Heat principles and airflow control – Giesen Webinar #2

This unique monthly Giesen webinar #2 hosted by Willem Boot cover topics like the perfect profile and how to achieve this. Together with live roasting sessions and exploring the features and functionalities of our coffee roasters and related equipment. What follows is the recording and a summary of the Giesen Webinar #2 of 26^th June 2020.

This webinar is recorded at the Boot Coffee Campus in California. Together with Marcus Young, the campus director at Boot coffee, Willem will help you unlock some of the misunderstandings and mysteries in roast profiling. Marcus and Willem together have half a century of coffee experience. They did a deep dive into roasting, quality management and cupping and continue to develop this.

What are we going to focus on in this Giesen webinar #2:

• Heat transfer and principles
• Airflow settings and how this affects the roast
• Live roast with Marcus Young on a W6A
• A cupping session
• Q&A with Willem Boot

Heat Transfer

In this webinar we are looking specifically at ribbon burners. This burner has individual segments which produces exactly the same amount of heat output as the other sections. It ensures a precise and controlled heat transfer which is very powerful for adjustments in gas pressures.

What type of heat transfer are you trying to produce?

Conduction

Conductive heat transfer is the process by which the kinetic energy of the burner is conveyed to another material (coffee beans) through direct contact of the object. In coffee roasting: Hot surface of the drum or by bean to bean heating.

Convection

Convection is the process by which heat energy is transferred by a fluid medium. In coffee roasting the medium is pre-heated hot air which is drawn by the roasting fan over the roaster’s burner and then through the drum and over the beans.

Airflow and burner power are related to the speed of your roast (rate of rise). In many machines a high flame with high airflow = a faster rate of rise due to the increase in convective heat transfer. High airflow with a low burner setting will result in a slower roast.

Radiant heat

Radiant heat is caused due to the cast iron materials. Moving a roaster around is hard because of their weight. The quality materials that are being used while manufacturing the roaster cause the weight but also a very high consistency during roasting. Just try lifting a front plate of a W15A and you will see it is really hard to do. The cast iron components contribute to radiant heat. Cast iron has the amazing ability to penetrate the bean with its heat.

Ideally as a roaster manufacturer you’d want to be able to give users the option to let the user control these different heat principles. Giesen has been very successful in that way. We can actually let the coffee roaster behave like a fully conductive heat roaster but due to the fan speed, users can roast with convection heat. A lot of different settings and heat transfer techniques can be modulated with Giesen roasters.

Airflow Settings

While roasting you control the Giesen roaster with the control panel, but you also have the possibility to control the roaster with Giesen Profiler. By increasing the Pa setting, the machine will increase the rotation speed of the roasting fan to maintain a higher pressure target.

Want to know more about Giesen Profiler?
Tune in for our next webinar on 31st of July at 09:00 PT | 18:00 CET
Or watch this video on how to roast with Giesen Profiler

The graph lines explained:

• Red line = Setpoint air in Fahrenheit
• Blue line = Air temperature in Fahrenheit
• Pink line = Bean temperature in Fahrenheit
• Yellow line = Rate of Rise
• Purple line = Pressure in Pa
• Orange line = Speed in Hertz
• Yellow line = Beans Infrared Sensor
• Green line = Power in percentage

Low airflow profile:

• 100 Pa setting

High airflow profile:

• 160 Pa setting
• Longer heat soak before the burners were turned on
• Delta is changed due to the airflow. More airflow means more convection heat. (The difference between the air temperature and the bean temperature is what we call ‘delta’.)

Variable airflow profile

• Start at 100 Pa for 7 minutes, then change it to 160 Pa until the end
• After the change the delta between air and bean also changes 

At 280°F the malliard reactions start happening. At around 310/320 °F the beans will caramelize. With the airflow pressure profiling you have the ability to control when you start to induce certain chemical changes.

Live roast with:

Guatamala Finca El Oregano. A natural processed caturra with a clean and fruity notes. It has not been measured but you can estimate a bean’s density by looking at it. Check the surface of the beans and if the center cuts are tight or closed. This is lets you know the coffee can handle a lot of heat. But it is also a natural coffee which means you need to be careful with the heat. Try to reduce the heat around the 7-minute mark for the best results.

Goal for the roast:

• Variable airflow and how that can be used to induce a faster roast with a higher RoR

 Before the roast

• Loaded a low airflow profile as a reference

The roast

• 00:00 Charge temperature 383 °F
• 00:00 Start with 100 Pa
• Increase the setpoint to have little bit more power
• 00:45 Turn burner on ‘auto’
• 01:01 Turning point with bean temperature of 159 °F
• Right after the TP you can already see the changes on the delta and on the RoR due to the power and the change in setpoint
• 06:40 Beans are at 325 °F and then the airflow is increased to 160 Pa
• 09:06 FC at 383°F (on the lower airflow profile the FC was at 10:48
• 11:05 Development time: 18% for 1:57 minutes
• 11:05 Bean temp 408 °F

Cupping session with Willem and Marcus

Roast A Low Airflow 100Pa	Roast B High airflow 160 Pa	Roast C Variable airflow
Chocolate Leather Dried berry/fig Thick mouthfeel	Fresh fruit More acidity than A Citric acid More dynamic than A Thin mouthfeel	More levels More body notes Less refreshing than B More dept and richness Citric notes produced by dried fruit

Q&A from Giesen Webinar #2

For general sales questions fill in the contact form at the bottom of the page

What does 18% percent mean?

This is the development time expressed in percentage. The time from the first crack until the end of the roast.

How does the RPM/Hertz affect the roast?

This is a subject for the webinar on 29^th of august

Do you have a preferred airflow setting for variety/process coffees?

Yes, I found that these coffees have very distinct floral notes. You want to treat those coffees with sufficient airflow. This seems to be a good principle to allow a slightly higher airflow setting later in the roast. Of course, there is not an absolute rule for this.

How about the flick and crash in the RoR at 10:40?

That flick is at the end of the roast and it happened when the drum door was opened. At this point the beans are pushing against the probe which then registers more heat (caused by more beans mass). It can also be caused by some brief “noise” in the data.

How can I get the same results but without the software?

By controlling the roast with the control panel and keep track of the roast another way. Giesen Profiler is not needed but it saves you a lot of time and keeps your roasts consistent.

Monthly Giesen Webinar:

Join us live on every last Friday of the month at 09:00 Pacific Time (PT)
Or 18:00 Central European Time (CET).