This is an essential tool to ascertain the quality of coffee. It involves organoleptic appraisal of the beans - a fancy way of saying that it involves using all senses to assess the coffee, primarily sight, taste and aroma. The same senses you would use in a wine tasting. The technique is slightly different.
The process of cupping is a long established method for testing the quality of coffee beans prior to the purchase of green coffee. Though one may have sourced beans from the same place the coffee can vary considerably. Crops vary from year to year, process methods change, even a change of managers can mean a variation in quality. Within a single crop variances in processing can mean a bad batch, especially if during dry processing some beans experience too much fermentation.
The grower or broker will typically send out a sample to a prospective buyer, usually a pound or so. The prospective purchaser will roast the coffee, generally light to medium roast as they show up more easily and defects. Then the coffee is ground, finer than French press, but coarser than drip. Two tablespoons of coffee are put into each cup. The beans, both the remaining roasted beans and the remaining green sample are set behind the cups. For quality testing it is important to use three or more cups of each coffee to ensure a proper sampling. Then hot water is poured over the grounds.
The aroma is tested first by breaking the “crust” of grounds that have floated to the top, and pushing the spoon down and back through the grounds on the bottom, releasing an intense aroma. Next, the floating grounds are scooped out of the coffee so that they are clear of the tasting. Tasting involves “aspirating” a spoonful of coffee so that it coats the whole tongue at once. This requires a very quick and strong slurp and it is a bit harder than one might imagine to get the coffee to coat your entire mouth in one go. The coffee is then spit out to avoid getting too much caffeine.