Advancements in thermal materials means that we can keep coffee hotter longer than ever before. Thoughtfully designed stainless steel carafes or coffee tumblers can keep your coffee piping hot for as long as 12 hours, and at a drinkable temperature for as long as 24. That said, is your coffee worth drinking just because it’s still hot?
We recently conducted a side-by-side analysis of three coffee samples at the same, drinkable temperature of 150° Fahrenheit. For the experiment, we used our Ethiopia Basha Bekele Kokese, which is notable for red-fruit flavors and pronounced sweetness. Side by side, we tasted coffee that was hot and fresh (brewed 20 minutes before tasting), coffee that was hot but not fresh (18 hours old), and coffee that was fresh but not hot (20 minutes old but 100°F.) We wanted to analyze how the taste changed among the coffees.
The results were head spinning. The freshly brewed coffee had a nice balance of acidity and sweetness that allowed its fruity flavors to shine. The mouthfeel was light and juicy, and the coffee delivered a heady aroma. Next to it, the old coffee seemed flat. It reminded us of neon colors transformed into pastels—all the vibrancy and energy of the coffee was muted and mellow. While there were still aromas and flavors of fruit, they weren’t as discernable and distinctive as in the fresh coffee, and the decreased acidity meant the overall brew tasted more bitter.
The fresh but cool coffee was sweeter and delivered more complexity than the older coffee but struck us as lackluster. The cooler temperature was also just less appealing on a winter day, and lacked some of the brightness of the hotter offering.
What does this mean? Your tumbler might keep the coffee on your desk hot all day, but you likely won’t get as much enjoyment out of it at 3:00 pm as you would at 8:00 am. The chemical compounds that provide the nuanced flavors in coffee tend to degas quickly, and after two hours, the flavor will noticeably flatten. If you keep your coffee in a glass pot on a heating element, your coffee will get bitter flavors and develop an oversaturated mouthfeel due to the liquid in the coffee vaporizing and the heat concentrating the soluble material in the coffee.
This is all to say, make yourself a fresh cup of coffee! Brew small amounts, such as with a pour-over cone, or use a batch-brew machine that can handle small volumes. You deserve the best possible coffee, and one of the only ways to treat your coffee and yourself with kindness is to keep your coffee fresh.