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A Deep Dive into Coffee Roasting: How Each Stage Impacts Flavour


A Deep Dive into Coffee Roasting: How Each Stage Impacts Flavour

When it comes to speciality coffee, extracting maximum flavour is always a priority, with many factors contributing to the flavour profile of each cup. Roasting coffee is one way that we develop flavour (processing and brewing are others) - and every stage of the process will have an impact on your favourite beverage.


Why does roasting matter?


You may not actually recognise a coffee bean that isn’t roasted. It is the seed of the coffee cherry, green in colour and tends to have a grassy aroma. It is the roasting of the coffee beans that turns them into what we know and love today. That’s because the roasting process develops up to 1,000 different aromatic and flavour compounds which, combine to give the coffee its unique character.


The different stages of coffee roasting


  • Drying. A green coffee bean has up to 12% humidity and needs to be dried before it can be roasted. This is an important stage as it allows the bean to collect the energy it will need for the roasting process, which is exothermic (heat-producing). Using a 15 kg traditional drum roaster, drying can take up to six minutes, it is vital to avoid burning or, scorching the beans as this can negatively impact the flavour.

  • Browning, also known as the Maillard phase, comes after drying and starts at around 160 degrees Celsius. It’s the moment when complex molecules start to convert into aroma compounds. Slowing down the roast at this part of the process can ensure better flavour development.

  • Development/roasting. When the coffee beans start to pop, also known as the first crack, they are heading for the last stage of the roasting process - when the reaction becomes exothermic and the energy the bean collected during drying and browning forces the bean to crack along its centre line. Precise control during this final stage is important to avoid undesirable, smoky or astringent flavours and to balance out the acidity whilst reaching the desired roast level.


Other important roasting factors


Roast degree. This is an incredibly important indicator within the roast and can be measured by colour meter or tasting. A light roast will typically have more acidity than a darker roast. Darker roasts can also be interpreted as more bitter. The general rule of thumb is that a lighter roast is more representative of the character of the coffee, and this is why many speciality roasters adopt this style


Total roast time. A fast roast can produce more aroma compounds - but also runs the risk of underdeveloped beans. Whereas roasting too slowly can develop baked or cereal-like flavours. Finding a balance requires experimentation, but, the reward is in the drinking.


The design of the roaster. For example, drum roasters are one of the main options out there and work by rotating beans in a drum that is either directly or indirectly heated. This is a traditional and proven way to roast. A fluidised bed roaster, on the other hand, is indirectly heated by hot air so that it’s easier to control the roast and develop more flavour without burning the bean.


These are the key stages of roasting your coffee that will ultimately determine how it tastes.


Bean Smitten offer a range of speciality coffee’s for all types of coffee lovers – whether you prefer a dark roast or a lighter roast. Shop our coffee roasts here.


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