Fruit juice or creamy almonds? Your guide to controlling cold brew flavors

James Harper:

One thing I love about cold brew is that it's easy, easy to make. Even a caveman could make cold brew. Don't believe me?

Me James, caveman, need coffee. Well picture me wearing a leopard skin leotard, dragging a wooden club behind me. Caveman James walks into the kitchen.

James Harper:

Me found bean. You find some random old coffee in the back of the cupboard. Must grind bean.

How much coffee?

James Harper:

Don't know. He dumps some beans into a pestle and mortar, crushes it by hand. Bean, now powder.

He finds a dusty Tupperware box in the back of the cupboard.

James Harper:

Me found container.

James Harper:

Chucks a coffee in, opens a tap.

James Harper:

Lid on container.

James Harper:

Caveman James leaves. Me back tomorrow. Sleeps in his cave overnight, comes back in the morning.

James Harper:

Me back, need coffee. Lid off.

James Harper:

And to filter out the coffee grinds, he finds an old rotten sock from the back of the cupboard.

James Harper:

Pour coffee in sock.

James Harper:

Have coffee. Me happy. And that's it.

I had caveman coffee and it tasted absolutely awful.

James Harper:

Seriously, this tasted bad. Jack, would you like your morning coffee? Yes, always.

James Harper:

I invited my co-worker Jack to try some.

Jack:

Bit of a grimace in your face there.

James Harper:

He confirmed it tasted awful.

Jack:

Yeah, I'm not sure I want that one as my morning coffee. What's wrong with it? It's very bitter or something.

It's astringent.

James Harper:

So yeah, look, cold brew, easy to make, but to make it well, you got to pay attention to the details, which is what I did in the second brew I made. Now I'm going to weigh out a very specific amount of beans. Using the exact same beans caveman James found, I made another cold brew where I paid attention to the details to see if it would actually taste any better.

I weighed out the beans, ground them up on a proper grinder, not with a mortar and pestle. I have it set to 13 on the Weber Workshops key grinder. I used filtered water, not just random tap water, and brewed it for the same 19 hours.

Jack:

Taste the other one. This guy? Yeah.

James Harper:

And it tasted pretty good.

Jack:

Yeah, I prefer that one. Yeah? Yeah.

By a lot? Notably, I would say. Okay, well, good news.

It really matters how you brew cold brew. You have to do it in a careful way. Okay, so you're not going to serve me up that first one as my morning coffee.

James Harper:

I don't think I brewed the coffee in the right way. Don't think about that. Don't think about what I did.

There's no need to think about it at all. It's not on my mind. Good.

James Harper:

All right, look, the fact that I started this episode saying cold brew is so simple a caveman could do it, I honestly believed that until I tried it and realized I was wrong. But I mean, that goes to show that I am not a cold brew expert. In fact, for the longest time I've been a coffee drinker, I very rarely ever drank cold brew.

I'm a filter coffee guy, pour over V60 Chemex, and that has been my jam for so many years. But in the last episode, which I recommend you listen to before you listen to this one, I discovered that cold water can bring out delicious flavors that you cannot get using hot water. Raisin toffee flavors.

Really nice. Yeah. And over this last year, I've been brewing a lot more cold brew.

When I had a new bag of roasted coffee to try out, you know, I would drink it as a hot brew, of course, but also sometimes as a cold brew. And what I quickly discovered is that cold brew operates nothing like hot brew. Huh, how weird.

I had to learn an entirely new syllabus of like coffee extraction science to wrap my head around why cold brew behaves the way it does.

Jessie (Jie Xin):

Dissolution happens in one way, and adsorption will also happen in one way.

James Harper:

It took me quite a while to figure out what I should be adjusting in my cold brew recipes to get different flavors from my coffee. And in this episode, I'm going to take you on my journey wrapping my head around how I learned to brew cold brew. So the flavors have shifted, but the strength hasn't.

And at the end of this episode, you're going to know what recipes work great for cold brew. You're going to learn a lot from the world's leading coffee scientists about the mysterious, wonderful things going on when water and coffee interact.

Chahan Yeretzyan:

Our liquid system is very unstable. This is why nobody really wants to store coffee in a liquid format.

James Harper:

And my partner sponsor for this episode, who provided me the means to go on this journey in the first place, is Toddy, the specialty coffee world's leading manufacturer of cold brewing equipment. So go over to your kettle right now and turn it off. Because we're brewing with cold water.

I'm James Harper, and this is Filter Stories, the untold stories hidden in your cup. And you're listening to series three of the science of coffee, a journey into coffee's hidden microscopic secrets. My journey into cold brew began one day when the Toddy cold brew cup arrived.

I opened the box and I found some flasks, lids, and filter papers. Now I just needed some coffee beans, but which ones? In the last episode, I showed you why cold brew works particularly great with very aromatic floral coffees.

And so for the first ever cold brew I was going to make inside my very own home, I chose some beans, which I knew were going to be an aroma bomb.

James Harper:

We're going to use Colombian coffee, a thermal shock 90 hour fermentation by the producer Oscar Hernandez. Lovely.

James Harper:

Now, like I mentioned, I'm a hot brew guy. Pour over V60 coffee. That's my thing, has been for years.

And sometimes when I get a new coffee, one that I'm not familiar with, one of the first things I do is try to understand what are the different flavors these roasted coffee beans can offer me. And the thing that I like to adjust to get different flavors is the grind setting. I grind my beans a bit finer, a bit coarser, make a bunch of brews, see which one I like the most.

And so that's what I decided to do with my cold brew as well. Pour some beans here, same amount of beans in both brews. I decided to make two brews.

One ground fine. And I'm going to make it significantly coarser. There we go.

One ground coarse. Cool. Now I'm going to add the exact same amount of water into both of these, 250 ml.

And let them both brew overnight. And the results of this experiment blew my mind. It helped change my understanding of the mysterious microscopic things taking place when coffee grinds are floating in water.

That's coming up next. So the next morning, I'm back in my studio. I put my two cold brews side by side.

One with finely ground coffee, one with coarsely ground coffee. I take some sips and taste the difference.

James Harper:

It's really hard to tell the difference here.

James Harper:

Or I should say, I tried to taste the difference. I mean, in both coffees, I was getting these beautiful, strong aromas, but I could not tell the difference between them. I needed a second opinion.

And my coworker, Jack, he used to not drink very much coffee, but don't worry. I've got him totally hooked these days. He came in begging for a coffee like he normally does.

James Harper:

You haven't had your morning coffee today, have you?

Jack:

No, I need coffee.

James Harper:

But before we could walk away with a cup of my coffee, I asked him to taste the cold brews.

Jack:

I'm not getting a huge difference.

James Harper:

And again, I couldn't taste the difference.

Jack:

No, no. To me, they are pretty much the same.

James Harper:

I found this really, really weird. The grind size was barely changing the flavor of the cold brew. And I started to wonder, like, are the coffees actually the same strength?

Now, let's do a TDS measurement for the finely ground coffee. And so I decided to measure the strength of the coffees with a refractometer, also known as a TDS meter. And TDS is total dissolved solids.

Basically, how many coffee particles have made their way into the water? Like, how concentrated is the water with coffee? And the numbers, they were different.

Two. Two percent. Bang on.

But not by much. 1.93. OK. They weren't exactly the same, but they were pretty similar.

So similar, in fact, I thought, hold on, hold on. Maybe I made a mistake somewhere. Maybe the difference in the grind size just wasn't big enough.

I mean, it was an entire 360 degree turn on my Weber Workshops key grinder. And so just to make sure that actually was a big difference in grind size, I used those exact same grind settings, you know, the big and the small, but made pour over filter coffees instead with hot water, like I normally would. And what I found is that when I changed the grind size that much, There's a difference.

Jack:

A notable difference.

James Harper:

Even my co-worker Jack could taste the difference.

Jack:

It's a bit more tangy. More tang, fruit, sour. Yeah.

Sour on the left.

James Harper:

And the TDS differences were way bigger, almost four times as big compared to those two cold brews with the same big and small grind size. And this was the first big learning for me. Grind size.

It just really doesn't matter that much when it comes to cold brew. But that flies in the face of everything I've learned over the years. When I make classic pour over filter coffees, finer grind size should extract more.

And I was dying to understand why. Why doesn't grind size matter when you're making, I don't know, a 12, 24 hour cold brew? And I might have got an answer.

Speaking with a coffee scientist from the University of Applied Sciences in Zurich.

Chahan Yeretzyan:

I'm Chahan Yaretzian. I'm here, the head of the Coffee Excellence Center in Zurich.

James Harper:

Professor Chahan Yaretzian, he gave me a new way to understand the mysterious chemical processes taking place between water and coffee particles.

Chahan Yeretzyan:

What I call the exhaustive extraction.

James Harper:

Exhaustive extraction. All right, so anytime you make a coffee, you're going to pull stuff from the coffee grinds into the water.

Chahan Yeretzyan:

And there is a lot of different stuff you can pull from coffee. You have volatiles, cogenic acids, guaiacol, vanillin, caffeine, coffee oil, organic acids, and a whole bunch of other stuff too. Now, some of this stuff is easy to pull into the water.

Some compounds come very fast that are very easily soluble.

James Harper:

Like, for example, aromas, technically aromatic volatiles. So if you make a cold brew and let it sit around, maybe hypothetically the five hour point, all the aromatics that could be extracted have been fully extracted by that five hour mark. You will reach at some point a plateau.

And so at five hours, the aromatics are fully extracted. We've reached exhaustive extraction. But maybe at that five hour mark, there are other compounds which have yet to fully extract.

Chahan Yeretzyan:

And others, which are much less soluble, bigger molecules, they take time. And so you give it a couple more hours for those bigger molecules to extract.

James Harper:

And you get most of them to 80%. Not all of them, because in cold brew, you're just not able to get exhaustive extraction for every type of compound. To get there, you probably need more water, pressure, heat.

That's not what we have here. And so what that means is that at a certain point, you are going to reach an extraction plateau. So that's the idea of exhaustive extraction.

But then why didn't grind size make a difference in my cold brews? Well, it almost certainly did make a difference. My cold brew with the more finely ground coffee, it probably got to that plateau where most of the stuff that could be got was gone a couple of hours sooner than the other cold brew with the larger coffee grinds.

But what's one or two hours difference when I'm brewing this thing for 19 hours? It just doesn't matter.

Chahan Yeretzyan:

I reached exhaustive extraction on both of them hours before. So if you go to exhaustive extraction, at some point, the grind size doesn't matter that much.

James Harper:

Okay, so grind size didn't make a difference because I was brewing these coffees for so long. And so then I wondered, okay, well, like, what else can I play with to change the flavors of my cold brew? And then I was like, well, obviously, brew time, like how long the coffee is in contact with the water.

You know, just like in a French press, the longer you brew, the stronger your coffee is going to be. All right, now we're going to find out whether time changes the flavor of the coffee. And for this test, we're going to use a Finca Mux Bal from the Union Juarez, Chiapas, Mexico, roasted by my favorite roasters here in Berlin, 19 grams.

All right, let's go. And so I made two identical coffees with the only difference being time. For one of them, I took out the coffee grinds at 12 hours, and the second, I stopped brewing at 24 hours.

James Harper:

Okay, 12 hours first.

James Harper:

Raisin toffee, like spiced cake. Lovely. So that was a 12-hour coffee.

And then I tasted a 24-hour brew. And they were pretty similar, again. I mean, okay, a subtle, very subtle difference.

Maybe the strength of the brew? The intensity is dialed up a little bit, not dramatically, just a bit. The 24-hour brew had flavors that felt to me a bit more concentrated.

But when I measured the strength of the coffees using a TTS meter, I could not believe it. 1.98. They're basically the same. They're basically the same.

But what's really weird is that, well, to me anyway, there's a distinct difference between the two. Like, one is slightly more concentrated. I can almost feel a bit more of an intensity in my mouth.

But that difference is not being reflected in the refractometer. So the flavors have shifted, but the strength hasn't. Huh.

How weird. What is going on? Like cold brew, it just operates by its own rules.

It refuses to do what a hot brew does, right? In a French press, if you double the brew time from, I don't know, two minutes to four minutes, it extracts more, it tastes stronger, there's more coffee stuff floating around. But that's not what I was finding here.

In cold brew, I doubled the brew time from 12 to 24 hours, and there was only like a very subtle change in flavor. A bit more intense, but the TTS hardly changed at all. So going back to what our first coffee scientist said, Chahan Yeretsian, yes, for sure, the principle of exhaustive extraction probably applies here, right?

By the 12 hour mark, most of the stuff that could be extracted was extracted. And then when I gave it like another 12 hours to brew, not much changed because most of what could be extracted was already extracted. But when I was speaking with a different coffee researcher for this series, I came across a different theory that might also explain why the coffee wasn't extracting more after the 12 hour mark.

And this other theory doesn't contradict this idea of exhaustive extraction. I think it's likely they're both true. And I want to tell you about it because this new theory, again, completely changed my understanding of what's going on when water and coffee grounds come together.

So I was speaking with a former coffee researcher at the UC Davis Coffee Center.

Jessie (Jie Xin):

My name is Jie Xin, but I go by Jessie. I did four years of graduate research in coffee, focused on extraction dynamics.

James Harper:

All right, guys, you ready? Here is a new theory for understanding how coffee extraction works.

Jessie (Jie Xin):

Equilibrium extraction.

James Harper:

Extraction equilibrium. Or equilibrium extraction. Take your pick.

When you brew a coffee, two things are going on. The water is taking compounds out of the coffee grinds. So coffee compounds are literally dissolving into the water.

Jessie (Jie Xin):

They'll go from solid phase to liquid phase. That is desorption.

James Harper:

But at the same time, those coffee grinds are pulling in compounds as well. And this is known as adsorption. Which, to be clear, this is not coffee absorbing things from the water.

Jessie (Jie Xin):

So adsorption is different from absorption. Absorption is something that happens to a sponge.

James Harper:

It's adsorption. So we have desorption and adsorption. Desorption.

Coffee flavor molecules. They're actually dissolving into the water, going from a solid into a liquid. But there's also adsorption, where coffee flavor compounds in the water, they undissolve themselves and reattach themselves to the coffee grounds.

They go from a liquid back to a solid state. Okay, so the theory goes, and again, it's a theory. When you first start brewing coffee, water is taking so much more from the coffee grounds than the coffee grains are taking from the water.

But over time, the water starts to take a lot, lot less from the coffee grounds. And the coffee grounds start taking a lot, lot more from the water.

Jessie (Jie Xin):

And when that rate of change doesn't change anymore, that's when equilibrium is reached.

James Harper:

When the rates of adsorption and desorption are the same, we have reached equilibrium extraction. Okay, so going back to those two cold brews. I had a 12-hour and a 24-hour cold brew.

And I have two explanations for why that 24-hour cold brew wasn't massively more extracted compared to the 12-hour brew. So we have exhaustive extraction, right? Like most of the stuff that could have been taken out of the coffee was taken out of the coffee by the 12-hour mark.

So giving it another 12 hours just didn't matter because we'd taken most of the stuff already. And now we also have equilibrium extraction. Like by the 12-hour mark, we had hit pretty much that equilibrium where the coffee just couldn't get more concentrated because the coffee grinds were pulling as many things out of the water as the water was pulling out of the coffee grinds.

But there was still something for me that was unexplained. That 24-hour cold brew tasted slightly more concentrated compared to the 12-hour brew, which means there should be more coffee stuff floating in it. And I should be able to see that when I measure the strength of the coffees.

But when I use a TDS meter to measure the strength of the coffees, the numbers, they were almost exactly the same. They had the same amount of coffee stuff floating in them, but one tasted stronger than the other. And it took me some more digging around before I could find an explanation for that.

Are you ready? Here it is. My third and final insight on extraction theory.

Coffee is always reactive. So here's a bit of chemistry I learned when I was speaking with Professor Csajandi-Retzin of the Coffee Excellence Center. Liquids are a very reactive medium.

Chahan Yeretzyan:

In a liquid, the reactions are hugely accelerated.

James Harper:

When something is liquid, rather than say solid or evaporated like a gas in the air, when it's liquid, it is really reactive.

Chahan Yeretzyan:

If you go into the liquid phase, then the processes are much more accelerated. And breaking news alert.

James Harper:

Did you know coffee is a drink? As in, it's a liquid. And so a cup of coffee is a very reactive place.

And there's lots of stuff floating around in a cup of coffee that can react. In a cup, some are reactive. For example, beautiful aromas or organic acids, chlorogenic acids, so many different things.

Chahan Yeretzyan:

And Professor Csajandi-Retzin explained to me how with a cup of hot filter coffee, it takes you minutes, you know, minutes to have significant losses and even now starting to degradation, formation of new compounds coming from the compound. So the liquid is very reactive.

James Harper:

And so one reason why the 12-hour and the 24-hour cold brews, they tasted subtly different yet had very similar strength. It's because that 24-hour brew, it had so much more time for reactions to take place in the liquid. All those flavor compounds that have been pulled out of the coffee grinds into the cup, over time they reacted with one another and changed the chemistry, changed the coffee's flavor.

And so after doing these different cold brews, speaking with scientists, I realized, okay, the things that I adjusted, which make a difference in hot brew, like grind size, brew time, they weren't going to make a big difference when it comes to cold brew. But then what do I adjust? Like when I get a new bag of roasted coffee in hot brew, I can get very different flavors from it depending what parameters I adjust.

But I began to wonder, what are those parameters in cold brew? What do I need to adjust to get different flavors, expressions from the same beans? And coming up, I get my answer.

I speak with a coffee researcher who tells me the lever, the thing that makes the biggest difference when it comes to brewing cold brew, the thing that will dramatically change its flavor. And it's something I had almost entirely overlooked because I'd always been brewing coffee hot. So the day my toddy cold brew cupping kit arrived on my doorstep, I tried to figure out, what can I adjust to get different flavors from the same bag of beans?

And I did everything that I would normally do with my hot brew pour over filtered coffees. I adjusted the grind setting, but that didn't make a difference. And then I adjusted the time, and there again, it barely made a difference.

And along the way, I learned some really interesting theories that explain why, like exhaustive extraction, extraction equilibrium, and the idea that liquids are just super reactive places. And so coffee flavors are always changing. But I still didn't have my answer.

What should I adjust when making a cold brew to get distinctly different flavors so I can try the full range of flavors that any coffee has to offer? And I finally got my answer, speaking again with Jessie, our coffee extraction scientist who worked at UC Davis.

Jessie (Jie Xin):

And what we found the most interesting, and I think this is the most beneficial to the coffee community, if you want to vary the TDS in full immersion brew, you should pay very close attention to the brew ratio.

James Harper:

The brew ratio, the amount of coffee relative to the water. I see, I see. So basically, to change TDS, right, it really matters kind of how much water you add relative to the coffee grounds.

Jessie (Jie Xin):

Yeah, exactly. It's very intuitive, to be honest. A lot of our coffee personnel, they know this is important, like you have coffee grounds and water, and then that is your essential recipe to play with.

James Harper:

And this totally chimes with what the Totti team had told me when I visited them in Colorado. So much of the conversation was around concentration, the brew ratios, the amount of coffee relative to water, TDS, strength.

Chahan Yeretzyan:

So it'll brew home usage concentrate.

James Harper:

Yeah, brewing a concentrate allows us to dilute it.

Chahan Yeretzyan:

I think we have a team member who drinks concentrate. He doesn't dilute it at all.

James Harper:

Wow, just pure shots of jet oil. Yes, pretty much. How strong you make your cold brew, like how much water there is relative to the coffee grinds, makes the biggest difference in flavor.

And so now I had a new question. So how does adjusting the concentration of my coffee change the flavors? Right, like if I make a weaker cold brew, do I get more nutty notes?

If I make my cold brew stronger, do I get more bitter notes? Do all coffees behave the same way? And I had a chance to answer some of these questions when I went to the Specialty Coffee Association's Expo in Chicago.

James Harper:

In the ginormous McCormick Place Conference Center, I walked for what felt like an eternity to find one of the conference rooms where the Totti team had set up a tasting.

Holger:

These coffees, we selected them because they are kind of like on both ends of the spectrum.

James Harper:

So dear Holger, one of the Totti team, his original plan was very simple. Taste two coffees. Natural Brazil and then a washed Kenyan.

Brut strong and weak.

Holger:

Taste the concentrate and then taste the diluted version.

James Harper:

But I couldn't help myself. I jumped in and suggested, hey, let's go even further. You know what would be interesting?

How about we try like, you know, one over eight, one over 10, one over 12, different dilution levels. That'd be interesting with the same coffee and see how that changes it.

Holger:

Sure.

James Harper:

Holger was on board as soon as he heard it.

Holger:

Here's a scale.

James Harper:

So fast forward a couple of minutes.

Holger:

Left to right, concentrate.

James Harper:

And the tasting began.

Holger:

Three to two, one to one.

James Harper:

We started with a naturally processed Brazil. Wow, what an interesting coffee.

Chris Pruitt:

Isn't it? Yeah.

James Harper:

Chris, a roaster who joined the tasting.

Chris Pruitt:

Oh, I'm Chris Pruitt. I'm a roaster for Akamai Coffee in Maui, Hawaii.

James Harper:

For him, each dilution of this Brazilian coffee offered very different flavors.

Chris Pruitt:

This is a really unique, interesting coffee. I find something like enjoyable in each one of these dilutions all the way to concentrate. That's true, yeah.

James Harper:

The most watery coffee on the table was offering nuts. It's a lovely Brazil. Very nutty.

Nutty, yeah. But as the concentration, the strength increased, we started getting dark chocolate. For me, the dark chocolate comes through extremely pronounced in that one.

Raspberry dark chocolate. And at its most intense, which was 5.5 grams of water for every gram of coffee, it was as if someone had plopped in some cream.

Holger:

And there's almost like a creaminess to the concentrate, kind of like heavy cream in your mouth. Buttery.

Toddy team member:

Creamy texture, yeah.

James Harper:

So this Brazilian offered very different flavors, delicious flavors at different levels of dilution. And I could taste these wonderful differences by adjusting the strength. And I have to admit, after so many years of making hot brew pour over filter coffees, I'd forgotten how important the brew ratio is.

Because, you know, when I make a pour over filter coffee, I'd always stick to the same ratios. One gram of coffee, maybe 15 or 16 grams of water. But with the cold brew here, we went down to almost 1 to 5.

That's almost three times as concentrated. Like, I just couldn't do that with a pour over filter coffee. Well, I mean, yeah, you could technically do it 1 to 5, but it's going to taste really strong, really acidic, very unbalanced.

To get a more rounded cup, the water needs to sit with the coffee grinds for longer. But you just can't do that with a V60 pour over coffee because the water is always being pulled down by gravity. There just isn't enough contact time.

And so now by adjusting the strength, I was tasting all the flavors these Brazilian beans could offer in cold brew. I now had a new problem to solve. Which one do you serve on your menu?

It's a tough call. What strength to choose? I mean, I say it's a tough call, but for this coffee, it really wasn't.

Everyone agreed their favorite was the concentrate. You like the concentrate? I think I do, yeah.

You're an intense man. But here's the funny thing. Different coffees will taste better at different concentrations.

Like what worked for this Brazil would not work. For example, with the Kenyan, we tried immediately after it. This was such a different experience that even Holger warned us about it.

Holger:

This one you probably get like hit with all these Kenyan attributes. And that could be, I mean, to me, sometimes it's a bit of an overload. You will see for yourself.

James Harper:

Oh, yeah. At the lighter concentrations, we were getting nice light fruit notes. Cherry, some kind of fruit.

Chris Pruitt:

Yeah, true. Yeah, vaguely red fruit. Little cherry there.

Raspberry.

James Harper:

But as the strength increased, it was undrinkable. I find this Kenyan concentrate hard to swallow. Yeah, the concentrate is tough on this one.

Yeah, it's definitely tougher. What? I crossed my tongue.

I was just getting sharp pangs of pain. My tongue is like super coated. Like, you know, like when you have almost like, it's not sensational, like when you have too much salt, like something too salty.

It's not obviously not salty, but it's that level of concentration. It's like, okay, yeah, this is just too much here. This Kenyan, at its most diluted, was like the opposite experience from the Brazil.

The concentrated Brazil offered so much creaminess, but here with the Kenyan, I was just getting pangs of pain. So going back to that Brazil, like you said you preferred the intensity of the concentrate, but now you're going to the, you know, the concentrated Kenyan. Yeah, it's too much.

It's too much. So it's really coffee dependent. Yeah.

We all loved the Brazilian when it was at its most concentrated, but the Kenyan was way better diluted. And this is the point. I realized that when making cold brew, different coffees taste better at different concentrations, which of course should not be news to any coffee professional.

Like we know this already. When we get a new bag of beans in and we're trying to figure out, should we brew it as a filter or an espresso? We know that lighter roasted Kenyans taste great as a hot brew filter coffee, but it is tough to drink as an espresso.

Painfully acidic, overload of flavor. And I find the opposite is true for Brazilian coffees. I find Brazilian beans to be very nice as a pour over filter coffee, but it is so good and creamy, luscious as an espresso.

I realized the same thing applies to cold brew. All right, guys, we have figured out cold brew. Now it's time to actually make it ourselves.

Coming up next, I give you some tips on how to brew delicious cold brew in your home, cafe, wood cabin, igloo, prison cell, wherever you are in the world right now. All right, you want to make cold brew? I have good news for you.

You can make cold brew right now with whatever's sitting in your kitchen cupboard. You just need five things, good coffee, a decent grinder, filter papers, filtered water, and a vessel. So I'm going to hold it all together.

Now when I was at my girlfriend's apartment and I didn't have the toddy cold brew cupping kit to work with, I actually made really good cold brews with like an old pot I found in the back of the cupboard. And what I'd do is I'd put the coffee grinds in the water just floating around freely and then I filtered it the day after through some Chemex filter paper. And my first couple of times making cold brew, it was great.

But then it started to get kind of annoying because it gets messy. Like the coffee grinds in my pot, they all stick to the side. It's a pain to wash.

An easier way to do it, the way I was able to do it at home with my toddy brewer, you put your coffee in the filter paper first and then you seal the filter paper and put it in the water. And so when you finish brewing, you just take out the soggy bag of coffee and voila, cold brew, ready to drink. But the details do matter.

Choose the filter paper carefully because it could impart flavors to your coffee you really don't like. Fantastic.

Toddy team member:

And then we have our filter water.

James Harper:

This is the funniest looking experiment I've ever seen. When I was with the toddy team in Colorado, they did this test where they went to the local supermarket and picked up loads of different types of filter papers made specifically for hot brew pour over filter coffees. And what they did was put these papers in water and then just left them overnight to see whether the water would soak up unwanted paper taste.

If you didn't know anybody, you'd be walking into like one of those alien labs. It was a very strange scene in the morning, walking in to see all these beakers full of globby filter papers floating like some kind of alien fungus. Yes, we have several different types of filters here.

And the tasting was surprising. Like, okay, some of the filter papers did a very good job. They hardly left any flavor in the water at all.

Fairly neutral. Pretty neutral. Yeah, not getting too much here.

Yeah. Tastes all right to me. Nothing offensive.

But other filter papers made the water taste bitter. Oh. Ooh.

Chris Pruitt:

Very papery.

James Harper:

Different astringency too, right? Synthetic? That is revolting.

Very plasticky. That's like tasting a plastic tub. Yeah, that one's pretty bad.

Or straight-up woody. Wow, it's like drinking sawdust. So be careful what kind of filter papers you use if you're going to submerge them overnight in cold water.

Make sure they don't impart a flavor. Now, the Toddy team explained to me that they actually spend a lot of time R&D trying to find papers that wouldn't detract from the coffee. Like almost like there's a sweetness to it.

And they had different kinds. One made from trees, which was a little bit sweet.

Toddy team member:

And it's basically made out of banana leaf.

James Harper:

And another tree-free version.

Chris Pruitt:

Yeah, very neutral, not imparting a lot of flavor.

James Harper:

And crucially, Toddy designs their filter papers so they don't break apart in the brewer. Because these filter papers are like sitting around in water for maybe dozens of hours.

Chris Pruitt:

One of the benefits of this material, too, is really difficult to tear.

James Harper:

Yeah, you're struggling there. By comparison, when Toddy's head of coffee, Matt Irish, then tried to tear apart the filter papers they had bought from the supermarket, guys, there were no better than wet tissues.

Chris Pruitt:

You know, and this is after being sat in water for a period of time. These are just going to really come apart. So if you're worrying about bags breaking or tearing during your brewing process.

James Harper:

Yeah, because you really struggle to break that Toddy filter bag, but the others are just coming apart super easily into your hand. So that's my first point of advice. Choose your filter papers carefully.

The details matter. And the details also matter when you choose your vessel to brew in. Because it, too, could impart a flavor you don't like.

For example, you can make cold brew in a French press. Glass vessels are great for making cold brew because they don't impart a flavor. But be careful you don't leave the French press's metal plunger in the water.

Because you're going to taste it like the Toddy team and I did. That's disgusting. Oh, that is vile.

It's like... Very tinny. It's like what's been like sitting in pipes for a long time.

Yeah. Old pipes. So James's top tip number two, choose your vessel carefully so that it doesn't impart a flavor you don't like to the cold brew.

And also, health and safety announcement. Take food safety seriously. Toddy's brewers have been tested to be safe for long cold water brew times.

And they're a million times safer than that old bucket you bought from Kmart that's now sitting in your basement. I know you thought about it. Can I make cold brew in that?

No, don't. Now while I'm on the topic, Toddy have lots of different brewers for different sorts of peeps. If you're a cafe, they have big brewers for you.

If you love camping, they have a brewer for you. I personally love their cold brew cupping kit. Each flask is enough for me to make four coffees and they're small enough that it's easy to experiment with different brew ratios.

And one thing I do appreciate about these brewers is that they have really thought about the details. For example, they put markings inside the brewers to tell you like how much water to add to get a certain ratio. Link in the show notes if you want to check them out.

And now let's talk recipes.

Toddy team member:

We have five different brewing ratio recommendations for the cupping.

James Harper:

All right. So let's say you have your cold brew kit. You got your vessel, got your coffee, got your filter papers, got your filtered water.

Where do you start? What brew ratio do you use? But for this, I turned to the Toddy team because in the shadows of the Rocky Mountains, they have been testing out how cold water interacts with coffee for many, many, many years.

And after a lot of trial and error, they found some good rules of thumb.

Toddy team member:

At the same time, we generally brew about a 16-hour coarse grind. It has consistently good results.

James Harper:

So brew it for 16 hours on a filter coffee grind setting. And as for the ratio, brew it as a concentrate first and then dilute it. Start at a 1 to 5, so 1 gram of coffee to 5 grams of water.

And then they get a sense of what the coffee tastes like more diluted. Add the same amount of water all over again. And so now you're at a 1 to 10.

And why a 1 to 10?

Toddy team member:

But we came up with a 1 to 10, for example, because we'd heard from the industry that a lot of people brew a 1 to 10 and that's their serving strength. So it's a strong ready to drink. And there it is.

James Harper:

You'll have your concentrate, which you should totally try with milk as well. And then you have your 1 to 10 ready to drink. And then you can play around from there.

And one thing you might want to do is brew shorter, like don't leave it overnight. Maybe brew in just six hours. But if you're going to do it that way, bear in mind that grind size and time now actually do start to matter quite a bit.

Because in six hours, you're not getting too exhaustive extraction or extraction equilibrium. And there are a couple of other details too, which I just didn't have time to get into in this episode. Like for example, don't put coffee that is too finely ground into your cold brew because it's going to clump together and like it won't extract very well.

And if you want to get the professional level cold brew, Toddy have actually made a cold brew cupping kit protocol link in the show notes and you'll find the Toddy team at all major trade shows doing demonstrations and teaching cold brew classes. If you're interested in that get in touch with the Toddy team link in the show notes. And now what do you do if still you have a bag of beans?

You're trying to cold brew it every which way, but you can't get flavors you like. Well, then of course you should stop cold brewing and try with hot water. No, no, that is wrong.

That is not what you should be doing. When I spoke to Professor Warriston Pott of the UC Davis Coffee Center, he told me after all his cold brew research that the biggest thing that affected the flavor was not the brew temperature. No, the biggest thing that affects the flavor of your coffee is, drum roll please, The roast level.

The roast, how roasted the coffee beans are. And anybody knows coffee will not be surprised by that at all that a light roast tastes very, very different from a dark roast. And that is what we're exploring in the next episode.

I'm exploring how roasting creates these beautiful flavors. We love in coffee. We are shrinking ourselves down microscopically to see the molecular reactions taking place during the roasting process that turns baby plant food into amazing coffee aromas.

So press the subscribe button in your podcast player right now, so you don't miss it when it drops. So guys, thanks so much for listening. Filter Stories is produced entirely by me, including improvising the piano music.

And you know, with these stories, there's always stuff that I have in earlier drafts that I can't keep in the final cut because it just doesn't really fit the story anymore. And one of those, for example, is why that Brazilian and Kenyan coffee, those concentrated cold brews felt so different in our mouths. You know, one was creamy and one was like painful.

I spoke to a tasting scientist who actually helped me understand why that happens. And I had that in an earlier draft this episode, but I took it out and instead would create an infographic on Instagram. So follow me on Instagram at filterstoriespodcast or follow link in the show notes for that.

And also, you know, there are a lot of stories behind the scenes creating this show, which I don't really have an opportunity to talk about on Instagram because it's not really the right place for it. But I do write about it in my newsletter. They come out very, very rarely.

I think in the last year, I've sent one. So hand on heart, you are not going to get spammed by me. I really haven't got time for that.

But when I do write a newsletter, I give you like all these behind the scenes stories, personal stories that you might find interesting. So subscribe to my sub slack newsletter by following the link in the show notes. And now, what's coming up in the rest of the series?

In the next episode, we go deep into roasting science with the world-leading roasted manufacturers Probat. Then, I'm in Brazil, understanding how coffee farmers sell their coffee, how they find buyers. And one way they do that is through the green coffee trading platform, Algrano.

In the next episodes, I'm in Colombia, where I look at how coffee goes from the mountains down to the ports, either through a commodity supply chain or through the specialty coffee supply chain run by coffee exporter, The Coffee Quest. And finishing off the series, we get philosophical. I explore the question, what even is specialty coffee?

Why have we drawn the line where it is? Where even is the line? And that journey is supported by the water filtration supplier, BWT.

Thank you so much for listening, and I'll speak to you next time.