Hello guys,

My recent focus on roasting was how to prevent the inside of the bean exactly the same as outside.

Unfortunately it looks like people have few comments and discussion on this matter.


For which, I also went through couple of threads including Willem Boots and Rob Hoos' opinion on this.
; I gave changes on my charge temp & heat back and forth, but it turns out it doesn't work so good so far.

One thing that I noticed is that It stands out clearly when I roast blended coffee from different countries.
It was not a big deal when I roast single origins.
In my opinion it was regardless of drying technique or moisture content.

Is it normal that the color has some difference outside and inside?

How do you guys control roasting or troubleshoot when it happens?

I have a fairly large thread related to this topic, it drove me absolutely crazy for a while. My conclusion at the time (thanks to peoples input on HB) was that roasting lighter and keeping development time to reasonable levels helped a lot but didn't eliminate the issue completely. Reasonable levels for a 10 minute total roast was to keep it under 2 minutes or 20% total.

Then I watched a YouTube video of Rob Hoos (I believe it was RH) where he said he didn't believe it was internal scorching but simply the higher concentration of sugars in the interior of the coffee bean caramelizing to a darker color compared to the outer most part of the coffee bean which contains less sugars. I'm paraphrasing big time but that was the gist of it.
He may or may not have also said that actual internal scorching is extremely rare. My memory is sketchy.

coffee_plXR wrote: Unfortunately it looks like people have few comments and discussion on this matter.

Who hasn't commented on this in the past? Internal scorching is less than myth. It doesn't happen unless it happens to the exeterior of the bean first. The difference in perceived color is attributed to the points mentioned above, noticed by Rob Hoos and others.

Bear with me Tom:)

Since I could only see someone quoting Willem Boots' experiment, I needed much broader background to this phenomena.
If you have bunch of thread and research on this topic, mind if you share the links here?