Did you know that you can roast coffee at home. Thats right take that light roast or green coffee and turn it into a dark roast coffee, Whether is a hobby or just for the fun of it or you’ve just want to see how the smell and taste of a coffee changes during the roasting process. Here are the steps you’d need to take to achieve this at home.

COFFEE ROASTING AT HOME

Roasting organic coffee at home is gaining popularity as a hobby for coffee lovers as a way to experiment with flavour profile and enjoy the absolute freshest roast. Home coffee roasters are available but roasting in a household oven is fairly easy, inexpensive and a great way to begin enjoying the aroma and taste of fresh roasted coffee. 

SUPPLIES NEEDED

  1. An oven
  2. A baking tray (the best kind is perforated like a pizza tray)
  3. Timer
  4. Oven mitts
  5. Wooden spatula
  6. Metal colander(s) 
  7. Water bottle with mist function
  8. Green coffee beans (1/3 and 1/2 pound)

STEP BY STEP INSTRUCTIONS

  1. Preheat oven to 475F-500F
  2. Fully cover baking tray with one condensed layer of coffee beans
  3. Ventilate the kitchen by opening windows, turning on vents and disabling smoke detectors
  4. Designate an area to safely cool the roasted beans (outdoors is recommended)
  5. If it is warm outside, have a water bottle filled with cold water ready to mist the roasted beans
  6. Place tray in oven once preheated
  7. Oversee the entire roasting process for colour, key roasting sounds and consistency
  8. Roast for approximately 10 to 17 minutes 
  9. Remove tray from the oven to stir the beans with a wooden spatula and return the tray to the oven to maintain an even roast (optional)
  10. Remove tray from oven and turn it off once the desired roast has been achieved 
  11. Transfer tray of beans to the colander at the cooling station
  12. Gently shake beans from one colander to another, removing the Chaff and mist lightly if the weather is warm
  13. Give the beans 24 to 48 hours to de-gas prior to brewing

OVEN SPECIFICATIONS

This is definitely one of those trial and error endeavors, so be prepared to go through a few batches before you have found the ideal formula as all ovens vary in temperature and time it takes to roast.

Ensure that your oven:

  1. Can reach 470F-500F
  2. Has a clear window for viewing
  3. Has a working oven light
  4. Has working ventilation (roasting coffee produces a lot of smoke)

The coffee will need to be inspected often during the roast, so it is important that you have adequate lighting and an unobstructed view at all times. A flashlight may be useful for inspection.

GETTING STARTED

Begin by setting your oven to a high temperature (475F for Gas and 500F for electric). Oven temperatures will vary.  A perforated baking tray with small holes works best, but any baking tray is fine to use. Spread the beans evenly over the tray, being careful to not stack. The coffee beans, once in the oven, will produce a lot of smoke depending on how many are being roasted and for how long. It is very important to properly ventilate your home prior to roasting to avoid the smoke detectors going off and your home possibly filling with smoke. Open windows, turn fans on, temporarily disable the nearest smoke detectors and inform others who may be in the home.  The final stage of preparation is to decide on an exit strategy. Coffee beans straight from the oven are very hot, and will be covered in a thin skin called Chaff. You will want to remove much of this outer layer before grinding. Also, to prevent further roasting, the beans will need to be cooled as soon as possible. To do this, I recommend determining the quickest route from the oven to the outside where the beans can safely cool and where the Chaff can be removed.

ROASTING THE COFFEE

Once you have properly prepared the oven, ventilated your kitchen, assembled your equipment and decided on an exit strategy, you are ready to begin roasting the coffee beans.  It is very important to closely monitor your coffee during the roasting process, as you do not want to burn the beans. Once your coffee beans are in the oven, start the timer. You will see the beans go from green to yellow to light and then darker brown. Colour is easiest way to determine the length of your roast. Be prepared to experience unevenness in the roast, as the beans closer to the edges will darken faster than the rest of the beans. If this happens, you can quickly and carefully remove the tray from the oven, use your wooden spoon to stir the beans and place the tray back into the oven. It is not a good idea to do this more than twice during a roast cycle as each time the oven will drop in temperature. Letting the beans roast completely then discarding any over roasted beans later is another option.

In addition to keeping a very close eye on the colour of your roast, it is equally important to be listening.  You will be listening for roasting sounds, specifically the second crack sound that the beans will make, indicating that they are ready to be taken out of the oven. You can leave them for a bit longer if you prefer a darker roast but be careful not to leave them in too much longer after hearing that second crack.  What you will be listening for exactly goes a little like the following:

Listen for the first crack that sounds like a popping sound

Several more popping sounds will follow

The popping will then fade and the beans will be quiet for a few minutes

You will then hear a second sound which resembles more of a crackle

Be sure to remove your coffee after this last sound or very shortly afterwards

A typical roast in a household oven is about 10 minutes. If you can reach 15 minutes without burning the beans, that is a reasonable duration for a darker roast.  

THE COOLING METHOD

Once you’ve reached your desired roast, turn off your oven and remove the tray. Take every precaution when making your way to the cooling area that is located preferably outside. Transfer your beans from the tray to the metal colander and lightly mist with cold water if it is a hot day or you live in a warmer climate. Use two colanders to gently shake the Chaff off of the beans while moving them from one colander to another.

FINAL NOTE

Roasting coffee at home requires patience, practice and precaution. Ultimately your success will depend on these three key elements and how dedicated you are. Ideally when roasting coffee, in order to develop more complex flavours, you would want to start your roast out low then gradually increase the heat. With a household oven however, unless you have a very responsive oven, you will need to keep the heat consistently high. With practice and your own technique and timing, you can perfect a method with your oven that will result in fresh, flavourful coffee just the way you like it.