Help with bland, grassy roast results

My first post on here. I’m pretty new to roasting with a Bullet and I need a little guidance with my roasts. I roasted three different beans yesterday, with very similar roast profiles and they all ended up very similar, bland, kind of grassy, cardboard like results. Two were Brazlilan and one Ethiopian. I have attached the second Brazilian roast. Any thought or pointers? Thanks in advance.

I am very new to the bullet, but have roasted on a nucleus link for about 200 batches so take this with a grain of salt or maybe even wait for other more experienced with the bullet to reply. But it seems to me your end temperature is very low and your ror over the roast was pretty low especially at the end. I would think going with a little higher preheat would help give the roast more energy and a better ror and get you to a better end temperature.

I agree that a higher charge temperature can help. Grassy notes are generally a sign of under roasting.

I can’t imagine that you are getting to 1C at 179C. I roast batches similar to yours and consistently get to 1C at 195-200C. Have you cleaned your bean probe and ITBS sensor lately? Grassy often indicates under roasted beans. With 23.7% development your beans should have been at least Full City or Full City +. Visually does that appear to be the case?

Quickly, because I have little time. The profile you’re seeing here is displaying the BT as the main probe. If you look at the roast on Roast World, you’ll see that the temps are OK. The only thing that comes to mind now is that you’ve tried it too quickly, and maybe some days of rest will help. I hope you’ve seasoned your drum properly. Other than that, give it some time, and the taste will change. By the way, how did you try the coffees?

Yes, I’d say they were at least Full City. I will clean the probes again, but they didn’t look bad a few roasts ago.

I bought the roaster used, so the drum has a hundred or so roasts on it so far. I tried the coffee with an Aeropress after 24hrs. Maybe I will give it some time. Just seems strange that I keep getting this grassy, bland taste with all of my roasts.

I have to roast 2 batches and get to the theatre on time, so I’ll be brief. Aeropress after 24h, hard no. Only 2 ways that can eliminate co2 and have something of a taste after that short are cupping and Turkish. Cupping 1/18 0.055g coffee for 1g water. Turkish 1/10 1g coffee 10g water.

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455g batch size, bean probe 179 degrees is too low. If it’s not a problem after cleaning the bean probe and ITBS sensor, the point where the first crack should be thought of at 190 degrees or higher.
The grass flavor is a negative taste that comes out when it’s not roasting well.

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I’m sure there’s a bit of variation regarding when 1C occurs. I wait until I hear 2 or 3 pops within a 1 - 2 second period. Are you marking 1C when you literally hear the first bean crack?

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I’m sorry, but I’ll have to disagree there. The BT is far less reliable on smaller batches, and I do have beans that crack around 180 with a 500g batch on the bean probe with no taste related problems. According to the IBTS the FC was at 202°C, so perfectly normal. I do agree that a thorough cleaning should have been done when the roaster was purchased used, but maybe it was. We don’t know.

I mark 1C when I start to hear several beans cracking for a few seconds.

My bad. I was reading FC temp from bean probe, not IBTS. Big difference.

OK, now that I had time to look at it properly, the only other thing that comes to mind is that you’re fighting the development phase too much and maybe hindering it. Underdevelopment could result in what you’re describing. Although the bean probe says differently, you have under 5°C on your delta temperature for almost 24% development according to the IBTS. Try keeping the P5 going and don’t drop to P4 when FC starts. You could also delay your F5 until after FC. Also, maybe change to IBTS readings in RoasTime settings if you’re roasting smaller batches. The bean probe is good from 800g upwards.

Thanks for the tips. I’m going to try a few more batches tomorrow (after I re clean the sensors) and use your ideas of delaying the P4 drop/F5. I did try the coffee again today and while a little better tasting, still nowhere near where I’d like it. Practice, practice…

To trust the bean probe, it must be perfectly included in the bean pile. The reliable FC temperature of the bean probe is above 190. To trust the bean probe, it must be perfectly included in the bean pile. The reliable FC temperature of the bean probe in a 500g batch is above 190. but I think bean probe inspection in bullet r1 is actually incomplete. for more reliable data, it is accurate to measure with ibts temperature on the bullet r1.

If that is the case, what should FC temp be with the IBTS?

Just a follow up here. I roasted a couple batches of Nicaraguan and Kenyan a few days ago and used a higher PH temp in both (230 and 250). Also had a an ending temp (IBTS) of 210 and 212. Grassy, underdeveloped flavors are gone. Whew! I still have a ways to go with nailing down everything, but it’s like night and day with just these changes. Thanks for the help and maybe this can help others.

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Grass can be good. It is just a flavor.

yep. It’s the difference in taste. I think of grass flavors negatively. I don’t feel the need to find delicious grass flavors.
This is because I think there are many better flavors.