Understanding your roaster

Are you are completely new to roasting coffee and have no idea what to expect? Or perhaps you have years of experience roasting on big commercial roasters and are wondering how roasting on the Kaffelogic is different? This article sets out to explain some of the key features of the Kaffelogic system to help you understand what is going on.

Responsive

• Tiny batch size

• Ultra-low thermal mass roasting chamber

• Naked thermocouple

What to expect

1. Roast logs are very finely detailed. Compared to logs from other roasting systems they may look ‘noisy’. This is because in other systems thermal inertia of larger batch sizes, roasting drums, and thermocouple sheaths causes smoothing that is not intrinsically present in the Kaffelogic system. The Kaffelogic system is so responsive that smoothing, where it is needed, is applied with moving means and regressions.

2. While the Kaffelogic system can mimic most other roasting systems with appropriate settings, it can also do things that other roasting systems cannot.

3. The tiny batch size allows for the possibility of very fast roast cycles which cannot in practice be emulated with large batches.

4. Ultra-low thermal mass allows starting the roast with the beans and roaster both at ambient temperature. This is pretty much unique to the Kaffelogic system and we believe it explains why results from the Kaffelogic can be astonishing: e.g. the ability to make coffee with beans straight out of the roaster.

5. The Kaffelogic between batch protocol returns the roasting system to ambient temperature ready for the next batch. This contrasts with other roasting systems. For more details see Between batch protocol.

Stable

• Proprietary roast control system

• True Bezier curved profiles

What to expect

1. The Kaffelogic roast control system has been developed from the ground up to emulate the strategic thinking of an experienced roasting professional during coffee roasting. This puts it in a different class from conventional temperature PID systems. It also means it will do some unexpected things:

   1. The control system is very good at getting the roast back on track if it departs from the temperature curve. This means that it is not necessary to tune the control parameters to start the roast off following the temperature curve. You will often see a log showing temperatures above the desired profile curve in the first minute or two of a roast. The log curve then bends and gets back on to the desired curve with great reliability and accuracy. This is not an issue for flavour so long as the return to profile takes place before the start of the Maillard phase. It means the control system has fully adjusted to the beans by the time Maillard begins.

   2. The control system will allow the roast to proceed above the desired temperature curve under specific circumstances. This is because the control system will not simply cut the power to the heater to get the roast back on track if doing so would risk stalling the roast. This is one of the most critical features to allow full flavour development. Do not be distressed about this when you see it so long as the behaviour is consistent, controlled, and yields good flavour in the cup. Roasting coffee is about flavour, not about line following.

2. Editing a Kaffelogic profile involves editing curves, not a set of straight lines between points. This does make editing more difficult, but permits the control system to be much better at following the profile. The system can adapt continuously to the beans, without having to also adapt to corners in the profile.

Tuneable

• Heat and fan settings precise to better than 0.5%

• User editable gain scheduling (zones etc)

• Users can access deep settings

What to expect

1. Roasting coffee on the Kaffelogic involves a delicate balance between supply of heat and air on the one hand, and the beans on the other. Although the core profiles are designed to deliver excellent results with just about any beans you care to throw at them, very fine heat and fan adjustments can be made via customised profiles where requirements are more exacting e.g. roasting coffee for a competition.

2. During coffee roasting the thermal properties of the coffee beans undergo changes. As beans dry their specific heat decreases. In addition there are exothermic and endothermic chemical reactions at different times, as well as significant latent heat changes. Sometimes these changes will happen and undesirable effects become established before the automated roast control system adapts. The Kaffelogic system of profile zones allows the roast designer to pre-empt some of these changes to avoid the undesirable effects. This is done by tweaking the control parameters during specific parts (zones) of the roast.

3. Profile tweaks and changes are not done 'on the fly' during the roast. Instead they are done by editing the profile in Kaffelogic Studio between roasts. The process is iterative: roast - taste - tweak - repeat. The ability to roast batches down to as small as 50g, and the ability to cup coffee directly from the roaster, make this process both economic and fast. Experienced users can dial in a specific result in as little as 3 or 4 iterations.

4. You are given access to a number of critical settings that affect the way the roast control system works. In most cases it is better to leave the deeper (engineering level) settings untouched. But the openness is there because we never want to assume that we know everything about the Kaffelogic system and we want to allow our users to generate new knowledge if they dare. This is great because if an expert user discovers a beneficial modification it is easy for them to share it with you. Just be prepared to ruin a lot of coffee if you want to go down that particular path for yourself. And no, experimenting will not void your warranty, although touch base with customer support first if you have any concerns about this.