Hi,

I am new to espresso home roasting. I am using a hot air popper for roasting. I got several single origins, and espresso blends in green form well known online stores. When I roast, only 20% of the time I get good results; at first I thought it was the blends that are not suited to my palate.

But, once I got a very nice espresso from one of the blends (let's call it A), while other two blends, which were roasted in the same session, were grassy in taste. The next time I roasted blend A, I got roasnable results, but not close at all to the previous result. I remembered later that The first time I roasted A I did with small batch compared to the other two. So, I concluded the temperature from the popper were not enough to roast larger amount. So, I repeated the process with less coffee. Again, the results are reasonable, but not that good. That was the case with all the blends.

BTW, I usually get good results by taking the roast to FC+/vienna. Otherwise, the coffee tasted badly no matter what I do, even when the recommended roasting level is C+ to FC+.

Any help would be appreciated.

Thanks.

Try with more coffee, enough so it barely spins at the start. You can help by tilting or stirring, more coffee slows the roast while less will speed it up.

"Grassy" can mean it needs more rest time after roasting.

Jack

Thanks, all.

I watched some videos and read that it is better to start a with "very hot", because you want the inside of the bean to get roasted, not just the outer shell--this is how I understood it, and maybe it is not the case. Am I wrong in this?
And I thought the same later because I remember when I started with stove top roasting, I always get grassy taste, no matter what. But with the hot air popper I get inconsistent results, but diffidently better than stove top roasting.

Also, I actually let the coffee rest for a week before starting to use it, and I noticed it gets better. Yet, some was left for three weeks, with no change in taste.

The problem now is I am unable to accept the pre-packaged I was using--though some of it were very nice--and at the same time frustrated I can not get good results most of the time.

It could be to do with the thoroughness of roast - I noticed this too, with a popper. Might take some experimenting to find the right batch size so sufficient heat can be generated quickly enough. The two main things that improved popper roasts for me was having a batch size which would agitate by itself and adding a chimney to retain heat.

For the more knowledgable popper-roasting members to be able to help, perhaps you could mention the type of popper, size of batch and roast times?

Grassy usually means the coffee did not develop completely during the roast. It can be the case that the whole bean is not developed or just the inside of the bean. You can actually have coffee that is burned on the outside but not developed on the inside resulting in bitter and sour/grassy taste in the cup.

The coffee needs time to correctly develop during the roast as it takes time for the heat to penetrate the hard bean. You didn't mention how long is your typical roast time. Also do you monitor the air or bean temperature during the roast? Judging the roast level just by eying the bean color is tricky and can lead to inconsistencies.

Ideally you would have some means of monitoring (and ideally controling) the bean temperature during the roast and you would write down the time it takes for the beans to reach three important temperatures: end of drying (beans turn from green to yellow), first crack (FC) and drop time.

I used to roast with a fluid bed roaster (SR-500 and SR-700) and I still use the SR-500 once in a while, usually to demonstrate to a newcomer how easy it is to get into roasting. In my experience, grassy taste usually comes from too fast a roast, especially the drying stage (up to yellow/light tan colour). Is your coffee also somewhat acidic? That would confirm my suspicion of a too fast roast, as an acidic taste also comes from too fast a roast, especially in the latter, finishing stage (1C onset onwards). To get a balanced roast, you need to spend about a quarter of the time in the drying stage and a similar amount of time in the finishing stage.

Of course, it all boils down to personal preference and that is also influenced by the kind of roasts you are used to. What you are experiencing is the reason many people characterise fluid bed roasts as being 'bright'. I actually got used to this in my coffees, as I used to only used fluid bed roasters. When I switched to a Quest M3-MK2, which is primarily a conduction roaster, I had a hard time getting roasts I liked, as conduction roasters generally are quite the opposite of hot air roasters. When I go back to using my SR-500, I notice the difference in taste, which I now no longer prefer, unless I pay strict attention to the ratio of the time in the three phases, drying, development and finish.

You don't say how your popper is set up, but to make it easy to use to achieve phased roasting you need to be able to control both the heat and the fan speed. This is one thing makes the SR-500 a good fluid bed roaster IMHO.

another_jim wrote:Um, Not on an air roaster; more coffee speeds the roast, since the slowed down airflow raises the temperature..

Jim's right, been too long since I roasted in my air popper, I got this reversed.