X
Table of Contents
X
Table of Contents
Contents
By
Ru Chen
Key Takeaways
Before your morning cup of coffee arrives in your hand, it has already undergone a long, transformative journey filled with chemical reactions. The humble coffee bean was first roasted around the 1400s. Since then, roasters have learned how to make coffee as we know it today using the Maillard reaction, caramelization, and other scientific processes.
From the crackling of beans to the release of aromatic oils, let’s break down the science behind coffee roasting and how each flavor is developed.
Coffee roasting is both an art and a science. It involves bringing the beans to high temperatures before cooling them down. ¨Plenty of different techniques are used throughout the roasting process to obtain a precise flavor, aroma, and roast type.
The first essential stage of roasting is to dry the coffee beans. This takes place between 320°F and 392°F, causing moisture within the beans to evaporate. Coffee beans commonly undergo the natural sun drying method and the washing method.
2. Browning
Temperatures further rise during the browning stage. With the rich aroma of the coffee beans thickening in the air, you’ve reached the browning stage. The coffee beans go through the Maillard reaction: a chemical reaction that occurs between reducing sugars and amino acids. The first crack occurs around 385°F as there is a loud crackling noise, marking that most of the water has evaporated.
3. Development
The development stage is the time between the first crack and the end of roasting.
If desired, a second crack occurs around 435-450°F, which is usually a louder pop than the first crack. Gases and oils previously trapped inside the beans are released after the bean’s cell waters break down from the heat.
4. Cool Down
The beans need to finally be cooled so they retain their aroma and quality. Cooling methods vary, with air cooling and water cooling being the two most popular techniques.
In air cooling, the drum or cooling unit will pass ambient air through the roasted coffee beans to ensure there is no extra moisture. Fewer beans are wasted, but the process takes longer than water cooling.
In water quench cooling, cool water is sprayed onto the roast, lowering the temperature of the roast. Some moisture will be left, but water-cooled roast tends to be more aromatic.
Coffee roasters carefully monitor and control parameters that can affect the roasting process. Here are the main factors that determine the success of the roasting process and the flavor of the batch.
Time: The longer the beans are roasted, the darker the roast becomes. Each stage of the coffee roasting process needs to be well-timed, and many coffee roasters experiment with timing to develop different bean flavors and aromas.
Temperature: The heat of the roast needs to be precisely controlled. If the coffee beans aren’t heated up properly, it can result in disappointing flavors. Improper temperatures may “stall” the roast, leading to a baked or flat bean.
Airflow: Airflow serves to control the heat within the drum that rotates over the heat source. Proper airflow regulates convection and ensures that the volatile oils preserve their characteristics necessary for a good, balanced roast. Excessive airflow can cause a sour taste, whereas too little airflow can “stall” the roast and cause a smoky flavor.
Weather: External environmental factors affect outdoor roasters more than indoor roasters, though all roasters need to consider humidity and pressure levels. Cold wind and weather can make roasting take longer.
Maillard reaction: Between 280–330°F, the carbonyl groups of the sugars and the amino groups of the proteins react with each other, forming flavor and aroma compounds. The 2-furfurylthiol compound produces the famous coffee aroma, but hundreds of other compounds are created as well. A shorter Maillard duration typically creates more sweetness and acidity in the coffee’s flavor profile.
Strecker degradation: This chemical reaction is a part of the Maillard reaction. It essentially involves amino acids being converted into aroma compounds like aldehydes.
Production of melanoidins: These large molecules are responsible for turning the green beans brown, while also contributing to how the coffee beans’ mouthfeel and texture.
Caramelization: Carbohydrates being broken down into simple sugars enables the caramelization process. As the sugars in the coffee beans start to caramelize, the sugar browns and releases aromatic, acidic compounds. Most of the sucrose within the beans will be converted to caramelized compounds.
Pyrolysis: At around 428°F, the coffee beans are heated above their decomposition temperature. They will release carbon dioxide due to the heat causing this chemical change of pyrolysis. The bean shifts to a medium brown, losing ~13% of its weight. Volatile compounds are produced and a solid residue of carbon and char will be left behind.
The sugars (sucrose, glucose, and fructose) play an essential role in the Maillard reaction. The amino acids of proteins react with these sugars to create the compounds that are responsible for the flavor and aroma of the roast.
During the roasting process, lipids undergo autoxidation and decomposition. They contribute greatly to the aroma and flavor of the final coffee.
Over 800 volatile organic compounds (VOCs) are emitted by roasted coffee. Many VOCs contribute to the aromatic and sensory properties of the coffee. Here are the aromas of certain volatile organic compounds that are formed during the development stage of coffee roasting.
* Aldehydes: Fruity
* Furans: Caramel
* Pyrazines: Earthy and nutty
* Sulfurs (e.g. 2-furfurylthiol): Classic coffee aroma
* Guaiacol: Smoky
* Ketones: Buttery
How the coffee beans are roasted greatly determines the flavor profile of the resulting coffee. Roasts can be more bitter, acidic, fruity, or floral depending on the duration and temperature of the roasting process. Let’s go into depth on the different roast types of coffee.
You can hear the first crack around 385 °F, which signals the start of a light roast as most of the water has evaporated. The light roast is almost ready as beans are roasted to 400-410°F without their oils breaking through the surface. Lightly roasted beans have a fruity-floral flavor profile and a light brown color.
A medium roast is roasted and burned between 410°F to 428°F. It has medium acidity and a brown color. Medium roasted beans undergo a second crack around 400°F.
Dark roasts are typically roasted between 482°F and 488°F, resulting in prominent oils and the lowest acidity. In general, dark roasts lack distinctive flavors since most of the original flavor has been roasted out of the beans. Contrary to common belief, dark roasts actually tend to be sweeter because they caramelize during a longer roasting process.
Specialty roasts involve single-origin coffee beans that are cultivated and harvested from specific geographic climates. There is usually more care and meticulous attention to detail when it comes to processing single-origin coffee, which may have more nuanced and rich flavor profiles.
Experimental roasting and processing techniques are always emerging as coffee roasters face the challenge of creating a better bean. Artisanal approaches can create more interesting and complex roasts that are unique and more expensive.
Coffee clubs deliver curated coffee straight to the doorstep of club members on a recurring basis. Many clubs let you choose your preferred roast and flavor profile, such as single-origin roasts from certain regions, signature blends, and limited-edition specialty roasts. With a coffee club membership, you can also benefit from perks and coffee recommendations.
Access to specialty beans: Coffee clubs often curate and have access to specialty, single-origin beans with unique and exciting flavor profiles. Joining a coffee club can open the door to a diverse range of limited-edition and rare flavors you might not encounter otherwise.
Freshly roasted coffee: As opposed to getting coffee online or from a supermarket shelf, coffee clubs often source beans directly from reputable coffee roasters and farmers. This means you can receive the freshly roasted beans of your dreams, resulting in a superior coffee experience with each cup of joe.
Convenience: A great advantage of joining a coffee club is you can get all your quality coffee delivered straight to your door. You won’t need to spend time researching and testing different brands – coffee clubs curate the best roasts and send them to you, often with notes that explain the history and origin of the beans.
Variety: Many coffee clubs offer fantastic collections that allow you to explore different beans around the world with various themes. This variety adds a note of excitement to each mug of coffee you brew.
Sustainable practices: As the industry better understands the , coffee clubs have grown to prioritize sustainable, ethical, and green coffee production. By joining a sustainable coffee club, members can feel good about contributing to fair wages and a more sustainable coffee industry.
Education and engagement: Coffee clubs are not just subscriptions, but they also offer the benefits and features of a club. Members can gain access to communities of fellow coffee lovers where educational resources, tasting notes, brewing guides, and enjoyable conversations can be found.
When choosing a coffee club, here are the top considerations to keep in mind.
1. Subscription price
These days, it can be tough to find quality . Coffee clubs vary in price, with some starting at $9 per batch and others costing over $30. Choose a coffee club that aligns with your budget. You can also choose a cost-efficient subscription, such as the large batches offered by . The Jot deliveries are freshly brewed to 20x concentration so you only need a tablespoon.
2. Shipping frequency
Most coffee clubs send out batches on a monthly or bi-monthly basis. If you desire a different shipping frequency, try out a coffee club like Trade Coffee that lets you choose between deliveries every 7, 10, or 14 days.
3. Themes and features
If you’re looking for a splash of adventure to go with your coffee club, we recommend exploring coffee clubs with special themes and curated collections. Atlas Coffee Club is our favorite choice since it delivers freshly roasted batches from 50+ countries, along with gorgeous postcards to go with the brewing tips and tasting notes.
4. Sustainability
Consider how the coffee club takes action to create an ethical coffee sourcing and roasting process. For example, Driftaway Coffee has carbon-neutral operations and uses eco-friendly packaging.
5. Roast type
The roast type determines the flavor profile, but how do you figure out what roast you want to try? Check out the so you can get detailed insight into what coffee subscriptions you should try out next. Some clubs are better known for dark roast, whereas others lean toward perfecting their medium-roasted beans.
Every sip of coffee is possible because of a well-developed coffee roasting process. Flavor and aroma compounds are mainly produced by the following chemical reactions and changes in the beans:
Maillard reaction: Sugars and amino acids react with each other, forming flavor and aroma compounds.
Caramelization: The simple sugars brown and release acidic, aromatic compounds.
Pyrolysis: Creates volatile compounds that contribute to the distinct aroma and flavor of coffee.
Roasting coffee is a complex science that has been developed over hundreds of years, with new techniques and ideas constantly challenging the current status quo. Thanks to scientific marvels and studies, we can enjoy coffee that is light and dark and everything nice.
Ru Chen
Content Writer
Ru Chen is a content writer with several years of experience in creating engaging and well-researched articles. She mostly writes about coffee, business, digital marketing, and law. In her free time, she can be found watching horror movies and playing board games with her partner in Brooklyn.
Ru Chen is a content writer with several years of experience in creating engaging and well-researched articles. She mostly writes about coffee, business, digital marketing, and law. In her free time, she can be found watching horror movies and playing board games with her partner in Brooklyn.
