You roast the same coffee, same profile — and it tastes completely different. The culprit is often hiding in your green coffee beans: moisture content and water activity. In this episode, Ingo from Roast Rebels breaks down what these two parameters mean, why they matter for green coffee quality and food safety, and how they directly shape your roast.

What you'll learn:
▸ Moisture content should sit between 10–12%. Below 8–9%: quality risk (hay, baked notes, fast aging). Above 12–13%: health risk from mold and bacteria.
▸ Water activity measures how freely water is bound in the bean (scale 0–1). SCA defines specialty coffee as below 0.7. Best practice: 0.5–0.6. Above 0.78: high microbial risk.
▸ Higher moisture = more energy needed in the drying phase. Lower moisture = faster drying, more careful heat management required.
▸ Proper packaging (GrainPro or Ecotact inside burlap) protects both parameters during storage and transport.
▸ Water activity has been underused in roasting due to expensive equipment — affordable tools are now changing this fast.
▸ Roast Rebels measures moisture content, density, and water activity on every green coffee delivery. Coffee at 13.5% moisture has been rejected.

Links & Resources
Green Coffee – A Guide for Roasters and Buyers
Measuring Devices at Roast Rebels
Roast Rebels Academy – Online Courses for Home & Pro Roasters
Roast Rebels Shop

About Roast Rebels
Roast Rebels is Europe's go-to platform for specialty coffee roasting. We sell small-scale roasting machines — including the Kaffelogic Nano 7e, Aillio Bullet, Gene Café, Behmor, and Nucleus LINK — alongside a curated selection of high-quality green coffees. Service centers in Germany and Switzerland. Free shipping across the EU.

The Roast Rebels Academy (academy.roastrebels.com) offers in-depth courses for home roasters and professionals, including the Aillio Bullet Masterclass: 11 chapters, 30 videos, 4+ hours of content (€249, free with hardware purchase from Roast Rebels).

Want to learn how to roast coffee but have no idea where to start? In this episode you get a structured overview of all learning paths – from in-person courses and online learning to books, coaching and learning by doing. And you'll find out what you should actually focus on first – the answer surprises most people.

What's covered in this episode:

• Why sensory skills are the most important foundation – before any technique
• Why your choice of green coffee has more impact on taste than any roast profile
• What you need to know about roasting basics and profiles – and in which order
• How to learn fast with a machine like the Kaffelogic Nano 7e
• Where online courses, YouTube, blogs and forums help – and where to be careful

ROAST REBELS COURSES & ACADEMY

In-Person Course Zurich – Coffee Roasting WorkshopDuration: approx. 4.5 hours. Content: green coffee fundamentals, roasting 4 different coffees, roasting theory, cupping, create and take home your own roast. Open to beginners and experienced home roasters. Usually in German; English documentation available on request; English courses 1–2x per year. Participants regularly travel from across Europe to attend.https://roastrebels.com/en/courses-events/

Roast Rebels Online Academy – available worldwideMachine-specific courses for Kaffelogic Nano 7e and Aillio Bullet. Covers: machine operation, green coffee selection, roasting theory, practical roasting exercises. Self-paced, available anytime. Included when purchasing selected machines from Roast Rebels.https://academy.roastrebels.com/courses

Roast Rebels ships machines and green coffee across Europe and offers online courses to roasters worldwide.

LINKS

Green coffee beans (EU shipping, free from €150): https://roastrebels.com/en/green-coffee/Books (Scott Rao, Rob Hoos, Book of Roast): https://roastrebels.com/en/books/Kaffelogic Nano 7e: https://roastrebels.com/en/kaffelogic-nano-7e/

ABOUT THE CONTENT

Coffee roasting is less complex than most people think – if you approach it in the right order.

1. Sensory skills: Understand what you like and don't like in a coffee before touching a roaster. Drink coffees with known origins side by side. Visit cuppings and coffee festivals.
2. Green coffee: Origin, processing method (washed, natural, anaerobic), density and freshness have a bigger impact on taste than the roast profile. Learn this through practical tasting, not just theory.
3. Roasting basics: Preheat temperature, heat input, airflow, roast darkness and speed – these concepts apply to all machines.
4. Roasting profiles: Once basics are solid, profiles let you dial in sweetness, acidity, floral notes, body and more.

Learning paths covered: in-person courses (incl. Roast Rebels Zurich, ~4.5h, English on request), Roast Rebels Online Academy (worldwide, machine-specific), YouTube, blogs, forums, books (Scott Rao, Rob Hoos, Book of Roast), coaching (Rob Hoos, Scott Rao, Morten Münchow / CoffeeMind, Nikolai Fürst, Gloria Pedrosa), learning by doing with Kaffelogic Nano 7e or Nucleus LINK.

ABOUT ROAST REBELS

Roast Rebels is your partner for specialty coffee roasting. From the best hardware like the Kaffelogic Nano 7 to high-quality green beans and expert-led courses – we help you roast coffee you'll love.Website: https://roastrebels.com/en

Rob Hoos is back! Three years after our first viral interview (50k+ views), we dive deep into his latest research on airflow, cultivars, and roasting physics. 👉 Rob's new book "Cultivar": https://roastrebels.com/en/cultivar-a-practical-guide-for-coffee-roasters/In this exclusive deep dive, Ingo talks to world-renowned roasting consultant and author Rob Hoos. Rob shares his most significant breakthroughs from the last three years of research and consulting.We’re breaking down the myths: Why is the genetic variety (cultivar) often more important than terroir? How does airflow impact the actual weight loss curve and flavor development? And how do you roast a Maragogype to bring out those elusive tropical fruit notes?Whether you are a home roaster or running a commercial roastery, this interview will fundamentally change how you approach your roast profiles.00:00 – Welcome back, Rob Hoos: A 3-year followup 00:32 – Who is Rob Hoos? Consulting, Books & SCA 01:43 – The biggest learnings from the last 3 years 02:15 – Focus on Cultivars: Beyond field blends 03:54 – Airflow Revolution: Impact on flavor & weight loss 05:45 – Convection vs. Conduction in drum roasting 07:22 – Why the deep dive into Coffee Cultivars? 09:50 – Terroir vs. Genetics: How understanding has shifted 11:43 – The Maragogype Revelation: Tropical fruit from PNG 16:20 – The "Cultivar Project": 8 years of research 19:35 – Coffee Science: The evolution since the 2000s 22:20 – Altitude & Terroir: Correlation vs. Causation 24:44 – The Galapagos Case: High density at low altitude 30:08 – Genetic Purity: Cross-pollination and seed banks 33:55 – The mystery of "SL-R": A hidden Castillo story 37:40 – The 4 Genetic Groups: Typica, Bourbon, Ethiopia, Hybrid 40:40 – Roasting Strategy: Why "Fast" isn’t always best 46:15 – Moisture & Density: Applying heat energy correctly 51:40 – Why wet coffee can "run away" from you 54:20 – The "Perfect Recipe": Roasting for maximum fruitiness 57:34 – Rob Hoos’ Online Community & Mentorship 59:30 – Conclusion: Final thoughts on the coffee industry► Find Rob Hoos’ new book "Cultivar" here: https://roastrebels.com/en/cultivar-a-practical-guide-for-coffee-roasters/► Visit Rob Hoos online: https://www.hoos.coffee ► Follow Rob on Instagram: https://www.instagram.com/robhoos/► Join the Roast Rebels Movement: https://roastrebels.com▬ About this channel ▬▬▬▬▬▬▬▬▬▬▬▬At Roast Rebels, our mission is to make coffee roasting easy. On the one hand we offer the most proven small scale roasting machines and high quality green coffees, on the other hand we want to support people who roast coffee with tips, knowledge, roasting profiles and tutorials to achieve good roasting results quickly. You'll find lots of information and roasting profiles on our website, as well as here on the YouTube channel. #homeroasting #coffeeroasting▬ More Information ▬▬▬▬▬▬▬▬▬▬▬▬You will find a lot more information as well on our website: https://roastrebels.com/en▬ Social Media ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬►Facebook: https://www.facebook.com/roastrebels/►Instagram: https://www.instagram.com/roastrebels/►Newsletter: https://eepurl.com/dxHgML►Podcast (Roasting coffee - made easy): https://anchor.fm/roasting-coffee►Onlineshop for European coffee roasters: https://roastrebels.com/en/►Onlineshop for coffee roasters in Switzerland: https://roastrebels.com/ch/en/#CoffeeRoasting #RobHoos #RoastRebels #SpecialtyCoffee #RoastProfile #CoffeeScience #Cultivars #HomeRoasting

We are sitting down with the current German Brewers Cup Champion, Urs Rotzinger, to discuss his journey from home brewer to winner, his mentors, and his competition strategy. And: Urs roasted his award-winning Carbonic Maceration Geisha on the Kaffelogic Nano 7 and shares his winning profile.Urs shares exclusive, detailed insights into what truly matters for success in the Brewers Cup championship – and the crucial lessons he learned from his first attempt.▶️ Urs Rotzinger’s Kaffelogic Nano 7 Competition Roast Profile (Free Download): will follow tomorrow🛒 Get the Kaffelogic Nano 7 at Roast Rebels: https://roastrebels.com/en/kaffelogic-nano-7e/🎓 Kaffelogic Online Roasting Course (Your perfect starting point): https://academy.roastrebels.com/course/coffee-roasting-kaffeelogic🏆 Follow Urs: https://instagram.com/urs_rotInterview Highlights:00:00 - Welcome & Introduction to Urs Rotzinger 00:42 - Urs' path to Specialty Coffee 02:50 - The First Brewers Cup: Learning the importance of gratitude 04:55 - The biggest learning: Mastering the "Cup Connection" 09:50 - Choosing the Champion Coffee: Nicaragua Geisha 11:30- Why the Kaffelogic Nano 7? Control, Batch Size, and making mistakes 14:00 - How Urs developed his winning roast profile (Trial & Error) 15:40 - Degassing Secrets: How long coffee needs to rest after roasting 18:15 - Urs' top tip for anyone considering competing 20:30 - Next up: World Brewers Cup in Brussels & filter coffee courses #RoastRebels #KaffelogicNano7 #UrsRotzinger #BrewersCup #GermanBrewersCup #CoffeeRoasting #SpecialtyCoffee #HomeRoasting #geishacoffee ▬ About the Kaffelogic Nano 7 roaster ▬▬▬▬▬ The Kaffelogic Nano 7 is a small and automatic fluid bed roaster. In 10 minutes, you can roast up to 120g of coffee. The roaster is shipped including 15 preprogrammed and high-quality roasting profiles so that you can roast a great coffee by just chosing the right profile, chosing the right roast degree and the machine does the rest for you. If you want to change the roast profiles, you can do that with the powerful free software that comes with the roaster. In addition to home roasting, the Kaffelogic Nano 7 is particularly popular for sample roasting - e.g. for professional roasters, producers and green coffee traders.You can find more about the roaster here: https://roastrebels.com/en/coffee-roaster/kaffelogic-nanoOr, if you come from Switzerland here: https://roastrebels.com/ch/en/kaffelogic-nano-7e/▬ About this channel ▬▬▬▬▬▬▬▬▬▬▬▬At Roast Rebels, our mission is to make coffee roasting easy. On the one hand we offer the most proven small scale roasting machines and high quality green coffees, on the other hand we want to support people who roast coffee with tips, knowledge, roasting profiles and tutorials to achieve good roasting results quickly. You'll find lots of information and roasting profiles on our website, as well as here on the YouTube channel. #homeroasting #coffeeroasting▬ More Information ▬▬▬▬▬▬▬▬▬▬▬▬You will find a lot more information as well on our website: https://roastrebels.com/enOr if you are from Switzerland: https://roastrebels.com/ch/en▬ More Videos ▬▬▬▬▬▬▬▬▬▬▬▬More home roasting knowledge: ⁨@CoffeeRoasting⁩ Mehr Heimrösterwissen auf Deutsch: ⁨@RoastRebels⁩ ▬ Social Media ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬►Facebook: https://www.facebook.com/roastrebels/►Instagram: https://www.instagram.com/roastrebels/►Newsletter: https://eepurl.com/dxHgML►Podcast (Roasting coffee - made easy): https://anchor.fm/roasting-coffee►Onlineshop for home coffee roasters: https://roastrebels.com/en/►Onlineshop for Swiss coffee roasters: https://roastrebels.com/ch/en/

We sit down with the brand new Swiss Brewers Cup Champion, Sierra Yeo, just three days after her incredible victory! Sierra shares all the details from one of the most competitive Swiss Brewers Cup in years , her mental preparation strategies , and the intense process of dialing in coffee under pressure.She also reveals the story behind her championship-winning coffee, the unique equipment she used, and, most importantly, the full recipe so you can recreate her brew at home! 🏆 Championship Coffee & ProcessThe Coffee: Mount Tumas pre-dried cold fermentation natural Geisha from Chiriquí, Panama. The Producer: Karen – who used a complex 5-day pre-dry, 15-day river water fermentation, and 8-week drying process. The Flavors: Rose, Grape, Peach, Mandarin, and lots of honey sweetness (you can even rap them). ☕ Sierra’s Winning Recipe Breakdown (Full Demo at the end!)Sierra shares her full recipe using a small dose to maximize bed depth and extraction: Dose: 14g Coffee Water: 230g Water at 94°C Pours: 40g Bloom, followed by three more pours. Target Drawdown: 2:45 Water Chemistry: Built with Magnesium Sulfate (for acidity vibrancy) and Calcium Chloride (for silky mouthfeel). 🛠️ Equipment UsedSierra sourced unique equipment from her travels, to maximize aroma and clarity: Dripper: Hario Flow Dripper (Designed by Eric Liu from Taiwan) – Features a slightly convex, spoke-like design with a center magnet for a donut-shaped bed. Server: Icosa Cyclone Mini – Features internal ridges to aerate the coffee and a dome to prevent splashing/oxidation. Glassware: Orea Sense Glass (used to serve judges) – Sierra notes it gives the coffee more clarity and sweetness. 🔗 Links & Resources (Shop Now!)Get the Coffee! Limited drops of the winning Mount Tumas Geisha are available at Rose Coffee Roasters: https://rose-coffee.com/Connect with Sierra Yeo: https://www.instagram.com/sierrasriracha/Sample and Home Roasters, Brewing Equipment and more: https://roastrebels.com/enChapter:0:00 Sierra Yeo, Swiss Brewers Cup Champion 202620:15 Sierra's Swiss Brewers Cup Recipe#SierraYeo #BrewersCup #GeishaCoffee #HarioFlowDripper #CoffeeRecipe #SpecialtyCoffee #BrewingTips #RoseCoffeeRoasters #RoastRebels▬ About this channel ▬▬▬▬▬▬▬▬▬▬▬▬At Roast Rebels, our mission is to make coffee roasting easy. On the one hand we offer the most proven small scale roasting machines and high quality green coffees, on the other hand we want to support people who roast coffee with tips, knowledge, roasting profiles and tutorials to achieve good roasting results quickly. You'll find lots of information and roasting profiles on our website, as well as here on the YouTube channel. #homeroasting #coffeeroasting▬ More Information ▬▬▬▬▬▬▬▬▬▬▬▬You will find a lot more information as well on our website: https://roastrebels.com/enOr if you are from Switzerland: https://roastrebels.com/ch/en▬ More Videos ▬▬▬▬▬▬▬▬▬▬▬▬More home roasting knowledge: ⁨@CoffeeRoasting⁩ Mehr Heimrösterwissen auf Deutsch: ⁨@RoastRebels⁩ ▬ Social Media ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬►Facebook: https://www.facebook.com/roastrebels/►Instagram: https://www.instagram.com/roastrebels/►Newsletter: https://eepurl.com/dxHgML►Podcast (Roasting coffee - made easy): https://anchor.fm/roasting-coffee►Onlineshop for home coffee roasters: https://roastrebels.com/en/►Onlineshop for Swiss coffee roasters: https://roastrebels.com/ch/en/

In this short but vital extract from the Aillio Bullet Masterclass, we deep dive into the technology that makes the Bullet roaster one of the most precise home/prosumer machines available: its innovative sensors!Understanding these sensors is key to unlocking consistent, professional-grade roast profiles.We break down the three main sensors, explaining exactly what they measure and how to use them for more consistent results:1. Bean Temperature (BT) ProbeThe classic probe, measuring temperature *in between* the beans. Useful for comparing against traditional roasters.2. Infrared Bean Temperature Sensor (IBTS)This game-changer measures the surface temperature of the bean (or the drum during pre-heat) for ultra-fast, precise, and volume-independent readings. Learn why the IBTS is the sensor you should be relying on.3. Pressure Sensor (FlowSense)Available on the R2 and R2 Pro models, FlowSense ensures a perfectly steady airflow by automatically compensating for chaff buildup. This makes your roast profiles more repeatable and reliable than ever.------------------------------------------------------MASTER THE AILLIO BULLETWant to master every function, technical detail, and maintenance step of your Aillio Bullet? Check out the full, 4.5-hour Aillio Bullet Masterclass here4.5 HOUR MASTERCLASS FOR FREEIf you get an Aillio Bullet coffee roaster from Roast Rebels, you will get a free access to the Aillio Bullet masterclass: https://roastrebels.com/en/aillio-bullet-r2-pro/

In this exclusive interview, we sit down with Mikaël Portannier, the current World Coffee Roasting Champion, to discuss his incredible journey. From his beginnings in catering school to competing in his first student championship, Mikaël shares the key moments that ignited his passion for coffee.Discover how a simple contest led him down a path of continuous learning, transforming him from a barista to a world-class roaster. Mikaël reveals the importance of daily cupping for quality control and the motivation behind his competitive spirit.Learn about the intense preparation that goes into a world championship, the challenges of working with unfamiliar machines, and the crucial role of his team. This is a must-watch for anyone passionate about coffee, roasting, and the pursuit of excellence.Mikaël on Instagram: https://www.instagram.com/mikae__lParcel Coffee: https://parcelcoffee.fr/Roast Rebels: https://roastrebels.com/Chapters:00:00 - Introduction to Mikaël Portannier, the World Champion00:50 - How Mikaël's coffee journey began03:06 - Competing in "Coffee and Good Spirits"05:00 - The importance of cupping for a roaster05:39 - First experiences in roasting competitions09:12 - Transition from barista to professional roaster11:19 - What motivates him to compete13:24 - Preparing for the World Championship16:31 - The coffees used in the competition17:03 - The team behind the champion17:49 - Overcoming challenges with competition machines37:27 - Where to find Mikaël online▬ About the ROEST Sample Roaster ▬▬▬▬▬▬▬▬▬▬The ROEST L100 Ultra is a highly advanced sample roaster designed for the needs of coffee roasters, importers, and competition participants. It operates with a convection-based roasting system, ensuring even heat distribution. With a capacity of 50 to 200 grams per batch, it is ideal for precise evaluation of green coffee. Its advanced sensor technology provides real-time data on temperature, airflow, and bean movement, allowing for precise control of the roasting profile.A key feature of the ROEST L100 Ultra is its automated roast profile management with adaptive algorithms. The machine detects the first crack automatically and adjusts the roast development accordingly to ensure consistent results. In addition to fully automated roasting, it also offers manual control for customization. With its integrated cloud-based software, users can store, analyze, and optimize roast profiles. The ROEST L100 Ultra is particularly suited for professional applications where consistency and efficiency are essential.ROEST coffee roasters with free shipping within Europe: https://roastrebels.com/en/roest▬ About this channel ▬▬▬▬▬▬▬▬▬▬▬▬At Roast Rebels, our mission is to make coffee roasting easy. On the one hand we offer the most proven small scale roasting machines and high quality green coffees, on the other hand we want to support people who roast coffee with tips, knowledge, roasting profiles and tutorials to achieve good roasting results quickly. You'll find lots of information and roasting profiles on our website, as well as here on the YouTube channel. #homeroasting #coffeeroasting▬ More Information ▬▬▬▬▬▬▬▬▬▬▬▬You will find a lot more information as well on our website: https://roastrebels.com/en▬ More Videos ▬▬▬▬▬▬▬▬▬▬▬▬More home roasting knowledge: https://www.youtube.com/@UC5xchx_vufvEIgRXgiXCjwQ Mehr Heimrösterwissen auf Deutsch: https://www.youtube.com/@UClk5nH5ijBrbyL5TBkomWSQ ▬ Social Media ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬►Facebook: https://www.facebook.com/roastrebels/►Instagram: https://www.instagram.com/roastrebels/►Newsletter: https://eepurl.com/dxHgML►Podcast (Roasting coffee - made easy): https://anchor.fm/roasting-coffee►Onlineshop for coffee roasters: https://roastrebels.com/en⁠

Win on purpose!

In this advanced session with Sam Corra and Jerome Rosler from Nucleus Coffee Tools, we break down how to design, validate, and execute competition‑ready roast profiles. Built for professional baristas, roasters, and coaches, this webinar connects green coffee physics, sensory goals, and stage workflow into a repeatable system you can trust on the world stage.You’ll learn how to translate sensory intent into curves, adapt profiles for espresso/filter/milk‑based service, control Maillard and development under time pressure, and leverage the Nucleus LINK Sample Roaster for precision and repeatability. If you’re targeting competitons like Barista Championships or Brewers Cup, this session gives you the frameworks and checkpoints to move from “good” to medal‑ready.👉 Nucleus Coffee Tools:👉 Roast Rebels — EU distribution of Nucleus Coffee Tools👉 Nucleus LINK Sample Roaster👉 Next webinars on Coffee RoastingChapter:0:00 Nucleus Coffee Tools and Coffee Competitions1:45 World Brewers Cup winning Profile3:10 Roasting Profile for Milk based Coffee5:28 Roasting Profile for Filter Coffee6:45 Martin Wölfl World Brewers Cup winning profile8:30 Roasting Profiles for Espresso9:50 Nucleus LINK Profiles in Development11:47 Eline Ferket's WBrC Profile14:50 Jason Bull's WBrC Profile18:31 Selecting Roasting Profiles for Cup Scores21:52 Get Roasting Profile Support from Nucleus Coffee Tools▬ About the Nucleus Link sample roaster ▬▬▬ The Nucleus Link is a highly accurate convection roaster. It has been specifically designed as a sample roaster - in particular, it allows the same roast to be produced regardless of external conditions. This makes it perfect for communication between coffee growers, traders and roasters, and as a sample roaster for farm visits.The unit comes in a shockproof box and with accessories to determine the density of the beans. It also comes with an app that selects the appropriate settings for the machine based on the altitude, type and density of the beans. Thanks to its ease of use, the machine is also suitable for ambitious and quality-conscious home roasters.You can find more about the roaster here: https://roastrebels.com/en/nucleus-link/▬ About this channel ▬▬▬▬▬▬▬▬▬▬▬▬At Roast Rebels, our mission is to make coffee roasting easy. On the one hand we offer the most proven small scale roasting machines and high quality green coffees, on the other hand we want to support people who roast coffee with tips, knowledge, roasting profiles and tutorials to achieve good roasting results quickly. You'll find lots of information and roasting profiles on our website, as well as here on the YouTube channel. #homeroasting #coffeeroasting▬ More Information ▬▬▬▬▬▬▬▬▬▬▬▬You will find a lot more information as well on our website: https://roastrebels.com/en▬ Social Media ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬►Facebook►Instagram►YouTube Channel on Coffee Roasting►Newsletter►Onlineshop for coffee roasters