How to Reheat Cold Coffee? Is Pour-Over Coffee Still Tasty When Brewed a Second Time?

Temperature, a perennial topic in the coffee circle, is crucial at every stage - from storing green beans and roasting to extracting brewed coffee and tasting. Each process relies on an appropriate temperature range.

Even if you're not in the habit of brewing coffee, you've surely been told "coffee should be enjoyed while hot" - implying that coffee doesn't taste as good when it cools down. But now it's winter, and before you know it, that steaming hot coffee becomes ice-cold, making you shiver with just a small sip, let alone finishing the whole cup. At such times, many who don't want to waste coffee will try to reheat it. So what's the best way to do this?

The Effects of Cooling on Coffee

FrontStreet Coffee has previously explained that as coffee cools from hot to cold, it mainly affects two aspects: aroma and mouthfeel. Freshly brewed coffee continuously releases its aroma as it cools. When coffee completely reaches room temperature, many of the high-temperature aromatic compounds have largely dissipated, naturally making it less enjoyable to drink.

Moreover, as the temperature decreases, coffee diminishes our taste buds' perception of sweetness and other pleasant flavors, while simultaneously making acidity and bitterness more pronounced. This is why a cup of dark roast coffee typically becomes "more bitter" when cooled, while a light roast with fewer bitter compounds often becomes "more acidic" as it cools.

Since this flavor transformation process is irreversible, reheated coffee cannot possibly taste as delicious as when freshly brewed. Therefore, since we cannot completely "revive" the coffee's original flavors, our primary goal when reheating coffee should be to preserve as many aromatic compounds as possible.

Comparative Heating Experiment

FrontStreet Coffee designed a comparative experiment using pour-over extraction to brew two different types of coffee beans. After allowing them to cool naturally to room temperature, samples were reheated using an electric hot plate, an alcohol lamp, and an espresso machine's steam wand to compare the taste differences between these methods.

Coffee Beans: Panama Butterfly & FrontStreet Coffee 2013·Yunnan Typica
Dose: 30g
Water Ratio: 1:15
Water Temperature: 93°C & 90°C
Dripper: V60
Grind Size: EK43s setting 10
Three-Pour Method: 50g, 200g, 200g

Panama Butterfly Coffee at Different Temperatures

Just Brewed (70°C): Bright citrus acidity accompanied by delicate floral notes and honey-like sweetness, with a mouthfeel reminiscent of clear green tea with vibrant fruit acidity.

Cooled to Room Temperature (28°C): FrontStreet Coffee observed that the Butterfly coffee became somewhat cloudy in appearance. The taste was predominantly tea-like with weak fruit acidity and unnoticeable aroma.

FrontStreet Coffee's Typica at Different Temperatures

Just Brewed (68°C): When consumed hot, the coffee displayed rich aromas of chocolate, nuts, roasted sweet potato, and toffee, with hints of dark berry acidity and excellent body.

Cooled to Room Temperature (28°C): The coffee became thick in texture with dominant nutty flavors. The smooth sweetness from when hot was gone, replaced by a slight woody note. After swallowing, an unpleasant aftertaste reminiscent of dry walnut skin lingered briefly.

Next, samples from both coffees were reheated using three different methods until reaching 50°C, with the tasting experience of each group carefully recorded.

Reheating Results

Electric Hot Plate Group: The reheated Butterfly coffee displayed berry and citrus peel acidity with a somewhat flat mouthfeel, though no negative flavors emerged. The FrontStreet Coffee Typica, while maintaining some nutty characteristics after reheating, also developed some pronounced acidity that seemed rather jarring.

Alcohol Lamp Group: When both coffees were heated with direct flame to 50°C, although their flavor profiles weren't as rich as when freshly brewed, the temperature increase did improve the mouthfeel. The acidity, sweetness, and bitterness were well-balanced with a round texture.

Steam Wand Group: Both coffees had almost completely lost their rich aromatic qualities. While acidity and bitterness were not pronounced, the mouthfeel became somewhat "watery" with a diluted sensation. FrontStreet Coffee speculates that this change occurred because the high-temperature steam vapor from the tiny holes was injected directly into the coffee, causing the dilution.

Conclusion

From this experiment, we can see that to some extent, using external heat sources like direct flame to reheat coffee cannot restore the original rich aromas, but it can effectively reduce the unpleasant tasting experience caused by cooling, making the coffee more palatable. Of course, besides the heating methods mentioned by FrontStreet Coffee, if conditions permit, you might try other approaches to improve cooled coffee, such as using a microwave.

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FrontStreet Coffee
No. 10, Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province