Discover roasting defects with Caffè Ernani

I maestri della tostatura media
Dettaglio della Tostatrice di Ernani, in particolar modo il cestello di raffreddamento dei grani rotante.

What can go wrong when roasting coffee beans?

After having gone through the Defects of green coffee, today we discover the four Roasting Defects!

Roasting is an art and the roaster is a true artist. Every single action must vary on the basis of the green coffee at hand, therefore on the basis of its origin, density, freshness, species, variety and desired result.

If he doesn’t work consciously and above all with a great deal of knowledge and training behind him, he risks getting out of the roaster brown beans but full of defects!

Let’s discover them together!

Roasting defects

The roaster’s job is to be able to apply the right amount of heat over time and in the correct way in order to obtain the best possible quality in the cup.
He also has a lot of leeway, to put his personal touch on the coffee, like a signature, in order to bring out from the beans what others would not be able to do.

However, if he does not work correctly, he will stumble upon the four roasting defects:

  • Scorching
  • Tipping
  • Facing
  • Baking

It is important for the roaster to know how to recognize them, understand the causes that have caused them and the possible remedies to avoid them.

Instead, it is important for the consumer to recognize them so as not to be fooled by the classic words used by all brands and written on the packaging like a mantra, i.e. words such as “quality” and “premium”. In this way you will learn to recognize a well treated and processed coffee yourself!

Let’s begin!

Dettaglio chicco di caffè tostato, con un cratere (buco) di colore più scuro

It is one of the most common faults in dark and very dark roasted coffees.

It appears as an irregularity that can be seen on the hump opposite the flat face, therefore on the back of the bean, in the shape of a black crater.


  • When the bean comes into contact with the surface of the roasting drum which is too hot, and therefore the part of the bean that touches it remains stuck to the wall;
  • Or when the rotation speed of the drum is too high and a centrifugal effect is created, as in a washing machine, and the beans are pushed towards the walls;
  • Or there is too much coffee in the roaster and therefore it does not have the correct space to keep moving.

NB. The roasting drum is like a sort of rotating washing machine drum, inside there are the beans hit by a flow of hot air to be cooked.

In the cup:

The final drink will have a lower quality, with possible burnt and smoky aromatic notes, with a bitter taste and a slight sensation of astringency.


This defect is less invasive than scorching, but no less important.

Tipping manifests itself with black dots that appear on the flat face of the bean at the ends of the furrow, then as darker spots at the two extreme tips.


  • It is generated by an excessive amount of heat transferred to the bean;
  • Or from an excessive contact time of the bean with the surface of the drum.

In the cup:

The drink will have aromatic notes of burnt and smoky with an increased intensity of bitterness and a slight astringency.

Dettaglio chicco di caffè tostato con le due punte, ossia le estremità esterne al solco centrale, con macchie più scure.
Dettaglio chicco di caffè tostato con delle macchie più scure sulla superficie piatta dello stesso.

It is a defect that is clearly manifested on the flat face of the bean, with more or less extensive, clearly visible black spots.


  • For an excessive amount of heat transferred to the bean;
  • Or due to an excessive contact time between the bean and the internal surface of the roasting drum, usually due to the rotation speed being too high and the subsequent centrifugal effect.

In the cup:

It produces aromatic notes of burnt and smoky with an increased intensity of bitterness and a slight astringency.


Baking or “boiled coffee” does not appear visibly on the bean and is therefore the most difficult to recognize. However, it can be found during the tasting phase in a simple and clear way.


  • Boiled coffee is the result of roasting really too long, combined with a temperature that is too low. Prolonging over time, beyond what is due, the bean does not develop its aromatic potential to the maximum, in addition to not even undergoing all the chemical-physical changes necessary to express itself to the maximum.

Without boring you too much it is just as if it were boiled and not properly cooked, as if we cooked the pasta over a very low heat for 30 minutes, when the indications on the package were 12 minutes, thus becoming soft and not very tasty.

In the cup:

The drink is characterized by few aromas in the cup and a “flat” profile… in short, little acidity, little sweetness, little bitterness and no aromatic complexity.

So here are the Roasting defects, did you already know them?

Next time buy the beans and check them and find out if there are any defects in the coffee you usually buy!

Marketing, E-commerce e Social Media Manager
Coffee Lover


Martina Mazzoleni

Marketing, E-commerce e Social Media Manager Coffee Lover

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