Coffee Roasting Basics

Did you know that the deliciously tasting cup of coffee that gets you going each morning starts out as green coffee beans? Regardless of what type of coffee beverage you like—such as espresso, cold brew, filtered or dripped—it all starts with the green bean which must be roasted to unlock its aroma and flavour profile. 

Coffee roasting is the process of subjecting green coffee beans to controlled heat. Through this process, green coffee beans are turned into the aroma-filled brown coloured beans that so many people across the world are so fond of. 

To find out more about the basics of coffee roasting, continue reading today’s blog article as we discuss how to develop flavour by roasting. 

The Importance Of Roasting Coffee

Coffee beans are normally stored in a green state to aid in their preservation without any loss in taste or quality. The aroma and flavours locked in coffee beans are brought out through a meticulous roasting process. 

Green coffee beans–which normally have a grassy smell and are spongy to bite–have none of the characteristics associated with roasted beans. As the beans are brought to very high temperatures, roasting causes physical and chemical changes within the beans. After reaching the desired roast level, the beans are cooled down quickly to bring the roasting process to a stop. 

Roasted beans weigh less as a result of losing moisture and are crunchy to the bite. These beans are also ready to be ground up and used to make coffee beverages. For the freshest coffee flavour, roasted beans should be used as quickly as possible. 

The 3 Main Coffee Roasting Stages

There are three mains stages of the coffee-roasting process. These include:

1). Drying Stage

Before the actual roasting starts, green coffee beans are dried as they normally have an 8 to 12 percent humidity level. When using the traditional drum roaster, the drying stage normally lasts anywhere between 4 and 8 minutes. A temperature of 160 degrees Celcius is reached at the end of the drying stage. 

During this stage, the beans normally accumulate the energy required for the exothermic final stage. However, it’s important to avoid burning the beans when using a traditional drum coffee roaster. 

2). Browning Stage

The drying process continues through to the browning stage. At 160 degrees Celcius, the coffee beans develop a distinct hay and toasted bread smell. This is when the aroma precursors start developing into aroma compounds. 

The Maillard reaction, which is responsible for browning, starts at the browning stage. Hundreds of different color and aroma compounds referred to as melanoids are made through the reaction of amino acids and reducing sugars during the Maillard reaction.

At this stage of roasting, the roast slows down naturally—with some roastmasters wanting it to slow down as well—in order to facilitate the development of flavour. The development stage begins at the end of the browning stage when the coffee beans start to pop—which is referred to as the first crack.        

3). Development/Roasting Stage 

As the reaction becomes exothermic, the coffee cracks at the commencement of the development stage. The coffee explodes after accumulating all the energy it needs during the drying and browning stages.

The period when the required aromas are developing is referred to as the development time. Failure to reduce the speed of the roast at this stage is likely to result in a sharp flavoured and smoky tasting coffee. 

Depending on the desired roast degree and flavour profile, the length of the development stage ranges between 15 and 25 percent of the total roast time. 

Coffee Roasting Basics  

3 Main Roast Levels And Their Characteristics

The length of the final stage is determined by the type of roast you as the roast-master want. Here’s a breakdown of the three main types of roast levels accompanied by their main characteristics: 

Light Roast 

  • High acidity levels
  • Sweet, fruity and floral flavours
  • Oil-free surface

Medium Roast

  • Balanced flavours 
  • Oil-free surface
  • Subtle dried fruit, nut and chocolate notes 
  • Medium roast also have medium levels of bitterness and acidity 

Dark Roast

  • The surface is distinctly oily and shiny 
  • Bold flavours 
  • Normally attained at second crack
  • Heavy body and low acidity 
  • Earthy, smoky and chocolate notes

If you don’t know your preferred roast level, it is a good idea to sample all and gain firsthand experience of how they differ from each other. 

Final Thoughts 

From what’s been discussed, it’s clear to see the important and demanding nature of coffee roasting. When it comes to coffee roast profiling, roast time and roast degree are the most important factors. Typically, dark roasted coffees are bitter and have burnt and roasty flavours, while light roasted coffees are known for being fruitier and more acidic. 

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