Behind the Beans: Unveiling the Intricacies of the Coffee Roasting Process

Behind the Beans: Unveiling the Intricacies of the Coffee Roasting Process

Espresso coffee, a beloved beverage that powers our mornings and fuels our creativity, owes much of its allure to the roasting process. This transformative journey from green coffee beans to aromatic roasted coffee is both an art and a science. Understanding the intricacies behind the beans unveils a world of flavour profiles, roasting techniques, and, ultimately, the magic in your cup.

Let’s embark on this journey, exploring the process behind turning green coffee beans into richly roasted coffee that captivates the senses of coffee drinkers around the globe. Our guide aims to not just inform but also to inspire your imagination and help you appreciate the nuances of coffee roasting, whether you’re a seasoned aficionado or a curious newcomer.


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Understanding Coffee Roasting

The Basics of Coffee Roasting

Coffee roasting is the process of heating coffee beans to bring out the rich flavours and aromas locked within the green coffee bean. It’s a craft that dates back centuries, evolving from simple, open-fire roasting to sophisticated, controlled methods. Roasting coffee transforms the chemical and physical properties of green coffee beans into roasted coffee products.


Types of Coffee Roasts

Roasted beans come in a spectrum of colours and flavours, from lightly roasted coffee, which highlights the bean’s intrinsic characteristics, to dark roasted coffee, known for its bold, fuller body and smoother flavour. Each roast level, including light, medium, medium-dark and dark roasts (often referred to as French roast, Vienna roast, or Italian roast), offers unique flavour profiles suited to different coffee drinkers’ palates and preferred brewing methods.


An espresso shot in a pouring glass, a thick, golden crema atop a dark liquid.

The Coffee Roasting Process: A Step-by-Step Guide

Selecting the Right Green Coffee Beans

High-quality coffee begins with the green coffee bean. Selecting the right beans involves considering the bean’s origin, variety, and quality. Specialty coffee roasters often seek out beans with specific flavour profiles to match their roasting style and the desired outcome in the cup.


Pre-Roasting Preparations

Before the roasting starts, beans are cleaned and sorted to remove impurities. The moisture content of green coffee plays a crucial role in the roasting process, affecting how the beans react to heat and the development of flavours.


Roasting Stages Explained

The roasting process comprises several key stages, from the drying stage, where beans lose moisture, through the Maillard reactions, where sugars and amino acids react to form complex flavours, to the first and second crack, signalling different roast degrees. Mastering the roast time and temperature allows coffee roasters to craft the desired roast profile for each batch.


Roasting Process Stages

The stages of coffee roasting contribute significantly to the coffee’s final taste, unfolding in several key phases:

Moisture Loss Phase: In the roast’s initial phase, moisture is driven out of the beans, changing their colour from green to yellow while releasing a grassy scent.

First Crack: The beans experience their initial crack as the heat increases, producing a sound similar to popcorn popping. This expansion and sugar caramelisation phase typically signifies a light roast level.

Flavor Development Stage: Following the initial crack, the beans enter a crucial flavour development stage. Here, roasters meticulously control the heat to enhance specific flavour qualities, leading to a spectrum of roast levels from medium to dark, depending on the targeted taste.

Second Crack: (If Applied) For beans aimed at darker roasts, a second crack may occur, characterised by the release of surface oils, giving the beans a glossy look.

Rapid Cooling: Once the desired roast level is achieved, quick cooling is employed to stop the roasting, crucial for avoiding over-roasting and preserving the developed flavours.


How do coffee roasting profiles affect the final flavours?

Each type of roast affects the flavour and characteristics of the coffee beans. Light roasts, such as Cinnamon and Half City, resulting in a light brown colour and a more mild-bodied flavour.

Medium roasts, like City and American, produce a medium brown colour and a traditional, flavorful cup of coffee. Medium-dark roasts, such as Full City, lead to a rich, dark brown colour and modest bittersweet aftertaste. Dark roasts, including Espresso and French, yield nearly black, oily beans with a strong flavour and heavy mouthfeel.


Roast Profile and Roasting Degrees

As we’ve touched upon earlier, coffee roasting leans more towards an art form than a strict science. Roasters must juggle numerous variables to consistently deliver the results they seek.

Degrees of Roast

Using a Drum Roaster: As discussed, roast levels are primarily distinguished by the roasting temperature, with the bean’s colour change—from yellow to darker browns—serving as a key indicator. As roasting progresses, oils start to surface on the beans. However, relying solely on visual cues isn’t always precise, thus a mix of bean temperature, aroma, colour, and sound is employed for more accurate control over the roasting process. Sound, in particular, plays a crucial role as an indicator during roasting.

Roast Profile: The roast profile is shaped by both the temperature and duration of roasting, emphasising temperature increase (how and when the beans are heated) and how the roasting temperature is decreased over time. This profile changes with the bean variety, influencing the coffee’s taste. Roasting times can range from 15-30 minutes at temperatures between 180°C and 250°C.

Alongside the roast profile, the origin, type, and processing of the beans also play a crucial role in determining taste—other factors include the moisture content of the raw beans, batch size, airflow, drum rotation speed, and cooling time. Special attention is given to two critical temperature points known as “Cracks” during roasting:

  • The “First Crack” occurs at 200-202°C, resembling the sound of popping popcorn, albeit quieter.
  • The “Second Crack” is reached at 224-226°C, marked by gases released during roasting.


Overview of Roasting Degrees

Light Roast

  • Cinnamon Roast (196°C): A very light roast right at the first crack, characterised by a light brown colour and pronounced acidity.
  • New England Roast (205°C): A moderate light brown colour with complex acidity.

Medium Roast

  • American Roast (210°C): Medium brown, occurring at the first crack, slightly sweeter than a light roast, with a full body and acidic notes.
  • City Roast (219°C): A medium shade of brown offering a balanced body with noticeable acidity.

Dark Roast

  • Full City Roast (225°C): Medium dark brown, sometimes with an oil sheen, beginning at the second crack with a pronounced roast character.
  • Vienna Roast (230°C, 446°F): Moderate dark brown with light surface oil, offering a bittersweet, caramel flavour with muted acidity.
  • French Roast (240°C, 464°F): Dark brown and oily, presenting a bittersweet caramel flavour with reduced acidity.
  • Italian Roast (245°C, 473°F): Nearly black and shiny, where burnt tones are more pronounced and acidity is almost eliminated.


The Science Behind the Beans

Chemical Changes During Roasting

Roasting coffee beans triggers a series of chemical changes. Acids break down, sugars caramelise, and aroma compounds form, contributing to the coffee’s flavour and aroma profile. Understanding these chemical reactions is crucial for roasters aiming to achieve particular coffee flavours.

The main chemical reactions include:

  1. Maillard Reaction: This non-enzymatic browning reaction occurs between sugars and amino acids, leading to the formation of flavour and aroma compounds, and changes in colour and nutritional content. It typically begins at around 150°C and is essential for the development of coffee flavour.
  2. Caramelisation: This process, occurring from 170-200°C, leads to the browning of sugars and the release of aromatic and acidic compounds, contributing to the flavour profile of the coffee.
  3. Pyrolysis: Although coffee roasting avoids charring, it does undergo chemical changes associated with pyrolysis, which is the decomposition of organic material due to heat, leading to the creation of volatile compounds and the formation of new flavour components.
  4. Changes in Organic Acids: During roasting, organic acids such as citric and tartaric acids that produce fruity and sweet notes are broken down, impacting the acidity and flavour profile of the coffee.
  5. Development: This stage occurs after the first crack, where the steam build-up is released, and it is essential for the development of the desired flavours.


What is the Strecker Degradation reaction and how does it affect coffee roasting?

The Strecker degradation reaction in coffee roasting is a chemical process that converts amino acids into volatile aroma compounds called aldehydes. This reaction occurs in the presence of an oxidizing agent and has a significant impact on the flavour profile of the roasted coffee. The aldehydes produced during the Strecker degradation are critical aromatic compounds in roasted coffee, contributing to floral, grassy, and nutty flavours.

Additionally, the CO2 produced in the reaction is responsible for the second crack in the roasting process. The extent of Strecker degradation in coffee can be influenced by the roasting process, including factors such as roast time, temperature, and the presence of oxidants. For instance, the Maillard compounds act as oxidants for Strecker degradation, and extending the Maillard phase of the roast can lead to a greater impact of this reaction on the final flavour profile of the coffee.

These reactions lead to the formation of over 800 compounds, with almost one-third representing important aromatic compounds. By now you can no doubt easily imagine that the control of the specific temperatures at which these reactions occur, and the duration of each stage of roasting, significantly impact the flavour profile of the coffee produced.


A top-down view of a frothy coffee drink.

Roasting at Home vs. Professional Roasting

DIY Coffee Roasting

Home coffee roasting is an accessible hobby for coffee enthusiasts looking to explore roasting. With tools ranging from a simple cast iron skillet to a dedicated home coffee roaster or even a popcorn machine, anyone can start experimenting with roasting their coffee at home, discovering the joy of crafting custom roast profiles.

Industrial Roasting Technologies

Professional roasters utilise advanced technologies, from drum roasters to hot air roasters, to achieve consistent results at a larger scale. As we have seen commercial roasting involves precise control over the roasting process, ensuring even roast and flavour consistency across batches.


The Environmental Impact of Coffee Roasting

Emissions and sustainability are significant considerations in the modern coffee roasting industry. Efforts to reduce the carbon footprint include investing in eco-friendly roasting technologies and practices, highlighting the industry’s commitment to environmental stewardship.

Innovations in Coffee Roasting

Innovations in coffee roasting have significantly transformed the industry, offering unprecedented precision, sustainability, and flavour enhancement.

Some examples of innovative coffee-roasting technologies include:

  1. Temperature Profiling and Airflow Control: Modern roasting machines offer advanced features such as temperature profiling and airflow control, allowing roasters to fine-tune the roasting process with precision, resulting in consistent and high-quality coffee.
  2. Portable Sample Roasters: The availability of new and interesting sample roasters, such as portable machines like the IKAWA, makes it much easier to test different roast techniques in micro-lots, enabling roasters to sample coffees literally on the farm, thus enhancing the ability to experiment with different roast profiles.
  3. Adaptive Roasting Technology: This technology allows for crafting the perfect roast profile by making personalised roasts for specific beans easy and consistent. It involves analysing the chemical composition and moisture content to draw out dramatically different flavours in a controlled manner.
  4. Hydrogen-Powered Roasting Equipment: Breakthrough hydrogen-powered roasting equipment has been introduced, offering a sustainable and environmentally friendly alternative for coffee roasting.

These innovations promise unprecedented precision, sustainability, and flavour enhancement, shaping the future of the coffee industry for the better.

Additionally, roasters are delving into the realm of natural flavour enhancements by adding ingredients such as fruit peels, spices, or herbs into the roasting process, crafting unique and innovative flavour profiles. The evolving landscape of roasting techniques promises a world of possibilities, where each roast is a canvas for creativity and exploration, shaping the future of coffee with exceptional flavours and a more sustainable industry.


Expert Tips for Appreciating Roasted Coffee

Appreciating roasted coffee is an art in itself. Learning to identify the nuances in flavour and aroma, influenced by the roast profile, can deepen your appreciation for coffee. Experimenting with different brewing methods and coffee origins can also reveal how the roast level complements or transforms the inherent qualities of the beans.

To appreciate roasted coffee like a pro, consider the following expert tips:

  1. Temperature Changes: Great coffees become more interesting and tasty as they cool. Pay attention to how the flavour evolves as the temperature changes. Avoid drinking coffee that tastes bitter when it cools.
  2. Cleanliness and Aftertaste: Evaluate the aftertaste of the coffee. Cleaner coffees leave the palate feeling neutral, while harsh coffees can linger with a singular flavour. This aspect can be influenced by the roasting method.
  3. Flavour Complexity: Look for a complex layering of flavours and how different taste notes interact with each other. Consider the timing of the tastes and the sequence of flavour experiences.
  4. Host a Mini Tasting: Consider hosting a mini-tasting to explore and compare different coffee flavours and profiles.
  5. Select Freshly Roasted Coffee: When selecting light-roasted coffee, choose freshly roasted coffee that is not more than 4 weeks old to savour the different natural flavours. Lightly roasted coffee tends to retain the original flavours of the coffee beans, offering an interesting and unique experience.
  6. Understand Roast Profiles: Familiarise yourself with different roast profiles and their impact on flavour development. As discussed throughout this article, light, medium, and dark roasts offer distinct flavour characteristics.

By following these tips, you can enhance your appreciation of the diverse flavours and aromas found in roasted coffee. Keen to know more about what it takes to become a professional barista? Read our article Training to be a barista on the Skills Training College blog page.


Summing Up

Delving into the coffee roasting process uncovers the meticulous craft behind every cup of coffee. From the selection of green beans to the final roasted product, each step is a testament to the dedication and expertise of coffee roasters. As we explore the intricacies behind the beans, we not only gain a deeper appreciation for our daily brew but also inspire a more mindful approach to enjoying coffee.

Are you feeling inspired to take your coffee journey to the next level? Whether you’re aiming to become a barista or simply passionate about coffee, enrolling in a nationally recognised barista course is a great way to deepen your understanding and skills.

Explore our coffee courses in Brisbane at Skills Training College, where you’ll learn everything from bean selection to the perfect pour. Why not turn your coffee passion into expertise and join a community of coffee lovers who share your enthusiasm? Enrol today and take the next step towards brewing perfection.


Frequently Asked Questions

What is coffee roasting and why is it important?

Coffee roasting is the process of heating green coffee beans to enhance their flavour, aroma, and colour. It’s crucial because it transforms the raw beans into the aromatic coffee we enjoy, unlocking a spectrum of flavour profiles depending on the roast level.


What are the different types of coffee roasts?

Coffee roasts range from light to dark, including light roast (with a light brown colour and pronounced acidity), medium roast (a medium brown colour with a balanced body), medium-dark roast (a rich, dark brown with some oiliness), and dark roast (nearly black beans with a heavy body and muted acidity).


How do roast profiles affect the flavour of coffee?

Roast profiles, determined by the temperature and duration of roasting, significantly impact coffee’s flavour. Lighter roasts retain more of the bean’s original character, while darker roasts develop richer, bolder flavours, with variations in sweetness, acidity, and body.


Can I roast coffee at home, and how?

Yes, home coffee roasting is possible using various methods, from using a dedicated home coffee roaster, or a popcorn machine, to a simple cast iron skillet. It allows enthusiasts to experiment with different roast profiles and discover unique flavours.


What are the main stages of the coffee roasting process?

The coffee roasting process includes the moisture loss phase (where beans dry and turn yellow), the first crack (where beans expand and sugars caramelise, indicating a light roast), the flavour development stage (adjusting the roast to achieve desired flavours), and optionally the second crack (for darker roasts), followed by rapid cooling to stop roasting and preserve the flavours.


What innovations are shaping the future of coffee roasting?

Innovations include temperature profiling and airflow control for precision roasting, portable sample roasters for experimentation, adaptive roasting technology for personalised roasts, and sustainable practices like hydrogen-powered equipment.


What factors should I consider when selecting green coffee beans for roasting?

When choosing green coffee beans, consider the bean’s origin, variety, and quality. These factors influence the bean’s inherent flavours and how they’ll respond to roasting, affecting the taste of the final cup.


How does the chemical change during roasting contribute to coffee’s flavour?

Chemical changes during roasting, including the Maillard reaction, caramelisation, and Strecker degradation, develop coffee’s complex flavours and aromas. These reactions transform sugars and amino acids, producing a wide range of flavour compounds and contributing to coffee’s distinct taste profiles.