May 21, 2020

A Beginner’s Guide to Roasting Great Coffee at Home


Home roasting means you can drink fresh coffee whenever you want, experiment with coffee origins, and more. And while the learning curve may be off-putting at first, the satisfaction of knowing that roasted and brewed your morning coffee will make it all worthwhile.

But what equipment do you need? Which green beans should you use? How do you know when the coffee’s done? Do you need an expensive roaster? To find out all this and more, I spoke with Evan Gilman, Creative Director at The Crown: Royal Coffee Lab & Tasting Room

Lee este artículo en español Guía Para Principiantes: Cómo Tostar Café Excelente en Casa

Credit: Jean Pierre Flores

Why Roast Coffee at Home?

Nothing gives you greater control over your coffee than roasting it yourself. Love Kenyans? Great, you can roast a Kenyan. Want a honey processed lot? Buy one and roast it. Wish your local coffee shops offered lighter or darker roasts? Do it yourself.

Yet this flexibility isn’t the only reason to roast at home.

Freshness is a big factor: some green beans can be stored for up to a year after harvest without going stale. Roasted beans, however, start to lose their flavours and aromas after just a couple of weeks. Buying green and roasting small amounts every week, or even every day, will ensure that your coffee always stays fresh.

On top of that, green beans are significantly cheaper than roasted ones. In the long run, once you’ve refined your technique and have all your equipment, you could find yourself saving substantial amounts of money.

Home roasting will also help you broaden your coffee knowledge. You’ll start to understand what makes your favourite coffee taste so delicious and how you can alter your roast profile or buy different beans to highlight that. Through time and practice, your palate will improve – allowing you to appreciate your coffee even more.

You might also like A Home Roaster’s Dictionary, From First Crack to Silverskin

Credit: Evan Gilman 

What Happens to Coffee Beans During Roasting?

Green, unroasted coffee beans have a significant amount of water retention. It would be impossible to grind and brew them. Nor would you want to: they have a distinctive grassy flavour.

Roasting kickstarts various chemical reactions, resulting in the development of more appetising flavours and aromas.

Find out more in What Happens During Coffee Roasting: The Chemical Changes

When green coffee beans enter a hot environment, the moisture content starts to decline. This is the first stage of roasting, and it’s known as the drying stage. Shortly into this phase, the beans begin to turn yellow. Many people refer to this as the yellowing stage.

It’s when the beans start to darken, which is known as the browning stage, that the most important chemical reactions happen: the Maillard reaction, caramelisation, and Strecker degradation. These create many of the flavour and aroma compounds, including those responsible for sweetness and fruity acidity.

The browning stage ends with first crack, which is when the pressure inside the coffee beans causes them to crack open. You’ll recognise it by a series of popping noises.

Eventually, all the water inside the beans evaporates and they reach second crack. The coffee steadily becomes darker and releases more carbon-like aromatics. The majority of the sugars break down, and as the roast progresses, the beverage will taste increasingly bittersweet with reduced acidity.

Light to medium roasts normally finish somewhere between first and second crack. Dark roasts typically finish after second crack.

Read more in What Happens During Coffee Roasting: The Physical Changes

Credit: Jean Pierre Flores

A Step-by-Step Guide to Home Roasting Coffee

Let’s look at how to roast coffee at home, from choosing your beans all the way through to storing them.

1. Sourcing Green Beans

At first, you probably won’t know which coffee you like the most. This is especially true if you normally drink the house blend. Experiment with small lots until you become more confident in your choices. Sample packs are a great place to start since they normally include a variety of regions.

Evan tells me, “Some home roasting forums have buying groups that will split bags of coffee among subscribed enthusiasts, but the easiest way is to just find coffee online. For instance, Royal Coffee sells 22lb boxes of green coffee, the Crown Jewels.” 

He stresses the importance of finding out as much as possible about the coffee, “just to be a bit more comfortable” when purchasing and roasting it. There can be significant variations even between coffees from the same origin, especially if it’s a large country or the processing method and variety are different.

“We publish a lot of information about each one of [our Crown Jewels],” he adds, “including their harvest date, an introduction to the origin and microregion, attributes of the green coffee such as moisture content and screen size, and suggested roasting and brewing methods.”

Once you have your green beans, store them away from direct sunlight in a cool, dry place at room temperature. This will preserve their freshness and quality for longer.

Credit: Neil Soque

2. Select Your Roast Method

There are several ways to home roast coffee, each with its own benefits and drawbacks. To choose between them, consider how much money you are willing to spend, how much coffee you will roast, and how much control you want over your roasting variables.

Oven and skillet-roasting are inexpensive options since you likely already have the equipment. However, they’re not recommended for beginners because they require a high level of skill to achieve an even roast. Controlling airflow is also an important part of roasting, but it can be difficult with these methods.

“If you’re just getting into it, try roasting on a popcorn machine,” Evan says. “The Poppery series are some of the best for the job, or you can find one like it for about US $20. If you’re going straight for the gold, try the Aillio Bullet – it will cost you significantly more, however.” 

Popcorn machines are easy to use and typically produce even roasts. For small quantities, they’re a great starting point. Bear in mind, however, that doing so will invalidate your warranty, and that you can’t use ones with a mesh screen at the bottom, as this can cause fires.

If you find yourself wanting to roast more coffee or have greater control over the process, you’ll need to purchase a home coffee roaster. Choosing between the different brands and models will come down to your personal preferences: how big a capacity do you want? How much control do you want over the roast? How many pre-sets and roast profiles does it have programmed in? 

“There are so many home roasting machines out there, and most of them strive to be easy to approach and safe to roast on,” Evan tells me. 

Credit: Evan Gilman 

3. Set Up Your Roasting Space

Good ventilation is crucial, not just for your roast quality but also for your safety. Use an extractor fan, open your windows, and consider roasting outside or in an open garage so that the smoke released from the beans can escape.

You’ll also need some equipment close to hand. Scales are a wise investment, so you know exactly how much coffee you are roasting per batch. For popcorn-machine users, a thermometer can also be helpful. Evan says, “I would suggest a set of silicon gloves for handling hot materials, a small fan for cooling, and a sieve for cooling your beans.” 

4. Roast Your Coffee

If you’ve bought a home roaster, the manual will talk you through the different profiles. Starting with pre-sets can be a good idea until you’re more familiar with the process. As for a popcorn machine, it’s even easier to operate. Just make sure to not overfill it and to have somewhere for the chaff to escape.

Air roasters and popcorn machines typically take 8–12 minutes, whereas drum roasters might take 14–20 minutes. Just like when cooking, the lower the temperature, the longer it will take.

Constant movement of the beans is imperative for an even roast. Both popcorn and home roasters should do this automatically; if they’re not, you need to speak to the manufacturer or, with the popcorn machine, check that you’re not overloading it. As for skillet-cooking, you’ll need to stir the beans yourself.

Credit: Neil Soque

5. Cooling and Storage

Once the beans have reached your ideal roast development, remove them from the heat and let them cool down. They’ll keep roasting until they’re completely cooled, so make sure you act quickly. You’ll also want to remove any chaff, which is the dried husk of the coffee bean.

“If you live in a cold environment, use that to your advantage,” Evan says, adding that when he lived in Seattle, he allowed the wind outside to cold down the beans. 

“Now, I use a small sieve and fan to blow air through the coffee. This also helps remove some chaff. In the Behmor [1600, a home coffee roaster], there’s an automatic cooling program, but I tend to take the drum out so that the beans will cool even faster.”

Once the roasted beans reach room temperature, they can be stored. “Heat, light, and oxidation are the enemies of fresh coffee, so anything you can do to avoid those is good,” Evan tells me.

“Technically, the best way is to store coffee in a sealed, foiled-lined bag. But if you don’t have a supply of foiled-lined bags and a heat sealer, storing your roasted coffee in a cool, dark place in an airtight container will be just fine.”

Don’t brew your coffee straight away; you’ll need to let it degas first. “Ideally, I like to wait at least three days,” Evan says. “For darker roasts, you’ll want to brew coffee a little closer to the roast date, no later than day 10 preferably. 

“For medium or light roasts, I wouldn’t wait longer than a month. Some very dense coffees that were roasted light, like a Kenya or Ethiopia, might taste best at least two weeks past the roast date! That said, know your coffee and brew often.”

Credit: Gaia Schirru

How to Avoid Common Home Roasting Errors

While home coffee roasting is relatively easy, there are several easy-to-make mistakes that can spell disaster for your beans.

Don’t be married to your roast time; you may need to change it at times. For example, roasting outside can mean your machine needs longer to warm up. Failing to adjust to this could lead to underdeveloped, under-roasted beans. 

The batch size can also affect the roast time and ideal temperature. Evan says, “You may be using such a large batch that the beans won’t absorb heat evenly in the roaster. Or, you may be roasting so fast that not all the beans are able to achieve a proper level of browning.

“Try balancing your batch size and heat application until you get a long enough development time to even out your roast. If your roast time is very long, and the coffee is still uneven, try reducing your batch size!”

Using the highest temperature setting to achieve a faster roast time can result in scorched beans. Bear in mind, as well, that a thermometer can measure the air temperature inside the roaster but not the temperature of the beans themselves. Pay attention not just to your readings but also the colour and aroma of the coffee, as well as first and second crack.

Evan stresses the importance of cleaning your roaster. Chaff and oils can build up, causing issues for future roasts and potentially even fires. “Keeping everything clean will keep your coffee tasting great,” he says.

Mistakes can easily happen if you get distracted during roasting or are tempted to multitask. “Don’t walk away from your roaster,” Evan says. “A roast can change very quickly, and even if you’re attuned to your machine, you’re still playing with fire if you look away to do something else. Always keep an eye on your roast.”

Credit: Neil Soque

How to Improve Your Home Roasting 

Feeling confident with the basics and looking to learn more? This is when the fun starts.

If you’re currently oven roasting or using a popcorn machine, try investing in a home roaster – it will give you more control over your roast and allow you to start experimenting. 

“Practice makes you better,” Evan says. “There is no perfect roast, and that’s the fun of it! You’re going to find something to improve in each roast that you do, and there’s no shame in that.”

Stay consistent with your variables so you can better understand the impact they have. Try altering just one factor at a time to see what happens and how it affects the coffee’s flavours and aromas.

Keep a roasting journal. “Every roast you do should be documented so that you can look back to see what worked best,” Evan says. “You’ll begin to see patterns, and be able to predict how your coffee will react to the roasting process.”

The more experienced you become, the more you’ll understand what’s happening during the roast. Evan recommends “getting to know your machine and your coffee” so you can better recognise and understand things such as first crack.

Roast a wide variety of coffee origins, varieties, and processes so that you can better understand your capabilities. Something that might not have a significant impact on a Guatemalan coffee might dramatically alter the profile of a Rwandan. 

And finally, be realistic. “You’ll never make a Colombian coffee taste Ethiopian or a Brazilian coffee taste Kenyan through roasting,” Evan tells me. “Get the best out of your coffee, but don’t expect alchemy!”

Credit: Evan Gilman 

Home roasting might seem like an intimidating step, but you’ll find that it’s surprisingly easy – not to mention fun. Roasting your beans allows you to create your own tailored product, and it’s incredibly rewarding. 

As Evan says, “Enjoy yourself! Getting closer to our food and beverages gives us another level of appreciation.”

Enjoyed this? Read A Home Roaster’s Guide to Buying The Right Green Coffee

Please note: This article has been sponsored by Royal Coffee.  Featured photo credit: Evan Gilman 

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