Mastering the Art of Coffee Roasting: Rate of Rise
Behind every exceptional cup of coffee lies a meticulous process of roasting. Paying attention to details during the roasting process is paramount. One crucial parameter to control and achieve optimal results is the Rate of Rise (RoR). In this article, we will explore the concept of RoR, its significance in coffee roasting, how to calculate it, and its relevance at different stages of the process.
Behind every exceptional cup of coffee lies a meticulous process of roasting. Paying attention to details during the roasting process is paramount. One crucial parameter to control and achieve optimal results is the Rate of Rise (RoR). In this article, we will explore the concept of RoR, its significance in coffee roasting, how to calculate it, and its relevance at different stages of the process. Understanding and harnessing the power of RoR can elevate your coffee roasting skills and help you consistently create exquisite flavors.
ROEST sample roaster and the web portal, where you can monitor the live roast and RoR.
Understanding the Rate of Rise
Rate of Rise (RoR) measures the speed at which the temperature of the coffee bean rises during the roasting process. It is a crucial metric that indicates the rate at which the beans absorb heat from the roasting machine. It is essential to distinguish RoR from the actual temperature of the bean. While the temperature measures the current state of the bean, RoR measures how quickly that temperature changes.
Roasters gain valuable insights into the roasting process by analyzing the RoR data plotted on a roast graph. Roast curves visually represent the temperature changes over time. RoR provides a dynamic view of the bean's temperature increase, enabling roasters to make timely adjustments and achieve consistent roast profiles. It empowers them to maintain control, anticipate changes, and avoid potential mistakes that could impact the flavor and quality of the final cup of coffee.
Calculating the Rate of Rise
Modern roasting technology, accompanied by specialized software, simplifies collecting RoR data. These software tools enable roasters to capture temperature data at different intervals, such as 1, 5, 10, 15, 20, 30, or 60 seconds. The choice of the time interval depends on various factors, including the specific roasting machine and the desired level of precision.
Different graphs from the ROEST sample roaster showing how the RoR looks in various time settings.
When selecting the appropriate time interval, it is crucial to consider the trade-off between precision and noise. A shorter interval provides greater accuracy but can introduce more noise into the data due to system interference and sensor fluctuation. This noise may lead to a graph with numerous spikes, making it challenging to analyze. On the other hand, a longer time interval produces a smoother curve with fewer spikes but at the expense of finer details.
For people using roasters with high idle noise or system interference, it is advisable to opt for a higher time interval, such as 60 seconds, when calculating RoR. This choice results in a smoother roast curve that is easier to interpret. However, shorter time intervals can be chosen for more precise analysis for those using advanced roasting technology with minimal noise.
If you are starting in coffee roasting and cannot access specialized software, you can still calculate RoR manually. The process involves measuring the temperature at regular intervals, such as every 30 seconds or every minute, and calculating the temperature difference between consecutive readings. This simple approach lets you gain insights into the RoR during roasting.
Ideal Rate of Rise Guidelines
While no ideal RoR suits all scenarios, there are specific guidelines to consider when controlling RoR to achieve consistent and balanced roast profiles. These guidelines consider various factors, including the coffee bean type, roasting profile, stage, and altitude.
A pronounced drop in RoR, also known as a "crash," especially around the beginning of the First Crack, can lead to undesirable outcomes. When the RoR drops significantly, the coffee may transition from roasting to baking, resulting in a flat, bland flavor profile with minimal sweetness and a cardboard-like taste. This phenomenon is commonly referred to as "baked coffee." To prevent this, it's important to have a steadily decreasing Rate of Rise (RoR) during the roasting process and ensure that the temperature increases gradually.
Graph showing the “crash” in the RoR on the ROEST sample roaster.
Conversely, a low and steady RoR maintained over an extended period can benefit denser coffee beans. It allows them to break down and develop their flavors to their fullest potential. This controlled approach ensures that the heat penetrates the beans evenly, producing a balanced and vibrant cup of coffee.
“A good roast is achieved when there is a continually decreasing RoR.”
On the other hand, a rapid RoR, especially in the final phase of roasting, can have detrimental effects. When the RoR moves too fast, the coffee beans take on the heat too quickly, losing complexity and an unpleasant burnt taste. This outcome is commonly known as "scorched coffee." To prevent this, monitoring the RoR closely and adjusting to maintain a steady and controlled rise in temperature is crucial.
Significant Stages of RoR
Throughout the roasting process, there are three critical moments where the Rate of Rise requires particular attention:
Maximum RoR: This occurs after the "turning point," which marks the transition from negative RoR to positive RoR. The turning point is the moment when the bean temperature stops dropping. After this point, the RoR experiences its highest rate of temperature increase. Monitoring the Maximum RoR allows roasters to gauge the intensity of the roast and make necessary adjustments.
First Crack RoR: The First Crack is a significant stage in coffee roasting when the beans release moisture and emit cracking sounds. The RoR may drop during this phase due to the water vapor released from the beans. Monitoring the RoR during the First Crack helps understand the moisture release and its impact on the roast.
End RoR: Towards the end of the roasting process, the beans become drier and more fragile. The RoR at this stage requires careful observation to prevent over-roasting or unevenness. The End RoR signifies the delicate point where the beans are susceptible to breakage, and fine adjustments can make a substantial difference in the final cup quality.
Understanding and harnessing the power of the Rate of Rise (RoR) is a crucial aspect of mastering the art of coffee roasting. By accurately controlling and interpreting RoR data, roasters can consistently achieve exceptional roast profiles, avoid undesirable outcomes, and continually refine their skills to create the perfect cup of coffee.
Enjoyed reading this? Check out our article on why you need a sample roaster for your coffee business.
Introducing a new feature: Inlet Temperature Sensor
After interesting discussions with Scott Rao and Luca Costanzo, we revisited the idea of implementing an Inlet temperature sensor based on the new inlet temperature sensors we have developed for p2000. The inlet temperature sensor is a prominent feature in the roasting community and several roasters worldwide use it. It is a great addition and improvement to the way you operate the ROEST.
We have learned that power profile is a favorite option of our customers, but it comes with some challenges. Changing room temperature and voltage fluctuation can impact the roasting and the final cup, making it harder to get consistent results and to share power profiles. We first tried to persuade our customers to rather use air temperature profiles, but they had some strong arguments so we decided to develop a better alternative.
After interesting discussions with Scott Rao and Luca Costanzo, we revisited the idea of implementing an Inlet temperature sensor based on the new inlet temperature sensors we have developed for P2000. The inlet temperature sensor is a prominent feature in the roasting community and several roasters worldwide use it. It is a great addition and improvement to the way you operate the ROEST.
Inlet profiles to improve power profiles
An inlet temperature sensor monitors the temperature that comes from the heating element and goes into the roasting chamber. It can give significant improvements to the roasting compared to power profiles due to higher precision.
This type of sensor is therefore a good improvement, or in addition, for those who mainly use power profiles when roasting on a ROEST sample roaster. If you use a power profile regularly, you might have experienced variations in voltage that have given different watts and thus different power between your roasting session. By using an inlet temperature sensor you will see that the temperature that goes into the roaster is more stable.
Luca Costanzo explained: “The inlet temperature sensor offers superior control to power profiles because the PID compensates for the different ambient temperatures, whereas the power profiles will only add a certain amount of power to the room temperature air. For example, if you make a power profile on a hot day, and roast exposed to the outside air at night, the power profile may need to be increased to complete the roast properly. An inlet temperature profile will not be affected by changes in room temperature.”
Higher precision, less variations
By using an inlet temperature sensor while roasting, you will notice that you’ll get a roast with fewer variations. This is because the roaster knows precisely the temperature that goes into the roasting chamber, and the sensor tells you how the coffee and other temperature sensors inside the drum react to the given profile.
To get the best, and most accurate results, we recommend using an inlet profile together with between batch protocol profile. Between Batch Protocol profiles (BBP) is to enhance consistency between batches and automate the process to make it easier. This feature will be available as an OTA update in December 2022.
You can manage the ROEST sample roaster with higher precision, which gives you a more stable and better result in the cup at the end. As every coffee behaves differently, an inlet sensor doesn’t get affected by this, in the way that air temperature profiles will.
“The inlet is the best location for such a sensor because it is before the roasting chamber, so the readings are entirely independent of the coffee in the roasting chamber. To give an example of why this matters, if you use an air temperature profile to roast a bean that is particularly prone to "crash" (eg. washed Kenyan) and switch to one that is particularly prone to flick (eg. anaerobic naturals), you don't know the extent to which the air temperature profile that you settled on for the Kenyan coffee reflected the tendency of that coffee to crash, which makes it harder to know to what extent you need to adapt it for the flicky coffee. This is because the air temperature probe is located on the other side of the roasting coffee from the hot air inlet.” - Luca Costanzo
Roast up to 200 grams of coffee
Since the inlet temperature sensor doesn’t get affected by the amount of coffee beans in the drum, we have tested it with a 200 grams batch, with very good and stable results. This is an increase of 100 grams from what we recommend with other profiles. This means that with an inlet temperature sensor you can roast bigger batches of coffee, without compromising the quality of the result.
An Inlet Temperature profile with 200 grams coffee. As you can see, the RoR is more stable with 200g batches.
What about air temperature profiles?
The advantage of air temperature profiles is that it takes into account the heat in the system so between batch protocols are not so important. This is therefore still our recommended profile for fast and efficient sample roasting up to 120grams.
Retrofit your sample roaster
If you already have a ROEST S100 Plus or L100 Plus and power profiles are your preferred way of roasting it will be possible to order a retrofit kit so you can install it yourself. Together with the inlet temperature sensor, we will provide you with all the information you need, and a guide on how to install it, and our support team is always here to help you!
To find out more about the retrofit kit and how to get it, read more here.
Enjoyed this? Then check out our article; Roasting coffee for research.
Interview with Katja Klein - Founder of Kontext Coffee Company
This week we had a chat with our fellow ROEST friend, Katja Klein, the founder and head roaster of Kontext Coffee Company.
This week we had a chat with our fellow ROEST friend, Katja Klein, the founder and head roaster of Kontext Coffee Company.
Katja told us how she got into roasting, what good coffee means to her and why she decided to purchase a ROEST.
So get yourself a cup of coffee, and enjoy!
Katja Klein and her sample roaster - ready for a day full of experimenting with different coffees!
For the people who don’t know, could you give us a short introduction to who you are and what you do?
My name is Katja Klein and I am the founder and head roaster of Kontext Coffee Company based in Monmouth, UK. We have been sourcing and roasting fully traceable and sustainably traded specialty coffee since 2019. We roast on a 12kg Probat P12 and brought the ROEST on board in April 2021.
What brought you into the coffee industry?
I started out in the coffee industry as a barista as so many do. I think I have always had this romantic notion of opening my own cafe one day and so during a gap year in Canada I felt like I ought to try working in a cafe first. I loved it even more than I thought I would and so I started taking classes to learn more about coffee - first an SCA barista class, then a coffee sommelier class and then I started working my way through the ranks, loving every step of the way.
I learned roasting as a production roaster for Right Side Coffee in Barcelona where I worked for 2 years. I couldn't have asked for a better teacher than Jaoquin, the founder of Right Side. Great people, great coffee, best place to learn and I would have stayed but sometimes life just takes you to new places and for me that ended up being Monmouth in the UK.
Cupping session at Kontext Coffee. Mmm, we can smell it from here!
What have been the most notable moments that have shaped your career?
That's a tough question. I can definitely still remember my first sip of specialty coffee - a natural coffee from Yirgacheffe which absolutely blew my mind. I had already signed up for my barista class by that time and couldn't wait to dig into the topic after that.
And while the sensory aspects of coffee and the more playful fascination of brewing it a million different ways roped me in further, I would have to say slowly discovering the complexities of the coffee value chain is what gave me a deeper sense of meaning working in this industry.
Finding out that something so mundane and at the same time so revered as a cup of coffee can be just taken for granted in the part of the world that can afford to enjoy it, is also responsible for providing a living for so many people in the global South has impacted my career in coffee greatly.
The challenges and injustices coffee farmers face and what I, as a coffee professional, can do about that is really at the core of what drives me in this business. That is ultimately why I decided to start my own roasting business: to be in a more empowered position to shape my own value chain and to have more of a say in how the value is distributed across this chain by choosing the right partners to work with. I try to let my values guide me in all of my business and life decisions.
And just to bring this back to why I like working with my ROEST sample roaster in this context: ROEST is not only a supreme piece of technology, it is both developed and manufactured in Norway with sustainability in mind and specifically not in another part of the world where regulatory standards around labour are lower and labour is therefore cheaper. That has definitely influenced my buying decision.
What does good coffee mean to you?
Good coffee means delicious coffee that is providing a decent living for every single link in the value chain that brought it to my cup - from the farmer all the way to the barista.
Katja is a proud owner of ROEST S100, which has allowed her to easily experiment with profiles to bring out the best flavors!
Why did you decide TO purchasE a ROEST for your roastery?
The main reason why I decided to buy the ROEST is because I wanted to be able to experiment with different roast profiles and learn more about how different approaches to roasting impact the flavour of the coffee. It turns out it is also extremely convenient for sample roasting. :)
Katja’s go-to profile is the Standard air temperature profile by ROEST, which helps reveal flavors and characteristics of most of her coffees.
In what ways has the sample roaster helped you so far?
It has made my life a lot easier because you can just run it alongside other activities during a production day without having to pay much attention really. And yet it produces roasts that are impeccable! More traditional sample roasters can be a bit smokey and roasty, and in my experience you have to be a good cupper with a good imagination to be able to assess the full potential of a coffee from those types of sample roasters. The ROEST is much more precise and to the point. It is also quite complex and gives you a lot of different options. In terms of using it as a learning tool I feel like I have barely scratched the surface of what it has to offer!
And finally, what advice would you give new roasters who are just starting out their careers in coffee?
Keep an open mind and be brave enough to ask all the questions that are on your mind! In our industry, it can often seem like everyone around you already has all the answers but if you look closer that isn't actually the case. There are many strong opinions about all things coffee out there but often they are just that - opinions. In my experience it is worth it to dig a little deeper and dare to question the way things are done in every aspect of our industry. The second piece of advice I have for anyone working in coffee is: keep working on your palate and learn to trust your own taste buds :)
Thank you so much, Katja. You keep on inspiring us!
Don’t forget to check out Katja’s Specialty Coffee Roastery, Kontext Coffee Company.
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Did you know that Tim Wendelboe is a fellow ROEST friend as well? Check out his 5 roasting tips here.