It is common knowledge among coffee enthusiasts that kona beans produce the best coffee when they are freshly roasted, when the beans are full of the oils that give coffee so much flavor. It is also common knowledge that beans should be ground just before brewing, if at all possible, for optimum flavor. While we talk a lot about keeping the beans fresh, we don’t spend much time talking about the temperature of the beans – other than to say that freezing them will extend their shelf life beyond storing them on your countertop.
It turns out that the temperature at which coffee beans are ground makes a big difference on the quality of the finished cup of coffee. A study recently published in Scientific Reports explains that the colder the bean, the more uniform the grind achieved and the more consistent the flavor of the finished cup. The uniformity of the grind is important because the rate of flavor extraction from the coffee bean is dependent on the size of the grounds. Larger pieces extract more slowly, while smaller ones release their flavor more quickly. The less uniformity you have in your grind, the less uniformity you’ll have in your coffee.
The study started with beans that were held at room temperature and went all the way down to the temperature of liquid nitrogen (-321F). You don’t need to pack your beans on dry ice to get the optimal grind (though you can if you want to give it a try. Instead, you can try storing your whole beans in the freezer and grinding them from frozen – not because the freezer will necessarily keep them fresher (though it will help), but because you’ll get tastier coffee if you do.