Tomi Nieminen //
// 1.6.2017

Coffee Roasting at Home: A Stupid Idea or a Culinary Adventure?

Roasting coffee at home can be difficult, but in the best-case scenario the result can be a nice and pleasant cup of delicious coffee. For me, it is about having fun by doing and exploring different flavours with the same raw material. Forget the repeatability and enjoy the uniqueness of your roasts.

I wanted to write about this subject for two reasons. Firstly, I have many customers who have been wondering if it is possible to roast coffee at home. Secondly, we have a strong but lost tradition with home roasting here in Finland. My father is always telling the same story about him being told to roast the coffee at home. It was always the youngest one of the family to do this task. He also got very often feedback about the flavour of his roast. At that time, in the 1950’s, almost every house had their own roasting equipment, which was basically a steel vessel with a crank handle to stir the coffee. Maybe this way of roasting coffee can be another form of this old tradition of ours.

Here is a simple list of how to get started:

1. Buy raw coffee

Go to a roastery and ask if they can sell you a small amount of raw coffee. 500 grams is a good amount, if you are making 50 grams’ batches. I think that ten roasts are ideal. It is enough for me to learn how the coffee acts while roasting but I won’t get bored with it.

Raw coffee beans in the hand

2. Choose your roasting method

There are many different ways to get those beans brown, but I would use oven, gas stove, or hand held heat gun. Be careful! Temperatures will become high, so do not make this at home – or I mean….

raw beans roasted on campfire

Roasting coffee by a traditional method with an open fire

3. What is your target?

Light or dark? I usually try to make light roasts because I like more acidic and sweet coffees than the bitter ones. Roasting time should be close to 10 minutes and not much more than 15 minutes. This depends about your roasting technique too. You can compare the colour of your favourite coffee with the coffee that you are roasting. But remember that every coffee is unique and thrives at different roast levels.

Coffee beans with different roasting level

4. Drying and browning stages

These are the first two stages in roasting. When the bean is at this stage you want to add a lot off heat to your coffee bean. If the bean doesn’t collect enough energy, the next stage, first crack, will not happen.

I have a fan oven, where I put 50 grams of coffee on a baking tray. I started with 250 degrees in a preheated oven. When the beans started to become light brown, I lowered the temperature to 220 degrees. Ovens aren’t very accurate in their temperature adjustment, so it takes time to find good settings with your own.

5. First crack

When the beans have collected enough energy, the coffee starts popping. This is also the beginning of the so called development time, which is one of the most important tools for a coffee roaster.  The crack is crucial for the flavour. It is also the earliest moment when the coffee can start actually extract properly. At my workplace in Paulig Kulma, we roast most of the coffee with around 15% development of total roasting time. You can keep this as a target on the first time when you roast. Start playing more with it when you find good adjustments for your roasting set up.

When I heard the first crack I checked the time, which was 10min 12s. I counted fast that total roast time with 15% development time should be 12min 0s. I also noticed that the coffee is getting darker quite fast, so I lowered the temperature to 180 degrees and opened the oven door a bit. I wanted to avoid too dark roast and took it out already at 11min 40s. I noticed that lowering the temperature more in the end of the roast would help me roast the coffee lighter with a longer development time. Note to myself.

6. Cooling

The last – but a very important – part of roasting is cooling. When we stop the roast we actually want it to stop. I use a hoover and a sieve to pull air through the coffee or cold pots where to stir the coffee.

7. Tasting

This is the most important part of roasting. It is time to evaluate, learn, enjoy, and share. The last two are for me the most important.

Check also Sampo’s blog post about roasting. He explains more theoretical way what exactly happens during roasting.