If you want the best tasting coffee you can make, the short answer… yes, you need a coffee grinder.
But why, when I can buy it pre ground?
Two big reasons to use a coffee grinder to grind just before you brew, oxygen and carbon dioxide (CO2).
- One of the big enemies of coffee is oxygen. Flavour is a combination of taste and aroma. There are only 5 identified tastes we can detect but many thousands of aromas. So one could easily argue that smell plays a more important factor in flavour than taste. As coffee oxidizes, the beautiful coffee aromas we all want to wake up to dissipate, and the coffee oils can become rancid. With whole roasted coffee beans, this is a process that happens over a few weeks if the beans are stored correctly. However, since so much more of the surface area and oils of the bean is exposed to oxygen, the process is rapidly accelerated. By the time you get home, your coffee will be significantly less flavourful than when it was ground at the shop.
- Another factor is carbon dioxide. This is what creates the beautiful crema we all want and where a lot of the aroma is lock up. It’s the same reason beer tastes better from the tap. Putting it in a glass allows the CO2 to release the flavours and aromas. It is also why flat beer, that has lost it’s CO2, doesn’t taste the same. CO2 is created during the roasting process and stored inside the bean where it slowly dissipates over the next few weeks. Like oxidization, this process is rapidly accelerated once the coffee is ground. The CO2 will dissipate within minutes rather than weeks. Less crema = less aroma = less flavour.