How to Brew “The Perfect Cup” of Coffee
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.
Coffee to Water Ratio
The proper way to measure coffee is by weight. If you are really serious about coffee, then you should invest in a scale that can weigh small portions of coffee accurately. A good scale is indispensable when blending your own coffee in small amounts, unless you want to spend a lot of time counting coffee beans. You can measure coffee by volume, but you lose a lot of accuracy because of varying bean densities and having to rely on visual estimation. The proportion of ground coffee used in relation to the amount of water used, constitutes the brewing ratio. After the coffee has been brewed, the amount of solubles that have been extracted in relation to the amount of water, constitutes the drinking ratio. The brewing ratio usually determines the drinking ratio, but it doesn’t have to. Hot water can be added to the infusion after brewing to reduce the concentration and flavor intensity of the brew, thus changing the drinking ratio. Experimentation will lead you to your own personal brewing and drinking ratios. It is always wiser to brew your coffee on the strong side and then “cut” it to taste with water. If coffee is brewed too weak, all you can do is start over. The Standard Brewing Chart gives the brewing ratios that are accepted as the standard by serious coffee drinkers. It can not be stressed enough how much personal taste should be the sole basis for determining brewing ratios. It is very easy to misjudge a coffee that has been prepared using a brewing ratio that is not suited to your particular taste.
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. SCAA says that a TDS of 120 ppm is ideal. 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. SCAA says 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) can be used, but it will alter (shorten) the extraction time, this is somewhat an on-going controversy. 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 at 205 F (96 C) or higher.
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.
Understanding the extraction process will enable you to learn how to brew coffee successfully. First, the grind (aggregate size) of the coffee is crucial. The finer the grind, the more surface in relation to mass is exposed to the hot water. A whole 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. If the grind is too fine, and the exposure too long, you’ll get much more than you want. Over-extraction of the aggregate will dissolve too many of the undesirable compounds, generally referred to as “bitters”. The trick is to get just what you want out of the coffee, and no more.
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. If you shorten the extraction time, you’ll fail to dissolve the essential flavor compounds that were so carefully developed during the roasting process. Again, over-extraction will dissolve too many of the undesirable compounds. For example, alkaloids are one group of compounds that dissolve more slowly than others, and are very bitter. The challenge is to get the aggregate size and the extraction time in perfect balance.
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 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 coffee in an Aeropress, I shoot for a 1 1/2 – 2 minute extraction. Or a pour-over method, I try for a 3 1/2 minute extraction time. By the same token, you can also use more coffee than usual in a drip brewer with a shorter extraction time. It’s all a matter of increasing surface area (finer grind), 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 with your personal equipment.
If you own a “normal” drip machine and want to experiment a little, here’s something to try. This could minimize, or eliminate, the over-extraction problem, and the resulting bitterness, that plagues most common units yielding a sweeter cup. First figure out how much water your machine runs through the basket in about 3 1/2 minutes (no coffee only a filter). Start the time from when the water enters the basket/carafe, not when you start the brew cycle. I’m guessing that with most machines this is about 6 cups. Next add your amount of ground coffee for the desired amount of finished coffee, say 10 cups = 106 grams ground coffee. Now only add, or brew with, the same amount of water that it took 3 1/2 min to run through. When that has finished brewing (hopefully at about 4 – 4 1/2 minutes) then add the remaining (hot) water to the brew/carafe cutting it back to the right strength. The goal here is to keep the extraction time around 4 minutes. Unfortunately, this still doesn’t change the water temp, assuming its on the low side of 195 – 200. You can try grinding a “bit” courser if your water temp is lower, it may help the taste.
If your wanting to experiment, I’d suggest starting with learning about how that surface area/grind size affects the taste of the coffee. https://baristahustle.com/blogs/barista-hustle/diy-extraction-tasting I think this experiment could be done with other brew methods than espresso.