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Coffee Roasting

Home Coffee Roasting Guideline

Home coffee roasting is as simple (or as technical), as you want to make it.

You can roast in your oven, re-purpose a popcorn popper, use a skillet or buy an actual coffee roasting appliance. Whatever method you use, you will be on your way to drinking much better coffee.

The basic process is simple: use heat to turn green unroasted coffee into brown roasted coffee. Roasting times vary, depending on the method and batch size, but you can expect the process to last about 10 minutes for smaller batches and about 16 minutes for larger batches.

Step 1: Choose Your Roaster

There are many ways to roast coffee. The method you choose should be influenced by how much roasted coffee you need and how much money you want to spend. Whether you choose a D.I.Y. approach or a small appliance depends mostly on if you want more or less automation.

D.I.Y methods are affordable and accessible.

We think using an electric popcorn popper is the best of the DIY methods. You can also use a skillet, a stovetop popcorn popper or a cookie sheet in your oven – while these methods are popular among home roasters, we think it requires a bit of experience to achieve good results.

Hot Air Popcorn Popper Instructions (Recommended)
Stovetop Instructions
Oven Roasting Instructions

Home Coffee Roasting appliances offer coffee specific features.

Depending on the model, machines made for home coffee roasting may offer chaff collection, smoke reduction, timers, temperature control, airflow regulation and digital automation. There is no “best” roaster per se, but there is a best one for you depending on how much coffee you want to roast per batch and how large of a machine you want to have sitting on your counter.  Air roasters are generally smaller, roast evenly without scorching, and are better for smaller batches. While drum roasters often roast more, these machines are typically larger, require more attention and generate more smoke.

Step 2: Choose Green Coffee

We always have a few dozen coffees to choose from so you shouldn’t have a problem finding beans that make your taste buds happy.

We suggest purchasing any cheap green bean to get started. Buy bean from multiple origin for better result. Starting off with a multiple origin is an best way to start roasting and become familiar with origin flavorOrigin Flavor is a term we use to describe coffee flavors that are intrinsic to a particular coffee from a particular origin, and in contrast to flavor we term “Roast Taste”: Origin Flavor is a More characteristics. From there, your palate will have an idea of which ones are more delicious. This will help you narrow down which coffees you want to buy next.

Step 3: The Roasting Process

Understanding the different stages of the roast will help you control the flavor of your cup and appreciate how different roasts result in different cup flavors.

Here’s an image that provides an overview of the process:

Coffee bean chart I created many years ago showing the degree of roast of each stage in the roast process from green to brown to black. The gray stripes on either side of this image are a photographic 18% gray card. To my delight, I have found my photo here shared around the world, sometimes even with credit! I have seen it translated into many languages and edited with improvements. Cool!

163 degrees C – Coffee bean macro image yellowing stage of roasting

Yellowing: For the first few minutes the bean remains greenish, then turns lighter yellowish and emits a grassy smell.
Steam: The beans start to steam as their internal water content dissipates. This is also known as the drying stage.

Just before First Crack – 200 degrees C – Coffee bean macro image browning stage of roasting

First Crack: The steam becomes fragrant. Soon you will hear the first crack, an audible cracking sound as the real roasting starts to occur: sugars begin to caramelize, bound-up water escapes, the structure of the bean breaks down and oils migrate from their little pockets outward.

Ending of First Crack – 218 degrees C – Coffee bean macro image during roasting

First Roasted Stage: After the first crack, the roast can be considered complete any time according to your taste. The cracking is an audible cue, and, along with sight and smell, tells you what stage the roast is at. This is what is called a City roast.

Ending of First Crack – 223 degrees C – Coffee bean macro image during roasting

Caramelization: Caramelization continues, oils migrate, and the bean expands in size as the roast becomes dark. As the roast progresses, this is a City + roast. Most of our roast recommendations stop at this point. When you are on the verge of second crack, that is a Full City roast.

Start of Second Crack – 228 degrees C – Coffee bean macro image during roasting

Second Crack: At this point a second crack can be heard, often more volatile than the first. The roast character starts to eclipse the origin character of the beans at this point and is also known as a Vienna roast. A few pops into second crack is a Full City + roast. Roasting all the way through second crack may result in small pieces of bean being blown away like shrapnel!

Ending of Second Crack – 240 degrees C – Coffee bean macro image during roasting

Darkening Roast: As the roast becomes very dark, the smoke is more pungent as sugars burn completely, and the bean structure breaks down more and more. As the end of second crack approaches, you will achieve a French roast.

Extremely Dark – 252 degrees C – Coffee bean macro image during roasting

Ack!! Too Late!: Eventually, the sugars burn completely, and the roast will only result in a thin-bodied cup of “charcoal water.”

Credited to: sweetmarias

What happens during the roast?

How does a dense, flavourless seed transform into a delicious, brittle, aromatic coffee bean that we can dissolve in water and enjoy? Heat! Adding heat to a coffee seed creates an incredible amount of change.  But what happens and when?  Last week we dove into our 3-part series taking you behind the scenes to give you a breakdown on what it means to roast coffee, how we approach it, what is actually happening to the coffee during a roast, and what are some of the variables we manipulate and control to make all that magic happen. This week, we’re learning all about the different stages of the roast, how the roast progresses and the sensitive chemical reactions and colour changes we carefully monitor to bring out the flavours we love in a coffee and avoid the ones we don’t.  

let’s roast…

Stage 1 – Drying

Green coffee is typically between 10-12% moisture, and in order to begin roasting and moving through the necessary chemical reactions the seed needs to shed the majority of that moisture which takes a significant amount of energy. Once the seed has released enough moisture, it will begin to transition from a green to yellow colour and enter the next stage of the roast.

The ‘drying phase’ of the roast is critical in setting the roast up for success, particularly when executing profiles of different total roast times and meeting other goals like the time the coffee will spend in different stages, the timing of first crack, development time, and end temperature throughout the remainder of the roast. The ‘drying phase’ can also have a large impact on the pattern or trajectory of how the roaster is transferring heat to the coffee.

Drying & Flavour – Quicker drying times will result in a more floral, bright cup, where longer drying times can yield a more sweet, balanced, and sometimes less nuanced cup.

Stage 2 – Maillard Reactions

Once enough moisture has been released from the bean the “maillard” stage begins. This starts when the beans begin to turn yellow and the aromatics transform from a green and vegetal quality to become more like hay or dried grass. These complex chemical reactions occur between the amino acids and reducing sugars in the coffee and have a major influence on the final cup character and the brown colour of a roasted coffee. The coveted caramelization of the sucrose in the coffee also begins during this stage producing the caramel tones, bitter compounds and some of the organic acids we all love in roasted coffee. This stage also is thought to contribute to the texture and body of the final cup due to the creation of melanoidins. The Maillard stage comes to a close with the onset of “first crack” but the Maillard reaction continues on for the duration of the roasting process.

Maillard Reactions & Flavour – Shorter times in the Maillard can result in more clarity, the perception of a lighter texture, and less complex sugar browning tones while longer times spent in this stage can allow for more chemical reactions to occur promoting more complex sugar browning tones as well as a heavier body and texture.

Stage 3 – First Crack & Post First Crack Development Time

The momentous first crack marks the beginning of development time. First crack occurs as water vapour builds up in the cellular structure of the coffee and pressure increases dramatically. Eventually, the pressure can no longer be contained and the coffee rapidly expands and releases steam into the environment. It’s called First Crack because an audible cracking sound can be heard similar to the popping of popcorn. This rapid expansion of the coffee allows for heat to penetrate the center of the beans more easily.

During development time, many important and complex processes and reactions are occurring simultaneously. As the temperature of the coffee increases and the time after First Crack progresses, the Maillard reaction and sugar caramelization continue along with the degradation of existing acids, the formation of new acids, and the progression of the colour and roast degree of the coffee. The relationship between the temperature of the coffee and its environment to the amount of time spent roasting after First Crack will dramatically impact a coffee’s final colour and roast degree as well as the flavour in the cup by affecting the acidity, sweetness, balance, body, and bitterness of the coffee.

Development Time and Flavour – A short development time will yield a cup with more acidity and vibrancy and often less sweetness, bitterness from roasting, and body. A longer development time will degrade the acids inherent in the coffee first and develop more bitterness, sweetness, and body imparted by the roasting process. In extreme cases, a very short development time leads to intense acidity and bitterness from chlorogenic acid that hasn’t been broken down enough as well as vegetal, metallic, and hay-like flavours.

Stage 4 – Cooling

Once the coffee has gone through its desired profile and reached its end temperature it’s extremely important to cool the coffee to room temperature as quickly as possible. If the coffee stays warm too long, it can dull the flavours or also continue to cook further and create over roasted characteristics. Our roaster drops the coffee into a large cooling tray where it blasts air and stirs the coffee continuously too cool quickly.