When it comes to roasting coffee there are two popular methods. Drum Roasting and Hot Air Roasting method.
What happens when you roast coffee?
Roasting coffee is complex.
When you roast green coffee, a lot of changes happen. Green coffee pales to yellow, then darkens into brown as the Maillard Reaction kicks in. This is when reducing sugars and amino acids react to form aroma and flavour (this is how we take a flavourless, rock-hard seed and transform it into everyone’s favourite morning ritual).
As roasting continues, moisture inside the beans begins to evaporate. This energy buildup explodes outwards, creating a cracking sound from the beans. From this point, the beans double in size but lose a fifth of their weight as they shed a layer of skin known as chaff. As we roast past the first crack, we can develop and highlight different flavours.
As with a lot of things when it comes to coffee, it’s a personal preference as to how much we let the coffee develop and roast, changing the result and overall experience.
What’s the difference between a light and dark roast in coffee?
The time you roast and develop coffee for affects the flavour in the cup. Roasting with a shortened development phase past the first crack results in brighter, more acidic coffee; this light roast style brings out more citrus, floral and herbal notes.
When we develop past this point, sugars in the coffee begin to caramelise, enhancing the sweetness. Developing further, the roast turns darker and brings out more body from our coffee, at the expense of acidity and sweetness. Go even further with a roast and you will eventually hear a second crack, resulting in very oily, roasty flavours dominating the experience.
The delicate balance between acidity, sweetness and body is what we strive for with all our coffee. This is particularly tough when every coffee around the world is different. However, the best thing about coffee is that there is no right or wrong way when it comes to flavour.
We’ve always felt sweet, clean flavour is best and that’s what we stand for. But it really does come down to personal preference, so get drinking and find your favourites!
What are the different methods for roasting coffee?
Two main roasting methods are used for this coffee transformation - the traditional Drum Roasting method and Hot Air Roasting. At Allpress, we Hot Air Roast our coffee, so we’re a little biased.
Drum Roasting
As the name suggests, drum roasting uses a large drum rotating over a heat source, roasting the coffee as beans meet the hot metal.
With coffee rumbling around a drum, it can be difficult to ensure every bean is roasted the same. There’s nowhere for the shedding chaff to escape, hotspots can be scorched onto the beans as chaff begins to stick and burn on the hot drum. This can result in an underlying smoky taste in the overall roast. With drum-roasted coffee, every bag you buy and every cup you brew can be slightly different from the last.
But when you get a delicious coffee from a drum roaster, know that it takes a lot of care, skill and precision to achieve that flavour!
Hot Air Roasting
With Hot Air Roasting, coffee is suspended in streams of hot air. This hot air envelops every single bean evenly. This level of control allows us to showcase the unique characteristics of coffee while achieving a consistent roast every single time.
The precision of Hot Air Roasting relies on sophisticated temperature control sensors. These sensors accurately gauge the real-time temperature of the coffee as it's undergoing these flavour changes. This allows our roasters to have complete control of the roast, taking the coffee to the very edge of flavour development, without compromising on the sweet, clean flavours.
As the coffee cracks and expands, chaff is pulled from the roasting chamber, so you’ll never get any undesirable smoky flavours from Hot Air Roasting. A medium roast with one hundred kilos of coffee will take twelve to fourteen minutes in our A.R.T. Roaster.
Once a roast is complete and roasted coffee is spread out on the cooling tray, we use recycled hot air for more roasts so we’re not consuming excess energy to heat the whole system up every time we start a roast.
Flavour impacts of your coffee roasting method
Roasting methods have huge impacts on how coffee develops and the end taste you get in your cup.
Traditional drum roasting utilises a conductive heat transfer that enhances the carbohydrates and oils in coffee; this leaves you with a thicker, denser flavour and aftertaste. Regardless of what origin is being roasted, there will always be heavier, oilier flavours punching through.
Hot Air Roasting uses a convective heat transfer to elevate the aromatics in coffee, resulting in a sweeter, cleaner flavour. Hot Air Roasting coffee will result in a pleasant aftertaste that you want hanging around for the day! Sweet, clean flavour is what we’re known for, and our Hot Air Roasting is how we achieve it.
Which is better — Drum Roasted Coffee or Hot Air Roasted Coffee?
At Allpress we’ve always chased sweet, clean, consistent flavour; it's what we stand for. Our Hot Air Roasting method allows us to control the roast throughout the entire process and nail the flavour profiles we set out to achieve, every time. Drum roasting will always hold a soft spot for the traditionalists out there but ask us and we’ll always favour the results of Hot Air Roasting.
