19 Jan 2017

WOLFRAM SORG, BACKYARD COFFEE | TRANSLATING A ROAST PROFILE FROM SAMPLE TO PRODUCTION ROAST

We love to hear back from customers about how they use the IKAWA to help improve the quality of their coffee offering, from origin, to traders and roasters. This post delves into some of the theory that Wolfram Sorg from Backyard Coffee Roasters applies when designing his roast curves.

Wolfram is the owner of Backyard Coffee Roasters based in Frankfurt, Germany. There, he roasts speciality coffee on his orange Giesen and uses the IKAWA Sample Roaster for small batch roasting.

He’s a former German Barista Champion, an SCAE Authorised Trainer, and it’s fair to say he applies a scientific approach to getting the best from his coffee. He’s been kind enough to share some of his research and principles to address a question we get asked a lot: “Can you translate a sample roast profile to your production roast?”

Wolfram Sorg and at Backyard Coffee roastery

In short, no, you can’t transfer a profile from small to big scale. But don’t worry, you don’t have to.

Read on…

OVER TO WOLFRAM

“The IKAWA Pro Sample Roaster is an excellent sample roaster. The major benefits, from my point of view, are these:

Consistency of the roasts. Each profile can be reproduced exactly over and over again. Sample roasting becomes very accurate this way, since roast profiles are used for everything you do.

Exploring coffees capabilities in a wider range. One can roast a sample using different profiles, exploring coffees capabilities a little more. The overall impression of what a coffee can deliver to you becomes clearer since you can roast completely different variations of it. What attributes of the coffee are more pronounced, which ones have diminished?

It saves you a lot of time. Since the IKAWA runs the roast for you, ends it, cools it down and waits for you to empty the beans, you gain time. Eight to ten minutes (including the cool down phase) per sample. That means you can use the time for something else.

Nevertheless, a general review of using the IKAWA Sample Roaster isn’t what this blog is about. Beside all the capabilities the IKAWA offers to you as a sample roaster (as above), the IKAWA is a great tool for developing roast profiles in general. In the most elegant way I have discovered so far.”

HOW DO YOU DEVELOP A ROAST PROFILE TODAY?

“Let’s assume you are an experienced roaster. You roasted numerous different coffees in the past, you know how an Ethiopian or Kenyan has to be handled differently to a Colombian coffee or one from Brazil. You are able to differentiate coffees that are washed, pulped natural (honey) or natural. So, how do you begin?

Since roast profiles are very much bound to the overall environmental factors, changing those factors affects the outcome of a roast big time. Weather conditions, air pressure, wind and rain, outside temperature, temperature of the green coffee, energy charging of the roaster, roasting and cool down times and many other factors come into play. One huge factor to consider is the capacity or batch size of a roast. One can’t simply put 5 kg of coffee into a roaster, develop a profile and use the same profile for a full 30 kg batch.

Since roast profiles are unique for the set-up they have been created for, roasters usually work with production size batches to develop a profile. Thus, the outcome might be somewhere between excellent and coffee from hell!!

If you are one of the experienced roasters (and you know your roasting equipment inside-out), you will start using profiles from the past, that turned out to be good. From there you will start to tailor the profile until you like the result better. You have never tried something completely different, which could have led you to amazing results. Why? You are “ruining” 30 kg of greens for every try, which is an expensive thing. From a business perspective, you must go with the one that is acceptable or might even be considered very good, but you never know if the coffee could have been amazingly different if roasted another way. Usually the tailoring happens over time which means that the best profile is nailed after several batches of roasting, cupping, adapting, repeating. For your customers, this means, their coffee is changing, too. You are not producing a constant quality.

None of this is entirely satisfying, but there are ways to change that.

How about developing profiles in the small scale and actually being able to reproduce them in the big scale? Even better, develop it in the small scale without pre-heating your big roaster and taking care of all of the environmental factors?

I have been working on this topic for over a year now and I found the IKAWA Sample Roaster to be the key to developing a production process that works and which allows to “dial-in” roast profiles easily, while discovering the possibilities of a coffee in a wider range.

In the beginning was the idea of being able to produce a profile in a small scale and bring to a production roaster later-on. Nothing new here, a roaster’s dream for years. I started to dig into this topic and asked friends of mine who work in the chemical industry tons of questions. We analysed roast results on a chemical level to be able to get some meaningful data that could be used for comparison. It turned out that a combination of three factors are enough to get a good evaluation.

- Roast Colour (Find out more about this here).
- Total Dissolved Solids (TDS) of the coffee when brewed to defined parameters and a sensory evaluation, usually blind cupping with experienced people. (Find out more about this here).
- Energy Transfer Level (ETL) of each roaster, which is a measurement of the average energy applied to the beans over the duration of the roast.

Energy Transfer Level means, that you know when and how much energy had been applied to the roast throughout a specific duration (roast time). If you do this, the plotted curves (bean temp and so on) will look different for every coffee you roast (say a Brazilian or a Kenyan etc). But the energy applied to them (ETL) is the same. The coffees just react different (mostly due to their density). But this is not important, since we map an ETL.

This picture simply shows the idea behind the concept that I call Energy Transfer Level (ETL). In summary it is the average amount of energy applied to the beans throughout the roasting process. The picture shows a simple example of two profiles for which it should be easy to understand that B applies more energy to the beans.

This is a simple 3×3 matrix (instead the 5×5 I use mentioned here). The idea is that you have three different profiles, each delivering a different ETL. For each profile you can stop the roast at three different points. This gives you a total of 9 different variations.

With this approach, you will need to create corresponding ETL profiles on the big roaster. If you set this up, you will be able to transfer anything from small to big scale easily in the future.

What I developed over time is a matrix of profiles on the IKAWA Sample Roaster for which I have a counterpart for my Giesen W15A roaster. The matrix consists of five completely different roast profiles, having different ETLs. For each ETL profile there are five variations, giving a total of 25 profiles. Depending on the type of coffee, I choose a set of profiles for the IKAWA, roast three to five samples of the coffee and compare them after a week. The one I like most is the one that will be roasted on the Giesen W15A, using the corresponding profile. From there you are starting to tailor the roast profile, whilst making very small changes that do not alter the characteristics of the coffee in general.

IKAWA profile alongside a Giesen production roast profile designed to achieve similar results.

Setting up this process takes some time, since you have to understand the specific characteristics of your roasting equipment.

What you have to develop is an understanding of how readings from the IKAWA map to readings on your production roaster. By readings I mean the measurements I took: roast colour, TDS, ETL and the sensory evaluation. What you develop over time is an understanding of the patterns: Which TDS combined with what colour, and which ETL on the big roaster are giving me the same sensory results as the TDS, colour and ETL on the IKAWA?”

We hope you’ve found this useful – many thanks to Wolfram Sorg from Backyard Coffees. Wolfram is working on a more comprehensive write-up on this subject, so keep an eye on his website to hear it first.

We’d love to hear how you get on with this, and if you have any other approaches to translating profiles from Sample to Production roasts…