The Art and Craft of Coffee (16 page)

Brewing Temperature and Contact Time

In all brewing methods, exposing ground coffee to water extracts the coffee’s flavor. Theoretically, you could soak roasted coffee beans in a pitcher of water and eventually the water would become coffee. But certain temperatures and time facilitate extraction of oils contained in coffee beans more quickly and in an aromatic and flavorful manner.

The recipe for making excellent coffee is well-established: Two tablespoons (10 g) per six ounces (180 ml) of water. It has been documented that Ludwig von Beethoven used to count sixty beans for each six-ounce (180 ml) cup—which happens to equal two tablespoons (10 g). Unless noted otherwise, this formula applies to all brewing methods.

This formula is an important starting point, but slight adjustments may produce a better batch, one that tastes better
to you
. Treat this formula as a relatively foolproof guide—
guide
being the operative word. Different coffee roasts, different origin coffees, and brewing-temperature variations affect strength and flavor. For instance, to brew a forty-eight ounce (1,440 ml) batch (eight six-ounce [180 ml] cups), begin with sixteen tablespoons (80 g) of whole beans. If the coffee turns out too strong, pull back to fourteen tablespoons (70 g); if it’s too weak, increase the beans to eighteen tablespoons (90 g). (And here’s a tip: Always treat your first batch of a new coffee as a test batch.)

TAKE ITS TEMPERATURE

How do you know whether your automatic brewer is performing to spec? Simple: Take its temperature. Hold a fast-acting thermometer in the stream of brewing coffee as the water emerges from the basket of grounds. The temperature should be more or less at the 200˚F (93˚C) mark.

Temperature

Although any temperature water will eventually become coffee if in contact with beans for long enough, hot water is the fastest means to this end. (It also results in a hot beverage which, historically, is the way most people prefer to drink coffee.) Water heated to 200˚F (93˚C) plus or minus a few degrees is considered the standard benchmark. Water not heated as high is less efficient. Water heated higher extracts bitter flavors.

Time

The longer the coffee grounds are exposed to water, the more the flavor is extracted. The shorter the grounds are exposed, the less the flavor is extracted. The appropriate average time varies by grind; a drip grind takes four to six minutes, but a coarse grind can take up to eight minutes. If using a manual machine that steeps the coffee in a reservoir, such as a vacuum or press pot, you can easily vary the contact time between the grounds and water. Press pot coffee with a finer grind and longer extraction time will taste significantly different than one with a coarser grind and shorter extraction time. (See
chapter 4
, “Grinding,” for more information.)

Water

The chemical makeup of the strongest cup of coffee is roughly 1.35 percent dissolved coffee solids. The rest, approximately 98.65 percent, is water. Water plays two roles in coffee. It complements the taste and acts as the solvent that seduces the coffee essence from the grounds.

Let’s address water’s taste first. Water’s flavor varies quite a bit around the world. Assuming it is potable, or healthy to drink, its chemical makeup can include different amounts of several ingredients. Calcium, which comes from rocks in the ground, is the largest likely suspect. Have you heard the phrase “hard water”? It usually refers to the calcium minerals within it. If the minerals in hard water are in high enough concentration, they can give the coffee a pronounced metallic taste.

Some say hard water extracts coffee poorly during brewing. Actually, this is less than true, although hard water does present problems. During brewing, the near-boiling water keeps calcium and other minerals suspended. Some cling to the pipes inside of the coffee brewer, clogging it after awhile. At least the minerals don’t affect actual brewing ability.

Water softened using salt—found in most homes and some municipalities—is more problematic. The residual salt following softening can form a gelatin-like goo in the coffee brewer’s filter, which can prevent extraction or even halt the whole process.

pH Level

Liquid’s acid-versus-alkaline value, represented by pH, can significantly affect coffee’s taste. Water should be 7.1, a neutral pH, for its role in coffee flavor. Acidic or alkaline water will throw off the finished beverage’s flavor balance. Alkaline water in particular, when used to brew dark roasts, can cause a dull, indistinct taste.

Water Checklist

Water for brewing should be as follows:

• One hundred total dissolved solids (tds) or less. This is soft-to medium-hard water. It will taste better and extend the useful product life of your brewing equipment without the need to delime (remove the mineral buildup).

• A pH level of 7.1. Water more acidic can accentuate coffee bean taste defects. Water more alkaline can make coffee taste bland. That said, if you can only brew using alkaline water, think light roasts. If your water is more acidic, consider darker roasts.

• Chlorine-free water. If you can smell or taste any chlorine in water you use to brew, expect the chlorine to affect your coffee’s taste. Get rid of the chlorine by using a charcoal filter or letting the coffee sit for an hour or so until the chlorine evaporates.

Does this mean you must use bottled water? In many cases, municipal (tap) water will brew excellent coffee. Most municipalities post their water specifications on their websites. Most likely, the water will contain chlorine, as many places overchlorinate to prevent contamination. As we mention above, chlorine is easy to address. Excess minerals and less-than-ideal pH levels, while less common, are harder to fix. If you come across this, consider using bottled water. Keep in mind that all bottled waters are not alike. Just as with tap water, verify the pH level and tds of bottled water before using.

Filters

By design, coffee filters separate grounds from brewed coffee following brewing. All coffee brewing processes involve some sort of filtration. Even the earliest (and simplest) brewing methods—tossing loose grounds into a pot of boiling water—used “filtration” by carefully pouring off the coffee, keeping the grounds separate from the finished beverage.

Filters differ in their ability to remove all grounds and sediment from the brewed coffee. This influences the perception of coffee’s taste, body, and texture. Some people prefer a super-clean, highly filtered beverage; others prefer one rich in sediment. Filtration methods that allow particles to pass through to the finished brew will affect taste (and bitterness). The tiniest particles continue to extract in the finished beverage.

Your personal taste—and your brewer’s function, of course—affect which filter you choose. Any time you change filter types, figure out contact time to make sure the new filter does not require finer or coarser grinds. A thicker paper will prolong contact; a fine metal mesh one will accelerate it. (The irony of this is that manufacturers often tout the “full body and rich flavor” metal filters produce, but speeding up the drip rate actually reduces contact time and weakens coffee strength.)

Clockwise from top:

Metal mesh filter

Percolater metal filter

Espresso porta-filter

Paper filters, both bleached and natural

Most metal mesh filters
included with drip makers prevent a significant amount of particles in the finished brew, although they tend to increase flow rates and thus reduce water’s contact time with the grounds.

Glass filters
, used in some older vacuum brewer models, contain tiny surface bumps that create a sieve in the upper bowl’s glass tube, allowing liquid but not grinds to pass through. Most glass filters create an excellent pot of coffee, but they break easily.

Some antique vacuum coffee makers use cloth filters
, which, in general, do an excellent filtering job. Also, modern, reusable cloths are an ecologically savvy choice. However, they are difficult to find and keep clean. Cloth tends to accumulate grounds and oils. When using cloth filters, discard if mold appears.

Some coffee buffs accuse paper filters
of not letting all of the coffee’s flavors through. More accurately, paper holds back sediment and thus results in an ultra-clean brew. Some paper filters now intentionally have holes that resemble mesh filters’ holes, allowing comparable sediment amounts to pass. Paper does not prevent the passage of oils, the most important flavor component.

Some people claim that bleached paper filters gives the brew a bitter chlorine taste. Though most paper filters are bleached with hydrogen peroxide, this is flavorless and odorless. (When in doubt, rinse a paper filter in cold water before using it to remove any possible taste.) Unbleached paper filters
do
have a distinct taste and odor, which is difficult to avoid. For all-around flavor, use hydrogen peroxide bleached paper filters.