Making coffee

Coffee beans are prepared in the following manner:

First, the ripe berries of the coffee tree are picked and the seeds cleaned by one of two methods. In the dry method, berries are exposed to the sun to dry and ferment, then the fruit is mechanically removed. In the wet method, most of the pulp is rubbed off by machine, and the remainder is liquified by fermenting microbes. Then, the seeds are washed and dried to 10% moisture. The parchment shell is removed, sugars and minerals are leached out, and finally the beans are roasted.

Raw green coffee beans are hard. Roasting transforms them into fragile pockets of flavor. Coffee beans are roasted for 15 minutes or less at temperatures between 375 to 425 degrees F. As the temperature approaches the boiling point of water, the moisture inside the beans turns into steam and puff up the bean (similar to popped corn). At the higher temperatures, proteins, sugars, and phenolic materials break and react with each other in typical Maillard (browning) reactions. The roasted aroma, dark pigment, and flavor develop. At 320 degrees F, the Maillard reactions become self sustaining. The molecular breakdown gnerates more water vapor and carbon dioxide gas. If roasting continues, oil escapes the damaged cells and provides a visible gloss to the surface of the beans. Medium roasts give the fullest brews. The darker beans tend to be more bitter from resulting browning reactions. Once the desired roasting is achieved, the beans are cooled off rapidly.

Coffee keeps reasonably well for a couple of weeks at room temperature and a couple of months in the freezer. Once the beans are ground, the shelf life is only a few days at room temperature.

The key to grinding coffee is to obtain a standard particle size. Too large of a particle makes it hard to control the extraction. Too small particles have a larger surface area that comes in contact with the water, which often leads to overextraction and a bitter flavor. Grinders that allow small pieces to escape before getting too small give more consistent particle sizes and better brews.