We're often asked why we recommend grinding beans just before brewing, rather than using pre-ground coffee.
The reason relates to the way coffee decomposes in it's various forms. Coffee after processing exists in four different stages; green bean, roasted beans, ground coffee and brewed coffee. Green beans can stay fresh for up to a year, freshly roasted coffee beans start to lose their flavour after a few weeks, brewed coffee after a few minutes, and ground coffee after only forty five seconds.
The reasons behind this relates to the behaviour of the aromatic compounds in coffee which give it aroma and flavour. The roasting process significantly increases the volume of these compounds, thus enhancing the flavour. But the problem is the compounds are volatile, meaning they have a tendency to 'sublimate' from a solid (beans or grinds) or liquid (brewed coffee) into the air.
The issue with ground coffee is that is has a much larger surface area than whole beans. This allows the compounds to escape much more quickly from the coffee. After just forty-five seconds you already start losing the aromatic compounds which can give a coffee truly special flavour. Therefore, for a great tasting cup of coffee it's ideal to grind the beans immediately before you brew. And for those interested, we recommended these grinders for that purpose.
However, we appreciate most people don't have the time to grind their fresh coffee and prefer the convenience of pre-ground coffee. In which case we recommend minimising the contact this coffee has with the air by decanting the grinds into an air-tight container as soon as you receive it. A modest investment in a decent coffee canister can indeed help maintain the coffee's flavour by reducing aromatic compound sublimation.