To roast coffee faster, you need to turn up the heat….right?

No! 

In this episode, we explore the three powerful methods of heat transfer that revolutionised roasting. We’ll journey from humble beginnings—when roasting three kilos took half an hour—to machines that now roast hundreds of kilos of coffee in the time it takes you to boil a kettle. 

But beans roasted at lightning speed look strange, and taste… well, you’ll find out. Join us as we test-drive an industrial tangential roaster where first crack remind me of fireworks crackers. 

We also see the whale-sized roaster so massive it’s worth you a Guinness World Record. 

We have the technology today to roast coffee faster than ever, so why aren’t we all roasting at recording-breaking speeds?

---------------

Please spread the word about The Science of Coffee!

Discover how I make these Filter Stories episodes by subscribing to my Substack newsletter

Check out the Probat roasters mentioned in this episode:

Emmerich Spherical Roaster - "Pink Hydrant"

Large ball roaster - “Sputnik in a pizza oven”

G45 early drum roaster - “Old school steam train” 

Early tangential roaster

Sample tangential roaster - "Shoebox"

Neptune 4000, the largest drum roaster in the world! - "The whale"

And there are lots of other specialty roasters from Probat I didn't have time to showcase, including their new hydrogen powered roasters. See them all for yourself!.

Theodor von Gimborn's wikipedia page

Go deeper into the science of roasting

Read Mark Al-Shemmeri’s coffee roasting blog

Do a Certificate of Advanced Studies with the Coffee Excellence Centre

Explore Barista Hustle's online roasting learning

Learn more from Morten Münchow and his coffee roasting courses

Read Morten’s paper in collaboration with the University of Copenhagen on Roasting Conditions and Coffee Flavour

Follow Filter Stories on Instagram for my infographics

Learn more about first crack on my episode Coffee Roasting, Part 1: How heat transforms coffee beans

Season 3 is made possible by these leading coffee organizations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

A mother coffee plant gifts its baby everything it needs to grow—a green seed packed with food. But when we roast coffee, we hijack that gift and turn it into something else: flavor.

But what is flavor, at a microscopic level? What actually happens inside the bean when heat meets those nutrients?

In this episode, we shrink down to witness the Maillard reaction up close—a wild chain of molecular collisions that transforms baby plant food into aromas we adore. 

Grab your popcorn - you’re getting a front row seat at the wildest chemistry show in coffee. 

---------------

Please spread the word about The Science of Coffee!

Discover how I make these Filter Stories episodes by subscribing to my Substack newsletter

Ethiopian forest sounds curtesy of George Vlad. Hear more nature sounds here.

Go deeper into the science of roasting

Do a Certificate of Advanced Studies with the Coffee Excellence Centre

Grab a copy of Anja Rahn's upcoming book on coffee science through her Instagram

Explore Barista Hustle's online roasting learning

Learn more from Morten Münchow and his coffee roasting courses

Read Morten’s paper in collaboration with the University of Copenhagen on Roasting Conditions and Coffee Flavour

Follow Sebastian Opitz on LinkedIn

Follow Filter Stories on Instagram for my infographics

Season 3 is made possible by these leading coffee organizations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

When I started making cold brew this last year, I treated it like hot brew filter coffee. But no matter how I adjusted the grind or tweaked the brew time, I hardly got any differences in flavor…

Then it hit me: cold brew isn’t just a slower hot brew—it’s a completely different game with its own rules!

In this episode, I speak with leading coffee researchers who break down the microscopic dance between water and coffee that explains why cold brew plays by its own playbook.

And I bring you in on the brewing secret that can turn your brews from fruit juice to nutty creaminess. 

---------------

Please spread the word about The Science of Coffee!

Discover how I make these Filter Stories episodes by subscribing to my Substack newsletter

Go deeper into the science of cold brew

Do a Certificate of Advanced Studies with the Coffee Excellence Centre

Read Jiaxin (Jessie) Liang’s equilibrium extraction SCA 25 article and her published article

Discover all of UC Davis' cold brew research through the Coffee Science Foundation

Learn how to do a cold brew cupping with Toddy

Follow Filter Stories on Instagram for my infographics

Season 3 is made possible by these leading coffee organizations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

For years, I used cold brew as a last resort—the only brew method to tame dark, oily beans that were too bitter for hot water. 

Then one day, I took a chance on a Guatemalan Gesha and brewed it cold. The result? A massive explosion of florals I’d never tasted before. That single cup sent opened my eyes into how extraordinary cold brew can be.

In this episode, I speak with world-leading coffee scientists who explain why brewing with cold water tastes so different from chilled hot coffee. 

You’ll learn how certain flavors leap into your cup (and how others mysteriously vanish) when you lower the brew temperature.

You’ll also discover there are hidden “cold brew gems” in beans you thought you knew. So before you grab the kettle, consider this: sometimes all you need is cold water.

---------------

Please spread the word about The Science of Coffee!

Discover how I make these Filter Stories episodes by subscribing to my Substack newsletter

Go deeper into the science of cold brew

Do a Certificate of Advanced Studies with the Coffee Excellence Centre

Listen to my episode on Coffee Extraction for insights into how polarity affects flavor extraction

Read the UC Davis cold brew vs chilled hot brew study

Listen to my episode on 'How to think like a scientist'

Learn how to do a cold brew cupping with Toddy

Follow Filter Stories on Instagram for my acidity infographic

Go deeper into Paul Breslin's work at the Monell Chemical Senses Centre

Discover all of UC Davis' cold brew research through the Coffee Science Foundation

Season 3 is made possible by these leading coffee organizations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

We’re back with another series of The Science of Coffee—and this time we’re diving even deeper into coffee’s hidden microscopic secrets!

Over the past year, narrative audio producer and coffee professional James Harper has scoured academic journals, ventured deep into coffee farms, and conducted bold tasting experiments.

Now, he’s weaving those discoveries into captivating audio stories that reveal why coffee tastes the way it does—and how we can make it taste even better.

In this new series, you’ll learn about cold brew extraction science, explore innovations in roasting, and follow the shifting business models that shape farmers’ livelihoods. You’ll also take a journey through commodity vs. specialty supply chains and examine the historical, sociological, and philosophical perspectives that define what “specialty coffee” truly means.

Press the “Subscribe” button so you don’t miss an episode!

https://bit.ly/3TdDnHO

For more coffee science and behind-the-scenes content, follow James on Instagram @filterstoriespodcast.

https://bit.ly/2Mlkk0O

The Science of Coffee is a spin-off series from James Harper’s documentary podcast, Filter Stories. 

https://bit.ly/3ajoT5e

Season 3 is made possible by these leading coffee organizations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

Deep inside your coffee grinder, tiny changes can have massive consequences.