what makes cold brew taste so smooth and bright but you have to be careful not to go too far to the other side.

With cold brew, the best way to prevent under-extraction from happening is to extend the steep time. Aim for 20-24 hours of brew time for the best results.

Another way to get better extraction is to go a touch finer on the grind.


Closely related to under-extraction is the ratio of coffee grounds to water you use. You can make cold brew with ratios from 1:1 to 1:10 (coffee grounds: water).

Of course, the more coffee you use for the amount of water, the stronger the cold brew becomes. Now don’t make the mistake of thinking that if your coffee is too sour, you should use less coffee!

How can you make good cold brew without a scale?

Try using more coffee grounds instead. The reasoning is the same as letting your coffee steep for longer. You can extract more from the coffee grounds. So instead of more time, give the water more coffee to extract from.

Different steep times and more coffee will have different effects on the taste though.

Especially if you’re using higher ratios (1:7 or higher), it’s worth a try. If your ratio is already pretty low, this is probably not the issue.

You might think this is a lot of coffee grounds to use but it also makes a lot of coffee. And the spent grounds can still be used for things like absorbing odors and much more. Check out here what you can do with spent coffee grounds.

Getting a coffee scale is the easiest way to get the ratio right and consistent every time you make coffee.


Another reason for sour or acidic cold brew is the roast you’re using. It might be a bit counter-intuitive but lighter roasts actually have more acidic tastes. Darker roasts have a less acidic taste.

Does cold brew coffee break a fast?

Mind you, it’s just the taste. This doesn’t mean there is actually less acid in the beans. A darker roast allows the flavor in the beans to develop a little more. This fuller-bodied taste is what balances out the flavor.

Now this isn’t necessary for all beans since they might be lower in acidity from the tree. A lighter roast leaves the way open for a more open, brighter taste. However, for cold brew a dark roast is better.

Flavor balance

Finally, a last reason could be the flavor balance. In that case, it’s not so much that the sour taste is very strong. It’s more that the other tastes are too weak and the sour just seems to pop more. Your taste buds have nothing else to do so they pick up the sour taste.

Acidity is not necessarily a bad thing. It creates a bright, open taste in the coffee. More acidity does not necessarily translate to the nasty sour taste in coffee nobody likes. Sour is usually a sign of something gone wrong somewhere in the brewing process which can be several things as you’ve seen above.

There is a fine line between a bright, open taste and a nasty sour one. The line might also be in different places for different people. A good acidity is like white wine whereas the bad kind of sour is like drinking vinegar.

The difference between those two comes from the freshness and quality of the beans and the brewing process, especially the heat.


It’s unlikely that this is the problem with cold brew but it could be an issue. When you apply heat to coffee, it changes the chemical structure.

Especially two acids named quinic acid and chlorogenic acid.

The longer you apply heat the more those acids develop and the more acidity you get. That’s why reheated coffee tastes so bad.

With cold brew, this is pretty unlikely since cold brew is kept in the fridge for most of its life. However, maybe you left the pitcher in the sun/next to the stove/on the oven, etc. That could cause more acidity than there should be.


Maybe your batch of cold brew is just old. Outside of the fridge, cold brew only keeps for about two days. Inside the fridge, it’ll keep tasting good for 4-5 days and stay drinkable for more than a week. Although even in the fridge the taste will degrade after the first five days.

Should you keep the cold brew in the fridge?

So if you’re a slow cold brew drinker, make smaller batches.


Now we know the most likely problems that cause sour and/or acidic cold brew, we can start looking at solutions. In the explanation for the reasons, you’ve probably already found some solutions in there as well. But for the sake of clarity, let’s go over exactly what you can do to make sure your next batch of cold brew is what you want it to be.


The best way to improve your cold brew is to get the basics right.

  • Get fresh beans. Whole beans are better than ground and will make a noticeable difference in taste. If you have a place around you where they roast the beans fresh for you, that’s even better. If you get freshly roasted beans, wait for about 2 days before using them.
  • Get a very dark roast. This will give a fuller body that balances out the taste.
  • Grind slightly finer. This creates more surface area on the coffee so the water can be extracted more efficiently.
  • Let your cold brew steep for longer. Allow for up to 24 hours of steep time.
  • Let it steep outside the fridge. The slightly higher temperature will extract the coffee a little bit faster. Just make sure it’s not near any heat sources.
  • Make smaller batches and only drink cold brew that’s up to 5 days old.

You don’t have to try all of these things at the same time. It’s unlikely that all of these things are going wrong at the same time.

The first things you should try are; Fresh, dark roasted beans and a longer steep time. If those don’t do the trick, you can move on to other solutions.

Cover up

Most of these solutions only help you to improve your next batch. So what can you do if you’ve got a bad batch you still want to finish?

Well, if you insist on finishing it, there is not much else you can do other than cover up the taste. This won’t actually solve the taste of the coffee but at least you’ll have a nicer tasting beverage.

Favorite cold brew tools

With these items, you will brew better cold brew

  • Grinder: Fresh beans have to be ground. A hand grinder like the Hario Slim (Amazon) is affordable yet effective hand grinder that will improve your cold brew.
  • Scale: The amount of grounds you use makes a big impact on what your cold brew tastes like. A simple set of scales will makes your brews more consistent. I’ve been using this one (Amazon) for over a year wit h great success. Not the most aesthetic but effective.


Welcome to CoffeeImproved! Since falling in love with coffee, I've been on a journey to improve my morning cup day by day. That means I've tried many different brew methods, beans and equipment and experimented with all of them to find what I like. This is where I share what I've learned with you.

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