5 Reasons Why Lukewarm (Cold) Coffee Is So Bad

black coffee lukewarm in mug

The difference between a fresh cup of coffee and one that’s left to get cold is clear to most people. But what’s not so obvious is why the taste changes so dramatically. The ingredients are the same. One reason is actually part of our basic survival mechanism, but more on that in a moment.

Cold coffee tastes bad because our taste receptors pick up the bitterness of the coffee easier at lower temperatures. Coffee also becomes stale as it oxidises in the water and environment. The flavor deteriorates as soon as the solubles mix with the air. The flavor of the milk also gets more bitter.

So when we drink coffee between the temperatures of 68 to 95°F we taste all the bitter flavors of the coffee, bitterness that we wouldn’t have tasted if we drank it while it was still hot, at least over 95°F.

The higher temperatures cause some of the bitter taste receptors to be inactive, allowing you to enjoy the more of the pleasant flavors the coffee offers.

That’s a very basic explanation of why cold coffee doesn’t taste good, but there’s actually a lot more to it than that.Below, we look at the primary reasons cold coffee is so different to hot. We also investigate iced coffee and cold brew, to see what makes them completely different from each other.

The 5 Main Reasons Cold Coffee Tastes Bad

While there are many reasons, and it differs based on preferences, there are 5 most likely reasons that cold coffee tastes worse than hot or iced coffee.

1. Taste Buds Work Better At Lower Temperatures

Thousands of years ago, people weren’t sure of what they could safely eat or drink, so they relied on their senses of smell and taste. Foul smelling, bitter tasting food is naturally unappealing to most people because food of that nature in the wild is mostly toxic. It’s part of our built in survival mechanisms that prevent us from consuming toxic food.

By drinking your coffee while it’s still hot, well over 95°F, you prevent your taste buds from identifying the bitterness the coffee contains. Once it reaches the temperature of the environment, your taste buds will perform at their peak and detect the bitterness.

Our bitter taste receptors are much more sensitive than the others, which is why it tastes so bitter at a low temperature.

2. Oxidation Makes It Stale

From the moment beans are crushed, they begin to oxidise. The more the coffee has time to mix with air, the more stale and unpleasant it becomes. The pH of the coffee increases a bit during the oxidation process, adding to its bitter taste.

As long as you’re smelling your coffee’s rich aromas, it’s losing its taste. Even if you fill your flask to the brim with freshly brewed coffee, the water content has enough oxygen to make the coffee stale within an hour or less.

Everyone’s taste is unique, so some people may be ok drinking coffee that was made hours before, while others won’t give an hour old brew the time of day.

3. The Milk In The Coffee Starts To Turn

If you enjoy milk in your coffee, it will make it taste even worse if you’ve left it to stand for some time. Milk starts to go sour as soon as you pour it into your cup, which adds to the bitterness of old coffee.

4. It Doesn’t Smell As Good

According to some scientists, cold coffee tastes bad because it doesn’t smell as good as when it’s hot. The sense of smell plays a large part in the way we taste. Basically, if the coffee isn’t hot enough to give off a pleasant aroma, it won’t taste as good. The same applies to everything we consume.

5. You Ignore The Bitterness Easier When It’s Hot

With your mind focusing on whether the coffee is at a safe temperature to consume, the heat distracts your senses from the bitter taste. Your mind can play a huge part in the way you perceive taste.

I remember an experiment in school where a kid was blindfolded and given an apple to take one bite of… Except it wasn’t an apple, it was a raw potato polished up to feel like an apple. He took a bite and chewed it once or twice as the teacher asked him what he thought. Unphased he said, “it’s ok…” then she told him to take the blindfold off. When he saw the potato, his face turned from boredom to disgust. He promptly spat out the remainder of his bite into the bin.

If you have a sip of coffee and realize it’s gone cold, your mind might be telling you that it tastes worse than it actually is.

Why Iced Coffee Is Good And Cold Coffee Is Bad

Iced coffee tastes good because it’s usually served at 40°F or less. At these icy temperatures, your taste buds don’t work well enough to pick up the bitter flavors of the coffee. The temperature is not at the optimal range for your taste buds to work 100%. The same reason your taste buds don’t pick up the bitterness at high temperatures.

Why Does Reheated Coffee Still Taste Bad?

Reheated coffee still tastes bad because it’s already gone through oxidation, which causes it to lose its pleasant flavors. Once coffee has gone cold and stale, it won’t lose that bad taste even if you microwave it.

Is Cold Coffee Bad For Your Health?

The temperature of the coffee does not affect its nutritional content. So if you’ve left your coffee to go cold, you can drink it without worrying. However, cold-brew coffee has some health benefits that hot coffee doesn’t.

Health Benefits Cold Brew Coffee

Cold brew coffee is brewed for 12 to 24 hours with cold water. It needs that amount of time because it’s more difficult for it to extract the flavors. One of the big advantages of this method is that it results in less acidity in your coffee. Here’s what that means for you and many other health benefits of cold brewed coffee.

It can reduce acid reflux

Cold brew coffee is around 67% less acidic than hot coffee. With less acidity in what you consume, comes less stomach irritation. It can also reduce your chance of developing heart burn for the same reason.

Cold brew coffee is better for teeth

The acidity in hot coffee contributes to tooth decay as it breaks through the enamel of your teeth. Cold brew coffee won’t be as destructive to your teeth because of the reduced acidity.

It can be more hydrating

Cold brew coffee is severed in the same way as iced coffee, plenty of ice cubes. So the water content can easily be higher than that of hot coffee. But that’s if you let the ice melt as you drink it, if you chug it down before the ice melts, you’ll lose out on all that healthy water.

Cold brew coffee has less oil

Oil in coffee? Yes, when you brew a hot cup of coffee, there are certain oils that are extracted along with the acids and flavors. With cold brew, you can taste the coffee better because the oil doesn’t block up your taste buds. This gives it a rich, smooth flavor.

Gentle on your stomach

Cold brew doesn’t cause irritation for people with ulcers and other stomach problems.

Does Cold Coffee Still Work?

When you made yourself a nice hot cup of coffee but got sidetracked and finally got back to your cup, the caffeine levels will still be the same and thus it will still be effective.

Does Cold Coffee Still Work?

Conclusion

For the most part, cold coffee tastes so bad because of oxidation and the way in which our taste buds work. The oxidation causes it to taste stale, just like other foods lose their flavor after being freshly made. When coffee gets to the temperature of the room it’s standing in, it’s very easy for our taste buds to zone in on the bitter flavor of the coffee.

The other factors that make cold coffee taste bad are more mental than physical. As explained further above, if you don’t smell the coffee, it won’t taste as good, our sense of smell and taste are closely related. Temperatures of less than 68°F and more than 95°F can also distract your mind from the bitter taste.

In the end, drink your coffee however you like, some people love the taste of coffee that’s gone cold and stale, although I’m definitely not one of them.

Tim S.

Tim loves roasting, brewing, and experimenting with coffee. After years of perfecting this craft, working as a barista, and owning a small coffee service in college, he has decided to share his knowledge with the world.

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