How to think like a scientist

So, in the last episode, I felt like I was lost in a forest with these dark clouds overhead, melting down rain.

I had a question about how to brew my coffee. Should I or should I not rinse my filter paper first when I'm making a Chemex pour over filter coffee? And the reason this question made me feel lost in this dark forest is because, well, most coffee blogs, coffee Instagram reels, YouTube videos, they would for the most part say, yeah, I should rinse my filter paper.

But I would see that sometimes it made my coffee better and other times it made my coffee worse. And to help me get through this forest, I decided I need to begin thinking like a scientist. You know, what would a sensory scientist do if this was the question they were investigating?

Well, the first thing they would do is a blind triangulation. Like, can you taste the difference? And I went on this whole journey to brew my Chemex pour over coffees as identically as I could.

And in the end, I discovered that no, I couldn't taste the difference. This was a revelation. I felt like the rain had stopped and beams of sunlight was illuminating the path for me through this forest.

And what was so powerful to me is that I was saving potentially over seven days of my life. If I spent 30 seconds every single day for the rest of my life rinsing the filter paper of my pour over coffees, that adds up to over seven days. So that time that I've now saved, I can put it towards things that I think actually really, really do matter in the world of coffee.

Coffee growers the world over are facing a sustainability crisis. Be it with prices and climate change and the younger generation not wanting to stick around in coffee like their parents have, these things really matter to me. And now I've realized I can save 30 seconds every morning, not rinsing my filter paper.

That allows me to get to work here in my studio a little bit sooner. Gives me that little bit extra time to read up and research these things. But you know, 30 seconds every day, I know it's not really that much, but then it occurred to me, if I continue thinking like a scientist, can I find other aspects of my coffee life where I can just save time and energy, avoiding things that actually don't matter?

What about the way I taste coffee? What about all the gizmos, gadgets I could spend for making espressos? What about the contraptions I buy to store my beans in to keep them fresh?

All these things that I spend my time and energy on in my coffee life, if I were to think like a scientist, how many of them actually matter? Instead of saving 30 seconds a day, I could be saving five minutes, 10 minutes a day. This is really now starting to add up.

I'd be able to explore the question of sustainability an extra week per year. And so I decide from now on, I'm always gonna think like a scientist. I'm gonna go about my life like I normally do in the coffee world, but every time I come across a concept or a way of brewing or anything, I'll just stop and ask myself, how would a scientist approach this?

And this episode is what that journey looked like.

I had and still have a lot to learn about how to think like a scientist. But in this episode, I'm gonna give you three aha moments that really helped me figure it out. The first story is about the practice of slurping coffee.

And it's there, I learned to think about what good evidence actually looks like.

The second story looks at espresso preparation techniques. And it's there, I grapple with the problem of, well, if I can't get good evidence, what do I do? And the third story is about the science of water.

The episode is sponsored by BWT Water and More. They manufacture water filtration kits for the cafe in the home. And it was while I was wrapping my head around the science of water that I learned the third thing about how to think like a scientist.

And that is, don't get too hung up on theories. Focus more on experimental results.

And I really hope that me sharing these stories are helpful for you. Because you know, in my circle of friends, in my family, I'm James, the guy who makes a coffee podcast. I am the coffee expert in my community and I know they take my advice really seriously.

And if you're listening to this, chances are you are the coffee expert in your community. And I really care about being accurate, honest, factual. And most importantly, I don't want to waste my time and especially not the time of the people I love the most.

I want to give them the gift of time. So they have more time to do the things that matter to them. And if you care about that too, this episode is for you.

I'm James Harper, and this is The Science of Coffee, a spin-off series from my Coffee Documentary Podcast, Filter Stories, and a journey into Coffee's hidden microscopic secrets.

Okay, here's the first story. A story about slurping. But actually, it's a story about how I learned to look for good evidence.

So, slurping. Slurping is when you take a cup of coffee, and instead of sipping it like normal, you suck it in really sharply, so the coffee sprays across your mouth like this. Now, I'm not a particularly great slurper, but people who taste coffee for a living, I mean, man, they're slurps.

They're amazing. And when you speak to people whose job it is to evaluate a coffee's quality, you know, farmers, mill managers, importers, exporters, roasters, they tell you they slurp because it helps them better evaluate a coffee's flavours.

For example, last year I was invited to present at a coffee conference in Shanghai, and it's there I saw a really good presentation from the 2023 World Cup Tasting Champion, Young Beck from Australia. And if you don't know, cup tasting is a competition where coffee tasters have to identify which coffee is the odd one out across a whole bunch of different coffees as quickly as possible. So Young Beck, he's on stage, he's in the middle of the stage, and he's going to be the first to introduce and he says sometimes he slurps his coffee especially sharply.

He's trying to better spread the coffee throughout his mouth and so he's able to pick up on aromas better.

And he was quite candid and said actually, I'm not sure if this has been proven scientifically, but he quickly followed that up with saying, you know, all us coffee tasting professionals, we think slurping this aggressively intensifies a coffee's aromas.

When I first got into the coffee world 10 years ago, I heard this exact same argument about slurping. And from the second I heard this, I have always been slurping coffee because it will help me better identify a coffee's flavours. On the count of three, clap with me five times.

Okay, three, two, one.

But I remember the day, the exact moment that I began to question it.

Yeah, cool.

Okay, great. So tell me, I mean, who are you? I was interviewing the coffee scientist, Kenzie Petali.

I'm Kenzie Petali. I have a PhD in food science from UC Davis.

And as we were wrapping up our conversation, I asked her, Is there anything, anything like a myth you want to bust? Is there anything you'd like busted in the world of coffee science? Like where the coffee community is doing things a certain way, but it's actually not backed up by the science?

And my last one is...

And she mentioned slurping.

There's no evidence that slurping is helping you taste better in the cupping table. And I personally find it annoying as hell.

Is that because there's no evidence because we haven't looked for it or because we've looked for it and there was nothing?

So this is not something that I have researched personally. This is something I've heard from a different sensory scientist, so...

Now, I have tried many times to get in touch with this sensory scientist, but it hasn't worked out so far. But nevertheless, this now made me start to question the act of slurping.

I feel like I'm lost in a forest again. Because on the one hand, I have the coffee community saying slurping really matters, but on the other hand, here I have an assertion from a scientist saying, no, it actually doesn't matter. What do I do?

Hmm... I need to think like a scientist. What do I need here?

Well, it's pretty obvious. I need evidence. I need evidence that slurping actually helps you taste better.

And so I go into the world of academia to see if I can find some evidence. I go into Google Scholar, type in slurping, and to be frank, not much actually turns up. But after 30 minutes or so, I come across this paper from a university in Naples, Italy.

It's a coffee study looking at the aromas that are released when we drink coffee. And I pick up the phone to the lead researcher, Alessandro Genovese.

Which is fun, I don't often get to interview in Italian.

I quickly realised though that that paper he wrote won't help me answer my question about slurping.

But he does give me evidence for why he thinks it's important to slurp. Because that's what they do in the olive oil industry.

Professional olive oil tasters, they put their teeth together and create this tiny little gap and then suck in the olive oil. Okay, so actually this act of slurping is more than just the coffee industry. I mean, I know they did it in the wine industry and now also in the olive oil industry.

If slurping didn't have an effect, why would you see tasting professionals do it across all these different industries? But hold on, hold on, hold on. Think like a scientist.

For sure it's evidence. But is it good evidence? I'm not sure that it is.

Because who knows what's going on in the minds of professional tasters when they're slurping. Maybe when they slurp, all they're really doing is activating their OK, I'm critically analyzing this liquid right now, part of their brain. And maybe if they really wanted to, they could perceive the aromas just as well by taking a normal sip and telling themselves, OK, I'm going to really pay attention now.

No, I decide I need to find better evidence. And so I'm back on Google Scholar. And then I come across another paper, which this time actually looks at the act of slurping itself.

I get on the phone with one of the researchers, Professor Georgiana Juravle.

I'm an Associate Professor of Neuroscience by Research at the Alexandri Wancusov Yash in Romania.

Now, a few years ago, Georgiana was in the UK and working with Charles Spence, the same cross-modal researcher I featured back in Episode 6, Sonic Seasoning, in the last series. And she and Charles got interested in the act of slurping because they were seeing what I was seeing.

For us, the trigger for the research was literally hanging out with baristas and wine experts and simply noticing how often they slurp.

And so they did this big experiment.

So the experiment was conducted in London and we gathered 207 regular consumers, British.

This is a great sample size, 207 people. And they gave each of them either a bowl or a mug of vegetable soup. And then...

For each sample, the participants were asked to first sip it, rate it, and then slurp it and rate it. And for the ratings, we had three questions. First, if they liked it.

Second, how flavourful they found it. And third, how self-conscious they felt while testing it.

I've got to say, as a design for an experiment, already I'm beginning to question whatever answers come out of this. Because if you were that person doing the experiment, you come in, you're given your bowl of soup, you're asked, sip it like normal. Okay, I sip it.

And then you ask, how flavourful is it? Yeah, okay, quite flavourful. And then they say, okay, taste it again, but this time slurp it.

And then tell me again, how flavourful is it? Because they've already asked me how intense the flavour was, when they asked me to taste it again, I'm now focusing on the flavours more. So, in the design of the experiment, I wish they had mixed it up, you know, half the people, for example, slurp first, answer the questions and then sip first, answer the questions.

But anyway, let me get to the results. The results show that the participants found the flavour intensity went up when they slurp compared to sipping. And the results are statistically significant.

There's a very low likelihood that these results came from random chance. Also, the standard error is small, which basically just means that it wasn't just a couple of people who noticed the difference, it was almost everybody. And so this is all good evidence that I should slurp rather than sip.

But then I came across how big of a difference it actually made. And it was a very small difference. Slurping only increased the flavor intensity by 3%.

And I wasn't really sure what to make of this and had a bit of a back and forth with Georgiana. Is that a lot? If we want to perceive a flavor of a drink more, we should always be slurping it.

Is it that level of conclusion?

Wow, this is a very big question after our paper. But if I were to take home something from our study, it would be definitely slurp it if you want to feel the intensity, because this is demonstrated and we show it very clearly.

So there it is. Georgiana's paper is the best evidence I could find. Is it the best evidence I could possibly ask for?

No. I mean, I wish they had changed the methodology a little bit, but for sure this is definitely better evidence than what I had before, which is the fact that tasting professionals in different industries all slurp.

Exploring the science of slurping made me appreciate what good evidence looks like. I mean, there is evidence everywhere, but what does good evidence look like? I decide that this is a question I am now going to ask myself every time I come across a concept in coffee that maybe I've heard before and have even done myself like slurping.

And with any luck, I will find enough evidence to reach a conclusion for myself.

And this is why I think it's going to help me in my journey as a coffee professional, a coffee lover.

Next time I'm at a coffee tasting and there are other coffee professionals around, I'm not going to spend this precious time worrying about my slurps. I just don't think slurping really matters that much. And instead, I'm going to have conversations about things that I do think really matter, like whether coffee producers can continue growing coffee sustainably.

These are the sorts of conversations that do eventually change the coffee industry. And that's where I want to put my time going forward.

So I had just come out of this journey exploring the science of slurping. A coffee scientist I really respected planted a seed of doubt. And so I decided, right, let me think like a scientist and figure out whether I should be slurping or not.

And on that journey, I realised it's so important I look for good evidence. Looking for good evidence was now the first thing I do when I come across a new concept or practice in coffee.

And coming up is the second lesson I learned, how to think like a scientist. What do you do when you can't find good evidence?

One day, I'm sat on my couch, relaxing, I'm on my phone, and I open up Reddit. Now, I lurk in many of the Coffee subreddits, and as I'm scrolling through, I come across this beautiful video.

This person is showing all the steps he goes through to pull one single shot of espresso in his kitchen. All his coffee beans are individually portioned in little glass tubes. He sprays his beans with water before he grinds them.

He breaks up the clumps in the coffee grounds with metal wires.

He puts a metal disk with very, very fine holes on top of the flattened ground coffee. This is a very elaborate espresso ritual, easily taking him 10 minutes for a drink he probably finishes in 30 seconds. And it seems like to me every year, home espresso aficionados add another element to the ritual.

Our recent trend I've seen is people putting cold metal balls into their cups, and so when the espresso drips into the cups, the drink is cooled down really quickly. Now look, I love a good espresso. I'm not an espresso nerd, and nerd in the best sense.

I'm a nerd about so many things, but I'm not a huge espresso nerd at home. I'm more into my filter coffees. But I do have a nine barista stovetop espresso maker, and as a treat I do make myself an espresso every once in a while.

But if I were to create a video on Reddit about how I make espresso, it would last literally five seconds. Coffee in the portafilter, bang it on the counter, tap it down, and jobs are good. Out comes my espresso.

But when I see such elaborate espresso preparation techniques, I think to myself, should I invest the time, the money, the energy to go to these lengths to pull my shots of espresso?

Here I am, back in the forest, not sure which way to go. I'm ready to invest 10 minutes into making my espressos. If I'm gonna be able to taste the difference and be like, wow, absolutely, these 10 minutes were worth it to me.

And so I remind myself, James, think like a scientist. How would they approach this? And I think back to the first question I am now gonna ask, is there good evidence?

But hold on, good evidence for what exactly? I need to choose just one of those elaborate espresso preparation techniques. Now for me, what's really important is the flavor.

And I think all the steps which might have the biggest impact on my espresso flavor are using these cold metal bowls. Okay, so my first question. Can I find good evidence that these cold metal bowls significantly improve the flavor of my espresso?

It is really good to have all of you here with me today.

So I know that a barista champion has used them before during a competition on the world stage.

But first, you'll notice these frozen metal rocks on my signature drink vessels.

This is the Australian barista champion Hugh Kelly during his 2021 world barista championship routine.

I call this technique compound chilling. Espresso is running straight over those frozen metal blocks.

So this is evidence that cold metal balls can improve the flavor of an espresso. But is it good evidence? Well, I mean, it was a really brilliant presentation.

Very interesting, very fun to watch. And he did get into the finals. But he didn't get into the finals because of the cold metal balls.

They're just one of many, many, many things he did very well to get into the finals. So no, I think I need better evidence. But Hugh does suggest there is better evidence out there because he says he collaborated with some coffee scientists to develop this cold metal ball technique.

And a technique I developed with Zurich University of Applied Science to brighten Yuhu Noida's flavor profile.

And one of those coffee scientists, Professor Chahan Yaretsian, he has said publicly that up to 30% more aromas can be locked into an espresso when you use these cold metal balls. So this is starting to sound like powerful evidence, but I haven't seen any published studies. And without that, I can't say how strong this evidence is.

Now, on Coffee YouTube, I found some other evidence.

This one was without the compound shelling. This one had compound shelling.

A coffee influencer made two espressos, one with cold metal balls in the cup, the other one without.

This one tasted like the same coffee, but elevated, almost like if this one was just slightly off extraction and it wasn't perfectly dialed in and this one was, it was it was that level.

And in that side by side comparison, he and his camera person both said that the coffee made with the cold metal balls tasted better. But I now thought right back to me and Sophie at the beginning of the last episode where we did a similar test for our Chemex pour over filter coffee. One where we rinsed the filter paper, one where we didn't.

But I now know that's not good evidence because I need to answer the question, can you taste the difference in a blind triangulation? Can you pick the odd one out? I need many data points and I need to know that the espressos are brewed absolutely identically with the only difference being the addition of a cold metal ball.

And this is where I'm in this forest and I got stuck because I could not find good evidence. It's not that putting cold metal balls doesn't matter. It might significantly improve my espresso.

I just don't have enough evidence either way to say whether it does or it doesn't. And so I wondered to myself, what do I do? Okay, well, what would a scientist do?

Yeah, what were we talking about?

We were talking about, go ahead and prompt it, yeah.

And it's here I remember a conversation I had with the scientist Jeremy Nelson of Socratic Coffee.

I'm a researcher for the US military, biotechnology development type stuff.

He's a massive coffee nerd and as a hobby runs this little group called Socratic Coffee that tests out espresso equipment. And he explained this concept to me, I hadn't heard before, a concept called Signal Detection Theory.

Problem is the world is full of noise and the thing about signal detection theory is it's a way of kind of looking at the world. Everything is signals and noise and we're trying to find the signal. And so the signal could be the truth.

Let's say we're testing some piece of equipment. Is equipment A better than equipment B? There's a truth there.

Or maybe there's some gray where it's better in certain conditions. So what is that truth? What is that signal?

And noise are all of the variables that influence it that some of them we can control. Some of them we're probably not even aware of.

So in this world, there is a truth. Using cold metal balls will significantly improve the flavor or it doesn't. One of those two things is true.

It is the signal in the noise. And the funny thing about signals in a noisy world, if the truth is in fact that cold metal balls do improve the flavor of your espresso, that signal will crop up over and over again until eventually you just can't ignore it.

The signal should emerge over time. That's just like, that's the nature of science, right? Like if something is truth, it will start to show up over and over.

But right now, this trend, it's so new I just can't find good evidence. I can't pick up on the signal, the truth. But I wanna know now, should I or shouldn't I put cold metal balls in my espresso?

Jeremy finds himself in this position all the time and this is what he does.

I'm gonna take a breath. I'm gonna hold my breath. I'm not gonna claim this is a proclamation.

There's no truth here necessarily. There's a hint of, and then I wait for it to be replicated or I wait for other people to find the results.

Jeremy just takes a long, deep breath and relaxes and waits. He waits for good evidence to emerge. And if the signal is strong, if indeed, putting cold metal balls in your espresso cups makes such a big difference, coffee scientists, sensory scientists, maybe some coffee influencers decide to take up the challenge and try to do their own controlled study.

Eventually, good evidence will emerge and we'll have our answer. And until then, I decide I will just relax. And you know, I won't put cold metal balls into my espresso cups, because that's going to add time to my espresso ritual.

And those minutes I'm shaving off from preparing my espressos, well, I might now have a couple more minutes sat on my couch. And next time I'm there, I might decide, I've got five minutes, I'm actually going to read this paper by the economist Jeffrey Sachs on the sustainability of coffee production. This is what really matters to me.

So let me recap the journey so far. I was lost in this dark forest, and I wanted to find the truth, but I didn't know where to go to find it. And so I decide, I need to start thinking like a scientist.

I stumbled into the science of slurping, and investigating that, I learned that there's lots of different types of evidence. What really matters though, is knowing what good evidence looks like. That's not the first thing I always ask myself when I come across a new theory or way of brewing coffee.

And then I stumbled into the world of espresso preparation, and came across this trend of cold metal balls. And here, I just couldn't find good evidence. And I learned, you know, when I cannot find good evidence, I just need to take a deep breath and wait.

Because the truth will emerge by itself.

But I still had one very important lesson to learn about how to think like a scientist.

This is when I dived into the science of water for coffee.

And while I was swimming in this confusing science, I learned I shouldn't get too hung up on theories and instead just stay practical. That story is coming right up next.

So about 10, 15 years ago, I was in London working as a regulator at the Bank of England, and I was in a job, an industry, that did not speak to my soul at all. And so while a lot of my time was spent sitting at a desk in a big glass tower, looking at spreadsheets, I would walk out of the building as often as I could and go to the local specialty coffee shops. And it's there, I was falling in love so much with the energy of specialty coffee, the people, the environment, the flavours.

And when I would talk to the barista about, you know, how should I make my coffee at home? They would talk about many things, how to brew it, what kind of grinder, you know, how freshly roasted. But one thing they would very, very rarely talk about is water.

And water as a topic would only ever come up if we were talking about espresso machines. Because if you're boiling water in a hard water area, your kettle will suffer from lime scale, you know, that kind of white chalky buildup. And in the case of espresso machines, lime scale is a real headache.

This is Frank Neuhausen, a director at BWT Water & More.

You can really see boilers, let's say, full of scale or even leaking tubes because of corrosion.

And if you own an espresso machine, the solution was simple. Reduce the amount of calcium in your water because that's the thing which is coming out as lime scale. But it was when I got off a plane in Melbourne, Australia to begin my coffee career in 2014, all of a sudden everybody is talking about water.

I would go to these public coffee tastings and people would be talking about water and its impact on the flavour of coffee. Because just before I landed in Australia, on the other side of the world, a UK barista champion had made huge waves at the world barista championships.

Please give it up for the barista champion of the United Kingdom, Maxwell Kelowna Dashwood.

I wasn't there in Rimini, but Cedro Babadizi, part of the leadership team at BWT Water & More, he was there and remembers the moment like it was yesterday.

It was in 2014, I'm sure you remember. 2014 in Rimini, it was the moment when at the world barista championship, a guy from UK, it's Maxwell Kalonadashwood, went on to the stage.

Specialised coffee takes each of us to some strange places. For me, it was a chemistry lab at the University of Bath about a year ago. Now the purpose of my visit was to collaborate with a computational chemist to try and answer some of the mysteries about the way brewing water impacts on the flavour of coffee.

In front of the judges, he started to talk about the fact that he roasted this coffee for the competition according to the water that he knew he was going to find in remaining in the competition.

And after testing the water here today and noting that the buffer is high, the roast I'm choosing to serve you has a lower end temperature and a shorter development time. I want to make sure that the complex sweet acidity that makes this coffee so special comes through that buffer.

And that was absolutely astonishing for the people. And the rumours spread so quickly into the halls of the World of Coffee show that everybody were rushing to the stage to hear this guy talking about the water. That was the real turnaround.

So, a few years go by, I begin Filter Stories, my podcast, and begin this series, The Science of Coffee. And I decide that the first episode in this series will be on the science of water. And one of the first things I did to wrap my head around the science of water was re-watch Maxwell's presentation in Rimini.

Now, coffee is predominantly made up of weak acids, and if we have no buffer, and what really jumped out at me was how we spoke about the role of magnesium in water.

Now, here we've got a very different water. We've got lots of calcium. Now, he likes to bring out heavy, creamier flavours, whereas magnesium has a preference to sharp, fruitier flavours.

Maxwell said that magnesium brings out more vibrant, fruity flavours in a coffee. Now, I love fruitier flavours in my coffee, so if there was a way for me to change my water to get fruitier flavours, I would absolutely invest the time and money to get fruitier coffees. But first things first, magnesium in water leads to fruity coffees?

This is a claim. And I decided every time I come across a claim, an assertion in coffee, I had to ask the question, is there good evidence? Well, many people in different corners of the coffee community were saying that magnesium made coffee taste better.

Frank Neuhausen heard it from his customers, who were using his BWT water filters, which replaced calcium with magnesium.

And then our partner said, what they tasted, the specialist tasted in the cup, was better, was more positive.

I witnessed how on Reddit, coffee lovers were now making their own water for coffee. They'll get distilled water, water with like no minerals whatsoever, and then they'd add back in certain minerals. And almost every recipe I come across suggests adding Epsom salt, which is actually just magnesium sulfate.

So that was evidence emerging, but I wanted more evidence. I wanted to see evidence from a more carefully controlled study. And the only study I could find was one that was actually paid for by BWT in partnership with the Zurich University of Applied Sciences.

Let me quickly tell you about it. So, where they used the same coffee and water with different ratios of magnesium and calcium.

25% of magnesium versus 75% of calcium, then 50-50, then 75% of magnesium, and only 25% of calcium.

Now, as an experiment, there were many things that gave me confidence. These were blind coffees, random order, the tedious strength of the coffees were kept the same across all the brews, but it had its weaknesses too. This wasn't a triangulation, you know, tasting the odd cup out.

So it didn't explicitly answer the question, can you taste the difference? And also, it was quite a small sample size. I would love to see over 100 data points.

But anyway, despite all of that, the outcome was that really the description of the taste was absolutely different. The higher the content of magnesium was.

The coffees tasted different. As you increase the amount of magnesium, the fruitiness increased by about 12% and bitterness decreased by about 25%. And for me personally, I decided this is good enough evidence for me to invest in a water filter at home.

I wanted a water filter anyway, because I live in a very hard water area. And I decided if I'm going to buy a water filter, let's get some magnesium in there as well. I tried out BWT's Penguin Water Filter, which introduces magnesium.

I also tried out another water filter company called Peak Water. And in the end, I decided to stick with my BWT filters. They were more readily available.

I liked the fact I could easily buy refills for the same cartridge that I would reuse over and over. And I did notice a change in the flavour of my coffee brews. A change that I preferred.

So that's me in my home. But if I ran a cafe, when I went to visit one of their offices in Wiesbaden, Frank Neuhausen showed me this contraption called the BWT Best Max Premium ROC. It looks like a giant double version of a SodaStream.

Yeah, you're right. It looks a little bit like that.

And I was really impressed because, you know, if I was a roaster and I had a cafe in Melbourne and Sydney, despite the fact that these cities have completely different waters, the water in my coffees would always be the same. Because water from the tap goes into the first cartridge where minerals are taken out of the water.

Calcium cannot pass this membrane.

And now that water with a lot of minerals stripped out goes into the cartridge next door where a better balance of minerals are added back in.

And exchange magnesium ions.

And so that is that. However, I encountered a problem.

So what would happen is, friends, family, they'd be visiting me, would be in my kitchen, and I'd be making them a coffee. And they'd see me use this BWT Penguin Water Filter, and they would ask me, so are you using special water when you make your coffees? And I say, yeah.

And they'd ask, what's different about it? Well, basically what it does is, it replaces calcium with magnesium. And they say, oh, interesting.

Why does that matter? And I say, well, because I think it improves the coffee's flavour. And then came the killer question.

But why does magnesium improve the coffee's flavour? So early on in my journey, trying to wrap my head around the story of water, if they had asked me that question, why does magnesium improve the coffee's flavour?

And this is a washed coffee.

I would have told them what I had learnt watching Maxwell Colonna Dashwood's World Barista Championship performance.

It's kind of empty and the acidity is slightly sour. Why is this? Well, let me introduce you to two people, calcium and magnesium.

These are the minerals we want in water because they have something called a binding energy, which means they can actually attach to and pull flavours out of the coffee.

Maxwell said that this concept of binding energy is the reason magnesium makes our coffees taste a bit fruitier. The idea is, you know, there are magnesium molecules that are missing a couple of electrons floating around in the water, and they bind better with some of the organic acids in the coffee, thereby kind of bringing them out into the coffee brew, making the coffees taste fruitier. And this theory was explained to Maxwell by the computational chemist, Christopher Hendon.

They went on to publish a book together, Water for Coffee. And I found this concept of binding energy cropping up in many different corners of coffee internet. So when someone asked me in my kitchen, James, why do you have magnesium in your water?

I say, well, it's because of binding energy. Magnesium is better at pulling out fruity flavours from the coffee. But a little bit later in my coffee journey, I learned that actually binding energy may not be the right explanation for why magnesium makes coffees taste more vibrant.

I travelled down to Zurich to meet the coffee scientist Samris Marquet at the Coffee Excellence Centre.

He and I found a little corner of the university where there was like this phone box recording booth, which was padded. And so he sat in there, I sat outside, pointed my microphone into the booth, pinning him against the wall. Poor guy.

Don't mind me invading your personal space like this. What I wanted was tape for this episode I was making about the science of water. I wanted a scientist to explain to me the science of water.

And so I could use that interview tape in the episode I was creating. So who are you and what do you do?

Hi, my name is Samus Mokka. I am a scientist at the Coffee Excellence Centre.

And on my list of questions was binding energy. I want a summary to explain it to me. Yes, binding energy.

This is what it is. This is why it works. This is why magnesium is important in your water.

Perfect, got the tape. That's what I wish had happened. Instead, I asked him the question, why, you know, Christopher Hendon proposed a theory for why, you know, coffee and water.

And then he said, you know what, James? I don't know.

The science is not exactly sure what is going on because there have been very little studies about this.

Now, he wasn't denying that binding energy is a thing. Like it absolutely is a thing and it absolutely has an effect on coffee flavour. He even brought up a little bit of research he had read recently about binding energy and how it interacts with acids in coffee.

Very recently, there was a student thesis about this topic.

But the problem was the water they used in those tests had extremely high levels of magnesium, much higher than you'd find in a cafe.

The clear effect was only found on citric and malic acetone concentrations of calcium and magnesium, which are quite higher than what you would normally expect in your brewing water, so maybe five times higher.

And then he suggested a totally different explanation entirely. Maybe magnesium is playing around with something on our tongues instead.

Perhaps they do interact with our receptors for saltiness at lower concentrations, but not that we are aware of this.

And here I was, lost in the forest again. Ah, it's like, okay, here I am. I'm trying to think like a scientist.

I came across this concept of magnesium in water changing the flavour. I was presented a theory, binding energy. This is why magnesium can change the flavour of a coffee.

And when I first heard it on the World Barista Championship stage, I believed this was the explanation for why coffees taste more vibrant. I Googled binding energy. I read about it.

The chemical explanations to me as a non-chemist, it seemed to me, yep, this must be the explanation. I mean, it was so clear. Here's the theory that explains how magnesium extracts citric acids better from coffee.

And the evidence, well, look, when you brew a coffee and your water has magnesium, ta-da, your coffee tastes more fruity.

There's a lot of theories around.

But here in Zurich, speaking with Samo, he presented me with lots of other possible explanations for why magnesium in water makes coffees taste fruitier, more vibrant. And this is the point. It's not that binding energy is wrong.

It's just that there are other explanations too. And it's not clear at this stage which is the right explanation that explains why magnesium in water makes coffee taste more vibrant. I realized that when I hear statements like this, what's actually happening is we have this practical result.

Coffee tastes like this when I do this. And then we have the explanation, the why this is happening. And the point is the why.

Oftentimes, we don't know why, but this now created a new problem for me. I thought back to the conversations I would have with friends and family in my kitchen, and they would ask me, but James, why does magnesium make coffee taste more vibrant? I mean, the true answer is I don't know at this stage.

I don't think really anybody does for sure, but it just doesn't feel right. Saying I don't know, it sits so uncomfortably with me. But back in Zurich, in the room with Samo, the more I spoke with him, I saw from his perspective how he works with explanations, theories.

And this is where I learned my third lesson around how I should think like a scientist. When it comes to theories, the trick is don't get hung up on them. Don't worry about it too much.

Focus more on the evidence.

To be honest, I'm a very experimental scientist. I do theory. Theory is always needed.

You need to have the theory to set up your experiments. But in coffee, I've experienced very often that until something we know experimentally, the theory can be very nice, but the experiments will show something completely different. Because it's such a complex system, it's very hard to theoretically take into account all the things that have an influence on our coffee brew.

This is where I learned I need to be very careful when talking about why. Because in so many cases, we're not actually sure why. Brewing your coffee this way leads to that change in flavour.

And so this is the third and final way I learned to think more like a coffee scientist. Just don't get hung up too much on theories in the first place. Focus on the practicalities.

Focus on the fact that, look, magnesium in water leads to a different flavour. That's what matters. And don't get too hung up on the explanation, the why.

They're important. We need them. But focus more on the raw evidence.

Next time I'm in my kitchen and someone asks me, James, why do you choose a water filter which adds in magnesium? I say, well, magnesium in water for me leads to more vibrant coffees. And we're not 100% sure why.

Coffee is an extremely complicated system. And there is still so much research we need to do.

And so, this was a journey I went on, to think more like a scientist. I realised three very important things. The first thing I always do is look for good evidence.

Two, if I can't find good evidence, then I just wait for good evidence to emerge. And three, in the meantime, don't get hung up on theories. Just focus on the practicalities.

Since I have been doing these things, I feel like I've stopped myself falling down some time-consuming rabbit holes. I mean, there are so many rabbit holes in the world of roasting, espresso, grinders, so many. My challenge is now, how do I stay disciplined to put this time that I'm saving into understanding these sustainability challenges for coffee growers?

But if there was just one thing you take away from this episode, it is this. As a coffee lover, as a professional, what would it look like for you to think more like a scientist? And what would you do with the time you save?

So, thank you very much for listening. Ah, this episode, woof, my lord. This was the hardest episode I think I've ever made in my life.

How do you make something as heady, philosophical, how to think like a scientist, interesting in audio? Ah, so I really just hope you enjoyed it. And if you're curious to know what that artistic journey looked like, I'm gonna write a newsletter about it on Substack.

If you're interested, follow the Substack link in the show notes and subscribe to my newsletter. Now, I'm really curious to know, like, what thinking more like a scientist means for you. And here's a suggestion, take a screen grab of your podcast player listening to this episode, post it as a story on Instagram, tag me at filterstoriespodcast, and write in that story what thinking more like a scientist looks like for you.

Maybe it's one thing from this episode, or maybe even just taking more time to think more critically about things. I don't know, just tell me. I'm really genuinely very curious to know.

And now let me tell you what is left in this series of The Science of Coffee. In the next and final episodes of this series, I take you into the science of coffee freshness so you can get the best flavours from your coffee day in, day out. And I go back to Zurich and I speak with the technical experts inside Malcoenig, an industry leader in coffee grinders trusted by baristas globally.

And as there I take you deep into the science of grinding coffee. And in case you missed them, there are a bunch of episodes before this one. In the first episode, I show you how you can become a better coffee taster by showing you how your sense of taste and smell works.

And what I do is I brew many batches of the exact same coffee using the SP9. It's an automated filter coffee brewer made for cafes by Marco Beverage Systems. Each batch of coffee is extremely consistent.

And what I do is I give this coffee to different people. And then I get wildly different responses as to how it tastes. And so I go on this metaphysical journey and ask the question, when you and me drink the same coffee, are we tasting the same thing?

And then I explore the science of roasting. The place where so many of coffee's delicious flavors are created. I hop on a flight to Norway to visit Roost, a company making fully automatic coffee roasters.

And I open up one of their prototype roasters, the P3000, to show you the cutting edge technology in it that enables anybody to roast coffee exceptionally easily. And in the episodes before this one, I take you with me to Honduras. And I show you what organic farming actually looks like.

What are farmers doing differently in organic farms compared to quote unquote normal farms? And then with the coffee importer Sustainable Harvest, I go down to visit a cooperative they work with, Rouse, who are one of the most successful organic cooperatives in the region, and I show you why it is so difficult to create an organic cooperative. And that maybe explains why less than 10% of the world's coffee is actually grown organically.

The Science of Coffee is produced by me, James Harper, and I also write and play the piano music. I wish you well on your scientific journey, and I can't wait to speak with you next time.