4 DIY Ways to Roast Coffee at Home

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Disclaimer: Coffee roasting can be dangerous, just so you are forewarned. You might start a fire. Please keep a fire extinguisher nearby and do not leave your beans roasting unattended. This article is for information and you roast coffee at your own risk.

The best coffee is freshly roasted coffee. Period. A friend of mine had the opportunity to travel to Ethiopia and she reported that the coffee she had there was unlike any she had ever tasted. It was fresh, so close to the source. The problem is, the stuff on the supermarket shelves is, well, not so fresh. Now I am not saying it is old (though it could be) but when you consider that coffee is at its best within 2-21 days after roasting you have to assume it is not at its peak. To get to the supermarket shelf it needs to go from roaster, to packaging, to distributor, to supermarket shelf.

Some of us are lucky enough to live in a town where there is a small local roaster. Artisan coffee roasters are on the rise and this can be a great option for those who can access it. For those who don’t have roasters in their neighbourhood you can order online, or get a little intrepid and roast some coffee yourself.

Roasting coffee yourself does not require investing in a lot of tools and you can get some good quality green beans for less than you would pay for quality roasted beans making this an inexpensive little hobby with gratifying results (an amazing cup of coffee).

There are several methods for roasting coffee as well as appliances that will do the job for you. We are going to keep it DIY here and save roasting appliances for another article.

The background information

First, let’s go over the general principles for roasting before getting into techniques.

According to Kevin Sinott in The Art of Coffee, roasting causes free amino acids to react with sugars which results in hundreds of aromatic compounds. Mmm. Sweet Marias has a slightly less technical overview of what is happening. The sugars in the bean caramelize, water is released (generally when foods lose water, flavor becomes concentrated), and the coffee oils move toward the surface of the bean.

Roasting coffee requires that the roaster pay attention to sights, sounds and smells. Professional roasters also mark the degree of roast by temperature, but this can be difficult to measure at home.

Sights: As the coffee beans roast they will turn yellow as they release water as steam. They will then begin to turn brown and become a progressively darker shade of brown. Very dark roasts are nearly black. There are coffee tiles available to help the roaster match up color to degree of roast. Another visual clue is that dark roasted beans will start to have a shiny surface due to the coffee oils coming to the surface.

Sounds: When coffee is just barely roasted (a light roast) the beans will begin to make a sound like popping popcorn. This is known as first crack. At this point, how long you continue to roast is personal preference. Stopping roasting at first crack will result in light roasts. Second crack occurs minutes later and is the beginning of the end of roasting. The crack sound is much more subtle so listen carefully. Proceed past this stage and you will be in danger of burning your beans. Second crack yields darkly roasted beans. For medium roasts, we will want to stop the roasting process somewhere right before second crack.

Smells: Smell is a little more difficult to put into words but the aroma from the roasting beans will change and move from grassy to nutty to toasty and burnt. For more about using smell to determine roast see Sweet Maria’s article.

Types of Roasts

For a process that takes between 10-20 minutes total, there are several types of roasts. One needs to pay attention to the sensory cues just discussed because you can go from light to dark roast in a matter of minutes. The National Coffee Association of America summarizes the types of roasts very nicely:

Light roasts include Light City, Half City and Cinnamon

Medium roasts include City, American, Breakfast and Full City

Dark roasts include High, Continental, New Orleans, European, Espresso, Viennese, Italian, and French

Putting it all together:

Sources: Sweet Marias, The Art of Coffee

Important Principles When Roasting:

1. Maintain even heating of the beans to prevent uneven roasting
2. Keep the beans in a single layer (oven) or keep them moving (almost every other method) to ensure even roasting
3. Cool the beans quickly to stop the roasting process

DIY Methods for Roasting Coffee at Home.

For all methods, good ventilation is a must as this is a smelly process. Some people prefer to roast outside if possible, however on a cold day it may be difficult to get the beans hot enough to roast them. If you have a gas grill with a side burner or a butane camp stove this can be a good way to roast outside.

How to Roast Coffee in the Oven

To roast coffee in the oven you will need a sheet pan (preferably with holes in it), an oven, a spatula or spoon to stir the beans with, and two colanders.

Preheat the oven to between 450-500F depending on whether your oven runs hot or cold. I would start around 475 your first time and then experiment with adjusting your temperature up or down as needed.

Spread the beans out on the baking sheet in a single layer. Don’t try to cram too many beans onto the sheet.

Place the beans in the oven. After about 5 minutes stir the beans around with a spatula. After another 5 minutes stir again. Once the beans start to change color you may want to stir more frequently but remember that every time you open the oven you let some heat escape making it harder to maintain a constant roasting temperature.

When the coffee starts to turn color, start paying closer attention and listen for first crack. Once you reach first crack it is up to your personal preference how long you continue to roast.

When you are done, remove the beans and immediately transfer to a colander. Begin moving the beans back and forth from colander to colander. It is a good idea to do this outside as the chaff released can be messy. The idea here is to cool the beans as quickly as possible to stop the roasting process.

Allow the beans to completely cool. Do not seal them in a container yet—they will release CO2 for the first 24 hours. After 24 hours you can place them in your storage container. They will continue to de-gas for a couple days yet but you can start using the beans after the 1^st day.

How to Roast Coffee in a skillet on the stove

For this method you will need a pan, a lid (optional), something to stir with (optional) and two colanders.

Preheat your pan on medium heat ( or a touch higher). Place the beans in your skillet in a single layer. If you have a gas grill with a side burner, you can do this outside provided it is not too cold out.

If you are using a lid, place it on the pan and start shaking the pan every 20-30 seconds as if you were making Jiffy Pop. If you don’t have a lid, stir every 20-30 seconds to prevent the beans from roasting unevenly.

Just as in the oven method, listen for first crack and then determine how long you want to roast past that. When you have reached your desired roast, pour the beans into your colander and cool as with the oven method.

How to Roast Coffee in a popcorn popper

There are two types of popcorn popper that can be used to roast coffee. The first is with an old-fashioned crank kettle such as the WhirleyPop. This is essentially the same as the stovetop method except you turn the crank on the popcorn maker to keep the beans moving. I won’t repeat all of the steps since it is so similar to the stovetop method.

How to Roast Coffee in an air popper

The final method uses an air popper. If you are going to try this, you may want to pick up an inexpensive popper dedicated to coffee roasting as it will smell like coffee after doing this. Personally I am not into coffee flavored popcorn. CoffeeGeek also point out that using an appliance for something other than its intended use can void the warranty.

Important: you should only use an air popper with vents on the side as vents on the bottom may collect chaff and catch fire.

Using the measuring cup provided with your popper, measure out one portion of green coffee beans and pour it into the popcorn maker. Do not overfill.

Turn on the popcorn maker and listen and watch for the signs of roasting. Once you hear first crack, watch the color and smell to determine your desired roast. Stop the machine when the roast is to your liking and pour the coffee into a colander and go through the cooling process described above.

This method is faster than the oven and stovetop method and you should have roasted coffee in between 5-8 minutes.

So there you have it, 4 easy ways to roast coffee at home and I’ll bet you have everything you need to try at least one or two of these methods. Now that you have your fresh roasted beans, find out the best way to grind them (yes, there really is a best way!).