Stop Reheating Cold Coffee In The Microwave And Use This Gadget Instead

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You may need coffee to get through a busy morning, but some days, it will get cold. There are pros and cons to reheating old cups of coffee, but according to Andrea Allen, coffee expert, co-founder of Onyx Coffee Lab, and 2020 U.S. Barista Champ and 2021 World Barista Runner-Up, the microwave can do a number on your morning joe. Instead, you might consider a coffee warmer: a small, electric heater shaped like a coaster that keeps your mug steadily heated.

Allen explained that coffee is something you should never put in the microwave because reheating it this way can mess up its flavor. "Microwaves change the structural composition of anything being used in them, so I'm pretty anti-microwave when it comes to coffee," she told The Takeout. Brewed coffee will always slowly lose flavor as it sits, even when it's hot, but reheating can create new problems. Too much heat from the microwave will extract flavorful acids from coffee beans, just like your coffee maker does, so you're basically rebrewing your coffee in uneven bursts from the microwave. Ultimately, this will make it taste bitter, stale, or flat.

That's why Allen recommended mug warmers. "I think that if you like your coffee to stay hot for a long period of time that mug warmers are a great idea. I've used mugs that will stay at a set temperature for an extended period of time, and they are super cool," she said, with "cool" here meaning hot, that is.

You don't need a microwave when you have a mug warmer. They provide an electrically heated surface, which is designed for coffee mugs. The sleeker, more elaborate models get pricier, as do the products that come with specialized mugs. Fancier models have more precise temperature controls, but any model should keep your coffee heated to a pleasantly warm 130 degrees Fahrenheit — like this straightforward Oracer coffee mug warmer.

However, Andrea Allen doesn't necessarily recommend mug warmers for anyone who likes their coffee on the colder side. Brewed coffee needs a couple of minutes to reach a safe temperature, but some folks cool it even more. "I know lots of folks like coffee to cool off, so it depends on preference," Allen shared. If that sounds like you, there's no reason to invest in a mug warmer. 

Allen also shared an alternative to buying this kitchen gadget. "I'm a fan of preheating a mug," she said. Just fill a cup with boiling hot water and let it sit while your coffee brews. Dump out the water before serving yourself a cup of joe, and you'll notice how much more slowly the coffee cools off. It's a solid hack, but a mug warmer gives you much more control and allows you to keep your coffee hot all morning long.