If you regularly buy coffee beans, you will see various roast levels available. From light Cinnamon and Half-City roasts to medium Full-City and dark Italian or Vienna, roasting is a crucial part of the farm-to-cup process, and roasting coffee beans at home will be more accessible for you!
Why do coffee beans get roasted?
Coffee beans start out green and are usually stored and transported in this form to keep them fresh before roasting.
Roasting coffee beans doesn’t only give them the brown colouring which we see on the supermarket shelves. The overall aim is to release each bean’s distinctive flavour. To be slightly more technical, it changes the chemical and physical properties of the bean, releasing sugars.
A green bean has the same amount of caffeine and acids as a brown one, but it is the roasting process which makes the taste.
Why should I be roasting at home?
You may have heard that grinding your beans at home just before using them means a fresher taste because once the beans are ground the freshness immediately starts to be lost. Well, roasting them at home increases this freshness even further.
A lot of independent coffee shops are starting to roast on-site, especially when they are using single-origin blends where the flavour is incredibly important, and freshness is key.
If you fancy yourself as a bit of a budding coffee expert, then grinding at home may not be enough for you. Roasting is a bit of a craft and will improve your drinking experience by a mile.
And depending on how adventurous you’re feeling, you can even eat your freshly roasted beans!
What do I need?
You will need to buy green, unroasted beans that fit the flavour you’re after and are also suitable for the roasting level you like.
You’ll also need a roasting device. This can either be a small mesh tool which you pop over a flame or a hob and roast them manually, a large drum which you put over a flame and either turn manually or with electricity, or a machine which will do the roasting and turning for you.
Some people also use woks or popcorn makers, which aren’t dedicated to the job but can be just as good if you get the technique right.
How do I roast the beans?
No matter your machine or device, the process is very similar:
- Colour change – During the first few minutes, the colour will start changing. It will be gradual, but the beans will go from green to a light brown/peanut colour
- First crack – Steam starts rising from the beans, and you should hear an audible ‘pop’. This is the water evaporating the beans drying out to such a level where the surface becomes wrinkled, and the cell structure of the beans breaking open. At this stage, light roasting is achieved, and you can stop if this is what you are after
- Caramelisation – If you leave them a bit longer, just before the second crack, this results in a medium roast. The beans expand, and colour darkens
- Second crack – This again will be obvious, even more so than the first. It results in a Full City dark roast level but may be alarming the first time you do it as it can cause the beans to throw off tiny pieces
- Dark roast – If you are after the strongest level, an Italian roast, you will need to wait until the end of the second crack. There is a fine line between waiting long enough to achieve this and over-burning the beans, so practice is required
- Cooldown – Once you have reached your desired level, you must cool the beans to stop the roasting process immediately as latent heat remains, just like with any other food. So try to remove them just before the desired roast is reached. If you don’t have a machine which will do this for you, transfer them into a colander and blow on them to remove any remaining chaff
Storage and brewing
Once cooled, store your beans in an airtight container to keep them fresh, but try to let them vent and release any remaining carbon dioxide before doing this.
Keep them cool and dry, and they should last for about six weeks this way. Green beans should be stored in the same way, but these can be kept for up to six months in their pure form.
The optimum time to use and brew roasted beans differs. Filter coffee will be best if the beans are used the next morning, but espresso tasted better if the beans are left to de-gas further for a few days. Roasting coffee beans at home will be more accessible for you!
Dan is a former competition barista and has been honing his knowledge of coffee for over two decades.
He has worked in coffee farms in Peru, as well as roasters in Australia. He now trains new baristas and hosts cupping experiences in Austin.