The Reason Why You Should Brew With Whole Bean Coffee
There is just one reason why a devoted coffee drinker would pick pre-ground coffee over whole beans, and that's convenience. Pre-ground coffee is ready to brew, and doesn't demand too much in terms of equipment or skills to produce a decent cup of coffee first thing in the morning. But, a little bit of effort could raise your home-brewed coffee game, and that effort begins with buying whole coffee beans.
The chemistry that makes freshly-ground coffee beans taste differently from pre-ground beans is simple. When whole coffee beans are ground, the bean's surface area is increased and spread out, making its compounds more easily accessible to the water that the grounds are soaked in. Fun fact: it's actually possible to soak whole roasted coffee beans in water, but it would take more time, yield a weak brew, and would be devoid of the coffee flavor we enjoy (via Perfect Daily Grind).
Coffee beans degrade as soon as they are ground
As soon as beans are ground, they release the fragrant gases that build up as coffee is being roasted, and the chemical process, called degassing, also allows for flavors and scents to escape, leaving your coffee tasting flat. Award-winning barista Ken Selby says that "the experiential difference that you're going to find [using pre-ground coffee] is two things. Aroma and acidity will be very minimized compared to if it was ground fresh."
Buying whole beans and grinding them at home may mean a bit of extra hassle, but as Koffeekult points out, you will get a fresher cup of coffee every time with just-ground beans. Coffee.org also says pre-ground coffee limits your ability to play with different brewing processes, which means you can prepare coarse grinds if you want to use a French press, or fine grinds if you have an espresso machine.
But if you must buy pre-ground coffee, the best way to slow down its descent into mediocrity is to put the coffee in an opaque, vacuum-sealed jar, and to store it in a kitchen cupboard. Avoid the fridge at all costs, because its extreme temperatures and moisture content could have even more of an adverse impact on grounds, which are already compromised.