Coffee beans, like any food product, oxidize when exposed to air. The grounds, since they have a much larger
relative surface area than the bean, and no covering, suffer this effect even more. Using a home coffee grinder
produces the least exposure to air and the freshest grounds possible plus the fact that you only need to grind what
you immediately need. However, nothing is without its price. Grinding is time consuming and messy, so if you choose
to invest the effort to reap the reward, pick the best Coffee Bean Grinder that you can afford.
There are three broad categories of coffee bean grinder which are burr, blade and crusher. The third type is
some kind of mashing device, often an ancient style mortar and pestle. These crush the beans, which is difficult
and produces a very uneven sized granule. Not recommended where you have a choice.
Blade Coffee Grinder
The blade grinders do not actually grind at all, they chop. A whirling blade slices the beans into smaller and
smaller sections until they approach something like a small grain. Unfortunately, the grains are invariably too
large and of inconsistent size.
As a consequence the surface areas of the granules vary, releasing varying amounts of flavor oils when brewed.
Another effect of slicing is often the production of excess heat, as a result of the high speed of the blades. That
friction warms the grounds and partially dissipates the aroma.
Burr Coffee Grinder
The first type is the first choice. Burr coffee grinders have a pair of motor driven plates with pyramid shaped
teeth that grind the beans to a consistent, small but not too small granule. The better models allow adjusting the
size of the grain and the speed of the grinding.
Adjusting the size is important in order to 'fine tune' the grounds to allow just the desired brew. Controlling
the speed keeps the warming effect to a minimum.
Even burr coffee grinders fall into two classes - the conical burr coffee grinder is preferred by real coffee
aficionados. Though noisier, they allow the most control of grain size and speed.
Good conical burr coffee grinders can rotate as slowly as 500rpm. By contrast other burr grinders spin at
10,000rpm or higher, blades between 20-30,000rpm. That allows very fine control and little heat. The fine grind is
especially important for Turkish-style brews. Some grinders have a continuous dial, others have a series of up to
40 steps to adjust the granule size.
Beyond those broad attributes, the home barista will want to look for solid construction, ease of cleaning and
low noise. A cleaning brush and removable upper burrs is essential. Different materials used can also affect how
much static electricity is produced - that causes the grains to stick to the burrs and container.
A timer switch and auto-shutoff is a nice addition and being able to see the beans as well as the grounds is
helpful for judging the results in the grinder. Dark plastic or glass may be aesthetically appealing but it
obscures the view. Grounds can change color slightly depending on the fineness.