5 Top Reasons For Sour Tasting Iced Coffee


5 Top Reasons For Sour Tasting Iced Coffee header image

Got some iced coffee but after the first sip you notice it’s way more sour than you like? What went wrong and how can you fix it? Here’s what you want to know. 

Iced coffee can taste a bit more acidic than hot coffee because the taste buds perceive the taste of the brew differently. If iced coffee is unpleasantly sour, the most likely reasons why it’s sour is that the coffee is stale or under extracted. The type of beans used can also be a cause. 

Let’s go through all the top reasons why iced coffee can be too sour and what to do about it. 

Reasons Iced Coffee Tastes Sour

There can be a few reasons why iced coffee tastes sour. Let’s go over what those reasons are and then we can figure out how to fix them. 

To be clear, we’re talking about iced coffee, not cold brew coffee here. There are differences. 

1. Taste Buds And Temperature

The taste buds perceive tastes differently at different temperatures. For each of the tastes, there is an ‘ideal’ temperature where you can taste a certain taste (sweet, sour, bitter, sweet, umami), the best. Everyone knows that foods and drinks taste differently the further they warm up/cool down. 

It’s not that the coffee is necessarily more sour when it’s iced. But it does TASTE more sour. And the reason also isn’t because the taste buds are more sensitive to sour notes in an iced drink. It’s that the taste buds are LESS sensitive to many other tastes in coffee. 

Sweetness is going to be quite subdued in iced drinks. And there is actually quite a bit of sweetness in coffee. It’s not sweetness like sugar or honey but it does provide a lot of taste notes to coffee. By reducing the intensity of this sweetness, the sourness is going to come out more. 

This is a big reason why most coffees taste a bit more sour cold. However, if it’s sour to a point where it’s really unpleasant, this isn’t the main reason. One of the other problems below is going to be a more likely culprit. 

image of a man tasting coffee

2. Stale Coffee

If you bought your iced coffee from a coffee shop, there is a chance the coffee is stale. Depending on the coffeeshop, they might brew a big batch at the beginning of the day and pour from that batch until it runs out. If you come later in the day, it can get stale. 

Suggested: Why does homemade iced coffee taste difference?

The compounds in coffee start oxidizing and this degrades the taste. If the coffee is kept hot this oxidation happens very quickly. In that case you’ll taste a significant difference in an hour. 

If kept cool in an airtight container, the staling process will be a bit slower but after a few hours brewed coffee will still taste significantly different. And if left cold but in an open container, it definitely will go stale. 

It doesn’t really matter if this is at a coffee shop or at home, coffee oxidizes over time whatever the location. 

Also, even if the coffee is brewed fresh but the used grounds were stale, you get similar results. This is more likely to happen at home. With iced coffee you just notice it more like explained above. 

3. Coffee Roast Level

If a coffee bean is roasted light, you have a higher chance at a sour cup of coffee. That is because there is more acidity left in the beans to begin with. Acidity in coffee is not a bad thing. It can provide a wonderful fruity, bright taste. However, this can become sour if not treated right or maybe it’s just not your cup of ‘tea’. 

Light roasted beans are also hard to extract. They are less porous than darker roasted beans and so the water has less ‘grip’ on the grounds. You want to get a certain amount of soluble material out of the grounds and with light roasted coffee, this is harder to get out. 

Roasting can be seen as caramelizing, it’s the same chemical process. The darker you make a caramel, the heavier and more bitter the taste becomes. The same is the case for coffee beans. The darker a coffee is roasted, the less acidity there is but more bitterness. 

If you buy coffee at the supermarket, there is likely no roast indication. In that case, there is probably a ‘strength’ indicator. In that case, a higher strength usually means a darker roast. 

coffee beans from green to dark roasted.

4. Type Of Beans Used

There is an unbelievable amount of coffee beans and they all taste different. While a really harsh sourness is usually not the fault of the coffee used, it can be a contributing factor. What is a nice fruity acidity for some people is unpleasantly sour for the next person. 

Where beans come from, where they’re grown, what height they’re grown at, where they are on a specific farm, how they’re treated after picking and more all has an impact on the taste of your cup of coffee. You especially notice this with specialty coffee but there are variation in ‘normal’ coffees as well. Looking at the tasting notes on the bag can help. 

Also, some beans are harder to extract which then leads to more sourness as well. 

5. Under extraction

If the iced coffee is brewed fresh and with the right beans, you can still have a situation where the brewing method is the cause of the sourness. 

To brew coffee you want the soluble material in the grounds to get into your water. However, you don’t want ALL of the soluble material, you want the right amount. If you dissolve too much, this is called over extraction. If you dissolve too little, it’s called under extraction. 

In general, if the coffee is bitter, the grounds are over extracted. If the coffee is sour, the grounds are under extracted. So in this case, we’re worried about sourness and there can be a good reason for this. 

The best way to brew iced coffee is to replace a part of the brew water with ice. You put the ice in the pitcher under the filter and the hot coffee drips on it, melting it and diluting the coffee. However, by reducing the brew water, there is less extraction going on. Less water through the grounds means less solubles are dissolved. And the sour compounds dissolve the easiest which is how you end up with a sour cup. 

How To Fix Sour Iced Coffee

1. Fresh Beans

Using fresh beans is always important. Without having high quality fresh beans, it gets pretty hard to brew really good coffee. Even if you use pre-ground coffee, make sure you don’t let it go stale. 

Buy a new bag and see if your coffee improves. Then get an airtight container to store your beans. Properly storing your beans will increase their lifespan. 

You can freeze part of the bag in an airtight container and those beans/grounds will stay fresh. Then just defrost the amount of beans you need for the week. Try to avoid opening the container too many times. So smaller containers are better than large ones. 

Leaving a big bag open for a few weeks is a guarantee you’ll have stale coffee at the end of it. 

ground coffee in a grinder

2. Right Beans

Freshness is one thing but the type and roast level of beans is another. A lot of this is down to taste which is obviously different for everyone. 

However, if sourness is an issue for you, there are two ways you can change your coffee beans; Choose a darker roast level or a type of bean that has more ‘dark’ taste notes on it. 

A higher roast does two things; 1. Darker roasted beans are more porous and therefore easier to extract. This will reduce sourness in itself. 2. Darker roasts have less sour/fruity notes and more bitter notes. 

Another thing you can do is to pay attention to the tasting words on the packaging. Usually people look at those words and don’t recognize any of those words in the coffee once they brew it. Forget the literal taste of those descriptors. Look at them to get an idea of the overall experience. If you see things like; fruity, citrus, lemon, grapefruit, floral, apple, that implies a fruity acidity which for some people could be too sour. Instead look for words like; caramel, black tea, nutty, honey, chocolate, syrup.

Also, use high quality beans. Higher quality beans will have a pleasant fruity acidity instead of harsh sourness. 

3. Brew Fresh

Always aim to drink coffee that’s brewed just before you drink it. It doesn’t matter whether you’re doing it yourself or buying it at a coffee shop. 

In case you brew at home, this is pretty easy, in a coffee shop, you might have to ask. Possibly even shop around at a few different coffee shops to find what you are looking for. 

4. Fix Extraction

Once you’ve got the right beans, it’s time to fix the extraction. There are a few factors you can change to increase the extraction. 

Use about 1/3 of the amount of coffee you want to brew and replace it with ice. That will get the coffee cold (not icy cold) and leaves enough water to brew with. However, there is still less brew water so you need to do increase the extraction other ways;

  • Grind smaller: Grind your beans a touch smaller than you would for a regular pour over. This increases surface area and therefore extraction. 
  • Use hotter water: Hotter water extracts faster. Use water that’s just off the boil. Especially with a medium or light roast. 
  • Use a longer bloom time: The bloom time can help ‘loosen’ some of the solubles. Add enough water to soak all the grounds and then let it sit for about 45 seconds before pouring. 
  • Pour slower: Add water to the filter a little bit at a time. Less water in the filter means less pressure and a slower flow which results in more contact time. 

5. Add Something

If you already have your coffee ready and it’s sour. The only thing you can do is to add in something that balances out the taste. This is going to be something sweet or creamy since those are the best at counteracting sourness. 

That means adding things like, dairy or dairy alternatives, sugar, honey, chocolate syrup, etc. 

A tiny pinch of salt can also help. Not necessarily to counteract the sourness but to increase the sweetness. Salt will also reduce bitterness. 

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