I noticed that the internal portion of the bean is darker than the outside, which I haven't heard of before. More common to me is a darker outside than inside. Anyone know what might cause this?
Below is three pictures, first one from the café, and second two roasted by me. It's exactly the same beans. As can be seen the bean from the café doesn't have this.


Bean from Café, tot. roast time something around 10-11min.


1st roast. tot. roast time 10:12, DE 5:55.


2nd roast. tot roast time 10:57, DE 6:20.

Thanks in advance!

Did you take a sample of ten or so beans from each roast? The third photo looks a lot like it was a shell (the green bean had no center).

The center of the beans have more oils, which will appear darker. Depending on the age of the first roast, (if it's a bit older) the oil could have migrated more and evened out. You can roast on a Loring and get a lot of coffee to look like that first bean as well, so it's partially roaster dependent.

Internal scorching. Willem Boot has a good article that helped me reduce ashyness with some Brazil's that I suspected the same thing was happening. I did not have a microscope and couldn't see as well as your pictures show. For me, I dropped my MET temperatures during first stages of roast and the issue went away.
https://bootcoffee.com/wp-content/uploa ... July05.pdf

Can you post the profiles for those two roasts of yours?
It would be interesting in relation the linked suggestion that a too-short dry time might be the culprit.

So I'm not a roaster, but how does a roast profile show if a green was properly dried? I'm following this thread because I noticed the exact same issue on a recent purchase of roasted coffee. I couldn't understand how the interior would be darker than the exterior...

It won't, but if the period of time it takes in the drying phase (i.e. up to about 150C) is too short, if the bean temperature rises too fast, it would be suggestive. Profiles give you clues. They don't tell the whole story.

another_jim wrote:Did you take a sample of ten or so beans from each roast? The third photo looks a lot like it was a shell (the green bean had no center).

Yes I did! It looks like that since it broke as I cut it.

EddyQ wrote:Internal scorching. Willem Boot has a good article that helped me reduce ashyness with some Brazil's that I suspected the same thing was happening. I did not have a microscope and couldn't see as well as your pictures show. For me, I dropped my MET temperatures during first stages of roast and the issue went away.
https://bootcoffee.com/wp-content/uploa ... July05.pdf

Interestingly enough the middle picture is the shortest dry phase but also show internal scorching to a less degree than the latter. These are just two roasts though so I'lll have to compare more I guess. But having them as base I get the opposite trend with the length of dry phase.

SJM wrote:Can you post the profiles for those two roasts of yours?
It would be interesting in relation the linked suggestion that a too-short dry time might be the culprit.

Here they are! Don't mind the jumps in BT as it is just electrical noise from touching something!

http://imgur.com/a/L6AeO
http://imgur.com/a/EY7G9

how is the taste? any bitterness with those internally dark beans?