What’s up everyone?! Of all the varietals I have the least amount of experience roasting Kenyans. I’ve never had much luck coaxing out the sweetness that we all love about them so I usually steer clear and gravitate toward Rwandan, Ethiopian and Burundi beans when I want East African profiles. A buddy of mine bought a nice looking Kenyan Peaberry and asked me to roast it up for him. I used a peaberry recipe I created for some PNG Peaberries a while ago that worked really well.
I have never had an EOR crash like this before! In the first roast I tried to compensate for a late increasing RoR and just thought I overdid it with the P6/F4 adjustment. I changed the EOR settings and ended up with a very similar HUGE CRASH.
I have a ton of experience on the Bullet with beans from all over the globe and haven’t seen something like this before. What do I not know about roasting Kenyan Peaberries??? 
Ah, this is super common on Kenyan coffees. Have you heard of the Rao dip? He proposed this a few years ago as a way to minimize the crash that can happen at or after FC.
I’ve used this on the bullet with some moderarte success as follows:
- identify the temp that crash occurs. (looks like around 198c or there about according to ITBS)
- drop power (I’ve used 2 steps down) about 45 seconds before crash, hold this power for 30 seconds.
- at the end of 30s, return power to original setting. (p7 on your graph)
- leave power high through the “crash” part of the roast, which looks like about 60 seconds
- adjust to avoid post crash ROR flick
You won’t be able to completely eliminate this crash, but it can help make it softer.
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Just a suggestion: you could try reducing Power to 8 a little earlier so the Maillard extends by 30 secs or so. Entering FC with a lot of thermal momentum causes an intense cracking, releasing a lot of water vapour that can cause crashes right after.
As @andrewcoe has pointed out, Rao in his book has talked about stepping down power towards FC to prevent crashes. He does not elaborate much on why crashes happen. Over the years, I have realised that the main cause of a crash is too intense a crack. A common reaction (which you have not made) is to crank up the power but that actually works opposite - like pushing the accelerator during a brake fail. Earlier power changes and a slightly longer Maillard should alleviate the issue.
Ahhhhh this is SUPER helpful, thanks dude. I had no idea since I very rarely roast Kenyan beans. I have not heard of the Rao dip but I’m down to try it. Thanks so much!
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Not a bad suggestion. The reason I leave P9 on for so long is that I’ve found I get a little dip for some reason if I reduce to P8 too early. I’m cognizant of the thermal momentum factor and have been able to manage it pretty well with all of my other varietals that I roast so I was just naive re: these Kenyans.
Re: crashes this is why LOVE coffee. It’s so complex and unpredictable in a lot of ways. Keeps you on your toes 
Per your comments on stretching out Maillard the reason I don’t is that I’m already a little nervous about my time to FC. I usually try to shoot for a window around 8:30-9:30 FC to avoid baking off light roasts. As it is, I’ve been having some recent roasts that weren’t hitting FC until around 10min which I found muted the floral and punchy fruit notes I try to coax out in my naturals.
Part of the reason is I recently dropped my PH temp to 260* even for my 775g loads to avoid scorching like Hoos suggests on his Bullet approach. When I had PH temps closer to 270* I was pretty consistently hitting FC around 8:30 but now that I dropped down to 260* it’s pushed maillard longer and FC around 930-10m pretty consistently with the beans I have on hand (Colombian Honey, Bali Natural, Ethiopian DP, etc)
