A question that has come up in working on roast profiles.
I am trying to figure out how ramp rates affect the shade change on the bean. Specifically I am trying to improve bean development without roasting to dark. I would imagine that moisture content/hardness of the bean would affect this but is there a general rule to how heat is applied early to get a well developed light roast?
Very generally speaking I basically break my profile in to 3 parts, start to 300f bean temp, 300f- first crack, FC to finish. I try to work in a 4-6 min. range for the first leg. Much depends on the roasters ability to transfer heat energy to the beans which can also be adjusted by batch size. I look for an even heating of the beans that should look even in color at the 300f mark. From 300f to first crack I aim for an average increase of about 20degrees/min. I level my temp slightly before first crack so my increase is in the range of 5-9degrees/min. during fc. After that much depends on bean origin, roast level, etc.
Well, this is somewhat of a can of worms huh, ....
These rates are all dependant upon origin, crop cycle, moisture, density, batch size and so on. While I find "farmroast" has valid points, his reference numbers pertain only to his varietal, condition, roaster, batch size etc..
I would address this issue by stating, pay close attention to your preheat temp/ charge temp and then create a "cupped" relationship to your bottom temp, time turnaround and rise before 1st crack, then all the way to the drop. regardless of what shade the bean is, your development lies within these rise variables. No tipping so be careful!
its all about rise yo,
Remember a bean roasted to 420f in 12min will be a different shade than one roasted in 20min. I would suggest buying some beans just to burn. Go out and get some real cheap beans and experiment with all these variables, you'll be glad you did and get to know your roaster a lot better.
Also sometimes it helps to graph the profile, come one use them college skills, log them notes. Which coffee's go crazy exothermic, do you adjust your temp accordingly, or just let em ramp up?
IN the end its all subjective, but the theme would be to learn your roaster well, IMHO.
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