How to Brew "The Perfect Cup" of Coffee
The water to be used must be right or the coffee will be wrong. The infusion you drink is mostly water. The flavor of coffee can easily be contaminated by other intruding influences. The best rule of thumb is, if the water you are going to use doesn't taste right, don't use it. It should have no discernible taste, or "character", such as sharp or astringent qualities. Bad water makes bad coffee. As a rule, bottled spring water is your best bet. Municipal water is usually not good enough for high quality coffee, unless you are using a good filtration system. Water that has been "softened" should also be avoided. It does not extract as well as non-softened water. Distilled water should not be used, because all of the mineral content has been removed. The minerals in water are essential to the extraction process. It is very important to note that if you're using any type of container to store water in, it is very important to frequently, and thoroughly clean the container. The build up of bacteria in water being used to brew coffee will have a dramatically negative effect on the coffee. This is one of the most commonly overlooked sources of trouble when brewing coffee.
The brewing temperature of the water used is very important. It should be between 195 F (91 C) and 205 F (96 C). The closer to 205 F (96 C) the better. Boiling water (212 F - 100 C) should never be used, as it will burn the coffee. Water that is less than 195 F (91 C) will not extract properly. Keep in mind that if frozen beans have been ground, the aggregate will drop the temperature of the water upon contact. In this instance the temperature of the water being added to the aggregate should be right at 205 F (96 C).
The Brewing Process Itself
There are two basic brewing concepts you need to understand, percolation and maceration. Percolation means water is allowed to flow around the particles and through the aggregate of ground coffee. Maceration means the ground coffee is soaked (or steeped) in the water.
Brewing a perfect cup of coffee is the weakest link in the full enjoyment of fine coffee. Buying the finest coffee is only the beginning and can go for naught if the brewing is not done correctly. It is very easy to ruin otherwise excellent coffee with improper brewing. We realize you would like to hear that once you have purchased excellent coffee beans, the rest is as simple as pushing a button, but, all we can say is: it's time to "wake up and smell the coffee". The grower, and the roaster do their parts, and you have to do your part. If either party drops the ball, exquisite coffee will not happen. The first thing that must be understood is what is going on during the brewing process. The aggregate (ground up coffee particles) is being exposed to hot water in order to "extract" the essential solubles (flavor compounds, solids, and oils) from the particles. That which is extracted winds up in the water, creating the infusion we call coffee. In theory, perfect extraction would get everything that's desirable out of the coffee bean and into the cup, while leaving behind all that which is undesirable. Is this possible? Currently, only in our imaginations. But some methods are better than others, and one comes pleasantly close.
Understanding the extraction process will enable you to learn how to brew coffee successfully. First, the grind, or aggregate size, of the coffee is crucial. The finer the grind, the more surface in relation to mass is exposed to the hot water. An un-ground coffee bean results in the least amount of surface area in relation to mass, and would be impossible to brew successfully. The tendency is to assume that the more finely coffee is ground, the better the resulting infusion will be. This is where you can destroy a good cup of coffee. The trick is to get just what you want out of the coffee, and no more. If the grind is to fine, and the exposure too long, you'll get everything. Over-extraction of the aggregate will dissolve too many of the undesirable compounds, generally referred to as "bitters". If you shorten the extraction time, you'll fail to dissolve the essential flavor compounds that were so carefully developed during the roasting process. The challenge is to get the aggregate size and the extraction time in perfect balance. It is of the utmost importance that you understand that the brewing time must be controlled exactly. Improper brewing time is one of the main reasons that people get different results when preparing coffee.
There is an important exception to "exact brewing time". 90 percent of the solubles are extracted during the initial phase of the brewing process. It is possible to get to achieve your best results with a grind that's slightly on the fine side, and shortening the extraction time. For instance, when I use our ground coffee in a French press, or the brew and filter method, I use a 3 minute extraction time. Since our grinder is calibrated to grind coffee that will achieve a 4 minute extraction time in a commercial airpot brewer, for my taste, 4 minutes in the French press over-extracts with our ground coffee. By the same token, you can also use more coffee than usual in a drip brewer with a short extraction time. It's all a matter of increasing surface area, reducing extraction time, and getting less of the bitter compounds that take longer to dissolve. It comes down to experimentation, and finding your perfect brewing formula.