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Gene Cafe Optimal Batch Size to Prevent Uneven Roast
I own a gene cafe coffee roaster and I've always had trouble getting even roasts. I generally roast around 230g of coffee per batch. The coffee tends to taste a little dull, and I've noticed that the beens are uneven. I roast a wide variety of beens from African to Central American although I tend to gravitate to the fruitiness of Ethiopian coffees. I prefer to roast on the light to medium side of the spectrum, somewhere around city+ (at least that's my goal lol). My friend is suggesting to lower the batch size further, but I would like to know if there is an optimal batch size with people experienced with this roaster. I don't want to lower it to the point where the roaster won't perform properly. Following is the two profiles I generally use.

Profile 1:
10 minute roaster warmup at 350 degrees before beens
482 degrees until start of first crack
456 degrees to extend first crack

With the above profile I'm hitting first crack in around 9 minutes and roast an additional 2:00-2:30 to develop roast. Some of the beens go way too dark while others are spot on. If I back off a little on the development time some beens haven't experienced first crack while others look good. Overall taste seems baked either way.

Profile 2:
10 minute roaster warmup at 350 before beens
462 degrees until first crack
452 to extend first crack

I haven't timed the 2nd profile because it's relatively new to me. Roast comes out a little more even but the taste seems to be dull.

As you can imagine either scenario leaves me frustrated. I would greatly appreciate everyone's advice to get more consistent results.
How long have you owned this roaster and did you buy it new?



I bought it new a couple years ago. I roast about 2 pounds a session every 10 days or so.
ok so you are saying you have never been happy with your roasts?

did you take this issue up with the seller?

I am surprised you seem to have an issue with City +, would suggest you start at 150 batch size and increase from there.

dump this roaster and get one you are happy with as two years seems a long time to tolerate baked beans unless their Bush's...


I'm on Atkins at the moment so I won't be eating beans loaded with sugar anytime soon :(

I believe my problem has gotten a little worse over time. When I got the roaster I had a hard time gauging the roast level, but when I did get the roast level correct, it was decent. However over the last year, I haven't gotten the aroma, and taste that I expect. I should be getting the same results that other people seem to enjoy out of this roaster. People seem to love it.

I don't mind improving the roaster myself if I can determine what may be the cause of the problem. Whether it be an issue with the roaster, or an issue with the roaster that uses the roaster :)

There are no other roasters in my price range that would be better than the Gene. If I splurged it would be for a used Diedrich HR-1 if I could find one. So my only option at the moment is learning how to use this one.
ok 79,

you need to remember that your overall physical health can change what you taste and from the sound of it you are going through some physical changes.

why not pretend that your roaster is new, get some beans out and use a moderate amount say 175 per batch for a few batches and see of you can achieve your desired roast level...

use sight and smell only or just sight as a marker for your desired roast and remember that they continue to roast so take them out early enough so they do not roast to a level you do not like.

this is interesting in that we have had several members who have found that their beans are not good and it has been directly related to their physical health.

being on a strict diet will change everything for you and can clearly make your beans taste like crap...

how old are the beans you have now, where did you buy your beans?



we have many Gene roasters here who will be happy to help once they see your post 79...
I've been on the diet two weeks :) I finally made the commitment to lose 20 lbs or so. Nothing has changed with regards to my health. I'm young (35), and I'm in fairly good shape otherwise.

I only purchase about 5 lbs of beans at a time so my beens don't sit for long. I've been purchasing from Sweet Maria's although a friend of mine highly recommends Roastmasters, so I just purchased a a few lbs from them.

I am due to roast some coffee in the next few days. I will report back with the results. Hopefully lowering the batch size will help.
John Despres
Hiya, 79!

Interesting problem. Let's start with the simplest solution.

If your roast results are changing and your profiles are not, the roaster is changing...

Turn the Gene Cafe over and vacuum out the vent slots in the bottom.

Then take your chaff collector apart and scrub it clean.

Your overall airflow may be compromised.

Drop your batch size to 226 grams (1/2 pound)

I hope this helps.

Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
Yesterday I disassembled my roaster and inspected the internals. My fan was completely clean, including the screen covering the intake. I went ahead and removed the lint screen to improve airflow. Should be ok because I'm roasting indoors in a dust free environment. I tested the voltage on the circuit I'm using. 123.5V idle, and exactly 120.5 with the roaster running. My voltage stays pretty constant unless my fianc? turns on both the washing machine and dryer lol.

I roasted some Kenyan to city the other night with much better results. I dropped the batch size to 200g. One thing I noticed with this machine is I reach first crack really fast, around 9 minutes or so. Dropping the batch size decreased it further by 30 seconds. Can you reach first crack too quickly?

Kenyan AA Batch 1
Preheat drum 350 for 5 minutes

482 to beginning of first crack: reached in 8:30
450 degree development time: 3:00
Cooled on large baking pan

Total Roast Time: 11:30 mins

have you gone through any of the Gene Cafe forum threads that discuss batch size and 1st crack?


Yes I've read a lot. The profile above seems to be a consensus of what people use. The whole reason I created this thread is because out of the dozens of posts I've read, don't seem to coincide with my results.
John Despres
It will help if you provide the times at which you reach 1st crack and 2nd crack.

Also bean density will make a difference in how fast they roast.

Have fun and keep roasting. These are good questions aand you're tasking my memory since I switched to a Quest M3 a couple years ago.

Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
I use your second profile on my Gene except I start at 465. Prewarm to 350 for three or four minutes. First crack from 10-11 minutes depending on bean.

I purchase from Sweet Marias, GCBC and Toastmasters generally. At the moment have Roastmasters Yemen Mocha Harazi and Panama Lerida Honey in my stash and dozen different coffees from SM.
Just roasted two 230G batches yesterday from SM, Guat Xinabajul Tres Fincas and Costa Rica San Martin de Leon Cortes(both gifted from friends).

My idle electrical read-out is just over 123 volts.

If you are unable to get a handle on your roasts or have doubts I would be happy to coordinate a roast with you. We could use the same roast and profile on the same day and we could each mail the other say 50 to 100 grams.

This morning sipping on a Toastmaster Bolivia Colonia San Ignacio from the farm of the Anacleto Uluri family at 5,575 feet in elevation.
Very sweet and berry flavors predominate.
I also do a lot of blends for milk drinks.

And if my roasts don't suit you? Not my fault. It goes right back to John. Everything I know about the Gene Cafe I learned from him. Ha
John Despres
Here's a thought to try...

This may be counter-intuitive, but reduce the size of your bean mass to slow it down.

After the initial ramp-up to temperature, the beans will become exothermic, heating the other beans, which is why when you turn the gas down they continue to heat up.

A larger bean mass provides more heat. A smaller one will not.

Have fun! Tell us what happens.

Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
Thank you guys for the help. I will definitely try your suggestions on my next batch. I posted a link below to some images I took of the last Ethiopian batch I did. I know it's difficult to analyze due to different monitor calibration profiles but it may still provide insight.
oh boy, have to add my 2 cents. I love my GC, been roasting in it since Dec. 2012, and today hit about 115 pounds. I never prewarm the beans. I know, I'm probably all alone there, but once or twice I did that and could not taste any change. Maybe I should try again. Here is my profile: Insert beans, 230g mostly, and rarely 235g, set temp to 482, time to 30.0. hit Go. When I start to see yellowing I take notes for the next batch. Funny but that really does not matter, I've noticed, lol. When I hear first crack, I note temp and time, and start a timer. After 20 seconds or maybe 30 seconds, depending on the cracking, I drop the temp to 455. If I want to go to just at second crack, I estop around first crack + ~4 minutes, which is typically just before I hear the first pop of second crack. Some beans go a bit longer, some start a little earlier. If I aim for a City + (rarely for me) or Full City, I stop earlier. I do track temp and time from Yellow thru the roast, but mostly I use sight and smoke and smell and the timer to determine when to end the roast. Maybe too simple but, well, it is simple, and it tastes incredibly good. So I promise to try warming the beans to see if I can taste brightness or something different and report back.
GC (red one!), Encore Baratza, Aeropress, Melitta dripper, Primula Stovetop, Yama, French press
Well I forgot to talk about the uneven roasted beans. Yes, I see that in my roasts, though not with all beans. But I believe it enhances the flavors in my FC and FC+ roasts. I can not comment on what that might do to City or C+ roasts.
GC (red one!), Encore Baratza, Aeropress, Melitta dripper, Primula Stovetop, Yama, French press
John Despres
Nice, Michele!

I use time to yellow as the first indicator as to how fast my roast may be moving along. If you're not using a clock, then it's likely to be of little help.

Have fun!ThumbsUp

Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
Time = 30.0 Michele! What level does your roast get to?! Gotta be vienna or beyond I would imagine. I have never taken any roast in my GC past 22.0 at 485*BBQ grill
John Despres
HA!!! I think Michelle sets the timer to 30, the maximum time, and pulls the roast well before the timer runs out.

I ran a test once to see how quickly I could burn a roast, and man, I don't want tot do that again. My wife won't let me, either...

Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
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