At the roastery, we often make coffee with a Chemex. We weigh the beans, grind them, add water—and the room smells wonderful before we’ve poured a single cup.
That smell is part of the answer to a question I hear often: Does it really matter if you grind coffee right before brewing?
Usually, yes. Grinding breaks each bean into small pieces, exposing much more coffee to air. Aromas can escape, and the coffee changes faster than it would as whole beans. Grinding just before brewing gives you a better chance of keeping those aromas in the experience you bought the coffee for.
But if you buy pre-ground coffee, please keep reading. You can still make a cup you love.
What happens when you grind coffee beans?
A whole roasted bean holds many of its aromatic compounds within its structure. Grinding opens that structure and creates far more exposed surface area.
You notice the immediate effect when you smell the grounds. Some of those lovely aromas are reaching your nose right then. Over time, others escape or change as the ground coffee is exposed to air. This is why coffee ground today may smell less vivid than the same coffee ground moments ago.
Grinding also makes brewing possible: water can reach into the smaller pieces of coffee and extract flavour. So the goal isn’t to avoid grinding. It’s to grind an amount that suits your brewer, as close to brewing as is practical.
Is it the coffee oils that disappear?
The original version of this article put most of the explanation on coffee oils. Oils are part of coffee, and some compounds can oxidize over time. But the fresh-ground smell comes from a complex mix of aromatic compounds, many of which are volatile—meaning they can move into the air.
It is more accurate to say that grinding speeds up changes to coffee’s aroma and flavour than to say its oils immediately disappear. Freshness is about the whole sensory experience, from the smell of the grounds to the taste of the finished cup.
What does CO₂ have to do with it?
Roasting produces carbon dioxide, or CO₂, and some of it remains trapped in the roasted beans. Coffee releases that gas over time; grinding makes it escape faster.
If you make a pour-over, you may have seen fresh grounds puff up when you first add water. That’s called the bloom, and escaping gas is part of what you’re seeing. In espresso, gas also contributes to crema.
But CO₂ is not what dissolves the desirable flavours and oils into your cup. Water does the extracting. A dramatic bloom can be interesting to watch, but it isn’t a guarantee that the coffee will taste better.
Is pre-ground coffee a bad choice?
No. I would rather you make coffee you enjoy than feel you need another piece of equipment before you can brew it.
Whole beans give you two advantages: they generally hold their aroma longer, and you can adjust the grind when you change brewers or fine-tune a recipe. Pre-ground coffee trades some of that flexibility for convenience. If that works better for your mornings, choose the grind that matches your brewer, buy an amount you’ll use reasonably soon, and close the bag well between brews.
When you shop our coffees, you can choose whole beans or a grind suited to the way you brew. The useful question is not “Am I doing coffee correctly?” It’s “What will help me make a cup I look forward to?”
How should I store coffee after opening it?
Keep the bag well sealed in a cool, dry place, away from heat, moisture and strong smells. If you have whole beans, grind only what you plan to brew. If you have pre-ground coffee, closing it promptly after each use is a simple habit that helps limit exposure to air.
For more on what happens before you open the bag, read our guide to coffee freshness after roasting.
Does grind size matter as much as freshness?
It matters in a different way. Freshness affects the aromas and flavours available to enjoy; grind size changes how water moves through the coffee and what it extracts. If your cup tastes unexpectedly sharp, thin or harsh, changing the grind may help more than changing the beans.
Our grind-size guide gives you starting points for different brewers. Try one small adjustment and taste the result. That’s how we learn what works in our own mugs.
I love the smell when we grind coffee at the roastery. If you grind at home, that moment is yours. If we grind it for you, make your cup, enjoy it, and don’t let anyone turn breakfast into a coffee exam.
Have a lovely and caffeinated weekend,
Adriana