Is Your Morning Coffee Still Safe to Drink in the Afternoon?

Learn about old coffee in all its forms—this is a safe space. 

It happens every afternoon: Around 4 o'clock, I start to fade and begin considering my caffeine options, always landing on the abandoned, half-consumed coffee at my desk. Every morning, I brew a cup, put a splash of milk in it, take a sip or two, then get distracted by my to-do list (looming deadlines are more effective than caffeine, I've found). And every day, I wonder, "Can I drink that? At what point does the potential risk outweigh the promise of caffeine? I turned to Google to find an (unofficial, but workable) answer: 

My coffee, circa 3 P.M. this afternoon

What if the coffee has milk in it? When properly stored and refrigerated, milk can last for up to a week past its expiration date, but milk should not be left at room temperature for more than two hours. So if your coffee has milk in it, play it safe and drink it while it's fresh.

Is the flavor of the coffee affected? Just as coffee beans go rancid after about two weeks, brewed coffee can start to taste bad after about 30 minutes, or the time it takes for the coffee to cool. Then you have about a 4-hour window before the oils in the coffee start to go bad, which further alters the taste. (We'd like to state, for the record, that Oliver Strand—coffee writer and guest on our Burnt Toast episode about coffee—would not condone our drinking of cooled coffee. Our product manager Michael Hoffman, on the other hand, confesses to drinking day-old cups during the same episode.)

Will microwaving the coffee kill bacteria? While microwaves can kill pockets of bacteria, because they heat from the outside in, they often leave pockets of cold in the middle of food and drinks where bacteria can thrive. So they shouldn't be relied upon to kill whatever might be living in that cup. 

Does the water in the coffee spoil? Water can absorb flavors from its environment which change its flavor (especially if it's left in a particularly pungent place like the refrigerator), but even uncapped, glasses of water are drinkable for weeks after they're poured. Unless water has something living in it, like flowers, it's difficult for bacteria to survive in it. Drink up.

So, is coffee safe to drink after several hours? Black coffee should be safe to drink, though it probably won't taste all that good. If it has milk in it, make a fresh pot instead—but if you're determined to still drink it (as I often am), make sure to microwave it all the way through, for an extra-classy, extra-safe 4 PM pick-me-up.

What is your stance on drinking hours-old coffee? Tell us in the coments below!

Photo by James Ransom