You’ve just brewed the perfect batch of French Press coffee, but there’s a good chance you have some leftover. Leaving excess coffee in a French Press may seem like no big deal, but it can seriously affect your coffee’s flavor.
In general, you should not leave coffee in a French Press after you’ve plunged it. Leaving it in the beaker will allow the water and coffee grinds to continue interacting, which will create an over-extracted and bitter-tasting drink.
However, this is just the beginning. Your coffee will undergo several changes if left in a French Press for extended periods of time.
Can You Leave Coffee In A French Press?
It’s very common to brew more coffee than you’re prepared to drink. However, leaving excess coffee in your French Press isn’t a good idea for at least four reasons.
- Coffee extraction continues if you leave it in the French Press
- Coffee oxidizes and quickly goes stale after it’s brewed
- Your coffee will cool very quickly and reheating it will completely alter the flavor
- If you leave your coffee long enough, mold can grow in your French Press
1. Extraction Continues If You Leave Coffee In A French Press
The French Press is an immersion brewing method, which means the coffee grinds are immersed in a universal solvent – water.
As long as the coffee beans are in contact with the water, the extraction process will continue. And the thing about coffee extraction is that different parts of the coffee are extracted at different times.
The acids and coffee oils are extracted first. Then after a while, the sugars are extracted.
But if the coffee grinds continue to sit in the water for too long after the sugars are extracted, the coffee’s fibers will start to break down and be extracted as well.
This will make your coffee over-extracted, bitter and astringent.
So, to protect your coffee’s flavor, don’t leave your excess coffee in your French Press – even if you’ve brewed more than you’re ready to drink.
2. Brewed Coffee Oxidizes And Will Go Stale Within Minutes
As coffee is exposed to air it begins to oxidize and lose flavors.
Whole coffee beans lose flavor slowly over months because not much of their surface area is exposed to the air, and the solubles are sealed away inside the bean.
Ground beans are powdered, so more of their components are exposed to the air. They oxidize and go stale within weeks.
But brewed coffee oxidizes the fastest of all.
Brewing a cup of coffee pulls the coffee solubles out of the bean and into the water. Once the solubles are removed from the relative protection of the bean, begin to oxidize very quickly.
This is why a cup of brewed coffee will go stale in about 30 minutes. Not only that, but the coffee’s oils will also begin to go bad after a few hours.
You’ll never be able to escape oxidation completely because even the oxygen molecules in water will oxidize the coffee’s compounds. But you can minimize the process by not leaving your coffee exposed to the open air.
3. Having To Re-Heat Your Coffee Will Alter Its Flavor
If you leave coffee in a French Press, there’s a good chance it won’t just be there for a minute. Instead, it’ll be sitting there long enough to get cold.
When you go to reheat your coffee, many of the remaining compounds will break down in the heat. These compounds are what give coffee its aromas and flavors, so in the end, your coffee will taste much worse.
4. Mold Can Grow In Your French Press Coffee
Leaving coffee in a French Press for too long can also allow mold to grow. In general, it only takes mold 2 to 3 days to grow on coffee.
Since old coffee is somewhat warm, moist, and full of organic compounds (coffee oils and sugars) it’s the perfect place for mold to take hold.
While it’s unlikely that you’d intentionally leave your coffee sitting out for days, there have been cases where people went away for the weekend and returned to find a moldy French Press.
If this happens, soak your French Press with soapy water or vinegar mixed with hot water.
What Should I Do To Keep My Coffee Fresh?
Instead of leaving your coffee in a French Press, your best option is to store it in an airtight and insulated container such as a carafe or thermos.
(Take a look at a thermal carafe or thermos on Amazon if you don’t have one already.)
By immediately pouring your French Press coffee into one of these containers, you can stop extraction, protect it from oxidation, and keep it hot.
How Long Should You Leave Coffee In A French Press?
While it’s not a good idea to leave coffee in a French Press for too much time, there is the question of how long is too long?
The general rule is that French Press coffee should be allowed to steep for 4 minutes. However, the time can vary depending on which brewing technique you’re using.
Blooming Adds 30 Seconds To Your Brewing Time
One technique of making French Press coffee is to bloom the coffee for about 30 seconds before steeping for an additional 4 minutes.
When blooming, you pour just enough water on the coffee to wet the grinds evenly. This allows the beans to release carbon dioxide which will make your coffee less sour.
After 30 seconds, you pour the rest of your water into the cafetiere and let the coffee steep for 4 minutes.
James Hoffman’s French Press Technique Can Take 12 Minutes
Another French Press technique is given by James Hoffman, a World Barista Champion, and YouTuber. This method allows the coffee to steep for 4 minutes like normal.
You then skim the grinds off the surface of the coffee, then let it steep for another 5 to 8 minutes.
Whether your brewing method takes 4 minutes, 4 minutes, and 30 seconds, or even 12 minutes doesn’t really matter.
The main thing to remember is that after your coffee is ready to drink, take it out of the French Press.
Leaving Coffee In A French Press When Making Cold Brew
When making cold brew coffee in a French Press, you’ll need to let the coffee sit anywhere between 12 and 16 hours.
The reason cold brew has to steep for such a long time is that cold water extracts coffee at a much slower rate than hot water.
But even though this method takes hours, you still have to deal with the issue of over-extraction if you let it sit for too long.
So, whether you’re making hot French Press coffee or cold, don’t let your coffee steep longer than the brewing recipe requires.
(By the way…if you want to try some great beans, check out our posts on the Best Coffee Beans For French Press or the Best Coffee Beans For Cold Brew Coffee.)
Key Takaways:
You have to let your coffee steep for at least a few minutes. But your coffee will undergo several undesirable changes if you leave it in a French Press for too long.
Within minutes,
- your coffee will become bitter due to over-extraction
- grow stale due to oxidation and
- get cold
Within hours,
- if you’re cold brewing it will take a few hours
Within days,
- coffee will grow mold
Cheers Coffee Lovers!
KEEP READING
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- Can I Drink Leftover Moka Pot Coffee? And How To Do it Safely!
- Can I Use A French Press With Pre-Ground Coffee? Pros And Cons
- Can I Use Coffee Grounds Twice? (Here Are Our Results!)
Oliver is co-owner of Coffee Break Lovers. The only thing he loves more than the process of brewing coffee is drinking it.
