Thinking of roasting some green coffee beans at home? Heather, Head Roaster at Bad Hand Coffee explains what you'll need and how to do it
Green coffee beans are unroasted coffee beans. Getting the beans to turn from green to brown is pretty simple, but doing it in a way that allows you to control and influence the flavour outcomes takes a bit more fine tuning.
Why is Bad Hand selling green beans?
We often have a kilo or so left when we finish batches of coffees, which is unfortunately too little for us to properly roast in our 12kg Probat (the smallest batch size we can do without compromising consistency is 6kg).
We’re always looking for ways to cut down on waste (and because a Frankenstinian blend of lots of scraps doesn’t always taste as good as you would hope), so we thought making them available to home roasters would be a great way to make sure they don’t go undrunk. We also wanted to give people at home a chance to get experimental with their brew and learn a bit about how roasting impacts flavour.
What do I need to get started?
Anything else I should keep in mind?
The whole process will probably take about 15-20 minutes. Ideally you will want control over the temperature and a way to agitate beans as they roast to keep the heat distribution (and cooking process) as even as possible. On a commercial roaster you can adjust the temperature as you roast, but this won’t be so easy in the oven.
If you’re using a baking tray or pan, start with just a single layer of beans so you can shake them more easily and help them cook more evenly. Now, let’s get roasting!
Stage 1: Green to yellow
Towards the start of the roasting you will notice the beans changing colours from green to yellow green and then to yellow. You might notice the aroma of the beans becomes a little grassy or hay-like. This is the drying phase and the stage where the acidity and intensity of the beans is most influenced.
Stage 2: Golden brown
The coffee beans will now turn from yellow to a golden brown and then a light brown. The skin of the beans will become a little wrinkled and smell more toasty.
This browning is called the Maillard reaction, which is a chemical reaction between amino acids and reducing sugars. This is the stage where the aromas are most influenced and the sweetness begins.
Stage 3: ‘First crack’
Once the beans reach a temperature of around 200 degrees Celsius, the moisture content of the beans becomes steam. That pressure releases forces the beans to ‘crack’ and expand (in the same way as popcorn). This is called ‘first crack’.
Stage 4: Development
After the first crack you get more of the sugars caramelising, bringing a more balanced sweetness to the coffee. But, like with any sugar there is a sweet spot (pun very much intended) between caramelisation and burning. This is the development stage.
If you’re aiming for a light-roasted coffee, you can stop your roast here. If you would prefer a medium or dark roast keep going for a bit longer.
Stage 5: ‘Second crack’
As the coffee caramelises, the oils in the bean will start to be drawn out to the surface. The colour will get darker, the cellular matrix of the bean will break down and create the ‘second crack’ (this is less loud and obvious than the ‘first crack’).
Here at Bad Hand, we usually roast between the first and second crack.
Stage 6: Darker roasts
If you want to continue and go even darker with your roast, the sugars will start to carbonise and this will bring out ‘heavy’ flavours. They can quickly turn to charred flavours, though, so be cautious.
Stage 7: Cooling
Once your coffee is roasted, you want to cool it as quickly as possible. If you allow the beans to cool too slowly then you tend to get flat, dull notes.
Move them to a metal colander (don’t use a plastic one, the beans will probably melt it). Carefully toss them to help circulate air around them to cool and remove the chaff.
Stage 8: Storing, resting and drinking
Now your beans are at room temperature, they are ready to store. You can drink them straight away, but be aware that because of the breakdown in the structure of the bean there are trapped gasses, which will dissolve over the next few days. These gasses will influence the flavour of the coffee and can make it taste flat and dry.
We would recommend resting your beans for a few days before brewing (if you can be that patient). Gasses will build up in an airtight container, so it’s best to use something with a one-way valve (like one of the Bad Hand Coffee bags or open the container every day to let them escape.