If someone here has pictures of the inside of the bean, at different stages that would be great. Or maybe somone could post a link to a page that shows the different stages of internal development. I am having quite a struggle with a Guatemala SHB bean (Guatemala Antigua Los Volcanos), that I suspect I am underdrying, but there is such a fine line between underdeveloped taste and burned taste. For some reason I get either burned or green/undeveloped taste in finished roast. I get 1st crack at 190 C/375 F, slow it down and spend 4 minutes til finish at 206 C/403 F I have not experienced a bean that has given me such problems.

I used a sharp knife and checked the drying development in different stages in the roast. I am very interested in seeing av SHB beans internal development at approx. 150 C/300 F. When I check the internal development at 300F, the bean is not 100% dried, should it be 100% finished at 300F? Or can the drying end as late as 320 F/160 C? Im roasting on a Diedrich Hr-1 roaster, wich can give longer roasting times than normal. At this roast My start temp is 340 F/170 C, and spend approx. 7,5 minutes to 300F.

Gismar wrote:When I check the internal development at 300F, the bean is not 100% dried, should it be 100% finished at 300F? Or can the drying end as late as 320 F/160 C? Im roasting on a Diedrich Hr-1 roaster, wich can give longer roasting times than normal. At this roast My start temp is 340 F/170 C, and spend approx. 7,5 minutes to 300F.

A shot in the dark here... I'd suggest a higher starting temp, so that it gets to 300F more quickly, but then try to hold it there for ~3min. Depending on the moisture content, 3min. may not be enough, but that's my average hold time. I always look for a color change before leaving the 300F hold point, that it's gone from green to yellow/golden.

Generally, 1st crack starts for me around 400F, obviously different for different beans. But this tells me that your 300F reading and my 300F reading are not the same. You may want to hold yours for the drying phase a tad lower, perhaps 280F, and then watch for the color change to yellow/golden.

The problem with moisture remaining in the bean is that it compromises and conflicts with some of the chemical reactions and will produce unwanted compounds and flavors.

Hi Gismar.

I have the feeling that your problem with burn flavor is the temp of your drum (ET) set too high. The green flavor can be controlled lengthening the finish phase.

All moisture should not be eliminated at the dry phase. 1C happens due to moisture.

I used to have problems scorching Brazilian beans (difficult). I was using the heat of the drum only + some little airflow. Once I incorporated an extra heat gun in my roaster, the problems disappeared all together. Excessive heat in the drum was the culprit. Relying on the heat of drum alone to raise BT fast was a problem (like roasting in a frying pan). If you have control over airflow, try increasing it (to heat the beans with air convection instead of heat conduction from the drum), that should help. The other trick is to lower your batch weight (ie. try half the batch) so that more hot air flows around the beans.

Cheers

I have a Diedrich HR1 that I have been using for more than four years. I also have a fair bit of recent experience with an Ambex YM2.

You do not provide much description of your profile, in terms of heat settings, airflow, etc. You also do not tell us what quantity of the SHB that you are attempting to roast.

I have never done a 1 pound roast in the HR1 for which 300F is an adequate starting temp. On my roaster, I usually start at 375 for hard/high-grown beans. Softer beans I might go as low as 350. 300 is the usual start temp for most things on the YM2, by the way.

I have the SS drum, which has a lower thermal inertia than the cast iron one. This may also necessitate lowering your charge temps a bit from what I have noted above, if you have the cast iron drum.

7.5 minutes is way too long to get to 300. It is a bit counterintuitive, but you are overdrying the beans when you do this. try to be in the 5-6 minute range for most beans. For SHB Guats, 5.5 minutes is a good place to start. You need to pour on the heat. Preheat on High, charge drum at 375, turn burners off 30 sec, medium 30sec, and back to high, if you are doing a full pound. There are some SHB Guatemalas and Panamas that I have had to decrease the charge mass to 0.8 lbs.

Slow the roast just before 1C, but be careful not to stall above 400. Never roast such a nice bean past the earliest snaps of 2C.

Hope this helps,

Mike

My charge temp was 340F. Preheat is High, Low for 3 minutes, then M for 1 minute. High at approx 280 F. I open for 50% airflow at Yellow approx 320 F, then full airflow at 360 F. This a full batch roast.

What ramp after 1st when aiming for a City+/Full City roast would be best, 4 minutes is what I spend on on the final ramp on this roast.

If you could say a few things about "charge-temp", "heat level"(Low medium high) on a drum roaster like the Diedrich Hr-1, I would be grateful. Would be correct to say this: SHB beans like Guatemala and Kenya can be dried at shorter times but at a higher heat level meaning charge temp and heat setting? Medium hard bean like a Brazilian will dry in a longer time but at lower heat level(lower heat setting and lower charge temperature)?

I think that your final ramp is reasonable. You might even stretch it to 5 minutes if you are roasting lighter than FC. It is likely that your gravest errors are before 1C.

Your generalization demonstrates that you are becoming clear on the concept.

Now go roast!

-Mike

Thank you for your information. I will reduce the batch to 350 grams, and aim for 5,5 minute drying phase - I guess that 1st crack at 10 minutes and finishing the roast in 14-15 minute will be the way to go. What is still unclear for me is how to do the second phase in the roast, and how it might have a negative influence on the result. Usally I go through that with the temp set on high til the point before first crack where I lower it to Medium, so I probably might have gone through second phase a little fast. I also start 50% airflow at 320 F, and open for full airflow just prior or just past 1st crack depending on what roast-stage Im aiming for.

Anyway, thanks for you help, Ill post the results later this week:-)

Update: I got much better result with shorter drying time, but it even had to be shorter than 5,5 min. Im now drying the beans for 4,5 minutes, Im really surprised by the short drying time on my Diedrich Hr-1. I also reduced the batch size to 400 grams. Another thing I also had to adjust, was the timing for slowing down the roast on 1st crack. It seems I was a little bit late on slowing it down, so it went through the beginning of the first crack too fast. The Hr-1 roaster has a really slow respons time when adjusting the temperature, so the adjustments must be done several minutes before first, combined with using the airflow to slow it down. I have tried both 4 and 5 minutes after first crack, and gotten acceptable results. The Guatemala Antiqua Los volcanes seems to get a burned taste if the roaster gets hotter than 404 F/206 C (my first crack starts at approx. 373 F/190 C), so I dont understand how to get a full city roast with this coffee, I know that alot of roasters recomend a Full City for this coffee. Every attempt I have made with this coffee has resulted with to much burned flavor passing the 404 F mark.