Basics of Coffee Roasting

Obtained from the seed of an exotic fruit, the coffee that nature bears is green. It is the roasting process that amplifies the goodness of the beans, thus turning them brown. If it had not been for this process, you would not have enjoyed an aromatic cup of coffee each morning.

Strange golden smoke taking away from coffee seeds

For all the coffee lovers, who are inquisitive about knowing the roasting process, given below is a quick lay down. The following points will equip with the perfect basic knowledge related to roasting of the coffee beans.

What is the Roasting?

An amalgam of science and art – that is just how we would like to explain this imperative process. Roasting is a heating technique that transforms the physical and chemical properties of green coffee beans. Also, the taste of coffee depends on the roasting process entirely. It is due to this procedure that we receive the fragrant, dark brown coffee products from the market.

Before roasting, the green coffee beans are in a soft and spongy state. These beans are then subjected to rapid temperature changes, which cause them to lose water content, become hard and change their taste, giving out that signature aroma.

Roasting causes the fats, sugars, and starches contained in the bean to caramelize, emulsify, and release. The coffee oil that results from roasting is responsible for giving coffee its exclusive aroma and taste.

Types of Roasts:

Depending on the intensity, the roasts are divided into four different categories:

Types of Coffee Roast

  • Light Roasts: This type of roast is mostly performed on milder varieties of coffee. The resulting product is light brown in colour. The surface of these beans will be oil-free as they are not roasted for enough time that the oil breaks out.
  • Medium Roasts: In comparison with the light roasts, the beans roasted to the medium are brown in colour and have a stronger flavour. Medium roasted beans are non-oily and are mostly known as American roast due to their penchant amongst the people of USA.
  • Medium—Dark Roasts: These roasts have a slight bittersweet aftertaste. Also, they are rich in colour with some oil on the surface.
  • Dark Roasts: The dark roasts are known for their distinct bitterness. They are shiny black in colour and have an oily surface.

Equipment Used:

Two basic types of equipment are used in roasting coffee: Drum and Hot Air.

Drum machines comprise of rotating drums, which topple the green coffee beans in a heated setting. The common sources of heat are natural gas, liquefied petroleum gas (LPG), electricity, and wood in most of the cases.

Hot-air roasters compel heated air to a perforated plate under the coffee beans with sufficient force that they lift the beans. As the beans tumble and circulate within this fluidized bed, heat is transferred to them.


Given below is a description about the process of coffee roasting:

  • The first stage of roasting comprises of drying the green beans so that they attain a yellow color. This is an endothermic part of the process.
  • Often known as the first crack, the second phase of coffee roasting includes heating the beans at a temperature of 200 °C.
  • In the next step, the temperature is raised to 220 °C. Loss of 13% of weight occurs in this case. The chemical process that takes place during this phase is known as pyrolysis.
  • Following the above process, a short endothermic period takes place after which an exothermic step called the second crack comes into play. This second pyrolysis occurs at around 230°C, and the roast attains a medium-dark brown colour.

With this process, we attain a well-roasted coffee that is further grounded or brewed to make enticing products.

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