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Homeroasters - Home Roasting Coffee Community » THE ART OF ROASTING COFFEE » Roasting Coffee

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Roasting a Rwandan Peaberry to the Dark Side, Questions
AMRoberts	#1 Posted on 05/31/2018 2:35 PM
Newbie Posts: 30 Joined: March 24, 2018	Note to any moderator: If this would be better in another forum, please feel free to move it, or tell me how to - thanks. The wife and I are fans of dark roast coffees, so I've been trying to take my sampler bags from Sweet Maria's into that territory. The latest attempt was with a Rwandan Peaberry. I haven't tasted the results yet, but the roasting process led to questions: 1. Does a peaberry bean not provide the number and intensity of cracks typical in roasting? My roaster (modded popper) is loud, but none of the other beans I've tried have given me nothing or at best 1-2 soft cracks at 1st crack, and nothing I could hear in the temperature range where 2nd crack should have been happening. For the most part I implied 1st crack by bean volume expansion (at the right temperature), and implied 2nd crack when I saw divots blowing out of the popper (again in the temperature ballpark where I was expecting 2nd crack). That leads to ... 2. Are some divots a given when roasting into 2nd crack? I did a small sample count, and perhaps 7% of the roasted beans have a divot. The last 5-6 minutes of my roasts have < 10degF changes in the thermocouple that I call "BT", so it doesn't seem like I'm throwing too much heat into the end of the roast, on the contrary my worry watching the thermometer is that the beans will stall. 3. I have a single darker area on one end of some roasted beans, but when I've pulled beans to look at them during browning and immediately after 1st crack, I don't see the dark tip then, as the 3rd picture in https://www.home-barista.com/home-roasting/coffee-roasting-defects-pictorial-t13587.html illustrates. I'm only seeing it at the end of roast. I sectioned one of the beans, and it seems to correspond to a small hollow in the bean end. Is this still tipping (as in a roast defect I should be trying to fix), or just another expected artifact of roasting dark? Photos attached, although I was driving my old phone to the close limit of its focus and using its electronic zoom to try and get these. DarkSide1 compares a roasted bean to the green, I think I'm getting good expansion? DarkSide3 is the sectioned end of a roasted bean, with the mid-tone contrast pushed way up to make the small hollow visible. Any advice appreciated, Alan AMRoberts attached the following images:


chaff	#2 Posted on 06/01/2018 8:51 AM
1/4 Pounder Posts: 81 Joined: May 24, 2017	I like the photos, the one on the left looks like a magma reservoir under Big Island ! yeah, my popper can do divots, there used to be a lot of them when I used full power. Nowadays they seem to happen when Roasts Go Wild and there's no slowing down after first crack or when the output power is over 85% or so. Do you suppose it's possible the beans are carrying excess moisture into the crack temperatures ? I'm thinking of those curves that show, for higher moisture content, the interior stays plastic ( or rubbery ) for longer, maybe explaining the muted first crack you experience; then, later, the vapour release is too much for the structure during second crack.


mkane	#3 Posted on 06/01/2018 9:13 PM
1/4 Pounder Posts: 151 Joined: October 23, 2017	To much heat to fast sealing the moisture in, then eruption? That's an uneducated guess. I never have an issue like that and the first crack is quite audible for over a minute. Always learning


AMRoberts	#4 Posted on 06/02/2018 11:16 AM
Newbie Posts: 30 Joined: March 24, 2018	Quote chaff wrote: yeah, my popper can do divots, there used to be a lot of them when I used full power. Nowadays they seem to happen when Roasts Go Wild and there's no slowing down after first crack or when the output power is over 85% or so. Well I'm somewhat surprised since I believe we have the same popper; I've never turned the output power down from 100%() after first crack. I don't think I've seen anything I would call a run-away roast, I'm riding the fan speed lower (so ET is well above BT) to keep BT from stalling out. If my fan speed adjusts are smooth/timely enough I get smoothly descending delta-BT, but the last few minutes of the roast end up in low single-digit (deg F) increases per minute for BT. () Full disclosure, I'm using an no-name SCR/TRIAC-based controller for the heating coils, and I haven't put a scope on the output to look at the AC waveform. So I suppose it is possible that I'm not really getting 100% when I set that on the control. Quote Do you suppose it's possible the beans are carrying excess moisture into the crack temperatures ? I'm thinking of those curves that show, for higher moisture content, the interior stays plastic ( or rubbery ) for longer, maybe explaining the muted first crack you experience; then, later, the vapour release is too much for the structure during second crack. Good question, I don't know of any way to measure starting moisture content with any equipment I have.


AMRoberts	#5 Posted on 06/02/2018 11:25 AM
Newbie Posts: 30 Joined: March 24, 2018	Quote mkane wrote: To much heat to fast sealing the moisture in, then eruption? That's an uneducated guess. I never have an issue like that and the first crack is quite audible for over a minute. mkane, three questions: 1) Are you roasting into second crack; 2) What is the background noise level of your roaster; and, 3) First crack was quite audible when roasting a peaberry? I'm not getting divots with lighter roasts, they occur with my attempts to roast to Full City+ or a bit beyond. My roaster is too loud, I've had trouble hearing first crack with all eight sample bags I've roasted ... The best (loud and sustained) were the Guatemalan beans, the Rwandan peaberry beans by far the softest. Thanks, Alan


mkane	#6 Posted on 06/05/2018 7:56 PM
1/4 Pounder Posts: 151 Joined: October 23, 2017	Roast just to the beginning of 2c. I use a Behmor. Background noise is talking level I suppose. Ic is quite audible roasting Rwanda Rulindo Tumba. It's not a peaberry Always learning

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