Home Roasting - Holes in Beans?

billagirly

New member
Mar 29, 2005
113
0
DFW, Texas
I don't know how else to describe the issue I'm having - they look like little holes, in the bean. I have a horrible camera and this is the best shot I can get. If you look at the bean on top, I think it's got the most visible holes. They don't go all the way through, just through a layer or so.

What are these, and why do they occur?

coffee.jpg
 

jlyon10

Super Moderator
Feb 16, 2007
436
1
Clemmons, NC
holes in beans

Although I can't see your picture, I have seen the same things in my beans from just about any where. I thought maybe they were caused by insects?
 

Davec

New member
Oct 18, 2006
314
0
Old England (UK)
billagirly said:
I don't know how else to describe the issue I'm having - they look like little holes, in the bean. I have a horrible camera and this is the best shot I can get. If you look at the bean on top, I think it's got the most visible holes. They don't go all the way through, just through a layer or so.

What are these, and why do they occur?
It's hard to see from the picture, but I don't believe you are talking about insect holes. To me it looks like "spalling", the black divots that look as if a circular or oval bit of the bean has been gouged out with a black patch below.

If so, it's usually a sign of too much heat in the roaster. Generally this would be during the roast not neccessarily at the drop. Tipping or scorching is often because of too high a drop temp in a drum roaster. The spalling usually results when it gets just too hot. Try roasting the same beans again, but at 1st crack try and reduce the heat input (not the temperature, if that makes any sense). Your objective would be to try to get the beans hot enough to have a decent 1st crack, but not to let them get too hot. A plateauing off of the temperature curve.

My guess would be that the beans are a soft bean of some kind, but with enough temperature abuse this happens on SHBs as well.

P.S. If the max temp is not too high and your still getting them, see if you can reduce the rate of temperature rise in the roaster a little (if you have that element of control). It would also be helpful if you state what kinf of roaster you use.
 

Fresh Roaster

New member
Jun 30, 2006
162
0
We call them "pop-offs" and we've talked with many, many experts about them and the answers were far from consistent.

What we have surmised is that it basically depends on the beans. Some do it, some don't. We've seen consistency across bean varities but not roasts so I think in most cases you can rule out your roaster being too hot and attribute these "pop-offs" to specific varietals. Just my $.02.
 

Temuri

New member
Nov 12, 2005
98
0
Tbilisi Georgia
These are not insect holes. I have seen how they are created many times. If you roast often you will witness it in your tryer too. It occers duering the second crack when/if too much heat is applied to beans and too noisy pop is heard. I may be wrong but I have really seen many times the small particles flying away from the surface of the beans together with strong crack sound.
 

topher

Super Moderator
Staff member
Aug 14, 2003
3,735
13
Boca Raton
sorry Freshroast...I have to disagree with you here. I do not believe that it "just happens". Maybe your laser is acting like the ship on the asteroids video game :wink: Just kidding...but seriously IMHO I think it is from applying too much heat to quickly during the second crack. It can also happen due to moisture blasting out the bean Not blasting like the laser in star trek but popping through the surface due to the bean density and its structure...but like I said this is just an opinion and I am not a scientist or laser tech :p
 

Davec

New member
Oct 18, 2006
314
0
Old England (UK)
Fresh Roaster said:
it basically depends on the beans. Some do it, some don't. We've seen consistency across bean varities but not roasts so I think in most cases you can rule out your roaster being too hot and attribute these "pop-offs" to specific varietals. Just my $.02.

I think for whoever is roasting those particular variatels where you see the spalling, they need to be a little more gentle with the heat and use only what they need to to achieve the cracks. I find with inexperienced roasters especially, the biggest cause of problems is too much heat. This goes for home roasters and commercial.....the Gene Cafe roaster is a prime example of a roaster where many people probably roast at too high a temperature. I have a Gene and find you have to be very careful not to let it get too hot, especially as when the ambient temperature rises, the thermal gradient across the roasting chamber steepens.

With my Toper I have a different problem, because the roaster is 70% IR thermal input to the beans and the way heating element is in the drum (good for many reasons), in summer I actually have to raise the roaster temperature settings and in winter lower them (because of the total amount of thermal energy being applied to the beans). Annoyingly this gives a little more chance of spalling in summer, unless you are careful.
 

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