Protecting your coffee’s flavours

So, in the specialty coffee community, one thing that brings us all together is a love for fresh coffee. Vibrant, interesting flavours. But freshness is a race against time.

Because once coffee is roasted, it immediately begins to get stale. At its worst, stale coffee is such a disappointing experience. When I think, how bad can it get?

I think back to a specific time in my life in London.

Do you remember when London was fun?

We're getting old, aren't we? It's 2010 and I've just began my career in finance. And I lived with some wonderful flatmates.

It was quite the domestic dream.

Like my friend Vas. And every Saturday morning, we had our little ritual.

Yeah, you'd wake up and probably at about 8.39, you'd say, you want to go for coffee?

We'd walk on down to Mum of Coffee, one of the most famous coffee roasters in town. I'd order a latte and also get some beans for home, which they would grind for me right there in the shop. Because it does a deal, right?

Buy a bag of beans, get your coffee free or something like that.

Yeah, still something I look for nowadays. And I keep asking for my free coffee. And people are like, what are you talking about?

Out of 2010.

And then? The next day and then for like the following weeks, right? Every morning, I'd make a Bialetti mocha pot, right?

I'd take out the coffee from the fridge, scoop some coffee into the mocha pot, you know, put it on the stove. And now it will come like a kind of thick, somewhat creamy espresso. And the next day on the Sunday, the coffee I would make at home in my mocha pot, it was so rich, delicious.

I forbid my poor flatmate Vaz to put any milk in it.

I like to think of it as your early puritanical days.

But then as the days went by, the coffee started changing.

Yeah, I remember the smell of the ground beans would change quite drastically. And you know, when you open a grinder and you just smell the empty grinder, it starts to smell like that.

And by the fourth week, our coffees tasted so flat, stale.

Later on, you would allow me to have a milky coffee, probably, because...

Because it wasn't sexy so great.

Thanks for watching! When I bought that coffee fresh, it was as if I was looking at a balloon party with like red balloons, blue balloons, yellow balloons. But then, every day, the saturation dial got turned down and down and down until those balloons were just grey.

Anyway, fast forward a couple of years. It's now 2012, 2013, and I am obsessed with all these amazing specialty coffee shops that are just popping up across London. And it's while I'm speaking with baristas that I began to learn about coffee freshness.

To get the best flavours from my coffee, I needed super fresh roasts, and I had to grind my beans just before I brewed them. And my brews were now tasting so much better. And then, armed with this newfound knowledge, I gave my poor friend Vaz more of a hard time because he was grinding his coffee in the morning at home, and then he would use that coffee five hours later at work.

But then you were quite insistent that I had to get it to work as quickly as possible in order to make it.

Why? Do you remember why I was saying that?

Because it would affect the flavour. It would oxidise it, and it would effectively go off.

And the way I presented it to Vaz, it was almost like a moral obligation.

It was about flavour, but it was also about justice.

I tell him, look, a farmer has worked really hard to produce this product, and you have to savour it at its most fresh and vibrant. It's like the farmer wrote this beautiful love letter to you. And by not grinding their coffee fresh, Baz, you're tearing that letter in half.

I mean, I was feeling anxious about it. I was giving him anxiety about it.

Of course it was stressful. I was being told that the thing I was using to wake up, I was doing wrong.

Many years go by and eventually I start this podcast and begin work on this specific episode on coffee freshness. And I discover, you know, what I told Vaz was wrong. I'm sorry you were doing the right thing all along and I just didn't know any better.

In this episode, we're going deep into the science of coffee freshness. And my hope is that once you understand how coffee freshness actually works, you're going to be a lot less anxious about having to always grind your coffee fresh. And you might even decide to age your coffee on purpose.

And this episode is sponsored by Mel Koenig, the leader in coffee grinders, trusted by Borises Globally. And not in this episode, but the next one. I'm gonna take you into the science of grinding coffee, and you're gonna see some of the R&D that is behind the one million burrs, like grinding teeth, that they manufacture every year.

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

So, this is, okay, so the idea is making an episode on coffee freshness. So, when I first started making this episode, I wanted to make the case, this is why coffee freshness matters. I'm going to get some experience, coffee professionals, have them taste the same coffee that's been ground fresh and also ground months ago, and show me and you, like, look, look at how the flavour is changing.

This is why freshness matters.

And so, one day while I was here in Berlin, I cycled down to my favourite coffee roaster in the city, 19 Grams. Six of their best staff very kindly gave me an hour for the tasting, in the line-up where their head barista, their education manager, their wholesale manager, their e-commerce manager and their head roaster and green buyer, Garrett.

And I set up a blind triangulation.

Three coffees, two are the same, one is different. Can you spot the difference? Now the middle coffee, the odd one out, it was ground up almost two months ago.

The ones either side to it, cups one and three, they were ground fresh. Same grinder, same grind setting. And most importantly, they didn't know what this experiment was about.

They had no idea what I had done differently between the coffees.

So the tasting begins. I'd asked everyone to write down their answers and not talk during the tasting so they wouldn't influence each other. And it was amazing watching their faces because, you know, when they started out, they were smiling, excited, curious.

And then they went round a second time and their smiles were fading. Brows began to furrow. They were looking at each other, worried.

After 20 minutes of silence, Garrett, the head roaster, he went round the table for a third time. You came back for a third round?

Yeah, it's necessary.

It's not easy. And then he cracked. He started talking and everyone started talking, saying they were really struggling to taste any differences at all.

And look, Garrett, he's Q certified, as in he's completed one of the coffee industry's most difficult sensory certification courses. And even he said...

Well, I would say that this is one of the harder triangulations I've done, basically.

All right, let's get to the results.

Clap for me if A1 was the odd one out for you. Okay, A2? A3?

A2 was the right answer.

Four out of six correctly guessed the middle coffee was the odd one out. It was the older coffee that had been ground up two months ago. And the team suggested that flavours had changed in these very subtle ways.

For example, Garrett, 19 grams head roaster, he said the acidity was a little bit more muted.

For me, what stood out was probably the acidity.

Peter, one of their barista trainers, The mouthfeel was close but different. He said the older coffee was a little bit drier.

One felt a little bit drier than others. At least there was some kind of roundness to two of them and then one always kind of felt a little bit different.

So the acidity a little bit more muted. The mouthfeel a little bit drier. This is not what I would call a dramatic difference.

The difference is they've been aged different amounts. And it was so funny to watch their reactions when I told them that middle coffee had been ground up almost two months ago. So that's the difference that a month and a half, two months of ageing makes on ground filter coffee.

They were literally speechless.

It's a podcast and I'm not saying that much.

Yeah, it's crazy.

But you know what, even I was super shocked by the result. It took me like a whole day to process and think about, well, what does this mean for the episode that I'm making? I was expecting this coffee that had been ground up two months ago to behave just like the coffee that had been sitting in my London fridge.

I expected the flavours to be flat grey. And to understand why it was still surprisingly fresh, let's now dive deep into the science of coffee freshness.

In the dying days of August last year, I took a train to Switzerland, Zurich, made my way down the lake, and walked into the Zurich University of Applied Sciences, where I met the scientist who did the research behind the Specialty Coffee Association's Freshness Handbook.

I'm Samo Smrke. We are here at the Coffee Excellence Centre, and we study coffee from the chemistry point of view.

Now, Samo, he got curious to know, what does coffee aging look like chemically?

So, you measure this by technology called gas chromatography. So, you take a sample of the gas above a sample of a coffee in a glass vial.

And to answer that, he did this experiment where he put coffee in glass jars. And on top of the glass jars, he stuck in these different probes that measured the chemicals that were in the air.

You inject this gas into this instrument. This instrument separates these compounds by their volatility. And then they are detected by an instrument called mass spectrometer.

Have you ever had a dream, Neo, that you were so sure was real?

And as Samo was describing this experiment to me, I began daydreaming of that scene in The Matrix.

Where Neo, he wakes up in the real world. He's working up out of the matrix, he's in the real world, and he's in this pod with all these wires attached to him.

And just like that, I'm back in the room with Samo.

And then they're detected by an instrument called Mass Spectrometer, an instrument that detects compounds based on their molecular weight.

Simply put, Samo measured how many compounds left the coffee into the air. And the more coffee compounds that are floating up in the air, the less there are in the coffee grounds, and therefore the less you're going to get in your coffee brew, making it taste more aged, less fresh. And some of his results were pretty dramatic.

Samo gave me a generic example, like for a specific flavour compound, half of it could disappear in just a month.

Let's say, you know, just to give some numbers, in one month's time, there would be 50% loss.

And when I hear these sorts of numbers, I think, wow, that's a lot. But this is not to say that the freshest of coffee is slashed in half after a month.

It's actually extremely hard to do this direct transition from the chemistry to the flavour.

Listen to my episode on smell and taste, and you'll get an idea of all the different layers, systems, connections between our receptors and our brain, and why it is that if you were to take out 50% of a specific aroma compound, it doesn't mean you therefore smell 50% less of that aroma compound. Now, the results of this experiment showed that there are two big processes at play that make our coffee taste more and more lame and worse. The first is called diffusion.

This is where coffee flavours in the coffee grounds travel up in the air and they leave the coffee.

The aroma molecules will travel from a place of high concentration to a place of low concentration.

Diffusion is mostly responsible for taking the vibrancy away from our coffees.

The aroma is flat, it doesn't have the complexity or the intensity.

The second process that's happening at the same time is oxidation. Basically, oxygen in the air is reacting with some of the flavour compounds in the coffee, changing its taste.

Bigger impact of oxygen is in generation of new off flavours.

And this process, oxidation, it's responsible for a quite pungent, slightly off flavour in coffee.

These are very unpleasant to specialty coffee drinkers.

And so in Samo's experiments, he would see that as soon as you finish roasting coffee, these two processes, diffusion and oxidation, begin. And they keep on going until what you have is maybe what I was drinking back in London after 4 weeks. Not particularly pleasant faint whisper of the coffee that I had drank fresh.

So why is it that the coffee I would drink in London would get stale so quickly, whereas that ground coffee in the 19g cupping, which was almost 2 months old, it barely aged at all?

Most of it comes down to how coffee is stored. Because in almost every single way, the way that I, young dumb James, back in London stored my coffee, I couldn't have done it worse. And the way I stored that 19g coffee, it was almost, almost perfect.

To the point where it barely aged at all.

So, for the 19 grams cupping, here's what happened. About two months ago, I got some beans, ground them up, and then immediately put them into this aluminium tin. I screwed on the lid, and it sat on my desk in the shade, untouched.

Let's shrink ourselves down and sit in that container. Imagine you are a flavour molecule on a piece of ground up coffee, sat next to you, to your left and right, a lot of other flavour compounds too, and you're all squished together and you want more space. And where is there more space?

Ah, it's the air just above you. And so you see that some of those aroma compounds that are left and right of you, as you're all squished up together, some of them get taken up into the air.

The aroma molecules will travel from a place of high concentration to a place of low concentration.

Now, here's the first reason why that 19 grams coffee was stored well. That container, it was quite small. So there actually wasn't very much air around the coffee powder.

And very quickly, the air got full saturated with aroma compounds floating around.

And they will travel until there's a certain equilibrium formed.

And eventually, those aroma molecules that were to your left and right of you, you know, they just stop going up in the air as much and stay put attached to the ground coffee. Limiting the amount of air in your container in the first place slows the process of diffusion right down. The coffee is kept fresher for longer.

Now, let's rewind time and open my old London fridge. So back then, every morning, I would open up my bag of coffee, scoop out my ground coffee, roll it up, and put it back in the fridge. Every day, I was refreshing the air in and around that coffee.

And so the flavour molecules kept finding new space to leave the coffee grounds up in the air. By changing the air all the time, I sped up the process of diffusion. And the coffee's intensity and vibrancy faded so much faster.

And so if you want to keep your coffee as fresh as possible, Samo's first tip is use a container with very little air.

That's probably the most critical. It's the head space in the back. So if you give coffee aroma space, it will diffuse out.

And once your coffee is in the container, don't open it until you absolutely have to.

Keep as much as possible of this initial aroma in the back for as long as possible. Thank you.

Let's look now at the packaging materials. What the coffee was stored in. Now, that 19 grams coffee, it was stored in an aluminium tin, whereas Melondon coffee was stored in a brown paper bag.

Picture that brown paper bag sitting in Melondon fridge. In and around that bag are gazillions of oxygen molecules bouncing around doing their thing. And the thing about oxygen molecules is that they're really, really small, and they will find their way through the tiniest of gaps.

When you pick up a brown paper bag and you put it to your eye and try to see something through it, like you won't see anything, it looks incredibly dense. But microscopically, if you are a piece of oxygen flying around, the gaps in between those layers of brown paper, they're enormous. Oxygen flies right through and slams into the flavour molecules sitting on the ground coffee.

And when oxygen hits these aroma compounds, oxygen can react with certain aromas to kind of degrade them.

So a little aroma compound, which gives us that beautiful note of jasmine, might just disintegrate, turn into something else which has no aroma, or worse.

Oxygen reacts with the lipids from the coffee bean.

Oxygen could hit some of the oils, the lipids, sitting in the coffee grounds. And in that reaction, a new flavour is created which actually tastes fermenty, you know, like a food that's going off.

So it does produce rancid flavours.

So, you know, young, dumb James, I may as well have put a sign next to my coffee bag that read, hey, oxygen, come this way, ruin my coffee flavours for me, degrade them, turn them rancid. Thank you so much. And this is why Samo suggests don't store your coffee in a brown paper bag.

It's very little that it does to protect the aroma.

But if you love paper bags, well, there's a very simple thing you can do, which will help a lot. Add an inner plastic liner. Because plastic is much better at keeping out oxygen.

It's not a full barrier.

Not perfect, but a lot better. But you know what is a full barrier? A material that oxygen cannot get through at all?

That tin of 19 grams coffee sitting on my desk. It's made of a relatively thick aluminium, and the website chemeurope.com informs me that this aluminium tin is thick enough that it is impermeable to oxygen. And so for the two months this tin sat on my desk, all the oxygen molecules that were whizzing around my room, bouncing around, could not get through to oxidise my coffee.

My flavours were protected. And so if you don't want rancid flavours in your coffee, store your coffee in a container that is impermeable to oxygen.

Now, here is another reason why that bag of coffee in my London fridge aged so much faster. And that's because it was ground much finer. When I was at the offices of Malcooneeg, I spoke with the head of their engineering department.

My name is Arnaldo Rodrigues.

I'm the Group Head Innovation and Technology for the Hammer Group.

And Arnaldo estimated that in a typical 18 gram double shot espresso, 90 odd coffee beans are smashed into maybe 40 odd millions particles. So the coffee sitting in my fridge in London, that was ground close to an espresso grind, which means every single bean was broken up into almost half a million pieces. Half a million pieces per bean.

Now in contrast, the 19 grammed coffee was ground much more coarsely because I was making a filter coffee. And for example, 90 odd beans ground for filter, much less than 40 million.

I would expect it to drop it to the lower millions perhaps.

So grinding for filter, that 19 grams coffee, each individual bean might only have been broken into 50,000 pieces. Now all of this matters because of surface area. More surface area means more contact with the air, which means faster rates of diffusion.

The distance from the inside of the particle towards outside is much smaller in the espresso. So it's then again, much faster loss of aroma.

So the coffee that was sitting in that brown paper bag in my London fridge, it was ground very fine, close to espresso. And so the surface area was enormous compared to that 19 grams coffee. So much more of the coffee's flavour compounds were directly exposed to the air, where they could diffuse out and be oxidised.

And so if you want to push coffee freshness to the max, hey, why don't you make a coffee particle as big as it possibly can be? Don't break it in the first place. Just keep it intact.

The oldest advice is specialty coffee. Buy your coffee in whole bean form and grind it when you want to use it.

So we've just covered three big things that young, dumb James did that ruined my coffees back in London. By using it all the time, I constantly refreshed the air in the bag. The bag itself was made of brown paper, so, you know, oxygen could fly right through.

And I ground it up super, super fine, instead of keeping it in whole beans. And so oxidation and diffusion would just rampant. And it doesn't stop there.

I made another terrible mistake. By storing my coffee in the fridge in a brown paper bag, humidity also ruined my coffee, because humidity tends to speed up the process of diffusion.

It's known that if coffee has higher humidity, the aroma rate releases from the material faster.

All right, fun fact.

Fridges, actually pretty moist environments. And so because that coffee powder was sitting in a brown paper bag, it was like an open invite party.

Moisture, heard the music, strutted past the bouncers, put their elbows on the bar, and made moves on my coffee powder.

Things go really smooth, and the water molecules in this humid air, they attach themselves to the coffee.

And they start to compete with the aroma molecules. The water will just jump in and take those spaces, and then it will push out the aroma. And that's why, that's like the basic mechanism why when you have water coming in, the aroma losses are a bit faster.

Now seems like humidity, it's a small effect.

From the data that I've seen in publications, it's not really dramatic.

But it plays a part. Now, in contrast, that 19 grams coffee stored in my aluminium tin, I sealed it on a dry day, didn't open it again, and so moisture couldn't get in. So if you want your coffee to be as fresh as possible, start in a dry environment.

Okay, so now, here are two things that young dumb James actually did well when it came to that London coffee sitting in the fridge. The first thing, light.

Anything from the blue light to ultraviolet and so can start chemical reactions. And I would say that this might be involved in the oxidation or helping the oxidation.

And actually both coffees, the 19 grams coffee sitting in a tin and my coffee sitting in the London fridge, both kept the coffee dark. But at this stage, the coffee community is actually not sure how much of an effect light makes.

I don't know of any studies of effect of light on the coffee.

But hey, if you want to play it on the safe side anyway, store your coffee in a dark container. And whatever you do, keep it away from the window. So up until now, if this were a game of tennis, that 19 grams tin has won four sets against that coffee sitting in a brown paper bag in my London fridge.

But for the fifth set, they've been added neck and neck because both coffees were kept away from light. And now is the moment where young dumb James with his old London coffee strikes and wins a set against that 19 grams tin.

Because there's one thing that London coffee did better when it comes to protecting freshness, temperature. Please take your seats quickly, ladies and gentlemen.

Thank you. Increasing temperature is actually quite dramatic. Temperature has a big effect on coffee freshness because the lower the temperature is, the slower the molecules are moving around the coffee bean.

And the slower everything moves, the slower diffusion and oxidation ruin coffee's flavours.

Cooling down reduces the reaction rates, reduces oxidation rates and reduces the diffusion rates. So everything comes much, much slower.

So the air in my London fridge was what, four degrees Celsius, which is four times colder than the air in my room, the 19 grams coffee was in. And so while that cold air did help that London coffee last a little bit longer, I had screwed up too many other things that ruined my coffee so quickly. And that is why that London coffee aged so much more than the 19 grams coffee.

So, summing it all up, if you want to keep your coffee as fresh as possible, buy whole bean coffee, make sure the packaging is impermeable to oxygen, keep the air unchanged for as long as possible, keep the coffee away from light and humidity. And I know that, you know, as a list, it can all sound a bit confusing, but literally, one of the simplest, easiest, most effective things you can do is just buy your bag of beans and don't open it.

The best recommendation for storage is in the original packaging.

And when you take your bag of beans home, store them somewhere cold. For me, the back of a cool cupboard works great, but you might be wondering to yourself, you know, if temperature is really that important, shouldn't I store my coffee in the fridge? And yes, hey, if you want to be really fanatical about it, store it in the freezer.

Once it's there, don't open it. And when it's time to use it, take it out, put it on the counter for a couple of hours so it comes back to room temperature, use it like normal and store it in the cupboard. But I kind of have bad news for you.

Putting coffee in the freezer, it won't stop oxidation and diffusion entirely. It's just not cold enough. Unless that is, of course.

You happen to work in a science lab and you find a little corner of their lab-grade industrial fridges where you can store your coffee and no one's gonna notice.

Typically, in a laboratory, we have minus 80 degrees Celsius freezer, then significantly stopping down these reactions.

So, I've just taken you through how oxidation and diffusion fade and age coffee's flavours. But there's more to the story of coffee freshness than just that. And this story begins when I came across something confusing, like this mysterious thing that kept happening to me every time I made a coffee.

So every morning, I walk over to my studio here in Berlin. But before I get down to work, hey, I need a coffee. So I weigh up my coffee beans, about 30 grams for a half litre pot of coffee.

I throw these 30 grams of beans into the grinder, get out some powder, pour it back on my scale, and then I notice something weird. I've just lost a little bit of coffee. The scale reads 29.7 grams.

0.3 grams have just disappeared in the grinder. And this happens every single day I make a coffee. 0.3 grams just disappearing.

By removing the burrs and the impeller, we can clearly see some coffee grinds all around the edge where the hopper fits in.

Now, I'm aware of a very well-known phenomenon in coffee circles, this thing called grinder retention. And you know, as I scroll through Coffee Reddit YouTube, I would see videos of people taking apart their grinders.

And you can see the coffee grinds all around the impeller.

And it's stuffed to the brim with ground coffee. And I look over to my grinder and think to myself, jeez, that grinder must be absolutely jammed. And then one day I think, okay, it's time.

Let's clean this thing. I take off some bolts and do some screws, open up the grinder, and it is whistle clean. I had this grinder for a year, and there was not a single fleck of coffee in between those grinding teeth.

Okay, so I put it all back together, made myself another coffee, and look, I just lost 0.3 grams again. Where was this coffee disappearing? And it's only when I spoke to Samo for this episode that it all made sense.

So early on in Samo's career, he went to this conference.

It's a conference which is called ASIC. It's a coffee science conference.

And he saw this presentation about how coffee loses weight over time, and he got inspired to try it himself.

And this is something we thought about that would be really interesting to have this method validated, used in our lab.

And so Samo put together an experiment. He ground up some coffee and then just put them on these super sensitive industrial scales.

If you grind coffee and put it on this scale, you can literally see the weight decrease.

Coffee was literally changing before your eyes.

Yes, it is, yes.

But to understand what exactly was going on, Samo put a glass jar over the top of the coffee grounds and measured the air pressure.

You see the pressure increasing, like literally within seconds you see this and then 10, 20 seconds you start to see a difference. So there's really such an amount of gas in and also the change is very fast.

This is the smoking gun in my mystery. Freshly roasted coffee, it's full of carbon dioxide created during the roasting process. And over time, this carbon dioxide degasses, it leaves the coffee into the air.

And as Samo explained to me, this CO2, it's found deep in the pores of the roasted coffee. But when you grind it up, it is released fast.

When you break up the coffee structure, you break up the pores where it's contained.

This is the reason my scales were telling me my coffee had got lighter after I'd thrown it into the grinder.

You literally have a gas release from the bean, it's literally flowing out as you break up the pore structure and you directly see this loss.

But one thing I couldn't wrap my head around was like, come on, how heavy can a gas be? It's a gas, like, it weighs nothing. But hold on, carbon dioxide, which is most of the gas being released, right?

You're saying it has a weight?

Of course the gas has a weight, yes.

And it's here I learned a thing or two about gases. Carbon dioxide turns out quite a heavy gas.

Carbon dioxide is about two times heavier than air, so denser than air.

But the main reason it adds so much weight to coffee is because that carbon dioxide gas is squished into the little pores of the coffee.

It's under pressure, so it's compressed.

It's a bit like scuba diving, a tank of oxygen, really, really heavy, because it is compressed gas.

And so that was my little Grindr mystery explained. But what does that mean for you?

Get a feel for what that weight loss is between when you weigh out your beans and the ground coffee powder, and then add a couple more beans to compensate. But the other thing that's really important here, especially if you're a home roaster, if you put freshly roasted beans in a sealed bag, you'd better make sure the gas can get out somehow.

That's why, especially in a dark roasted coffee where it has a lot of gas, the bags really need to have a valve on them.

You know that valve, where if you squeeze the coffee bag, you can smell the coffee inside.

Because if they don't have a valve, they will explode sooner or later.

So, up until now, there's been an undercurrent in my story. Fresher is better. I mean, just look at the language I've been using.

Who likes flavours that are ruined? Stale coffee? Rancid, pungent flavour notes?

Obviously, fresher is better, because it's the most vibrant coffee can be. And for the decade or so that I've been in this specialty coffee industry, I never questioned the premise that fresher tastes better. And while I was at the offices of Mao Koenig in Zurich, I set up a tasting, because I wanted to show to you and me, like look, look how awful stale coffee actually tastes.

When you do a side by side comparison, same coffee, just one much more stale, look at all these beautiful flavours you're losing.

But the results shocked me.

So what I had done, about a month before, I picked up these two freshly roasted bags of this Kenyan coffee from 19grams. It was super fruity, acidic, very vibrant. I mean these sorts of high end Kenyan coffees, they're famous for just blowing your head off with an intensity of fruit flavour.

So one of those bags I kept completely sealed and only opened it on the day of the tasting. This was Coffee Freshness Best Practice.

So we start from left to right?

But then, for the second bag, I did something sacrilegious. You won't believe what I did here. I opened a bag of beans and I put it in a pot and left it in my room, which got up to 30 degrees during the day, because it was in the middle of Italy during the summer.

And I left it there for about a week and a half, and then I put it back in the bag. So all the beans were exposed to a lot of air. The tasting begins.

And like I expected, the fresh coffee, it tasted so much more intense. The one on the right hit me more generally with intensity, straight up. And then the second coffee, it was a little bit less intense.

It was a slower flavour experience. But actually, I preferred it more.

Like, if this was music, that fresh canyon, the gain was just too high, too much information, too hot.

But when I turned down the power, the intensity of the flares by aging it for a week...

Thank And this is when the bombshell hit me. Sometimes, fresh is not always best. And actually, that message, I'm seeing it in many different parts of the specialty coffee world.

Samo himself brought it up.

Because some coffees, they need a certain time before they are the most desirable flavour.

I scroll through Instagram, and I see a Barista Champion saying, guys, for me, espresso tastes better sometimes when it's a month old.

And just also the experience of the cup is not as enjoyable if you would have them well rested coffee.

When I'm speaking with Peter, 19 grams Barista Trainer, he gives his students the same advice. Let your espresso roast, rest for an entire month at least.

Where the acidity tends to be a lot sharper, but if you rest it, it's more enjoyable. It's a bit rounder, it's sweeter.

Now, of course, an espresso who resting your coffee is a much more established idea. But I think in some cases, it also applies to filter coffee.

And so, going on this journey, this is where I've landed.

By storing your coffee well, you can dramatically slow down how fast your coffee ages. And if your coffee does age quite a bit, yes, the flavours change, but not necessarily in a bad way. I might actually like that change.

And I implore you, do some blind tastings yourself, replicate what I've done, and let your taste buds tell you what you like. For the last 10 years, I've had a mantra in my head. Fresh is best.

But you know, push it away. Don't listen to it. Listen instead to what your taste buds tell you.

They will tell you what you like.

And one of the beautiful things coming out of this journey, now that I've realised that fresh is not always best, it's like a weight was lifted off my shoulders. I can just relax a bit more. Oh shoot, I found the bag of coffee that was roasted three months ago in the back of the cupboard.

Well, if it's been sat there unopened in the same packaging, it's probably gonna taste really good. Oh shoot, when I made my coffee this morning, I accidentally ground up too much coffee. And now I have too much ground powder.

I'm gonna have to throw it away. No, don't throw it away. I'm gonna put that excess coffee in a small aluminium tin and I'll use it tomorrow.

The difference, if there's a difference at all, is gonna be tiny. Realizing that fresh is not always best. Ah, it just takes off the pressure from my relationship with coffee.

And then I thought back to my friend Vaz.

Of course, it was stressful. I was being told the thing I was using to wake up, I was doing wrong.

I had laden him with anxiety, shame for grinding his coffee in the morning and then brewing it, what, five hours later in the office? I felt bad about that. And so when I was on the phone with him, I told him everything that I learned in this episode.

Okay, so what happened is I actually did a whole episode about freshness, coffee freshness, and the 19 grams cupping. The differences were super subtle. A small difference in body, a small difference in acidity.

Like if you weren't paying attention, you wouldn't notice. So for me it was a revelation, right? I've been so obsessed by freshness and stressing myself out and stressing you out to some extent.

Are you telling me that I could have done a big grind on a Sunday and then my whole week will have been just that little bit smoother?

If you had stored it in a way which protected it, which you do, yeah, you totally could have done that. So I feel like I owe you an apology. I'm sorry for being puritanical and stressing you out, wasting your time.

For grinding me down with this dreadful behaviour over multiple years.

I'm sorry, you were doing the right thing all along and I just didn't know any better.

Well, you're forgiven because I probably learnt a lot about just how food goes off. And you know, it was all part of my journey of respecting the things that I eat and I drink.

Bye So, thanks so much for listening. If you enjoyed this episode, it would mean so much to me if you spread the word to your friends. I don't have a big marketing budget or anything, so I really just rely on you liking what you hear and spreading the word.

You can do that by tagging me in an Instagram story, take a screen grab if you listen to this podcast, or if you're on LinkedIn, share it there and tag me. This is the second last episode in this second series of The Science of Coffee. Next up, we're going deep into the R&D lab of Malko & Egg to learn how grinders, teeth, particle sizes, all work to produce delicious coffee.

And in case you haven't heard it yet, let me quickly tell you what else is in this series. So in the first episodes, I show you how you can become a better coffee taster by unpacking how our sense of taste and smell works. And I do this test where I brew up many almost identical coffees on Malko Beverage Systems SB9, which is this automated filter coffee brewer for cafes.

And so with these almost identical batches of coffee, I give them to different people and they give me wildly different responses as to what they're tasting. And it sets me off on a metaphysical journey to answer, when you and I drink the same coffee, are we tasting the same thing? Then we go deep into the science of roasting, where so many of coffee's flavours are created.

And I visit Roost, a Norwegian company developing a fully automatic coffee roaster. And I show you how their cutting edge technology enables anybody, including me, to roast exceptional coffee very easily. Then we hop on a flight to Honduras.

I attend Coffee Importer Sustainable Harvest Let's Talk Coffee Gatherings. And it's there where I, for the first time, actually appreciate why organic farming is so much better for the environment than conventional agrochemical coffee farming. And even though it's great, why don't we see more organic coffee farms?

And I answer that question, exploring how one of Honduras' most successful organic cooperatives, RALSE, managed to overcome so many hurdles. And then, in the episode before this one, I take you on my personal journey, where I realise the importance of robust scientific methodology and how it helps me brew better coffee at home. This journey was made possible by BWT Water, More, who make water filtration kits for the cafe and for your kitchen at home.

And as it turns out, me learning the science of water helped transform me from a naive coffee professional to a little bit less naive home scientist.

The Science of Coffee was produced by me, James Harper. I also write and play the piano music. Thank you again for listening, and I'll speak to you next time.