How much of a punch would you like? The higher the number the stronger and deeper the flavour.
Acidity in coffee is not a negative. It’s distinctly different from sourness. A fresh green apple would have a high acidity, a juicy red one a low one. In coffee it’s that tingle on the tip of your tongue.
Development Time Ratio [DTR%]
During the roasting process, the DTR% measures the time between first crack (see meaning below) and the end of the roast, as a percentage of total roast time. The higher the number, the more time the beans have to change their molecular structure, resulting in darker, and richer flavours and deeper body.
First Crack and Second Crack
In the roasting process the coffee beans have two stages when they make a distinctive cracking sound. At first crack the last of the water vapour is pushed out through the porous skin of the beans. At this stage the beans are cinnamon in colour. Only after the first crack do flavour and body development occur.
Around an equal amount of time later, there is a second crack caused by the release of carbon dioxide. At this stage the beans are going to get notably darker. Shortly after the second crack, the beans will charr and eventually start to burn. It is an art to go beyond second crack and not ruin the roast.
Coffee is graded at the source, depending on the unique characteristics of the origin country. Some countries grade by hardness, others by growth elevation (higher grown coffee is better). On top of this there are size grades as well, so that bean sizes don’t vary too much.
Coffee beans fresh from the bush need to be dried and hulled (the outer layers of the bean removed) before we can roast them. There are three main processing methods that all influence a coffee’s distinctiveness. The same coffee bean processed in different ways will have different characteristics in your cup.
Beans are spread out on large patios or raised beds and let to dry in the sun. Hulling occurs naturally as the beans dry. The outer skins simply fall off. Sun-dried coffees are generally darker in flavour and have a richer body.
Washed coffees are going through a complicated washing process to remove the outer layers of the coffee beans. Drying often occurs on patios, raised beds, or in mechanical driers. This method is often used in countries where sunshine is unreliable, or it is used by choice, for the specific character the coffee ends up having. Washed coffees are generally lighter and body and more acidic.
This is a mixture of the first two methods, where not all the outer layers of the coffee beans are removed in the washing process and the last step is sun drying. With this, certain sugars and other compounds migrate back into the bean, giving the coffee a nice balance between body and acidity.