The idea of DTR (Development Time Ratio) is super popular among the roasters. “What’s your DTR for washed Colombians?” – these types of questions are notoriously asked on roasting forums. And they couldn’t be less precise.
DTR is supposed to tell what proportion of the total roast is the time from the first crack to the drop, and it’s expressed as a percentage. So many theories are being born at that point. These are real quotes that I came across on the internet:
“The best DTR for filter coffee is 18%-20%.”
“19% and more always results in coffee tasting too dark”
“You cannot have a dark roast with DTR 15%”
Using only this variable causes a lot of confusion. Different roasting machines will have different optimal roast times and will need less or more time to reach the FC, that’s for a start.
Also repeating the profile with DTR as the most important factor can be tricky, since “the same” 15% DTR while being a couple of seconds slower/faster on the crack will result in a different roast degree most probably, hence a different taste profile.
There are many more important questions to ask before focusing on the DTR.
How effective is the heat transfer on your machine?
What roast degree would you like to hit?
Should you end the roast with the same drop temperature even if you’re slightly slower compared to the reference?
Should you “lock” your FC temperature for this profile or should you mark it differently each time?
To name a few.
Always think how to be more precise and look suspiciously at random, anecdotal theories on the internet! 😉
Our Roasting Tips are brought to you by Piotr Jeżewski (88 Graines Q Grader & Sourcing Director)
