# PRO Roasting



## soundklinik (May 31, 2013)

I got a question for professional roasters that use commercial gas fired machines.

Size 5-15kg. Machine is equipped with a PID.

The question is, how long do you roast in these machines? I roast for a cafe shop and try to do my batches in about ~12min time.

I put ~5-6kg to arrive at that time.

My friend that uses similar machine, fills his up ~15kg (capacity), taking 20 minutes...

I believe 20 minute roast "bakes" the beans, not roasts....or am I wrong?

Thanks


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## DavecUK (Aug 6, 2013)

soundklinik said:


> I got a question for professional roasters that use commercial gas fired machines.
> 
> Size 5-15kg. Machine is equipped with a PID.
> 
> ...


Currently I am not using any gas fired machines and have only used machines in the 1kg electric or 25kg gas class. Would my comments be any use to you?

I would also be interested in

1. How long have you been roasting

2. What roaster you are using (capacity) and type, charge temperature, airflow strategy (if any)

3. What beans re you roasting and to what level (light, med dark), minutes past 1st, to second, into second?

This all adds some context to the question


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## ZachChipp (Apr 10, 2014)

General rules of thumb;

The sweet spot of a roaster is 70-80% of its max capacity (eg. 10kg roasters work best at 7-8kg).

There is also a lot of variables in roasting, work out your roasters charge temp, best air flow rate etc, a general roast shouldnt be much longer than 15-18mins. Your first crack should be at around 80% of the roast time (Obviously dependant of the level of roast you are after).


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## soundklinik (May 31, 2013)

DavecUK said:


> Currently I am not using any gas fired machines and have only used machines in the 1kg electric or 25kg gas class. Would my comments be any use to you?
> 
> I would also be interested in
> 
> ...


Of course it is useful I would like your feedback.

I don't believe that there is a (lot of) difference in quantity of beans being roasted. In gas fired roaster anyway. (Fluid bed is another story)

The beans are brought up to temperature to go through their chemical reaction inside of bean.

Time can't be too short or they will be green inside and burnt on outside and will smell like hay. (already happened to me at home, lol)

Too long roast, and the chemical process is too slow and may not even take place...Lively cracking will not happen etc...

Anyway this is my understanding.

1. Been roasting for 10 years or so, on home made roasting machines, gas fired, small quantities 500g max...

2. The roaster is a French made (forgot brand) out of business, I think ~10-15kg, not sure since there are no manuals or anything. The PID is set a bit too low I think...The French for most part drink very light cafe, so the roaster was set for that....I have hard time to bring the temp past 205C. I usually do about 6kg batch, in order to get ~12min time...until I dump them into the cooler

3. Roasting espresso blend, some Central American, couple of Kenyas and Colombia, about 8 types of beans.

Beans are not fantastic quality like what I get for myself @Bella Barista for example, they are nice commercial quality, could get better, but the owner doesn't let me pick something better...

I found this, (roasting was a 12kg batch...but it is an older article)...:

https://legacy.sweetmarias.com/library/content/using-sight-determine-degree-roast

Thanks both for reply.


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## DavecUK (Aug 6, 2013)

soundklinik said:


> Of course it is useful I would like your feedback.
> 
> (a) I don't believe that there is a (lot of) difference in quantity of beans being roasted. In gas fired roaster anyway. (Fluid bed is another story)
> 
> ...


(a) Batch size can make a lot of difference. I have used a 25kg gas fired 1960s Probat and if you tried to roast 10-15kg in it, it would go really fast. The Burners were either 1/3, 2/3 or 1/3+2/3 e.g. 100%. , most gas roasters in the 10-15kg class will go quite quick with half a charge. Different roasters have different strategies for airflow, some you can vary it others you need to leave it at one setting. Heat can be dumped by air, or increased by it. Drums are perforated or solid. The amount of heat by different methods also varies and has different effects on the beans.

(b) Yes of course, roasting very fast requires a lot of heat input, this means everything is hotter than it needs to be if it's a full charge, perhaps not so much on a reduced charge. There is a trend for super fast roasting, one I don't agree with at all.

© Yes too long a roast kills everything good in a bean...20 minutes for your type of roaster would be far too long. Of course roast times can be longer than the usual range (not 20m of course), if the charge temp is particularly low. As another poster has said no longer than 15-18m, but I would even go so far as to say 16m 30s should be your absolute max for that type of roaster, assuming normal charge temps.

If your roaster is indeed 10-15kg, a 6kg batch is pretty small and if your struggling to get a light roast inside of 12m, the thing may need some maintenance, or the airflows looked at. Also as you say, perhaps the PID is a bit low. is it a perforated drum, or solid drum, are there holes at the back or closed at the back. is it direct flame on drum or indirect via a heat shield, what's the airflow set like.

The other problem is crap beans, for the sake of a very small amount of money roasting real commodity stuff must be soul destroying and of course it's harder to get decent results. Is the owner a roaster, did he teach you to roast or were you self taught?

I've read the sweet Marias article before....roasting perhaps a little too fast for my tastes. You also mentioned a lively 1st crack, although it's good to hear it, if it's too lively and very short, it's a sure sign things have got a little too hot....with a big roaster it's then hard to reduce the heat energy being input to the beans, the roast races along towards second and kills all the good stuff.


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## soundklinik (May 31, 2013)

HI Dave, thanks a lot for your help.

Sorry for not replying a bit sooner....

I appreciate all your comments on the roasting procedure. So far I had no negative comments on my roasting, actually people like it a lot...I try to roast a bit pass the 1st crack, and stop before 2nd crack, depending on the origin of coffee. Acidic coffees get a little darker roast to get rid of the acidity. (roasting is a bit slower in the shop, than when I roast @ home)...

Meanwhile, since my first post I raised the temperature a bit on the PID and now I get a better roast...(I can always manually cut off the gas heat)...

Before, they were doing 12-15kg and temp set to cut off on 204C!!! Way too low IMO. I am on 215C now,.

I will try to post a photo of the setup next time I roast.

The roaster has a heavy solid drum, not perforated with direct flame under. Takes ~20 minutes to preheat it to 190C...

The owner knows absolutely nothing about coffee, I met him on a local coffee forum, after he did a crash course for barista with some clowns that charged him 900 Euros!!! for one week, got him a cheesy "Barista Diploma" and thought him how to tap the portafilter with the side of tamper, to break the puck...lol

I am self thought roaster, (cafe was my passion since 1980, I worked in Coffee connection in Boston)... started roasting 20 years ago on our boat, (for me and other people, in the Pacific good fresh beans were impossible to find), was using a Pop corn roaster and got pretty good at it, but this was the old time roasting to more dark beans as a rule. First wave? isn't it called something like that?

I have to get more precise with the roaster in the coffee shop, tune it in better ...

The problem that the Cafe shop has, is fresh roast does not get sold in the 2-3 weeks from Date of Roast. So I need to make smaller batches in order to have fresh coffee, whioch is not the best to do in a Big capacity machine...but I am slowly getting to know the machine...

Thanks for your time and avice Dave, appreciate it.


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## DavecUK (Aug 6, 2013)

soundklinik said:


> HI Dave, thanks a lot for your help.
> 
> Sorry for not replying a bit sooner....
> 
> ...


Sounds like it could have been set a bit cool, especially if that probe for temp is in the exit air pipe. 190 can be quite a high charge temp for a roaster like yours and you might want to experiment with bringing it down a little try 180 and possibly even less.

I like you always roast past 1st crack and either stop before second or just as second begins. I tend to use the time from 1st crack starting and the duration for many of my roasts (as well as tryer, smoke sound etc..), so a roast might be x min after 1st begins, but I don't ever drop a roast until at least 1st has finished. I do find lengthening the roast with dry processed stuff is hugely beneficial....as getting too much heat energy into it absolutely kills it. I guess my rule of thumb is only use as high a temperature as you absolutely need to get the coffee roasted in a specific time and sometimes it takes a little faith to resist turning up the heat (or reducing the airflow) and to just be patient

The real killer is having to muck about with small batches in a largish roaster....but one thing you don't mention is packing. I found it can give a massive improvement to ensure it's packed well and quickly after roasting. Some places pack into big bags, then days or weeks later break those down into smaller bags for sale. Some even put it into "air tight" tubs with 1 way valves and then pack it to order.....try to never do this.


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## soundklinik (May 31, 2013)

Hi Dave,

thanks again for your advice.

OK, I will load at ~170C. The probe is in the lower part of the door, front of machine that flips open, covered by beans.

I always use a timer, (because it's easy to get distracted by curious customers) and time up to 1st crack and than start again from 0 up and listen, look, smell from the scoop sampler etc...

Actually I have no idea about packing. What I do now, is after a roast, beans go into these barrels (made for that purpose) and are left slightly opened till next day. Then closed, not airtight though, just a lid.

I never used to do this, I simply closed them air tight, but everyone is talking about de-gassing, and on roaster forums I read to let them breathe 24 hours, and then close the box airtight.

So I really don't know. Anyway we let the beans rest for ~1 week, minimum 5 days.

We don't have any special one way vent containers etc...

The company we buy from is called Belco, in Bordeaux, France. There is also some from Bob-o-Link...

Anyway, thanks for help and advice.


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