17 Oct [Roasting] How to Roast Coffee Well

Coffee Is Science.

Have you ever tried coffee roasting?

As Gertrude Stein said, ‘Coffee is more than a drink,’ most of us first come to coffee captivated by its aroma and drawn in by its analog sensibility.

I was no different. But once you go deeper into this world and approach roasting, you come to feel much more strongly that it is closer to science than to sentiment.

In fact, roasting is a process of physical and chemical change. It is an extremely delicate process in which external heat acts as the variable, heating the moisture inside the green coffee to bring about chemical change. In this reaction, about 2,000 different aromatic compounds are produced, giving coffee its attractive flavor. The process of change is so delicate and impossible to measure that, truthfully, no one can claim to have achieved perfection.

When you think about it, it isn’t only coffee. The cooking process of any food is the same.

Even so, there are always famous chefs and skilled roasters. What characteristics do they have?

I believe their secret is the alchemy of ‘difference and repetition.’

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The Alchemy of Difference and Repetition

What matters most in a scientific experiment? It is the process of clearly identifying cause and effect. Once you understand a phenomenon that way, its secret is finally unlocked and you gain control over it. That is why what matters in an experiment is ‘control of variables.’

Any single phenomenon involves many variables acting in combination. Working out, one by one, how each variable affects the result is what control of variables means. That is why, in coffee roasting as well, we keep the various external conditions as uniform as possible, change only one variable at a time, and watch the result.

These results then become data, which you can use as a yardstick for understanding roasting.

And only once you understand how each variable affects the result can you begin to create a ‘difference.’

If you do things carelessly every time, every result will naturally be different, but that is uncontrolled chaos, not anything meaningful.

And if you can create that difference and repeat it, then you have truly reached the stage of gaining control.

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The variables we can think of in roasting are, broadly, the type of green coffee, the charge weight, the heating power, the exhaust speed, and the drum speed.

Since the output is roasted coffee, if you fix the type of green coffee and the charge weight and then test the remaining three roasting variables, treating only one at a time as the independent variable, the meaning of each will emerge. The more you do this, the more your skill will naturally improve.

The most important thing, of course, is tasting. Sensory training can never be emphasized enough.

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During this process, make a note of the best result. And if you can then repeat that profile, that is real skill.

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When repeating a profile, you don’t need to consider the chemical changes at all. The only stage where you need to consider them is once, when you design the profile. After that, all you need to check are the physical factors that can be evaluated sensorially.

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Coffee Is Food

What I introduced above is a way to train your roasting skills; now let me talk about what is obvious in principle.

Coffee is a food product.

And we roast it, because that is what roasting is.

Then, when roasting, there are things that are absolutely unforgivable, and we must not do them.

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First, you must not burn it.

Second, it must not be undercooked.

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If you simply observe these two most basic rules, coffee will show us the potential it holds.

After all, the chemical changes occur naturally through heat.

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For this, there is one roasting principle that matters most.

The foundation of roasting is to ramp down from high heat to low heat.

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The core of the Nordic approach, the Northern European style of light roasting, is how to avoid underdevelopment in light-roasted coffee.

Of course, the premise is that it must not burn. And it must be cooked through properly.

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There is only one answer: the early heat must be sufficient! But, as always, only within the range where it does not burn!!

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However, some beans can’t withstand it.

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Soft beans and natural-process beans are like that. In that case, if it doesn’t work, move on to the next option.

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Also, what works in your favor can vary depending on the type and characteristics of the roaster you use. For example, with a fluid bed roaster, which relies mainly on convection, roasting quickly can sometimes burn the outside while leaving the inside underdone!

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Cooking Is About Practiced Skill

Now, once you have built a profile of your own, understood the characteristics of your equipment, and gathered your own data for each type of bean, you are at the stage of building proficiency.

A roaster is not a theorist. A roaster is someone who roasts beans: a skilled craftsperson.

A good craftsperson is someone who produces results as intended. Because they understand the whole, they can predict outcomes to a fair degree.

There is no shortcut to this. Like the ‘masters of everyday life,’ you become comfortable with it by doing it a lot.

What I am pointing out is the big difference between simply doing a lot and repeating with a clear concept in mind.

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A Few Tips

Now, finally.

Here are a few handy roasting tips.

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First, I’ll stress it once more: the early heat is what matters! A well-insulated machine doesn’t need an excessively high early temperature, but if the machine isn’t well insulated, at least raise the charge temperature! But!! Only up to the point where there is no tipping or scorching.

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Second, chaff burns easily because it contains no moisture. Moisture conducts heat, but it also protects against heat. Chaff, which has no moisture, burns and gives off smoke, and ultimately adds a spicy off-note. So check the agitation speed and the exhaust speed so that chaff is expelled well.

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Third, run extreme experiments!

If you find the critical point at which the coffee gets ruined, and how, the range of your roasting will inevitably widen. To gauge that, pull the sample trier in the middle stages! Don’t just strike a pose and sniff odors that aren’t even good for your health!!