Brewing coffee is not just mixing water and coffee grounds. In the Coffee Industry, the essence of coffee brewing is in the extraction process. According to Lani Kingston in his book, “How to Make Coffee : The Science Behind The Bean”, 30% of the coffee will dissolve, and from the 30% dissolved it contains all the flavor, aroma and character of coffee that we expect to taste.
Before the extraction process, coffee will pass through the first phase which is blooming or pre brewing. This phase aims to reduce carbon dioxide levels. Only then, it will go through extraction process. Extraction process is, however, the only part in coffee brewing that we can control because not all the compounds are on the same level every time. This process aims to bring out a balanced character of the flavor such as fruity, acid, sweetness, which depends on the character of each coffee. To get optimal extraction, several important factors need to be considered. Here are the important factors (the things that we can control) in the extraction process: contact time, grind size, temperature, water ratio and coffee.
As we already know, each brewing method has its own way to obtain an optimal coffee taste. The level of grind size varies depending on the brewing method that we use. The coarser the coffee, the more watery it will be. On the other hand, the finer the grind, the coffee will be dense and more bitter. It also affects how fast or slow the extraction process occurs.
For the ratio of coffee and water. Based on references from the Speciality Coffee Association of America (SCAA), the ratio of coffee and water is 1:18. It means, 1 gr of coffee requires 18 ml of water. With water temperature used around 90-96oC. Good quality coffee should be at the level of 70-180 ppm and soluble with a pH of 6.5 to 7.2. However, each coffee is unique. This scale is just a reference and not a benchmark. The uniqueness of these coffee is what make brewers eager to learn to get an optimal taste and character.
Another thing that affects the extraction process is the contact time or duration of infusion. The length of time this brew depends on the brewing method used. For example, if brewing using V60, it takes no more than 3 minutes. Agitation also take on the role to obtain the optimal extraction. Many ways are done to manipulate agitation, one of them is pouring water using kettle. The higher the water pours, the higher is the agitation level. Thus, lower pouring will reduce the level of agitation.
By doing some exercises and experiments and comparing with the previous results, it certainly helps us get optimal coffee extraction results and help to prevent over extraction or under extraction. How do we detect if coffee is over extraction or under extraction? Find the answer in the next article.