How To Roast Coffee Beans At Home
Coffee roasting today has become extremely technical.
With numerous temperature probes tracking the temperature of the coffee beans at each stage so the roaster knows to adjust certain variables.
Rightly so too, there has already been a huge amount of research and expertise for the beans to get this far, before they are even dropped into a coffee roaster.
Although traditional drum or convection roasters will have roasted the majority of the coffee that is consumed throughout the world there are still a few places that roast coffee the ‘even more traditional’ way, in a large skillet/pan over a flame.
It is seen often in African countries, particularly Ethiopia however I came across it for the first time when visiting a coffee farm in Cuba.
After a tour of the Finca (farm), we gathered around a fire to watch the farmer stirring raw coffee around a huge steel pan over a flame.
The coffee took minutes to roast as the temperature was so hot and basically burnt the beans.
The coffee was later ground in a huge manual grinder that was attached to the end of a bench.
The coffee did lack in any notes other than roasty flavours, which were muted by adding a customary spoon full of Panella (raw sugar).
Although I would have never wished this method of roasting on a high-quality coffee, it certainly was a magical thing to watch and a great way to begin learning the processes and sensory cues of coffee roasting.
Roasting coffee beans at home in a pan, oven, or popcorn maker is something that I would recommend everyone who wants to learn about coffee try once.
It is definitely not a method that I would advise anybody to use as their only method of roasting coffee but it’s a great way to see the coffee change colour and experience the multitude of aromas that permeate from the pan.
When you have graduated from one of the below methods it will be time to invest in your own home coffee roaster.
Why Do We Roast Coffee?
First of all, going all the way back to the origin, coffee begins as a fruit that is picked from a tree.
The red (sometimes yellow) coffee cherry is removed leaving the seed (the bean) which is then processed further, removing a slimy layer called the mucilage and then dried in various ways.
The outcome is green/raw coffee that is exported from the source and arriving in (usually 60kg) coffee sacks throughout the coffee importing world.
Green coffee like many other seeds has a fairly high moisture content, this results in a fairly tough composition making them hard to grind.
If you were to brew green coffee though the taste will be plant-like and grassy - all together pretty unpleasant.
The tale goes that an Ethiopian goat herder discovering coffee beans when his goats were dancing later sharing them with a monk who disapproved and threw the beans onto a fire when delicious smells permeated from the flames.
Read more about the Origins of Ethiopian Coffee.
Today the process is a little more delicate and we roast coffee to dry the beans and then provoke certain chemical reactions that trigger desirable outcomes in taste, here are the stages of coffee roasting;
Stages Of Coffee Roasting
Raw Coffee.
Green coffee is first loaded or emptied into the roaster.
At this point, the coffee green coffee is at around 10% moisture level.
Drying.
The roaster is preheated and coffee immediately starts to dry and lose moisture as the coffee is rotated to give an even roast.
The coffee at this point will start to gradually change colour and appear a lighter shade with grassy, vegetal aromas.
Yellowing/Maillard.
Coffee begins to change colour into various shades of yellow.
The Maillard reaction begins when the coffee beans hit around 150℃ and the sugars react with amino acids to commence coffee browning.
You may start to smell aromas of the roast as the coffee beans start to swell and shed the thin papery outer layer called chaff.
Browning.
As the bean temperature rises the colour will deepen into light shades of brown.
Here the aroma starts to become pleasant and resembles the smell of toast as the sugars begin to caramelise.
First Crack.
The most significant part of a roast and probably the most enjoyable.
As the beans approach 200℃ the build-up of gasses burst out of the coffee bean creating an audible pop or crack.
This will last for a few seconds and is a similar sound to making popcorn.
The aroma still resembles the pleasant smell of toast.
At this point, the coffee is at a moisture level that will be easy enough to grind and brew.
Many light roasted coffees are dropped at this stage, extenuating delicate flavours in the coffee particularly acidic notes.
Development.
For the next minute or so, the roaster has to really pay attention.
This is where coffee is expertly crafted to highlight various flavour notes and attributes.
All the variables like airflow, drum speed and temperature have to be carefully regulated while temperature gauges inside the drum are fluctuating because of gas escaping from the bean.
Traditionally the sample spoon is used to monitor the colour and the smell of the coffee beans, while modern roasters are sometimes programmed to roast a specific profile.
Second Crack.
A point of the roast that very few speciality coffee roasters will ever reach.
Here, oils move from inside the bean through to the surface, the sound is attributed to the structure of the coffee bean changing.
Coffee that has reached the second crack will be dark and oily.
Aromas start to become more burnt and roasty.
Cooling.
You will see the cooling tray of commercial coffee roasters on any of their Instagram feeds.
It is normally a large circular tray with rotating arms that mix the coffee.
Air is drawn through the beans cooling them down.
This is a very important part, as like your dippy eggs in the morning if you don’t cool them they carry on cooking.
DIY Coffee Roasting Methods?
To give you an idea of what the temperatures are like in a coffee roaster most roasts will start at around when the machine has been charged to around 200℃ (depending on the size of the roaster and batch) and end around 210℃ in between is all about regulating the amount of heat, drum speed and airflow.
The type of green beans, ambient temperature and roaster temperature all contribute to the variables.
Roasting Coffee Beans in a Pan
The first time I tried to roast coffee at home I used a skillet pan.
It’s easy to do, extremely hard to master and even when mastered the end results are mediocre.
This all said I would recommend this method first and foremost if you would like to roast your own coffee because you are right there with the green beans manually tending to them and observing each stage.
Preheat the pan on the hob. You’re aiming for something similar to the drum roasters charge temp of 200℃ however as long as the skillet is heated through on a medium/high heat you should be ok.
This may get a little smokey so whack the extractor fan up and open a few doors.
Pour your green coffee into your pan making sure you only have roughly 1 layer of coffee beans.
With a whisk start to continuously stir.
It is important that you keep stirring the coffee beans as otherwise, the ones on the bottom will burn.
Enjoy the sensory experience of roasting your own coffee beans and take note of the stages highlighted above.
You should be aiming for the first crack at around 7 minutes but that depends on the size of your pan.
When you have a colour that resembles the coffee you are used to drinking pour the beans into a sieve or colander.
Now pour the beans from the colander into the sieve continually, to cool the beans and lose the chaff.
Typically roasts should be rested for at least 4 days before brewing, however, why not try the coffee after it has cooled to experience the most freshly roasted coffee you have ever tasted.
You shouldn’t have to adjust the temperature of the hob once you have started to roast, however, if your roast time is over 11 minutes then next time make the pan hotter.
Likewise, if the roast lasts 6 minutes, try a less intense heat.
Try to keep everything consistent and change one variable at a time.
This is very similar to brewing coffee, with so many variables, it is so easy to brew and roast inconsistent coffee.
You will achieve the perfect coffee quicker by keeping everything the same and altering one variable.
Roasting Coffee Beans in an Oven
I would recommend oven roasting coffee beans at home if you for some reason don’t want to roast the coffee in a pan or you’ve already had a go at that with little luck and now you’re after an alternative.
It’s very hard not to just bake the beans in a domestic oven as they struggle to reach the insanity of a commercial roaster (which is essentially a big revolving oven).
It’s also hard to rotate the beans with this method as opening the oven to stir the tray will drop the temperature.
You also won’t have the sensory cues that pan-roasting offers.
That said, you can still roast coffee in an oven and it is worth doing on a small scale to see how you fare.
Preheat the oven to around 250℃ and make sure you’ve given the outside of the oven time to hold some heat and stabilise at that temperature.
Open all the windows.
Spread the beans on a baking tray.
Preferably on a tray with tiny holes on the bottom or a perforated tray so the beans will roast evenly.
Place the tray inside the oven and close the door as quickly as possible.
If your oven has a window then you will be able to pull the beans out when they reach the desired colour.
If you don’t have a window start your timer.
Observe the beans and if they look as though they are roasting unevenly open the oven and stir.
Try to avoid doing this more than once though as the drop in temperature will bake the beans and create a flat-tasting coffee.
If you’re using a timer pull the coffee out at around 12 minutes.
Similar to the skillet pan coffee roasting above, pour the coffee into a sieve and continuously pour back and forth between the sieve and a colander.
Rest the coffee or try some after it has cooled.
Roasting Coffee Beans in a Popcorn Machine
Popcorn poppers come in various different sizes, shapes and functionality.
I never really came across popcorn poppers until I was an adult, we always used to be a ‘popcorn-in-a-bag’ sort of family growing up.
Alas, they make pretty good coffee roasters and you can pick one up pretty cheap online today it’s definitely worth a go, especially if you’ll use it for making popcorn too (it tastes better than microwave any day).
Preheat the popcorn popper, whether it’s electric or stovetop.
Place green beans into the popcorn popper, the amount will vary depending on the particular model.
It’s always better to go less than more initially as too much coffee will result in inconsistent under roasted coffee.
Stir the coffee (sometimes this will involve turning a handle on a stovetop popper while some are automatic)
Listen, watch and smell for the various stages of roasting.
When the coffee has reached your preferred roast level empty the beans into a sieve and pass between the sieve and colander, cooling the beans.
Is it worth home roasting coffee?
It completely depends on what you think you will get out of it.
Like with any skill or craft there is a lengthy process before you can reach an outcome close to what you purchase from a shop.
However, if you are willing to invest time and find enjoyment in making something for yourself then roasting coffee at home is worth it.
Do you dry coffee beans before roasting?
No, coffee beans are not typically dried before roasting.
In fact, coffee beans are first dried after they are harvested to reduce their moisture content and stabilize their quality during storage and transportation.
This process is called "coffee bean drying" and typically involves spreading the beans out in thin layers and allowing them to dry naturally in the sun or with the aid of mechanical dryers.