Buying a good quality coffee is only part of the journey to a great tasting cup of coffee. Knowing how to brew and understanding the factors that influence the brew is the rest. Firstly, however, it is necessary to explain what's happening during the brewing process.
When you brew coffee, the hot water is acting as a solvent. Coffee grinds contain solubles (flavour compunds, oils) which will be bonded into water, creating an infusion we call coffee. In theory, a perfect coffee extraction will result in extracting all desirable compounds from a coffee grind.
Brewing methods that use a paper filter will only have soubles in the cup resulting in a cleaner cup. Other methods, such as cafetiere, will contain particles of insolubles, which can sometimes taste a bit gritty.
Main factors influencing your coffee brew:
1. Grind (coffee particle size)
A size of the grind may be crucial to the result. A finer grind basically means a more surface area of the coffee bean is exposed to the hot water. Brewing methods with long extraction time, such as a cafetiere / French press, require a coarse grind (less surface exposed to water). Espresso on the other hand requires a much finer grind as the grinds are exposed to the hot water for fraction of second.
2. Coffee to Water Ratio
In order to avoid over or under extraction it is a good idea is to measure grinds and water each time you brew your coffee. Over extraction resulting in a bitter cup is caused by grind being too fine, too much ground coffee or water being too hot. On the other hand the under extraction results in a weak, thin cup of coffee and it's caused by too coarse grind, not enough of ground coffee water not being hot enough.
3. Water Quality
Try to use good filtered water or bottled spring water. Do not use distilled water as all the minerals essential for a good cup have been removed. The tap water is usually not good enough for a high quality coffee.
4. Water Temperature
The ideal water temperature is between 91 C (195 F) and 96 C (205 F). Boiling water should never be used as it burns the coffee grinds and colder water would not extract properly.
5. Contact Time
The time coffee and water are in contact. This depends on the brewing method.
6. Agitation (stirring)
Stirring the infusion increases the extraction rate.
Other important factors:
- Quality and roast of the coffee - some roast levels perform better in different brewring methods than others
- Cleanliness of the brewing equipment - old sediments can affect the taste