Why Rate of Rise is a bad reference point for optimizing flavour in coffee roasting

why rate of Rise is a bad reference point for optimizing flavor in coffee roasting this text is simultaneously a podcast episode and a blog post on our website and I'll refer to it as the article and you can find the links in the show notes and also find the links in context in the blog post so you can be referred to all the things outside this particular text that supports the claims in the text and you will also find some illustrations in the blog post that deepens your understanding of everything that is discussed so if you listen to this as a podcast please also visit the blog post um and if rate of Rise as a concept is unfamiliar to you I would recommend you to read another blog post on our website called roast profile analysis I am aware that this subject is a bit controversial as it seems that many educators are operating as if this is best practice for education and product development as a consultant and trainer I'm constantly confronted with the concept of rate of Rise as a superior reference point for improving Rose profiles with my scientific background and strong commitment to only use Concepts that are explicitly helpful for coffee roasters to create successful products for con for customers I have to speak up about the misleading nature of how rate of Rise is often obsessed by by students all over the world it is the single most discussed concept that I have to handle during all of my courses and dismantle in my students Minds before we can get to the useful Concepts that actually makes a difference in their lives and are actionable from a business strategic perspective let alone a flavor perspective the last five years I have experienced this all over the world from U.S to Europe the Gulf region Asia Australia just to mention a few so the content of this blog post is the result of of discussions with hundreds and hundreds of students and clients so I think it is relevant and useful to make a separate blog post about it even though this subject was also dealt with from many different angles in our podcast series about coffee science if you have not heard the science Series in the podcast yet please find it now and you can also go to our website under education and podcast to find all our podcast episode it will show you how our thoughts are not just our opinion but deeply embedded in the scientific Traditions all the way back to Plato and through the centuries of refinement and Improvement of scientific thinking where the science podcast series was structured from the point of view of science this article or this text is a good example of how science can be used to use practically on a single technical subject that has caused a lot of confusion this article is a condensation of the approach I have when the subject of rate of Rise is discussed during courses and consultancy sessions to save time and get this subject over with before these types of sessions we will systematically refer students and clients to this article and podcast before the event before education and consultancy just to save time of course the following points make sense only in the light of the overall approach we have in coffee mine to roasting education I do acknowledge that all my colleagues are colleagues out there have different experiences and different approaches and that some of our Concepts only make sense in our context of teaching also of course I am aware that I'm not right all the time but the identity of coffee mind is to be the ones asking the questions wait a minute does this make sense at all and sometimes it seems that that the general Global education community and the universities as well are more eager to add more opinions more approaches and complicated Concepts than to weed out all of the old nonsense that has piled up in the global coffee or roasting community over the years so here you have it the following article is a critical approach to the concepts of using rate of rice as a quality indicator in coffee roasting given coffee mine's particular approach to teach coffee roasting which has been developed since 2005 through teaching more than 1600 individuals in small groups of six to eight here in Copenhagen and London and London School of coffee and also conducting more than 30 research projects at the University of Copenhagen and University of Southern Denmark of which 12 are now scientifically published and also we've been Consulting more than 30 small and big coffee roasting businesses around the world since 2007. that does not make us right in everything we say I'm just mentioning our experience uh and the background we have and the reason uh we are so deeply embedded and passionate about the scientific implication for coffee roasting education so in the following please think less about who is right or who is wrong but which Concepts make sense in themselves and why in the light of the purpose behind using the concepts in the first place hopefully this article ended the derived discussions will bring us all forward including coffee mind and the blind spot that we have that we still haven't realized where the who in the question uh is a waste of everybody's time as the beginning it seems suitable to start with a question where is the concept of rate of rice useful in coffee roasting well the rate of Rise can be used for predicting where the roast is heading just like the speedometer in your car as it represents the fundamental speed of the process at any given moment you can use it in your car to estimate if you'll be early late or on time for the meeting that you're heading for similarly you can use the rate of rise to see if you'll hit a waypoint that you are aiming for for during roasting um and it could be for example first crack or if you are roasting faster or slower than initially planned and therefore deviate from your plan you can also use it to flavor categorize your different Rose profiles into your portfolio even though you already have the information just specifying the development time and color of a roast which would be the most aligned with Occam's racer I think it could make sense to quantify the average rate of Rise after first crack and use the number to categorize your different profiles this number is highly machine dependent so you can only use it to compare your rows on your machine this way of categorizing your different roast is aligned with our research which has shown that a shorter development time which has a higher rate of Rise if you keep the color the same it will give you a more fruity and acidic flavor and a longer development time will have a lower rate of Rise as you if you keep the color the same gives you less fruity and less acidic and more chocolatey nutty flavors relative to the short development time this was demonstrated in our scientific paper on the subject which is available for free on the journal website with the catchphrates title the effect of bros development time modulations on the sensory profile and chemical compositions of the Coffee brew as measures by NMR and gcms so my point is not that the concept does not make sense in itself and indeed I consider it one of the most important and useful Concepts in mathematics see differential calculus but aligned with my model for a good theory it is dangerous and highly confusing not to restrict yourself to using the simplest possible concepts with the fewest assumptions aligned with Aristotle and Occam William of Arkham and it also needs to be explicitly relevant which is what I call form follows functions in the science podcast it needs to be explicitly relevant for what you are trying to do it is dangerous which with what with that I mean confusing and decision inhibiting and time wasting to use an over complicated and highly assumption burden Concepts such as Raiders of rice as default declining rate of Rise is a natural behavior in a roaster anyway even if you kept the flame setting constant throughout the roast the system would show a pretty stable declining rate of rise with very few fluctuations on the curve the reason being that the constant flame with a constant airflow would at some point reach a steady state ending in a pretty constant temperature of the air going into the roasting beans and since the temperature always goes from a hot substance to a colder substance with the speed of energy exchange proportional to the temperature difference between the two sub two substances so set plainly the hot air heats up the colder beans and as the air succeeds heating up the beans the temperature difference between the air the beans declines and hence the heating of the beans slows down which gives you a progressively slower roast leading to a constantly declining rate of rice with the flu few fluctuations only and since our data shows that small fluctuations leading to small differences between roasts can't be detected even by coffee professional coffee professionals it seems that the focus on the small fluctuations of the rate of Rise curve is below sensory threshold even for coffee professionals please see the sensory data presented in this passage of the YouTube webinar that where you can find the link in the blog post with the same title as this um podcast episode since this is not a science episode per se I'd like to start with some unfortunate practical consequences of using rate of Rise as a reference point to optimize rows profiles really what science says and it does does not matter if it does not have any practical implications for daily life and decision making as a coffee roaster the only reason we are so passionate about science is that if applied correctly it has deep liberating and purpose-filling implications for how you make decisions in the light of the purpose of your organization and therefore your life because your life quality depends on your success or not to make your organization a picture of your passion and dreams too many are struggling with making their organization aligned with their deepest dreams and struggling with Clumsy Concepts not aligning with the overall purpose of the organization with this is not helping uh you getting to one where you want so first I would like to point out some practical implications the first problem is I often see people improvising with the gas during roasting to keep it on track people who use rate of rice as a reference point for optimizing Rose profiles are often seen improvising with the gas setting during roasting to smoothen the rate of rice curve which is very unfortunate because it shows that they don't understand the fundamental thermodynamics of the machine in the first place if they did understand the thermodynamics of the machine they didn't have to improvise during roasting as they would just execute the plan that they developed during experimentation that provides deep knowledge on the thermodynamics of their own machine in coffee mine's way of teaching this is a step in itself you learn during the control step in our overall roadmap competency roadmap which you can see in the illustration as well in the blog post um and this is also what we teach you in the um e-learning Rose profile design Basics that you can get done for only 30 Euros here on our website so this is a separate exercise with the only purpose of understanding the thermodynamics of the machine that you can then use to create Rose profiles where you don't have to interfere or improvise during roasting and just leave the gas button alone until of course the plant changes improvising with the gas setting during roasting is not only a sign that you don't understand the thermodynamics of The Roaster it also has the unfortunate consequence of compensating too late for a bad decision made earlier during the roast if you realize that your roast deviates from your plan you should have made an adjustment at least a minute or two earlier to avoid it and compensating after the fact doesn't really help and will not give you the same result as if you did the reduction earlier this is why we in the coffee Mite roasting trading tell people never improvise but follow the iterative and circular process of plan execute learn plan execute learn until you get the result that you planned if you don't follow the bad plan to the better end you don't know the magnitude of error in the plan which is the basis and the specific material for your learning so that you can improve the next plan for the next roast until you have created a rock solid and simple plan for each of your profiles if you know the thermodynamics of the machine you always get the result you set out to do and if you don't the deviations are probably too small to taste if you keep the color the same in which case micromanaging the flame waste your time without giving you a different result if you overcompensate with the flame you might burn your beans and neither of these cases leads to a better result so either a worse result or the same result remember that small variation in rows profile typically cannot be detected by anybody not even skilled coffee professionals as long as the color of the coffee is the same it doesn't help you predict customer preferences because that's another practical problem that it doesn't help you predict customer preferences because it Advocates and assumes that there is one Optimum with lack of specific predictions of flavor you can't use it for product development another big problem is that the theory doesn't offer a clear intensity prediction in between the rose profile data and the consumer so even if it is a preferred um a flavor it's not clear why it's preferred from a flavor intensity perspective it's also difficult to compare and translate rose profiles between machines using rate of rise and from an educational consultancy point of view the rate of Rise is difficult difficult to compare between machines as you get very different shapes of rate of Rise curves due to probe type and placement where simple and fundamental concepts like time temperature and color are more easily transferable from machine to machine of course you still can transfer rows one to one from roaster to roaster but using more fundamental concepts such as time temperature and color you are very quickly close and final small tweaks can be made based on experimentation and sensory analysis and you can hit your goal so that was a few practical problems and the next section goes through some pure conceptual problems not even really scientific more mathematical or the essence of a theory really as a theory the claim of the superiority of a constantly declining rate of Rise is not well structured at the heart of a theory is the notion of cause and effect and in research design is called input parameters and output parameters so it's called different things um so it cause an effect is is one um that's easy to understand perhaps and in research design you will also call it just input and output and in in research sometimes it's also called the independent variable that's the input or the course and the dependent variable is called the output or the effect so when you build a theory thinking about this Simplicity is really King in a good theory it's very important that both the input parameters and the output parameters are resting on the simplest possible concept concepts with the fewest assumptions such as good old time temperature energy and color another problem with the rate of Rises that you don't need to see the curve or calculate it you actually only already have the data strict sticking with Simplicity it is striking that rate of Rise is not a deep separate piece of information in the Rose curve since it's just a quantification of the shape of the bean temperature curve that we already have just looking at the curve itself so why make such a fuss about it looking at the curves is also it's also striking that the big jumps we see on the rate of Rise curve is a magnification of the really small bumps on the bean temperature itself that we can already see in itself the bumps on the bean temperature curve does not look major no alarming but when making the calculations of of the rate of rice the noise of the signal of The Bean probe is Amplified uh combined with the noise created by the different complicated computer calculations involved with calculating the rate of Rise Live While roasting this limbs itself to overestimation of small fluctuations just because it is visually bigger on the rate of rice curve you don't taste the curve you taste the coffee and only if big impacts are applied to the coffee does it show up in the sensory properties of the coffee at all it's like putting a magnification glass on a small spider it does not make it more dangerous just because it looks bigger in the magnification glass so let's analyze each of the steps in the conceptual idea of the elements of a theory so let's start to look at the input variable in this Theory even though rate of Rise is a derived value of temperature and time there are too many unfounded assumptions about using it as a rock solid course or input or independent variable in a theory the temperature that a probe shows is a bit of an artifact already and it does not show the real temperature on the coffee anyway and for me it is a it is primarily a relative reading telling us how much energy we've added where the points like first crack and collar are the absolute indicators of how much energy has been added to the coffee at the different moments in the roasting so putting too much emphasis on the shape of the progression of a relative and artifact burdened reading such as the bean temperature is an extremely flimsy parameter to use as the course or the input in any Theory it is simply not a theory resting on Solid Ground from the get-go then let's look at the output variable in the theory since the theory of the superiority of constantly declining rate of Rise has no specifically defined flavor consequences defined from a sensory perspective it seems like also the output parameter of the theory is too vague to provide a good basis for a theory an example of a specific outcome prediction of a theory could be if it predicts if a rose becomes lesser more acidic or less or more bitter the underlying concepts for a good theory should be the simplest possible and most specific concepts with the fused assumptions otherwise it's difficult to be specific and therefore practical in the use of the theory as I also mentioned the podcast aligned with Carl Poppa's critical rationalism a theory does not a theory that does not predict something specifically in the first place can never be caught in being wrong because it never predicted anything specific anyway looking at the causal chain of events during a roast in a roaster the heat source is the first course of everything as coffee roasting is basically about applying heat so this parameter is number one the flame heats up the medium between the Heat source so that's kind of Link number two in the causal change and the beans are heated up as the third link in the chain the rate of Rise of the beans is derived is at the right value of the third link in the chain causality chains and coupled with all the artifacts of bean probes in general the probability that this value gives us deep insight and deep intuition about coffee roasting seems a bit far out to provide you with just a very very simple visual picture of a good theory just think about a simple linear function where a linear function is depicted in um in a coordinate system where you've got x and y axis and then you have a line that just goes through with as a certain steepness and the interesting thing with a function like that a linear function is there are not two points on the y-axis for a point on the x-axis there is specifically only one point on the y-axis for each point on the x-axis I'll this sound perhaps a bit uh abstract but think about it it's very important for a theory that it is specific in the exactly the sense that there's that one point on the excess x-axis translates to only one point in the y-axis another problem with the theory is looking at the type of of the variables that you're using in the linear um a model you have a yeah a linear and continuous relationship between X and Y only in extreme cases with extreme differences it is beneficial to use categorical variables such as done in the original scaa roasting defect curriculum which included the categories baked scorched faced tipping underdeveloped we did our first piece of research mapping out extreme differences and that was published in the article called with the title common roasting defects in coffee Aroma composition sensory characterization and consumer perceptions and since then I've started to avoid using those categories at all as they are too relative and not useful from a product development perspective where these clumsy Concepts can stall your thinking as the only relevant question is how would you like it to taste and which type of green coffee should you choose to make it taste like that and how should you roast it to achieve your flavor objective as long as you don't go extreme you don't need to worry about the extreme defects and you can focus on just experimentation and evaluation iteratively until you've achieved your flavor objective so I prefer the the leaner or continuous relationship if you extend this that happens rather than kind of just claiming that's now it's baked now it's something because it's we're dealing with small differences already so the probability that something changes category is very small for small differences next step is to look at this scientifically so where the conceptual approach to the theory is more mathematical the more practical scientific approach is a bit more diverse as there are several sciences and in our case we have to look at how sensory science deal with deals with theories Concepts and research design the first thing I'd like to discuss is something that I've called Peng bones racer the theory of the superiority of the constant declining rate of Rise violates the fundamental distinctions of sensory science which has been developed by Rosemary pengbone at UC Davis at least 50 years ago and I've called those distinctions from for pangborn's racer in the podcast to illustrate the usefulness of this distinctions as a way of Shaving away nonsense or unclear Concepts in Disguise of complexity just as Occam's razor it does in theory of science Pangborn advises a series of questions with corresponding experimental setups where you can clarify One Step at the time in a certain sequence so the first of the three steps is the related to the question is it worth investigating at all so that's Hank bones discriminative test so the intuition behind pangbon's racer is that before investigating too much attention in an elaborate theory of flavor differences the very first criteria for even spending time with the theory is to test if the claims of the theory makes any perceivable sensory differences at all so according to fundamental distinctions and sensory science you have to be very aware critical and skeptical about theories dealing with only small differences in the input parameters this first criteria is surprisingly often not really mentioned or taken serious at all and is dismissed to reference to personal experience and that hundreds of students and clients has been convinced from a scientific point of view this is a highly biased setup and I've been there myself many years ago I also convinced hundreds of students about my theories where I started doing but when I started doing sensory data at the University and you can read the blog post called your perfect Coffee Roastery I think and I think of coffee mine's approach to Coffee Roasting as a pre and post Pangborn phase after which I have a completely different perspective on what I expect to be a big difference and a small difference and an extreme skepticism for claims of the relevance of small differences and I transformed through the pain of publicly being wrong and this is where I um hired either to get to the next level of all this and this is eight years ago and we've had a lot of progress since then there's the everything else being equal principle scientifically it also violates the everything else being equal principle which is a fundamental setup of an experiment where you make sure that only that one and only one parameter changes between the different input samples in the setup to see how this one input parameter changes the output parameters this is the most often violated scientific principle in experiments done by non-scientists who are not aware of this fundamental principles on research of research design this happens for example when people are doing drum speed or airflow experiments without making sure that all samples end at the same color in which case the samples will end up with different colors later in the coming at the cupping table when I preferred a sample is found the superiority of the preferred cup is wrongly associated with either the drum speed or airflow or any other experiential Factor where really the preference is related to the color of the sample without them knowing it color is in this scenario a confounding Factor on the decisions on the copying table and since the person is not aware of this a wrong conclusion is made another problem with the theory of the superiority of a constant declining rate of Rise is that it cannot be tested as a theory where the everything else equal principle is applied because you cannot treat a sample with a constant declining rate of rise and compare it to a non-constant declining rate of Rise under the same color and same development time as they would end up with either different development time and or different color due to the constraints of the Dynamics of the curve in a live roast this is a consequence of the theory not being formulated probably in the first place with simple and practical or specific input and output parameters that rest on first principles of science and here you need to use the principles that are already well described in thermodynamics in chemistry and here temperature time and color is the first principles then another um problem that's later in penguin Peng bones uh three steps here um the distinction between the descriptive and effective step which is a step number two and three in Pang bones model so from a sensory science perspective a big problem about the theory about the superiority which is an effective claim of the constant declining rate of Rise that you assume as universal preference maximum without being specific you don't have the descriptive step about the intensity involved in making it a maximum and all and even if the intensity was mapped out the assumption that there is a universal preference across consumer segments is violating pangbang's racer this is exactly the same criticism that we have on the sca cupping form the Assumption of a universal agreed quality yardstick it's not helpful and it's wrong seen from pangborn's model then I'd like to talk a bit about variation of input and output in experimentation and that's because at the heart of science is the heart of the experiment and at the heart of the experiment is variation of one and only one input parameter to map map out how the variation of this input parameter varies the output parameter remember the conceptual sex section right causing an effect to follow the idea of a constant declining rate of y's rate of Rise is an advice that does not encourage you to do your own experiments with flavor modulation because it assumes one Optimum in coffee mine we want to empower people to do flavor experiments so we don't uh so we don't paint people into a preference caller Corner already during during education the question of optimizing flavors should be left to the specific business model of a specific product development process with a specific customer segment as a goal then from a scientific perspective as well only specific and big things matters it's worth noting that a good theory provides a linear relationship between input and output parameters such as more or less acidic or more or less bitter where category differences requires big differences an extension of this you might argue that I did that this myself when arguing that you could use the rate of rise to categorize your roast by specifying the average rate of rice after first crack but remember that I only do this because in the research we were looking at pretty extreme differences even in the development time research which was spanning from one and a half to six minute development time between samples and I only suggest to categorize the extremes where it seemed in our data that the century descriptors modulated pretty linear when going from one extreme to the other and the linear tendency we mapped out lends itself perfectly to product development and customer preference mapping completely aligned with pangbon's model for intensity mapping and subsequent customer segmentation not assuming that one flavor fits all getting a sense of what is a big and a small difference is where the reluctance to even think of the rate of Rise cause to be relevant comes in coffee mines General General flame framework in coffee mind we have noticed a general Trend in the coffee Community to drag student students down rabbit holes with very complicated unclear Concepts that simply drowns their minds to the extent that they missed the big picture and the and the purpose of it all this is why we in coffee mine have created a competency roadmap for startup roasteries with really simple and specific competition competency steps that are finite in scope and very practical in the application so that you could go to the next step after finishing a step this way it's very clear how each step fits into the next and aligns with the overall purpose of the organization our framework has the following steps First Step personal purpose of having a company in the first place business Vision should be derived from this personal purpose from the founder of the company after that step you've got the control step and which explores the thermodynamics of your machine where it is installed once you've done that you can go to the flavor experimentation step where you play around the step after that is the intensity mapping Where You Are um evaluating the intenses of the flavors of your experiments and then there's the quality control step after that you've got the consumer mapping step where you are exploring the preferences of the consumers that you've decided to include in your business model and then ongoingly the organized organization is reenranged through continuous Improvement all the way back to the passion and purpose of the founders of the company to keep the company filled with passion and purpose notice how we've applied the fundamentals of a good theory by isolating each step as an input out output system in itself the personal passion and talent is an output into the input of the business vision which is defined by the customers the organization is committed to serve the business model needs predictability which is why the control of the production equipment is the first competency step needed in the organization after the business vision this consistency output is the input to the experimentation step which can't be done properly without sufficient control of the machine so in the roasting equipment the input is the settings of the heat source and the output is the Rose curve in that particular step but we don't stop here of course my criticism with the rate arises that often it stops here right so we don't stop with the Curve because the curve is the output of the experimentation step which is the input into the evaluation step and the output of the evaluation step is the flavor intensities mapped out the input into the consumer step is the output of the experimentation step namely the flavor intensities and the output of the consumer step is the liking of the intensities in the different consumer segments all is connected but nicely separated for each step so it is manageable and success is achievable without missing the big picture which means not getting stuck in rabbit holes which seems to be the trend so you're not missing the big picture of the organization and your life quality as a coffee printer only by following a simple rigorous and practical education framework like this can we make sure that we educate Coffee Roasters to be able to align their methods and efforts with any business model they might find themselves embedded in in the future regardless if it's their own or if they are employed or even if they want to impress family and friends as home Roasters don't serve the same coffee to your hipster friends as your mother-in-law as people educated with our methods are not painted into a preference corner by the Educators who educate them in the first place this is completely aligned and in the spirit of pangborn's distinctions and therefore the gold standard of science for product development and where to spend your energy in the different in the different processes and questions in the company in coffee-mind experimentation and not unification coupled with expected diversity and preference is at the heart of coffee roasting education

Channel: CoffeeMind Academy

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Length: 42min 29sec (2549 seconds)

Published: Fri Jan 06 2023