|
Commercial coffee grinds vary from brand to
brand. Coffee companies set and monitor coffee grinds by using mesh
sieves stacked in a series with the coarsest mesh at the top. The level
at which the particles of a grind stop falling, as well as the
percentage of particles arrested in other sieves of the stacks, gauges
not only the basic degree of grind, but also indicates the uniformity of
particle size. If, for example, a coffee company wanted to check its
medium-grind coffee, intended for a percolator, it would expect that a
high percentage of particles from a sample of ground coffee would stop
at Gauge 9. If too many particles were to fall too far, or perhaps never
even drop through to the Gauge 9 sieve, the company would know that the
grind was faulty, and that the grinder might need re-calibrating.
Also, beans grind differently depending on
the degree of roast. For example, darker-roasted beans become more
brittle with moisture loss and are more prone to break into various
sized pieces and powder. The grinder might need some adjustment in order
to produce the same degree of grind as that obtained with a different
roast.
An excellent way to determine the
correct degree of grind to suit the brewing method, is to obtain a small
sample of commercially ground coffee. Rubbed between thumb and
forefinger, the degree of grind is relatively easy to judge. Commercial
grinds are specifically designated as Turkish, espresso, filter fine,
and medium grinds. Grinds coarser than medium are practically
non-existent commercially. They are generally used only in a jug
brewing, and are not very economical, since the same amount of beans
ground coarsely produces less volume, less extraction and therefore less
flavor than if it were ground finer.
In recent years, certain coffee
companies have attempted to gain a larger share of the market by
producing in-between grinds, promising consumers of filter and cafetiere
coffee alike that the same "omnigrind" works for both. Another grind
(which defies the laws of physics) is one that supposedly satisfies the
requirements of both filter and espresso machines. Not only does the
production of such grinds result in the wrong extraction in one or the
other of the brewing methods, it also confuses people who want to
understand why coffee is ground to different degrees.
One good result of the "omnigrind" for
machines requiring a fine or a medium-ground coffee, is that it provides
the perfect alternative grind for the Neapolitan flip machine and the
Cona vacuum machine. Both of these methods of brewing benefit from the
greater extraction rate of a near-filter grind, and the fact that the
very slightly larger particles of the "omnigrind" are not as prone to
fall into the coffee liquid because of the machine design. One tip for
espresso perfectionists; in Italy, to maintain the production of a
perfect espresso, the barman (barista) will alter his grinder to produce
a very slightly coarser grind on a day of high humidity.
|