Coffee roasting is a centuries-old craft.

Art of coffee roasting has made great improvements in recent times, but still requires years of dedication to achieve perfection. Although hundreds of articles and books have been written about this fascinating matter, and almost everything (yet not all) is known about the chemistry and the thermodynamics of roasting coffee, it cannot be considered an exact science. Even less for espresso coffee, which requires a particular care to roast it successfully.

Excellence for an espresso coffee roaster is an endless search, even for the most experienced roastmaster. If you are willing to become a professional - or just an amateur - coffee roaster, be prepared to try, try, and try again until you master the perfect roast. You may talk to an espresso roastmasters with 20 years experience and he will surprisingly tell you that every day he learns something new: roasting espresso coffee is a perpetual learning journey.

The whole espresso coffee roasting process consists of 5 steps: cleaning, roasting, cooling, grinding, and packaging; each of them contributes to bring the best espresso coffee to the consumer' cup, but in this article we focus on roasting only.

Two 'T' factors are decisive for a successful espresso coffee roasting: Temperature and Time. Roasting coffee just means applying a certain heat to green beans for a period of time: this process breaks down the carbohydrates and fats that produce the oils necessary for creating flavour and aroma. Technically speaking, coffee roasting is a chemical process by which aromatics, acids, and other flavour components are created, balanced, or altered in a way that should make the flavor, acidity, aftertaste, and body of the coffee as desired by the roaster.

Roasting temperature typically ranges from 700°F to 1000°F. Roasting time may vary from 3-5 up to approx. 20 minutes, depending on the type of coffee beans used (often multiple blends), on the desired colour and flavor of the output coffee, on the equipment, on the interaction between the coffee beans and the air within the equipment itself, and even on the outside weather conditions.

During the first stage of coffee roasting, the beans turn from green, to pale-yellow, to yellow. If you stop the coffee roasting process at this stage, the beans retain much of their origin characteristics and their origin traits are not masked by the roast characteristics. If the coffee roasting time is too short for a particular coffee bean, not all the chemical reaction will take place. The longer the time, the darker becomes the roasted coffee. But if coffee roasting time is too long it can destroy many aromatic compounds, giving the coffee a bitter taste or burnt aroma.

That's why the experienced roastmaster frequently checks the roasting status of the beans: no sophisticated machine can substitute his 'feeling'.

At the end of the process, roasted coffee beans have their typical flavour and aroma, and get their definitive dark brown colour, characteristic of Italian espresso coffee. Weight is now 18-20% lower than the original green beans.

Mastering the mix of Coffee beans + Air in the roaster + Temperature + Time + Weather is therefore an ART (not a science) that reveals the true Italian espresso coffee roasting wizard. Computer-controlled roasting machines and scientific roasting profiles can definitely help - but will never substitute - the experience and the continuous visual control that must be adopted by the good roastmaster. How to manage all the involved factors is often kept secret: it is the magic formula that each roastmaster will never publish.

By the way, that should not sound strange at all: have you ever been able to discover the secret of the recipe of the delicious pie prepared by your grandmother? Nobody was. And she was not either, most likely. You never heard her say 'X grams of butter, Y grams of sugar, Z centiliters of milk, at this precise temperature for exactly 22 minutes', isn't it? Viceversa, you can recall her saying: 'just a little bit... some more... but not too much... for a few minutes' etc... She was not very scientific, right? But what about the final taste!? (I can still remember the 'budino di semolino' made by Nonna Ada...)

Same with roasting espresso coffee: the 'art effect' wins against science. Of course new machines and knowledge help a lot to avoid major mistakes, and allow everybody roast an average espresso coffee. But the human factor, the experience of the roastmaster, is what will distinguish a generic commercial product from the real gourmet espresso coffee.

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