Roasting coffee at home has become increasingly popular in recent years, but it can be difficult to know where to start when you’ve never tried it before.
Here at Green Coffee Collective, we’re passionate about helping home roasters every step of the way. For coffee enthusiasts, the opportunity to craft your own blends and flavours is an incredible experience – and brings rewards every step of the way.
With that in mind, we’ve gathered a few frequently asked questions below as a beginner’s guide to help you on your road to home roasting.
We’d advise keeping notes as you go – it’ll help when replicating some of your favourite batches.
Happy roasting!
Can you roast coffee at home?
The simple answer is yes – absolutely.
Roasting is the process of heating up green coffee beans until they turn brown and develop their unique aroma and flavour.
By choosing to roast your own coffee, you’re taking control of the entire process – choosing the origin of the beans you’re roasting, deciding exactly what level you’d like to roast them to, and what flavour you ultimately prefer.
It really is your own brew!
What happens to coffee beans when they’re roasted?
Roasting involves increasing the temperature of the beans to bring out their flavours. The process generally includes a drying phase, a first crack (for light to medium roasts), and potentially a second crack (for darker roasts). Each phase contributes to the development of flavours.
When green coffee beans are initially heated up, their cell structures begin to break down and they lose their moisture.
From there, a series of chemical reactions take place – including The Maillard Reaction. This happens at around 150°C, where the heat causes amino acids and reducing sugars in the coffee beans to react, creating new flavours and aromas – as well as a yellowing and then browning of the beans.
A major milestone in the roasting process is the first crack, where carbon dioxide and steam combine and the pressure cracks the bean open. From there, roasters often go on to apply more heat to vary the flavour and intensity, but the coffee is drinkable from then on.
Depending how long you continue to apply heat, you may then get a second crack. Filter coffee roasters will usually stop the process before that, as the second crack can create more of a bitter taste.
Can you roast coffee using normal kitchen appliances?
There are many ways of roasting coffee beans at home, but perhaps most effective is using a coffee roasting machine.
However, if you’re new into it and want to keep initial costs down, you can roast beans using a frying pan, the oven, a popcorn maker, or even an air fryer.
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Hot air popcorn maker
Popcorn machines are considered the more reliable home appliance to roast with, as they help to achieve a more even result compared to heating in a frying pan or in the oven.
The constant heat and circulation give an even result, while the machine helps to contain any emissions. It’s recommended you do it outside, however, as chaff (the dried skin from a coffee bean, which comes off as you roast) will be blown off the coffee throughout.
A roast will typically take between 4-10 minutes to reach the first crack using a popcorn machine.
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Frying pan
For stovetop roasting, a heavy-duty pan or skillet is essential. Cast iron skillets are particularly popular because they retain and distribute heat evenly, which is crucial for achieving a consistent roast.
If you do use a frying pan, ensure the beans are spread as evenly as possible and stir them constantly while heating, always listening for that first crack.
Unfortunately, the beans are often roasted very unevenly when using a pan, which can impact flavour. There are also safety concerns such as beans popping up at you during the first crack, and a lot of smoke, so ensure you wear safety goggles where possible and have a good ventilation system.
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Oven or air fryer
Line a baking tray with baking paper. Try to choose a quality baking tray with a rim to keep the beans contained and make stirring easier. An aluminium or stainless steel baking tray will provide even heating, helping you achieve a more uniform roast.
Line up the beans evenly. When heating, you’ll need to open the door and turn the beans every few minutes to try and ensure they’re roasted as evenly as possible.
This method is considered safer than pan frying, and there will be significantly less smoke, but you’ll need to keep on top of cleaning your oven between roasts.
You can also roast beans using an air fryer, in a similar way to the oven.
Just remember, good ventilation is crucial when roasting coffee using all of the above methods.
What equipment do I need to roast coffee at home?
Depending on your roasting method, you’ll need to start with your basic roasting equipment – whether that’s a roasting machine or an appliance mentioned above, and a good ventilation system.
It’s also handy to have a bowl or tray nearby to catch chaff.
Whether you're a beginner or looking to refine your roasting skills, having the a few extras, however, will ensure that you can roast coffee beans to perfection. Here’s a few:
- Home roasting machine
- Measuring tools
- Cooling tray or colander
- Airtight bean storage containers
- Temperature and moisture monitoring tools
- Cleaning and maintenance equipment
You can find out more in our essential equipment guide HERE.
Do I need a magnet to ensure there’s no metal in my green beans?
Although you can check your coffee with a magnet or hand sort, if you purchase coffee from a reputable supplier then you shouldn’t find any foreign matter.
That being said, it’s not 100% accurate, and the less you pay for your beans typically correlates to a lower quality, increasing the likelihood you’ll need to check for foreign matter.
What are the best home coffee roasting machines?
If you’ve decided to purchase a dedicated roasting machine. There are various types of home roasters, including air roasters, drum roasters, and stovetop roasters. Each type has its own advantages and disadvantages.
When choosing what’s right for you, we recommend you start by assessing the machine’s ability to handle your production needs, control temperature and airflow, save energy and adjust roasting profiles:
- Drum Roasters: These machines use a rotating drum to heat coffee beans evenly, ensuring consistency and control in the roasting process. Ideal for small to medium-scale operations, drum roasters are reliable and produce consistent results.
- Fluid Bed Roasters: Also referred to as hot air roasters, these machines suspend coffee beans in a stream of hot air, resulting in even roasting. They offer a faster and more energy-efficient process than drum roasters, highlighting the unique characteristics of specialty coffee beans.
- Combination Roasters: Hybrid machines that blend features of drum and fluid bed roasters, providing flexibility and control. Designed for roasters seeking versatility, combination roasters enable experimentation with various roasting techniques.
You can see a more in-depth guide to the equipment you’ll need HERE.
What are the best green coffee beans for home roasting?
Historically, finding where to buy green coffee beans online for roasting was challenging, with limited options.
In recent years, however, several online green coffee bean suppliers have emerged, simplifying the sourcing process for roasters.
A major advantage of buying green beans to roast at home is the longer shelf life they have. In fact, green beans can stay fresh for up to a year – as opposed to roasted beans which tend to lose their aroma and flavour quicker.
The Green Coffee Collective offers the same high-quality beans to home roasters as it does to professionals, with flexible purchase options starting from 1kg.
We’ve pulled together a guide to get you started HERE.
How do I assess the quality of green coffee beans from home?
Buying online always comes with its risks, so before purchasing, it's crucial to vet online green coffee bean suppliers with the same due diligence you'd apply to traditional models.
Established roasters can provide insights, and online reviews are invaluable for newcomers. Ensure that the suppliers you choose align with your ethical values and sourcing standards.
Every roaster, including those at home, should look out for a few warning signs:
- Broken or chipped beans
- Discolouration
- Damage
- Defects or debris among the beans.
Beyond that, it’s possible to get a good idea of quality based on the beans’ density. Denser beans are generally higher quality.
To delve deeper into bean selection, consider the Coffee Quality Institute's (CQI) Q Grader system, which evaluates coffee quality.
For the coffees listed on our site we offer a cupping report, which covers the industry-standard for assessing coffees used by the Specialty Coffee Association (SCA). This format is used to give a coffee a score out of 100 with 80-points or higher categorising coffee as “speciality”.
The SCA also grades coffee on a scale of 90–100 as Outstanding, 85–89.99 as Excellent, and 80–84.99 as Very Good.
What are cupping scores and what do they actually mean?
Coffee cupping is used by coffee professionals and enthusiasts alike to score and compare the quality and flavour of different coffee beans.
The results then help producers, importers and roasters to understand the best coffees in their chosen area of the industry.
The Speciality Coffee Association (SCA) recommends a coffee-to-water ratio of 8.25 grams of coffee per 150ml of water, when organising a cupping session.
The SCA also has a standard scoring system which most people will follow, whether professional roasters or home roasters. You can see that here. Each sample is scored on elements like its flavour, aroma, acidity and fragrance.
Some may also follow the Coffee Taster’s Flavour Wheel, developed by the SCA and the World Coffee Research (WCR) - which you can see here.
How should I store green coffee beans?
The trick to achieving that coveted barista-level cup of coffee at home lies in storing green coffee beans correctly. Even the finest beans can lose their magic if improperly stored, leading to a flat, uninspiring cup.
You can see a guide which highlights the crucial dos and don'ts of green coffee bean storage, backed by expert insights to help you preserve the essence of your beans, HERE.
How long will green beans keep for, if buying in bulk?
Some green beans can be stored for up to a year without going stale, so they have a much longer shelf life than roasted beans.
It’s important to store them in a cool, dark and pest-free environment to avoid deterioration in quality.
How fresh should coffee beans be before roasting?
As a general rule, the fresher the green beans you purchase, the better the roast is likely to be. But as green beans can stay fresh and avoid deterioration for up to six to 12 months, you should be fine anywhere within that window.
That being said, some coffees don’t start to “open up” until much later after being processed. One of our coffees, for example, didn’t get to tasting its best recently until around seven months after it had arrived. Therefore, it’s always best to do your research and chat to your supplier for their top tips.
What temperature is best for roasting coffee at home?
Coffee roasting machines will each come with their own instructions, while popcorn makers will usually have a main heat setting.
However, if you’re roasting in an oven, it’s recommended you preheat the oven to at least 240-250℃.
Ensure good ventilation during the roasting process, as it can produce a lot of smoke and chaff.
How long do you roast coffee beans at home?
This will depend entirely on what equipment you use and the results you’re after. The key is to listen out for the first crack – which can often happen within around six to 10 minutes.
If you’d prefer a medium roast with little bitterness, it’s recommended you stop heating between the first and second crack.
How long do you leave coffee after roasting?
Once the beans reach the desired roast level, quickly cool them to halt the roasting process. This can be achieved by transferring them to a cooling tray or colander and using fans or ambient air.
Allow the beans to rest for a day or two to allow gases generated during roasting to escape. This period, known as degassing, enhances the coffee's flavour.
What is degassing?
After roasting your coffee, it’s essential to let your beans rest—a process known as degassing. During roasting, coffee beans release carbon dioxide (CO2), and much of this gas remains trapped within the beans immediately after roasting. Degassing allows this gas to escape gradually, which is crucial for brewing, particularly with methods like espresso.
For espresso, it’s best to wait four to six days, or even up to 10-14 days, for the beans to degas fully. Filter coffee has a bit more leeway, usually requiring just three to four days of resting. However, a minimum of 12 hours of resting is recommended before brewing any coffee to avoid unpleasant flavours.
Where and how should I store roasted coffee?
Store the freshly roasted beans in airtight containers in a cool, dark place. Avoid exposing them to oxygen, as this can cause the coffee to lose its freshness.
Several environmental elements significantly impact the freshness of coffee beans:
- Air Exposure: Oxygen starts an oxidation process that deteriorates the beans’ essential oils, leading to flavour loss. This process can commence two weeks after the roasted beans, highlighting the importance of immediate and airtight storage solutions.
- Moisture: Given their high absorbency, coffee beans are particularly susceptible to moisture. This can lead to undesirable musty or mouldy smells, signalling that the beans are no longer in their prime condition.
- Temperature: The freshness of beans is heavily influenced by the temperature at which they are stored. Extreme temperatures can hasten the aging process. Ideally, beans should maintain a crisp texture, indicating they have been stored optimally.
Find out more in our guide to storing roasted coffee HERE.
Can I freeze roasted beans for keeping?
Yes, you can freeze roasted coffee beans, but there are a few factors to consider:
- Ensure the beans are well sealed and there’s limited chance for oxygen and moisture to reach them.
- Freezing beans increases the chance of them moistening, so airtight storage is key.
- Always defrost your beans thoroughly before using them.
What factors influence flavour during coffee roasting?
There are a number of factors at work here, each of them having direct impacts on your results:
- Roasting time and temperature: Higher temperatures and roasting for shorter times tend to result in lighter roasts, while lower temperatures and longer times result in darker roasts. A light roast retains more of the bean's natural characteristics, with bright acidity and floral notes. As you progress to medium and dark roasts, the flavour evolves, offering rich, full-bodied profiles with chocolate, nuts, and spices notes.
- Airflow and environment: Proper airflow ensures even roasting and prevents scorching. As mentioned above, coffee roasting machines and popcorn makers tend to be best for this.
- Bean origin and characteristics: The beans’ origin, variety, altitude, and soil composition contribute to their unique flavour profiles.
- Moisture content: Moisture content influences the roasting time and the final flavour of the coffee. The less moisture, the better.
How long do home roasted coffee beans last?
Roasted beans start to lose their flavour and aroma after just a couple of weeks unless sealed well in an airtight bag – but they can last for a few months if stored well.
Generally, the coffee will taste fresher and have the most flavour the closer to the roast, so consuming them quickly and roasting smaller batches is best when working from home.
Can I roast more than one coffee in a roasting session?
Yes, but consider the capacity of your roasting machine or appliance and whether you’re trying two different types of roasts.
Some appliances may also need a thorough clean between them.
How will the quality of my roasted coffee beans compare to those of a similar price which are already roasted?
Generally, the fresher the roasted coffee beans, the better the flavour, so there’s nothing quite like roasting your own blends.
Some coffee may be better quality if it’s from a certain origin, or if it’s been roasted using professional equipment, but it’s entirely down to your taste and preference.
However, it’s worth noting that a professional roaster will have a lot more experience with dialling in a roast, having tested multiple options and combinations of temperature and roast time to find the optimum result - all while using a specialist coffee roaster. While you won’t have this level of control at first, it’s something you can build up with time.
Is it cheaper to buy coffee or roast coffee at home?
The cost of roasting coffee from home will depend on the equipment you use and the amounts you’re working with - but the longer you continue, the more likely you are to make up any equipment costs quickly.
If you’re all equipped, then it’s only the green beans and electricity you’re paying for, so it’s likely cheaper to do it from home than spending money on coffees from cafes and out and about.
How can I ensure I’m safe when roasting at home?
The number one rule when roasting coffee at home is making sure you’re always doing it in a well ventilated area. That may be outside, on a balcony, or in an open room with a good ventilation system.
If you’re using a popcorn machine, it’s worth remembering to check for any mesh at the bottom which may catch fire too.
When using coffee machines, It’s also important to ensure you keep them well cleaned. Fires usually start due to poor air flow and/or chaff and tar build up in the machine.
A good way to ensure you keep on top of the safety side of things is to keep good records of your roast times, temperatures and cleans. It’s also worth always having a water hose and fire extinguisher nearby.
How can I be consistent with my roasts and record keeping?
A good rule of thumb is to keep digital records for all your coffee roasts, ensuring you update them with times and temperatures immediately after each one.
As soon as you start missing the odd roast, you can immediately fall behind and either risk safety, or forget some of your favourite roasts.
Good information to store each time can be:
- Name or unique identifier of the coffee
- Origin of green beans
- Temperature of roast
- Time taken to roast (including first and/or second crack)
- Cooling time
- Storage
If you purchase a dedicated roasting machine you’ll have access to software that will provide you with far more comprehensive information than what is listed above, but for the average home roaster the information above should give you a good idea of what’s working.