It’s all in the grind

September 5, 2005

If you undertake to learn a bit about coffee, you’ll soon find that most serious coffee aficionados will tell you that the single most critical piece of equipment you own is a grinder.

A grinder is often a person’s first “step up” into the world of better coffee — once you grind coffee, the flavor begins to dissipate within seconds, so buying whole bean coffee and grinding it yourself just before you brew gives you much better flavor.

Unfortunately, many people stop there, and never realize that the type of grinder, and how it works, makes a vast amount of difference to the final result in the cup. This is true regardless of the type of coffee you are drinking — espresso, drip brewed coffee, or press pot coffee.

The reason the grind is so important is due to the nature of coffee — most of the flavors we want in our cup are in the first two-thirds or so of the flavors we can extract from the bean. The remaining flavors include all of the bitterness and nasty flavors that we want to avoid.

The size of the grind controls the amount of surface area that flavor can be extracted from — imagine that you had a “cube” of coffee, smooth and 1 inch square. The surface area of that cube — where hot water can reach it and extract flavor — is exactly six inches. Now if you grind that cube up into match-head sized pieces, you have much more surface area to extract flavor from. If you grind it to sugar-crystal sized pieces, you have even more.

Since our hot water will be in contact with the grounds for a relatively fixed amount of time, how fine we grind the coffee controls how much flavor we will extract. If it is too coarse, we will underextract and end up with a weak cup of coffee that is missing some of the desireable flavors of our bean. If our grind is too fine, we will overextract and end up with a bitter, bad-tasting cup of coffee.

Due to the way coffee makers work, our grind also tends to control our contact time (the amount of time hot water is in contact with the grounds) — in a drip brewer, too fine a grind will clog the filter excessively, and cause hot water to stay in contact with the grounds longer; this can result not only in overextracted flavor, but in hot water and grounds overflowing the brew basket, and making a mess inside the coffee maker and on our counter. Too fine a grind can also cause an espresso maker to not be able to pump water through the grounds, or make it difficult to press the plunger in a press pot.

Last but not least, in some coffee brewers, too fine a grind can lead to fine grounds or “silt” in the cup.

Grinding too coarse has the opposite effect, causing water to pass through the grounds very quickly with little resistance, lowering contact time and leaving us with a thin, watery brew.

We can see from this that consistency is also important — low-end grinders (particularly the “blade” or “whirlybird” grinders that are available for $20 – $40) don’t grind coffee at all. They chop it, and the result is a lot of mixed size pieces of coffee — little pieces and big pieces (think “dust” and “boulders”). This will naturally result in the big pieces being underextracted, and the little pieces being overextracted, so you end up getting the worst of all worlds — a cup that is missing some flavors it should have, but including some flavors that we don’t want (the overextracted portion).

Blade grinders have a few other problems — they have no ability to control the fineness of the grind (other than how long you hold the button down), and the chopping action tends to overheat the coffee beans, further damaging the flavor.

The alternative is a burr grinder. A burr grinder actually grinds the coffee between two metal burrs. These grinders give you the ability to select the size of the grind, which changes the distance between the burrs. A functional burr grinder will cost you roughly $100 – $600. The lower priced ones are usually fine for most purposes other than espresso — espresso makers can be very sensitive to the quality of the grind, and it’s not unusual for a good grinder to cost more than the espresso maker.

Once you’ve got a proper grinder, it’s time to dial in your grind.

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