Posted in Kafevend Blog
Ever wondered how coffee beans are roasted? Well, before roasting begins, the green beans are screened to get rid of any bits of plant matter such as skins and shells not previously removed. They are then fed into the roasters. The more common roasters used are drum machines and hot air roasters. Drum machines consist of horizontal rotating drums which help to ensure an even spread of heat to all the beans inside. The drum is typically heated from below, using a variety of fuels like gas, wood and electricity. Hot air roasters blast hot air through a screen that the beans are sat on, buoying them up. Heat is then evenly transferred as they circulate.
Whilst roasting, the beans will lose moisture, expand and change colour, and depending on the time spent roasting, will emit up to two audible cracks, similar to popcorn. A combination of the colour change and the cracks are used to generally define the roast types: light, medium, medium-dark and dark.
The act of roasting coffee has a very pronounced effect on the characteristics of the final drink, affecting the flavour, acidity, body, aroma and sweetness. As such, the act of roasting is one that takes a long time to perfect. The body becomes heavier, and the aroma stronger in the medium/medium-dark roasts, with the sweetness peaking in the medium-dark roasts. The acidity drops off in darker roasts, along with the sweetness and aroma as the oils and sugars in the beans are essentially burnt off. Unlike the lighter roasts where the coffee's origin has an impact on taste, dark roasts will possess overpowering burnt undertones. Light roasts are typically very acidic, with a lighter body and less sweetness as the sugars have had less time to caramelize.