Many people roast just fine with out a bean mass probe but after adding one to my Hottop a couple of years ago I really don't want to do with out one. Here is a link to a bean chart for color and smell and the bean temps that go with it (sorry it is all in F) http://www.sweetmarias.com/roasting-VisualGuideV2.php
Air flow should be going past the burners to heat it so I don't think there should be a huge drop in temp but I will know better in a couple of weeks. After hundreds of roasts I understand so much more about the roasting process but applying it to a commercial roaster is still just theory. The 3 phases of roasting apply to any type of roaster though... Drying phase, yellowing to 1st crack, 1st crack to finish.
Dave7779 Senior Member Joined: 12 May 2009 Posts: 20 Location: UK Expertise: Just starting
Roaster: Diedrich IR-2.5
Posted Wed Sep 15, 2010, 7:16am Subject: Re: Air in the coffee roasting process
Very nice roaster indeed, are you sure it only has 2 airflow setting as from what i read last night it states it has 5. Click Here (www.diedrichroasters.com)
Again the vent is changed from closed to open at the last 40-50 secs of the roast. Now airflow wise it looks like it is needed from 1st crack but is it needed at any other point during the roast process for example the drying phase.
Thanks for the link to sweetmarias, it is a very usefull guide.
germantownrob Senior Member Joined: 2 Dec 2007 Posts: 2,041 Location: Philadelphia Expertise: I love coffee
Espresso: Duetto 3, A Dead Oscar Grinder: Vario-W, Preciso w/Esatto,... Drip: Brazen Roaster: Diedrich IR-1, HT B
Posted Wed Sep 15, 2010, 7:31am Subject: Re: Air in the coffee roasting process
Hmmm, Off, full for bean cooling, 50% in drum, 100% in drum but the 5th stumps me, maybe 50% drum and 50% bean tray.
My experience with drying phase depends on beans and what the roast is for. If roasting for espresso I find no need to add airflow (what little I had with the Hottop) since I am looking for close to 5 minutes from start of first crack to finish. Same bean for drip I will add some fan when beans start to pale to help get rid of moisture and I do a 3 minute from first crack to finish. Low grown beans and water processed beans I will use the fan much more in the drying phase and go with lower heat here to help get center of beans to heat.
oldgearhead Senior Member Joined: 25 Jan 2010 Posts: 355 Location: Go Colts! Expertise: I like coffee
Grinder: Virtuoso by Baratza Drip: Chemex,Dilongi DCM900 Roaster: 1/2K Fluid-bed
Posted Wed Sep 15, 2010, 7:32am Subject: Re: Air in the coffee roasting process
I don't know how helpful this is, but the Hottop profile shows fan: __ 0% until near the end of the drying phase __Increase to 100% until 1.5 minutes before first crack __Decrease to 50% until one minute before second crack __Increase to 75% to finish
With my two-speed fan, I leave it at 75% until BMT = 380DF, then go to 100% until finish in the 410-435DF range...If I wanted to roast without a bean mass temperature probe, I wouild have purchased a Gene'..
Dave7779 Senior Member Joined: 12 May 2009 Posts: 20 Location: UK Expertise: Just starting
Roaster: Diedrich IR-2.5
Posted Wed Sep 15, 2010, 7:50am Subject: Re: Air in the coffee roasting process
i have used the old version of the roaster you are getting and the setting on the lever was either either off (airflow going to cooling tray) or on(airflow going to roasting drum). so maybe it will look something like this.
1/Off (cooling tray on) 2/25% 3/50% 4/75% 5/100%
I think if someone could explain why the air was added at certain points that it would really clear up the confusion.
Regarding what to look for in a roaster, the September/October issue of Roast has an article by Willem Boot. The web page does require subscription. Guess he and I had similar thoughts; it was the reason I got the Mini 500.
Dave7779 Senior Member Joined: 12 May 2009 Posts: 20 Location: UK Expertise: Just starting
Roaster: Diedrich IR-2.5
Posted Thu Sep 16, 2010, 9:22am Subject: Re: Air in the coffee roasting process
In amendment to my my post where i said the guy roasting on the toper opened his air vent, i checked my roaster and now know he actually turned the burners off and shut the vent....
So with him doing that and the guy from buddy saying open the air im just as lost as i was.
So ive watched the buddy coffee video again from start to finish and he has the vent open at the start for the drying phase then shuts the vent off at yellow, then opens it again to full at first crack. As soon as i get chance ill try this out and see how it works. Let me know if any of you folks have anymore luck with this.
Chang94598 Senior Member Joined: 24 Oct 2007 Posts: 209 Location: SF Bay Area
Posted Fri Sep 17, 2010, 12:07am Subject: Re: Air in the coffee roasting process
I'll throw in my 2 cents.
The vent is open at finishing of drying. At this stage, the bean volume decreases due to evaporation of water from the extracellular matrix. The chaff is loose, therefore opening the vent increases the negative pressure to separate the chaff from the bean. It is important to do this at this stage. Although the chaff does not generally contribute to defective flavor, when it is not charred, if the majority of chaff is not separated at this stage, it will be roasted and charred when the beans enter first crack. The excessive smoke particles then adhere the beans, causing bitterness.
I generally open the vent fully at around 150-160C for one minute, then close. The gas is increased. This equilibrates the bean moisture and temperature, and when the vent is closed, rapid rise in temperature occurs to properly "roast".
The vent is open slightly again at onset of first crack, to evacuate smoke. Excessive smoke particles contribute to defective flavor. There is actually a vial in the Le Nez du Cafe for "smoke", and one of the exercises in the Coffee Cuppers Handbook is to identify this defect.
Another approach to the vent is by opening the vent fully, and use the gas as sole control of heat. The gas is turned off at a set temperature, often before onset of first crack, and the roast is allowed to coast to desired duration after onset of first crack to second crack. This type of roasting style is more suitable for dark roast of dense beans, and not suitable for softer beans like Brazil, Kona, or dry processed Ethiopian. The reason for dark roast for this style of roasting is, again, to avoid excessive smoke defect with dark roast. Additionally, this is more easily done with cast iron drum. The set temperature obviously will vary with each roaster, and I suspect can be different even with the same model roaster from the same manufacturer, and exhaust vent length.
Dave7779 Senior Member Joined: 12 May 2009 Posts: 20 Location: UK Expertise: Just starting
Roaster: Diedrich IR-2.5
Posted Fri Sep 17, 2010, 8:34am Subject: Re: Air in the coffee roasting process
Ok so i messed about with air flow today and found that the coffee looked ok and Flavour wise tasted nice, but after taking a few mouth fulls my mouth and throat started to really dry out. I have had this issue for some time but today was one of the worst times, does anyone know what it is that causes this?
Smokey_Joe_from_UK Senior Member Joined: 27 Dec 2011 Posts: 6 Location: Norwich, England Expertise: Professional
Posted Tue Dec 27, 2011, 10:54am Subject: Re: Air in the coffee roasting process
Hey All, my first post here!
I've just got my Toper 3Kg set up and I've had about 5 trial runs at full capacity. I'm having trouble controlling the roast profile. The roasters I have used before have always had flame control i.e. low, med, high where as the toper only seems to have on/off.
This means I need to start seriously understanding the use of airflow control. From what my roasting instructor told me, there should be minimal airflow for the first 5 mins. This is because the moisture realised from the beans is then contained within the drum and protects the surface of the bean through the drying cycle. After 5 mins the airflow should be opened, but that's as much as I can remember him saying on air flow.
My issue is, in my first trial run on the toper I opened the airflow to 50% @ 5mins. With the burner still on the temp within the drum sky rocketed and basically toasted the beans (they are brown but smell like burnt toast). After looking through the notes from my instructor - he did say that the burner needs to be turned down when increasing the air flow. As the toper only has an on/off flame - that means I would have to turn the burner off and open the airflow, but then wouldn't that cause the bean temp to plummet?
I'm gonna have a good play around tomorrow but wondered what you guys thought?
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