Grind Your Coffee Beans Frozen.

Brewing extracts the flavor from coffee grounds. The smaller the grounds the faster the extraction. If coffee grounds are not uniform then brewing will over-extract the smaller grounds resulting in bitter tastes in the cup. At the same time extra-large grounds will under extract creating sour tastes in the cup. Over and under extraction do not cancel each other out. Instead the cup will have both bitter and sour flavors.

Chemists at the University of Bath investigated what effect temperature had on grinding coffee.The effect of bean origin and temperature on grinding roasted coffee http://www.nature.com/articles/srep24483 They found that the colder the coffee beans the more even the particles were in the ground coffee. Since freezing coffee is already a good method of maintain freshness, putting the frozen beans directly is a no-brainer. Freezing Coffee Beans Keeps the Fresh https://goo.gl/pL1Q9u