Why Does Coffee Taste Different When You Microwave It?


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Why Does Coffee Taste Different When You Microwave It?

We’ve all done it before. Brewed the perfect, piping hot cup of delicious coffee, then promptly forgotten about it. It seems such a waste not to drink it, so the most convenient solution is to pop it into the microwave for a quick blast of heat. The result, however, is less than satisfactory, so why does it taste so different?

Microwaved coffee tastes different because the rapid heating process causes the coffee to release compounds like caffeic and quinic acid. These chemicals give coffee to have a bitter, astringent taste that many people find unpleasant. 

What, if anything, can you do about your cold coffee? Let’s look at what affects coffee taste, particularly when you microwave it. I’ll also give you some handy tips on what you can do to rescue that forgotten cup. 

Why Does the Microwave Change the Taste of Coffee?

Coffee contains chemical compounds called “chlorogenic acids.” These acids are known as “esters” and generally have a pleasant fragrance. They are also commonly found in perfumes, flavorings, and other fragranced products like cosmetics and foods. 

You’ve probably already guessed that these chlorogenic acids are what create coffee’s aroma and flavor, and you’re right. They do. However, when you heat coffee, chlorogenic acids turn into quinic and caffeic acids.

When released moderately, these acids are responsible for the slight bitter taste we all enjoy in our coffee. When there’s too much of them, you end up with an over-bitter unpleasant tasting coffee.

The heating process is short and severe when you put coffee in the microwave. The coffee heats up too quickly and too much, causing an excessive amount of quinic and caffeic acids to be released and a significant reduction in chlorogenic acids. 

Can You Microwave Instant Coffee?

Microwaving any type of coffee will result in the over-production of quinic and caffeic acids. Even instant coffee, which is highly processed and therefore lacks the flavor nuances that fresh coffee has, will be victim to a more bitter taste when microwaved.

Instant coffee makes an excellent iced drink, so don’t throw it away—throw it over ice! More on that later. Here are some amazing choices from Amazon.

Does Microwaving Coffee Affect Caffeine Levels?

It’s a prevalent and widely circulated thought that reheating your coffee causes it to lose its caffeine. We’re happy to report that this thought is entirely a myth.

During an interview with Inverse, Christopher Hendon, AKA “Dr. Coffee,” states that caffeine is a pretty stable molecule, and once it’s been extracted into the water, “it isn’t going anywhere.”

So, if you don’t care about the taste of your coffee and only want it for that sweet boost of energy, swig it down any way you like.

Is It Harmful To Drink Microwaved Coffee?

While microwaved coffee may taste pretty bad, it’s not going to do you any harm. Reheating coffee doesn’t release any harmful compounds or damage the body. Your taste buds may disagree, but even they’ll be fine—give them a decent cup of coffee to compensate!

What Is the Best Way To Reheat Coffee?

There is a short answer to this question. Since heat affects the coffee’s taste, there is no best way to reheat coffee. You’re better off drinking it cold.

However, I appreciate that many people don’t enjoy drinking cooled coffee, especially if it’s the middle of winter. Reheating that cup may be your only option if you don’t want to waste it.

When it comes to reheating, you have two methods at your disposal:

  • Microwaving
  • Warming on a stovetop

Warming your coffee very slowly in a saucepan is widely considered the best method to reheat coffee, even though it does release bitter notes into the flavor. The key here is to put it on as low a heat as possible and let it gradually warm. Don’t let it get too hot, or you’ll blow it.

That said, you can successfully warm your coffee in a microwave without resulting in too terrible a taste. The secret is to use the microwave on the lowest setting and do it in short bursts.

Interestingly, this blind taste test YouTube video of coffee expert James Hoffman results in the microwaved coffee tasting the nicest out of all his reheating methods. Check it out:

Our recommendation: if you’re a serial coffee forgetter, try both reheating methods and see which tastes the least awful!

What Is the Best Way To Enjoy Cooled Coffee?

You can quickly rescue cooled coffee by turning it into a delicious iced coffee drink. Of course, this is best enjoyed during the warmer months, but it is a solution to enjoying your forgotten coffee without ruining the flavor. Mmmm, a couple favs are Victor Allen pods or HALO Hydrating Iced Vanilla Latte in convenient packets, both shown here from Amazon.

Making iced coffee is as simple as pouring your cooled coffee over ice, but you can easily zhuzh it up and make it a bit fancier. Here’s a quick YouTube video from Munch Library showing how you can make five different Starbucks-style iced coffee recipes:

What Affects the Overall Taste of Coffee?

We all consider the main ingredient in coffee to be caffeine. But although caffeine is undoubtedly present in coffee, it only makes up 2-3% of the bean’s composition. Coffee beans are made of over 1,000 chemical compounds, including carbohydrates, proteins, and lipids. 

If you’re keen to dig into the science, this detailed report on The Chemistry of Coffee and Its Analysis by Hemraj Sharma is helpful.

With such complex chemistry going on, almost anything you do to a coffee bean affects its taste. Here are just a few examples of what can affect the flavor:

  • The species of the coffee plant – Robusta is more bitter, while Arabica is sweeter
  • Where and how the coffee is grown
  • Whether the beans are wet or dry processed
  • How the beans are blended together
  • How the coffee is brewed
  • Whether the coffee is reheated or not

How To Get the Best Flavor Out of Coffee?

The science of coffee can get very—well, sciencey and complicated. But it needn’t be this way. If you’re the average coffee enthusiast who simply wants to enjoy a great-tasting cup of joe, stick to the following rules, and you won’t go wrong:

  • Buy the best quality beans or ground coffee you can afford. If you can buy organic, specialty beans, then even better.
  • Store the coffee away from heat, light, and air. In other words, treat yourself to a coffee tin and keep your coffee safely tucked away.
  • Use filtered water, particularly if it’s hard water. Hard water can ruin the taste of your coffee.
  • The brewing water should be at a temperature of 195-205 degrees Fahrenheit (90.5 – 96.1 Celsius)
  • Keep the coffee-to-water ratio in the sweet spot. One part coffee to 15-18 parts water.
  • Try not to forget about it. Drink it while it’s hot!
  • Choose a suitable quality brewing device.

European Coffee Trip covers all the different methods in this handy YouTube video: 

Final Thoughts

With all that said, you’ll still forget the odd cup of coffee here and there. I know I do, especially if I’m busy working. I like to prepare ahead by having ice available to transform my tepid brew into an ice-cold spectacular. 

If iced coffee isn’t your thing, try out one of the reheating methods but keep it slow and steady. You’ll probably have more luck with the saucepan method, but using the microwave at a low intensity should also work. I’d love to hear your results and how the coffee tasted.