Development Time Ratio – AKA (DTR)– A term often used by coffee Connoisseurs while describing the roast profile of a Coffee, or to justify and give an in-depth understanding of the notes and flavors.
Well to understand DTR, lets dig a bit into the ABCs of Coffee Roasting.
One coffee coming from a single processing technique and a single estate can be roasted into various profiles. Numerous profiles can be identified and designed to highlight different characterisitics, flavors and notes and what is to be desired from the coffee. Depending on the basis after evaluating these profiles on the characteristics like Acidity, Sweetness, Aftertaste, Balance, Intensity, Body, Consistency etc. the most suitable profile is identified and finalized.
The coffee roasting process typically consists of several stages, each with its own characteristics and effects on the coffee beans. Here are the common stages of the coffee roasting process:
1. Drying: This initial stage involves removing the moisture content from the green coffee beans. The beans are heated gently to evaporate the water within them. Drying is essential to prepare the beans for the subsequent stages of roasting.
2. Yellowing: As the drying continues, the beans undergo a chemical transformation, and they start to change color from green to yellow. This stage is often referred to as the “yellowing stage.” During this phase, the beans become more fragile, and their flavor and aroma begin to develop.
3. First Crack: The first crack is a significant milestone in the roasting process. As the temperature increases, the beans undergo a rapid expansion due to steam pressure buildup within them. This expansion causes a cracking sound, resembling popcorn popping. The first crack marks the transition from light to medium roast levels. At this stage, the beans start to develop more complex flavors and aromas.
4. Development: After the first crack, the coffee beans continue to roast and undergo further chemical changes. The sugars within the beans caramelize, and the flavors become richer and more pronounced. This stage is crucial for achieving the desired flavor profile. Roasters carefully monitor the color and aroma of the beans to determine when to end the roast.
5. Second Crack: In some coffee roasts, a second crack can occur. It is similar to the first crack but is usually more rapid and less distinct. The second crack is an indicator that the beans have reached a medium-dark to dark roast level. At this point, the beans may develop a smoky or charred flavor.
6. Cooling: Once the desired roast level is achieved, the beans need to be cooled rapidly to halt the roasting process and prevent overroasting. Cooling helps to lock in the flavors and aromas developed during roasting and prevents further heat transfer.
It’s important to note that the duration and temperature at each stage can vary depending on the desired roast level and the specific coffee beans being roasted. Roasters employ their expertise and sensory evaluation to make adjustments throughout the process, ensuring the best possible flavor profile for the coffee beans.
Development time ratio (DTR) is a measure of the time that coffee beans spend in the roaster after the first crack, compared to the time they spent before the first crack. It is an essential factor in controlling the various flavor profiles in coffee.
A higher DTR means that the beans spend more time in the roaster after the first crack, resulting in a darker roast and a more significant impact on the development of flavor. A lower DTR means the beans spend less time in the roaster after the first crack, resulting in a lighter roast and less impact on flavor development stage.
Different DTRs can create various flavor profiles, including acidity, sweetness, and bitterness. A low DTR can create a brighter, more acidic coffee with a fruity flavor, while a higher DTR can create a bittersweet coffee with a more caramelized taste.
For example, a coffee with a DTR of 1:1, where the time after the first crack is equal to the time before, will have a balance of sweetness and acidity. A coffee with a DTR of 1:2, where the time after the first crack is twice as long as the time before, will have more caramelization, resulting in a sweeter, fuller-bodied coffee with less acidity.
The Development Time Ratio (DTR) can influence the acidity and bitterness of coffee by affecting the degree of caramelization and the breakdown of certain compounds in the coffee beans during the roasting process.
When coffee beans are roasted, various chemical reactions occur, including the Maillard reaction, which is responsible for the caramelization of the sugars and amino acids in the coffee beans. This reaction occurs when the beans are heated to high temperatures, causing the sugars to break down and form new compounds that contribute to the flavor of the coffee.
A higher DTR means that the beans spend more time in the roaster after the first crack, resulting in a darker roast and a longer time for the Maillard reaction to occur. This can lead to a more significant degree of caramelization, resulting in a sweeter, fuller-bodied coffee with less acidity but more bitterness.
On the other hand, a lower DTR means that the beans spend less time in the roaster after the first crack, resulting in a lighter roast and less time for the Maillard reaction to occur. This can lead to a brighter, more acidic coffee with less bitterness.
Moreover, the DTR can also affect the breakdown of certain compounds in the coffee beans during the roasting process, such as chlorogenic acid. Chlorogenic acid is responsible for the acidity in coffee, and a longer roasting time can break down this acid, resulting in a coffee with less acidity.
