Why You Should Never Leave Coffee In Your French Press

If you want a bold cup of coffee that accentuates the flavor of the fresh grinds, the French press is your friend. But before getting too excited and making big coffee batches in the ceramic or glass carafe to drink throughout the morning, take a pause. Leaving coffee in the French press is actually a big no-no. According to Matt Woodburn-Simmonds, Ex-Barista and Founder of Home Coffee Expert, you should never leave coffee in your French press since the coffee grounds continue to extract as it sits. "If you leave it there, then all the super bitter flavors that you don't want in your brew will be drawn out making a very harsh and bitter cup of coffee," the java pro told Tasting Table.

Besides going cold and over-extracting the coffee grounds, room temperature coffee also tastes bad because of chemical reactions that occur as it sits, like pH changes, oxidation, and the development of bitter aromatic and taste compounds. To prevent astringent bitter flavors from developing past the first cup, Woodburn-Simmonds recommends transferring extra French press coffee to a thermos. This keeps the brew hot but not in contact with the grinds underneath the coffee maker's plunger and sieve, so you won't risk your coffee developing off flavors. Conversely, he says he likes to keep different-sized French presses on hand and brew just what's needed without having to "worry about coffee sitting and over-extracting or having to find something else to decant into to keep it hot."

Your morning cup of coffee should be life-giving, not bitter or astringent-tasting. While over-extraction of coffee grounds can occur if prepared coffee sits too long in the French press carafe, it can also happen for a variety of other factors. Another surprising reason your coffee is bitter could have to do with using water that's too hot or steeping the brewed coffee for too long in the first place. The water temperature should be hot but not boiling — around 200 degrees Fahrenheit. So, if you bring it to a boil, let it cool down for 20 seconds to a minute before pouring over the coffee grounds. Then, brew the coffee for about four minutes before plunging the sieve to separate the coffee from the extracted grounds. If you brew the coffee much longer, you risk over-extracting the coffee grounds.

Overall, time is of the essence when using a French press for your morning cup of joe — so don't brew French press coffee too long or let it linger in the carafe unattended. The grind size of your ground coffee can also impact the flavor. It's best to use store-bought coarse ground coffee (or coarsely grind your own) since the larger granules exhibit greater surface area and take longer for the flavors and oils of the coffee to extract. Finer grinds extract more quickly and thus are quite susceptible to over-extraction as they sit in the French press (read: bitter coffee).