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Gene Cafe - Replicating roast profiles for different batch sizes
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d0me
Senior Member


Joined: 12 Feb 2014
Posts: 10
Location: Denmark
Expertise: I love coffee

Grinder: Baratza Virtuoso Preciso
Roaster: Gene Cafe
Posted Wed Feb 12, 2014, 1:03am
Subject: Gene Cafe - Replicating roast profiles for different batch sizes
 

Hello everyone!

I have recently done my first steps into home coffee roasting. I acquired a Gene Cafe. Since I am a newbie in this field I decided to start experimenting with different types of beans and small batches (75g). Once I find the roast profiles I like, I would like to extrapolate them to batches of 250g. I have read that this is possible if the bean temperature is known. However, this is exactly the data I cannot get out of the Gene Cafe.

Do you have experience with replicating roast profiles for different batch sizes in the Gene Cafe? How do you do it?

Thanks a lot in advance for your help.
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boar_d_laze
Senior Member


Joined: 21 Nov 2006
Posts: 1,483
Location: Monrovia, CA
Expertise: I live coffee

Espresso: La Cimbali M21 DT/1 Junior...
Grinder: Ceado E92; "Bunnzilla"
Vac Pot: Royal Coffee Maker
Drip: Chemex + Kone; Espro Press
Roaster: USRC Sample Roaster
Posted Wed Feb 12, 2014, 7:30am
Subject: Re: Gene Cafe - Replicating roast profiles for different batch sizes
 

With luck, some Gene person will jump into this thread and give you some better information -- e.g., specific temperatures and times -- assuming such is to be given; and you might also want to ask around at HRO where there are a couple of very active Gene users, and at H-B as well.

Bad News, Good News

That said, as a general rule, you can't move a profile -- at least not as a recipe, with fairly exact timing, etc., -- without both accurate BT information and a very agile roaster.  

The best you can do using small roasts for sampling is note bean defects, bean characteristics (which should help you decide on what profile you eventually do want when you move to full size charges), and best finish roast level (which you determine by color, how close to the cracks, etc.).  The charges for these sample roasts may be the minimum amount necessary to get an even roast.  

(I don't know what that is in a Gene; but for example, it's about 80g in my old Hot Top, and about 100g in my new USRC.)  

Once you get that information, if you do have a BT thermocouple, many roast masters roast a larger sample, one just large enough to get accurate BT information in order to determine the temperatures of the roast milestones, including end of drying (EOD), start of first crack (1stCs), end of first crack (1stCe), (possibly) start of second crack (2dCs), and (always) end temp (Drop).

Small sampling roasts can save you a lot of money and beans in the end, but unless you have real time BT information (and, as I said, a roaster which allows you to use it in real time), you'll have to develop your profiles with charges large enough to be in your roaster's sweet spot.  

Using all the information gained in sampling, the next step is creating an initial profile with rate of rise (RoR) for the intervals between the milestones, if you have BT information; or times for the intervals if you don't.  These profiles are usually based on the roast master's knowledge of the bean type as well as the information gained from sampling.  They are more hypothetical than ideal and subject to a lot of tweaking.  

The idea behind creating an initial profile is not just to guess at what should work, but to have a plan so you're roasting on purpose, and have some idea of what to change depending on results.  

You don't really need BTs to profile.  Once you have some experience with your roaster, some knowledge of bean types, and an ideal finish level, you can do a good, repeatable job of profiling (and later following a profile) by taking good notes, and paying attention to roast milestones as you go.  

You can do your proposed initial profiles in your head, but graphing them before roasting in the same notebook you keep your logs in will keep you honest, and be more helpful in tweaking as you follow the refinement process from "initial" to "best" profile.  

Rich
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,466
Location: UK
Expertise: I love coffee

Posted Wed Feb 12, 2014, 8:36am
Subject: Re: Gene Cafe - Replicating roast profiles for different batch sizes
 

Batch size has a profound effect on the roasting in the gene cafe a 75g batch adds so little air resistance that the results bear no relevance to a 250 or 275g batch. This is due to the way the Gene cafe roaster works.

Some background reading and articles I did after extensive use of the roaster over many years, including modifications you can do to improve performance.

http://coffeetime.wikidot.com/gene-cafe-coffee-roaster
http://coffeetime.wikidot.com/online-roastlog-application

You can filter the roast logs down to the particular roaster/mod your interested in.
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Frost
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Frost
Joined: 26 Jul 2007
Posts: 2,116
Location: Sierra
Expertise: I love coffee

Espresso: Isomac Venus
Grinder: Lelit PL53
Roaster: Poppery I w/variac, MET, BT
Posted Wed Feb 12, 2014, 8:51am
Subject: Re: Gene Cafe - Replicating roast profiles for different batch sizes
 

I would recommend you pick a single batch size for all your (at least initial) roasts based on results from other users. Batch size is a roast profile parameter. (esp. with the wide range 75-250g) The different bean temp. rate of rise per ET is so wide, it won't be the same profile: ET will be higher or rate of rise slower for the larger batch, take your pick.

Picking a single batch size will eliminate one variable you won't have to deal with getting dialed in.
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d0me
Senior Member


Joined: 12 Feb 2014
Posts: 10
Location: Denmark
Expertise: I love coffee

Grinder: Baratza Virtuoso Preciso
Roaster: Gene Cafe
Posted Wed Feb 12, 2014, 1:03pm
Subject: Re: Gene Cafe - Replicating roast profiles for different batch sizes
 

Oh wow! Thanks a lot for your replies.

Small sampling roasts can save you a lot of money and beans in the end, but unless you have real time BT information (and, as I said, a roaster which allows you to use it in real time), you'll have to develop your profiles with charges large enough to be in your roaster's sweet spot.

boar_d_laze, I absolutely agree with you. The Gene Cafe is not professional coffee roaster and therefore it has its limitations. I hope I can get experienced enough to find that "sweet spot" you are talking about.

...if you do have a BT thermocouple...

Can you actually get one installed in the Gene Cafe? Would it be useful considering that the only parameter I can change is the drum temperature?

Some background reading and articles I did after extensive use of the roaster over many years, including modifications you can do to improve performance.

http://coffeetime.wikidot.com/gene-cafe-coffee-roaster
http://coffeetime.wikidot.com/online-roastlog-application

Thanks DavecUK for the articles. I haven't had time to have a good look at them yet, but I will definitely read them thoroughly and perhaps come back to you with some questions.

I would recommend you pick a single batch size for all your (at least initial) roasts based on results from other users. Batch size is a roast profile parameter. (esp. with the wide range 75-250g) The different bean temp. rate of rise per ET is so wide, it won't be the same profile: ET will be higher or rate of rise slower for the larger batch, take your pick.

Picking a single batch size will eliminate one variable you won't have to deal with getting dialed in.

Frost, indeed, for the initial batches I will work with small samples. Simply because I am learning by doing (mostly screwing up the beans). But as I get more experienced I think should move to samples of 250g. First because it will save me time and money (i.e. energy bill). And secondly because with such small samples I am having real troubles to hear any cracks at all! Currently I am pretty much relying on my sight.

Cheers.
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