Coffee Preparation

Roasting coffee transforms the chemical and physical properties of green coffee beans. When roasted, the green coffee bean expands to nearly double its original size, changing in color and density. As the bean absorbs heat, its color shifts to yellow, then to a light "cinnamon" brown, and then to a rich dark brown color. During roasting, oils appear on the surface of the bean. The roast will continue to darken until it is removed from the heat source.

The whole coffee beans are ground, also known as milling, to facilitate the brewing process. The fineness of the grind strongly affects brewing. Brewing methods that expose coffee grounds to heated water for longer require a coarser grind than faster brewing methods. Beans that are too finely ground for the brewing method in which they are used will expose too much surface area to the heated water and produce a bitter, harsh, "over-extracted" taste. There are four types of grinding coffee for brewing. See here.

Coffee can be brewed in several different ways, but these methods fall into four main groups depending on how the water is introduced to the coffee grounds: decoction (through boiling), infusion (through steeping), gravitational feed (used with percolators and in drip brewing), or pressurised percolation (as with espresso). See here for more information

Proper brewing of coffee requires using the correct amount of coffee grounds, extracted to the correct degree (largely determined by the correct time), at the correct temperature. More technically, coffee brewing consists of dissolving (solvation) soluble flavors from the coffee grounds in water. Specialized vocabulary and guidelines exist to discuss this, primarily various ratios, which are used to optimally brew coffee. The key concepts are: extraction, strength, and brew ratio.

Coffee in all these forms is made with roasted and ground coffee and hot water, the used grounds either remaining behind or being filtered out of the cup or jug after the main soluble compounds have been extracted. The fineness of grind required differs for the various brewing methods.

Instant coffee is made by freeze-drying and spray-drying the concentrated extract of roasted coffee beans. After brewing, the water is removed by evaporation from the extract and frozen to create dry granules or powder.