Whatever type of coffee or coffee brewing equipment used the objective is usually the same.

Cup of Coffee

That is, to extract and put into solution, the coffee oils and the soluble (and semi-soluble compounds) that are formed when the coffee bean is roasted.

It is possible to extract as much as 30% of the coffee beans mass into solution, by grinding the bean into a powder and steeping in hot water. These soluble compounds however dissolve at different rates and not all of them are beneficial to the coffee taste. Tannin and caffeine in higher concentrations for example can cause the final beverage to taste sour.

18%-22% is the optimum extraction rate for good coffee.

Under Extraction occurs when the brewing time is too short and not enough coffee soluble are extracted into solution. This can occur if the water is not hot enough or if the water passes through the ground coffee  too quickly. An insipid, thin brew lacking in body and flavour will result.

The opposite, Over Extraction occurs when the water is in contact with the ground coffee for too long and too much of the coffee soluble are extracted than is desirable. A harsh tasting bitter brew will result.

Freshness – Coffee is best enjoyed as soon as it has been brewed. Oxygen in the atmosphere causes the taste to rapidly deteriorate and the beverage loses its aromatic oils and may soon become sour, flat and lifeless. Freshly brewed coffee should be consumed within 30 minutes if left on a hotplate and should never be reheated. The use of a thermos type flask can extend this time up to an hour or so before the flavour is impaired.

The quality of the brewed coffee beverage will depend on several factors, all of which are important to produce the perfect cup of coffee.

• Grind size of the coffee
• Quantity of coffee used
• Water quality
• Water temperature
• Contact (infusion) time
• Type of brewing method used
• Hygiene and cleaning practices