Coffee Roasting Fundamentals — Scott Rao

DTR

Sometimes I wish I had never invented the concept of Development Time Ratio. Despite it being just one concept in a 100-page book, 99% of comments about the book have focused on DTR. DTR is often misunderstood, so let’s address that: the book wasn’t written for only those who roast on very lightly (that I am fond of light roasts); it was written for all of the world’s roasters. If you think 15% is the perfect DTR for your middle-of-first-crack drops, please know that you are in the 1% of the world’s very light roasters. It may be appropriate for you, but I would have done a disservice had I written a book full of advice that excludes 99% of the world’s roasters.

DTR is useful as a QC tool, as a target, and as an indicator of a balanced roast curve. However, if your ROR is crashing and flicking all over the place, your DTR doesn’t matter. DTR is also not a good reason to drop a batch; please drop batches based on color or bean temperature. STEP ONE in roasting is to control and smooth your RORs. Step two is to worry about DTR and everything else.

SMOOTH RORs

I’ve saved the most important issue for last: First, please trust that 99% of roasters’ RORs are not smooth enough to eliminate all roast defects. I know this because for some reason people ping me weekly on Instagram showing me their “smooth” curves, but less than 1% of those curves have in fact been smooth. (PS Please don’t DM me on IG with your curves, my inbox is a disaster :0. Thanks.)

It’s very difficult to master smooth RORs. So difficult, that when roasters tell me they don’t believe smooth RORs are good, I know they haven’t actually mastered—and I do mean mastered—smooth RORs. I know this because I’ve consulted for about 600 roasters and 99% of them have been happier with their roasting once their RORs became pretty smooth. Only 10% of those clients are what I would call ‘masters’ of smooth RORs. Mastery takes time and practice, like it does in any pursuit. By definition, it cannot be a formula or something you attain in a few weeks or months.