I've always seen people talk about driving enough heat into the interior of the bean so the interior gets developed by the time you drop, as if it's some sort of difficulty in roasting, but using a Huky (solid drum) I've literally never had the interior come out lighter than the exterior. It's ALWAYS the opposite. I don't have an Agtron, but the grounds are definitely darker than the whole bean, when everyone always talks about their grounds being lighter

While I may be able to drop lighter to compensate for a further developed exterior, I'd like to address root cause if possible. It makes me suspicious if it could be a contributing reason why I have such a hard time with getting great tasting roasts going beyond the end of first crack, and usually tasting bad if I get within 10°F of second crack.

So if an underdeveloped interior would imply not getting enough heat penetrated into the bean by drop, would the logic be that I'm managing to get heat into the interior too early and really cooking those interior sugars early on?

Over the last year I've experimental with a lot of different schemes and haven't been able to stop this from happening. Maybe the closest I've been is when I was experimenting with very low fan for the whole roast (35 on my Variac, significant back pressure pushing out of the tryer hole). The last month or so I've been using 55 fan (moderately pulls flame through tryer hole) the whole roast and have got some nice well controlled profiles with a decent flavor but still get a slightly darker interior.

3Kpa is max heat on our machine and if the load was charged @ 420° and the gas was upped to 3kPa @ Tp R0R would go through the roof.

I would try and soak less and use a lower gas setting at start. Your numbers look great.

I can get it up to the 4.5-5kpa range. Whether the true burner output actually scales with it, not sure.

Have you tried cutting roasted beans with a sharp x-acto knife to see if that will help confirm your suspicions about interior color differences?

When you say you can't get great tasting roasts as you get closer to 2C, can you use some descriptors of what you mean? IMO, with most any coffee flavor decreases and roastiness increases as you roast longer.

In my experience with the Huky I've never found it to overdevelop the interior of the bean even when using 5kPa during the drying phase. Have you also tried a gas-off soak after charge to see if that helps?

EDIT: you could also try a lower charge temp too. I routinely charge at 375F on my Huky.

Brewzologist wrote:Have you tried cutting roasted beans with a sharp x-acto knife to see if that will help confirm your suspicions?

I haven't cut it, but I always crack a few open and can see the cross section of a lighter exterior and darker interior.

Brewzologist wrote: When you say you can't get great tasting roasts as you get closer to 2C, can you use some descriptors of what you mean? IMO, with most any coffee flavor decreases and roastiness increases as you roast longer.

In these I'm not looking for the light roast fruity complexity I can get from dropping before the end of first crack, I'd like to be able to roast something like a well-rounded Colombian, a chocolatey nutty Brazil, a heavy and interesting Indonesian, etc. All of which frequently get recommended as something that taste nice at a higher roast level. Right now the ones I try to do end up tasting mostly harsh, even without going to second crack. And to bring it back to my topic here: there's lots of times where the whole bean is a solid, rich, smooth brown color that doesn't look very dark at all, but the ground is dark brown and blooms like a mfer

Interesting. Thanks for the reply. Try cutting if you can. I use a magnifier on my phone to look at it. More enlightening than cracking IMO. Would be great if you could post magnified examples too.

As far as blooming excessively, how long do you rest your coffee? I find coffee that isn't rested well to be flat, astringent and club soda tasting.

As for tasting notes from others, I put less faith in them than times past. I found myself gravitating to lighter roasts in general, even if that isn't the norm for a particular coffee. Worth asking yourself if your taste preferences have changed?

Hope you take all this in the spirit of trying to help.

Also, with my Huky 3 kPa wouldn't generate the kind of heat you're showing. I'd have to be 4 kPa or higher for that. What's your roasting environment like? EDIT: and any preheat routine you use?

I too start off with 4-4.5 KPa, get to FC at a similar temp my drop temp is a lot lower (404-407 ish) and my roast also minutes shorter.
Never seen insides much darker than the avg outside color.

I wonder if this is just some terminology thing. A reasonably light or even medium washed bean will often have a really mottled exterior that might look "lighter" than when you grind it because of the unevenness in exterior color from how the processing affects the browning.

I've certainly never had this issue on my huky and have plenty of roasts that are practically exactly the same as that curve in the OP.

olutheros wrote:I wonder if this is just some terminology thing. A reasonably light or even medium washed bean will often have a really mottled exterior that might look "lighter" than when you grind it because of the unevenness in exterior color from how the processing affects the browning.

could well be the reason! although I wonder if the drop temp in that graph is medium roast ?

edit it is, so I'm firmly in th elight roast then, phew who would have thought that...