It is easy to measure temperature during the roasting process...but what about smell? Do you fine tune roast profiles based on what you smell during the roast?

The chemical changes that happen within the bean from 320F and 420F are fairly well documented, and on these forums we can all read techniques like: "fast ramp up to 1st crack, then slow thereafter".

My question to the forum is: "Can I fine-tune my roast profile based on what I can smell?"

If I smell sourness and acidity does this mean that I am roasting out the acidity or creating acidity? If I smell sweetness during the roast, does this mean that I am destroying sugars or creating carmelization?

Lets spend some time talking about what we smell during our roasts and dive deeper into understanding the roasting process.

Don

Roasting by smell is easy on air roasters and well ventilated drum roasters, not so easy or impossible on low ventilation drums, where the smoke drowns out the aroma.

The start of the first crack is a good place to "cup" the green coffee -- this is where taints in the prep smell like sewer, mud, sauerkraut etc.

For light roasts, sniff at the end of the first crack and note the grassy, vinegary, almost mist-like aroma. Wait till that stops before ending the roast, and you'll going to get the sweetest possible cup.

For medium roasts you are looking to sniff complex toasted nut and caramel aromas. The moment their complexity and deliciousness has peaked, pull the roast

For darker, rolling 2nd roasts, you are looking for a heady mix spice and complex fresh tar/tobacco. Pull as soon as you start getting a hint of burnt or ash.

I don't do French roasts, so I don't know the sign posts.

This works for some people, but not everyone. You need the right roaster, and you need to be able to ignore the particulates and smoke. I'm not sure if this can be trained or not. I suppose if you like snifing the backyard BBQ, you're good for this

Ending a roast by smell is a bit like ending an espresso shot on flow color. It is not particularly consistent in terms of time, temperature or roast color, but it does usually get you to a tasty spot.

This is an interesting topic. There's hugely more information in the roast aromas than in the color or temperature. Figuring out a good way to use it would be nice.

Nice topic.

I've been trying to smell the trier (loaded with beans) but with little success. I wasn't able to tell the difference between different stages. After reading your post I'll try opening the chimney door (charging door) and see if that makes a difference.

Thanks

Roasting by smelling the roast: may be a lagging indicator... I think you may end up shutting down to late - Though I definitely notice the odor changing as the roast progresses with my Behmor.

Howard

Smell is my key indicator that first snaps of c2, my normal dump point, are imminent. Pretty easy on my CO/UFO. I am of course watching ET/BT and listening.

This evening, I roasted with the intention of trying to document what I smell during the roast to create a smell +temperature vs. time map. Unfortunately I do not think my nose is sensitive enough, nor trained enough...yet.

Except between C1 and C2, I noticed a very funky harsh odor and I was trying to find the the point where that smell stopped per Jim's tip. I hit the eject button on my Hottop right when I thought the smell went from funky to sweet and at that very moment, I heard 2 snaps of C2 as the beans were dumping into the tray.

Is there a way to decide by smell that the beans have been sufficiently dried before ramping up the temp?

I haven't noticed a cue myself. The early roast smells vaguely like peas, but I don't think it changes early enough to indicate that the beans are still too wet

I roast in a bread machine with a heat gun and smells throughout the roast pretty much bombard me. Even people standing nearby comment on the wide range of smells that go on from start to finish. If you really want to try this more I would suggest trying to build one of these roasters. They are pretty cheap and can even be free if you talk to neighbors...many people seem to have a bread machine they never use lying around.