common sense of coffee

Overall Factor

Coffee quality depends on a combination of factors. Fresh beans, measured by both how long it's been since the beans were roasted and the time elapsed since grinding the beans, are imperative. High quality beans (measured by the specific crop, processing, handling, etc.) are, obviously, desirable, but the highest quality beans are all but useless if stale. Clean good-tasting water must be used, and the coffee must be brewed with clean equipment at the proper temperature for the proper amount of time.

Simply buying top-quality beans is no guarantee of great coffee; if those beans are stale, the water quality poor, the brewing temperature low, or your equipment dirty, you will have wasted money on those expensive beans. Lesser quality yet freshly roasted beans, ground before use, will almost certainly be superior to a higher quality sample that is stale.

With all brewing methods, the goal is to balance strength and yield. These two elements are distinct but often confused. As noted in the section on water quality, brewed coffee is over 98 percent water; this is a measure of its strength--i.e., how much extracted coffee there is as a ratio to water. Not counting espresso or Turkish coffee, this mainly refers to the concentration of solubles; with espresso, that can be broadened to include emulsified oils (Turkish coffee often has a significant component of suspended solids). If your ratios fall outside of the proper range, the coffee is perceived as too weak or too strong. Most commonly this is a function of the quantity of ground coffee used for any given volume of water. However, the quality of solubles that are extracted determine another factor, the yield. If too little is extracted from the ground coffee (because the grounds are too coarse or the water contact time is too short), then the coffee will miss essential taste components. If too much is extracted (the coffee was ground too finely or the contact time is too long), then the brew will be bitter. Rather than being a measure of the total quantity of solubles extracted, yield is a measure of the desirable range of extracted solubles. To put it grossly, if you mix hot water and coarsely ground coffee in a one to one ratio and allow it to extract for thirty seconds, you will have a cup with a very strong grassy taste. A lot was extracted just because of the sheer quantity of coffee, but not enough of the desirable components. Similarly, if you add a tablespoon of finely ground coffee to a quart of hot water and let it steep for ten minutes, you will have a weak yet bitter brew.

                                                                                  Sheng Wu