All you need to know about coffee roasting

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Roasting is the magic of coffee work, it is the trial by fire, the memory of Jupiter’s lightning and Hephaestus’ cave. “You can’t play with fire. Roasting is the third part of a four-part work: cultivation, fermentation, roasting and preparation. Although it is essential, it remains little known and unsafe. Yet the specialty coffee community is very connected.

If it remains in the shadows, it is because it concerns only a few practitioners, who remain cautious as the parameters are so numerous. Moreover, it has long been neglected by craftsmen and literature, scientific except for industrial roasting.

The art of roasting remains to be written and synthesized, but few really venture to do so, as the variables, conditions and laws are relative. It’s a job of experience. However, over the last twenty years or so, artisanal roasting has benefited from numerous transfers from the industry and from an unprecedented deepening. Techniques and equipment are changing at a rapid pace.

What is roasting?

Roasting is cooking raw coffee. To bring the coffee from a room temperature to over 200 °C and sometimes over 230 °C, the craftsman uses a machine, the roaster, his senses, his experience, his knowledge and, finally, measuring tools. Roasting is a complex chemical phenomenon combining several transfers (heat, water and mass) and pressure differences. When heated, the water in the coffee beans, which is 10-12% moisture, evaporates.

A flow of water thus goes from the heart of the grain to the outside. In addition, this heating creates a flow of thermal energy from the outside to the inside of the grain. Roasting is therefore characterized by a double, contradictory flow triple if we also consider the gas exchanges that take place from the inside to the outside.

These flows circulate through a dense material, grain. They are slowed down by its structure, especially the cell walls. As it passes from the liquid state to the vapour state, the water causes the pressure to rise until it breaks all the cell walls and thus definitively releases all the oils present in the grain. The transformation of the bean during roasting is therefore important and violent: it totally changes colour, going from green to brown, loses up to 18% of its weight, doubles in volume, becomes less dense, more porous, and alternates the phases of endo and exothermicity.

So the coffee bean is experiencing a kind of Big Bang. Finally, roasting is fast, between 1 minute 30 minutes for industrial roasts, which we will not talk about here because they are too specific, and about fifteen minutes for artisanal roasts.

The taste and colours of roasted coffee

So strength does not necessarily come from numbers. While roasting gives coffee its taste, for a long time people have confused the “taste of coffee” with the “taste of roasting”.

It must be a means and not an end. This is why burnt aromas must be definitively considered as defects. Roasting is cultural. It varies according to places and times.

It is probably for this reason that baking stadiums are named after cities or countries. For example, there are Nordic, French, Italian and Vienna Roast.

the tradition is more analogous. The traditional artisanal roasting thus seeks the colour “robe de moine”, in reference to the Franciscan’s canvas, which would correspond to the City colour. These names give information on the final colour taken by the bean. This is considered to be one of the essential indicators of the development of the roasted grain and therefore of its expression in the cup.

It is measured with instruments, colorimeters, and on different scales from 1 to 100. But be careful, color doesn’t tell the whole story. Two different roasting profiles can result in the same bean colour, but the taste will be different. So we look at the colour of the beans and the colour of the ground coffee. In the following table, you will find ways to choose your coffee from the colours.

The temptation to establish an “official” roasting profile for each coffee is great and sometimes crosses some people’s minds.

However, every profile is relative to the material, the conditions and the craftsman. The roaster’s daily requirement is therefore both melliorative and repetitive: follow these profiles, take measurements, taste the coffee to understand the effects of each of the parameters, roast again, changing only one parameter at a time, if necessary.

Roasting, through the contact it forces between man, fire and matter, is more a path than a truth. The uncertain language of colours: each roasting colour has its own personality:

Where to find freshly roasted coffee?

These few lines have surely made you want to enjoy a good coffee! Come and discover our roasted coffees, available in bean and ground coffee, in our coffee shops in Paris. You can also buy your coffee online, delivered to your home in 3 clicks and packaged in 100% airtight bags to protect all the aromas.

Read more related posts here How to Roast Coffee Beans at Home

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