Fermentation, Pt 1 — Nature's lottery and coffee's 3,000-year lag

James Harper (Filter Stories narration): Welcome back to Filter Stories. I'm James Harper, and today we have the third episode of the Coffee Producer Toolkit. It's a podcast I made with my friend and fermentation specialist Lucia Solis, which is great for us, because this episode is about coffee fermentations.

To remind you, this is a series that Lucia and I made for coffee farmers, to help them have more profitable farms, But I think you are going to find it extremely valuable too, because what happens on the farm is incredibly important for the coffee industry. The future of the flavours we're going to get in our cups. And what we're going to pay for those beans. It all comes down to what happens on the farm. And coffee farming is, frankly, not very well understood.

So here's my promise to you. By listening to this entire series, you are going to have more knowledge about coffee farming than most of the coffee professionals you are going to meet at a coffee trade show. This knowledge is going to shape the rest of your coffee journey, and I really hope you use it to mould this industry into something better.

So, like I mentioned, this episode is about coffee fermentations. Now, coffee is a fermented product, just like wine and bread — which I actually think a lot of people find surprising. But coffee is a bit different from wine and bread, right? So in wine, you have grapes, you crush them down until you have a kind of grape juice slush, and then microbes ferment that slush until it becomes wine. So when you drink wine, what you're drinking is fermented grape juice. You drink the fermentation. And it's the same with bread. You have flour and water, then you add yeast, and then what you're eating is fermented dough. You are eating the fermentation.

But in coffee it's different, because you're not eating the fermentation. The fermentation isn't happening to the bean — it's happening to the coffee flesh surrounding the bean. But nevertheless, it has a tremendous impact on how the coffee tastes. The way it works is that these microbes eat sugar, and as they eat the sugar they excrete waste products, and these waste products have flavours, which this coffee bean then sucks up. Now, sometimes these flavours can be very nice, or they can be very bad. It really depends on how well the fermentation is controlled. We're going to talk more about this later. Now let's hear the intro to the episode, and then I'm going to come back in and set you up with more context for the next section.

James Harper: Welcome back to the Coffee Producer Toolkit.

Lucia Solis: A podcast series built specifically for coffee farmers, to help you run a more financially sustainable, better managed farm.

James Harper: I'm James Harper, a coffee journalist, creator of Filter Stories, a documentary podcast about the history, science and culture of coffee. And I like to go deep and understand why the industry works the way it does, and I tell those stories,

Lucia Solis: I'm Lucia Solis. I'm a fermentation and winemaking specialist working in coffee. I live on a coffee farm in Guatemala, and I work directly with producers to improve their coffee lots and their livelihoods. My podcast, Making Coffee with Lucia Solis, explores the latest science and the future of coffee production.

Across the series, we're covering the topics that matter most to your bottom line. Agronomy, post-harvest processing, storage, today's topic — fermentation — coffee quality assessment, sales and marketing, and more, Each episode features best practices from leading coffee farmers and experts, and presents it in a way that's practical and easy to act on.

James Harper: And this series is made possible by our partner sponsors: The Coffee Quest, Pinhalense, GrainPro, Novonesis, BWT and InterAmerican. We're launching it first in English, and then all episodes will be subtitled on YouTube in Portuguese, Bahasa, French and other major languages spoken by coffee producers,

Lucia Solis: Whether you're a producer, you work with producers, or you're just curious about what it actually takes to make coffee farming a viable business —

James Harper: — we think this is going to be a very useful series for you. And if you're not a producer, guaranteed it's going to change how you see this industry entirely.

In this series, every episode we do comes back to one question: how do you run a more profitable, more resilient farm?

And in this episode, we're looking at fermentation.

Lucia Solis: When it's done well, fermentation is insurance. It's your single most powerful tool for protecting quality and improving consistency across the whole harvest.

James Harper: We'll cover the basics of fermentation — what it is. Five practical ways you can use commercial microbes. We'll show you what a well-run fermentation actually looks like on farms of different sizes. And we'll go into the commercial microbes, Finally, how you can talk about your fermentation practices with your buyers.

James Harper (Filter Stories narration): Pressing pause. Okay, so, fermentations. Here is some historical context. Fermentations in the wine and the bread industry stretch back thousands of years, and over those millennia people have perfected how to control the fermentations to get the flavours they want. Now, in the coffee industry, yes, farmers have been using fermentations for hundreds of years. But they're not fermentation experts. In the commodity world, producers used fermentation to clean coffee. So what would happen is, once a coffee cherry is pulped, it then goes into a fermentation tank, right? So what you have is a green bean surrounded by the cascara — which is like a soft pistachio-shell kind of casing — and some degree of coffee fruit stuck to it. And the objective in the washed process was to clean the coffee. Therefore, you ferment it until all those microbes eat away the sugar, and then what you have is a clean coffee ready for drying. That was the point of fermentation: to clean coffee. It was done in volume, and it happened by itself. Producers didn't have to worry about it, because — as you'll soon discover — microbes very easily came in and proliferated. So that is why the typical coffee farmer isn't a fermentation specialist.

Then along comes specialty coffee. And people realise: whoa, fermentations have a dramatic effect on how our coffee tastes. And especially in these last 15 years, we have seen an explosion of fermentation experiments on coffee farms. It has been a very exciting time. Wealthy producers, they could afford to take the risks. And they took the risks. Some of these fermentations resulted in really bad coffees that they had to sell at a loss. But others were incredibly delicious, and that really excited the specialty roasting community. And now many coffee producers, big and small, are all thinking about how to control their fermentations.

But like I mentioned, we are only 15 years into this revolution. Wine and bread have been doing this for thousands of years; we here in coffee are only getting to grips with this in the last 15 years. So most producers are very early in this, just like specialty coffee professionals in the global North. And so what Lucia and I do in the beginning of the episode here is just offer a lot of context and explanation, which is great for you, because producers are not ahead of you on this knowledge. You're both at the same place. So what you're going to hear now is just great explanation on the basics. What is a fermentation? How does it work? What is the role of commercial microbes? All right. Pressing play.

James Harper: When we think about fermentation on coffee farms, most producers — most of us — think that it really happens only in the fermentation tank. You know, the stage right after coffee pulping, and before coffee drying.

And we're in very good hands with you, because, I mean, fermentation — you have built a career on coffee fermentation.

Lucia Solis: I have, James. This is where I feel... this is my happy place. This is where I feel most comfortable. I studied microbiology and winemaking at UC Davis in California, and I went directly to work in the Napa Valley. So I spent nine years fermenting wine. In 2014 I took my expertise from working in the wine industry and applied it to coffee, and I've been doing that since then. So now we're going on 12 years of processing coffee, fermenting coffee, using different microbes, working individually with coffee producers, as well as hosting workshops where I work in large groups with a lot of producers. And then also, as we mentioned earlier, I have two podcasts. A podcast in English called Making Coffee, and a podcast in Spanish called Cabal Café, that speaks directly to coffee producers.

James Harper: Now, Lucia, these last 20, 30 years have been a very confusing time for producers, because fermentations went from this thing that you wanted to avoid entirely — it gave you bad results — to something you now wanted to prioritise, because it gave you great results. Take us through the history: what's been happening?

Lucia Solis: That's right, James. We're going to focus on the fermentation in the tank, but I want our audience to know that while this is the main site of fermentation, the tank is not the only place where fermentations happen.

For example, there's an opportunity for unwanted fermentation when the cherries are harvested, put in sacks, and transported into the mill. I'm sure many producers have had this situation where the coffee arrives and the sacks are hot to the touch. And it's not just the heat of the sun or a hot day — it can also be heat produced by an active fermentation. And in the case of a honey process, or a washed process where the mucilage isn't completely washed off, the coffee continues to ferment even if it's in the first stages of drying.

So, all this to say: unwanted fermentations can happen in multiple places, and they can definitely reduce the coffee quality. In the show notes you can find other podcasts where I cover these hidden sources of microbes, But for today, just like you said, James, we will focus on fermentations in the tank. Historically, I think it's fair to say that fermentation has been seen as a highly risky step. It's where a lot of producers can lose quality by inadvertently creating defects. And that is why fermentation got this, like, reputation. We wanted to keep fermentations short, because the alternative was over-fermentation. That's a term that a lot of producers know that is equal to defects. Over-fermentation means defect — something went wrong. So historically, the point was to make the fermentation as short as possible. That was the best advice at the time. And one of the technologies that came out of that were the eco-pulpers, to mechanically wash the mucilage off the coffees. So, because fermentation was such a risky step, producers could skip it — could avoid a fermentation entirely — and mechanically wash their coffees. And what happened was, there were really two camps. Some people experienced their best coffee ever and had incredible results. And then some people experienced their most boring coffee ever. And so both of these things were true, and it was really hard for people to integrate. Like, can the opposite result be true for so many people?

James Harper: Right. And then things get even more confusing, because fermentations then become a priority for the specialty coffee industry.

Lucia Solis: Yeah. So now you have something else to add to the mix. Before, producers were being told: ferment as short as possible. And now specialty coffee is saying: no, let's ferment as long as possible. And absolutely, that can feel really confusing — to be getting conflicting advice, and saying that both of these create the highest quality coffee.

So today I talk to a lot of producers and I hear the same thing over and over again. And they feel like they're back at square one, unsure how to get the best quality out of their coffee. They want to participate in fermentation, but they also realise that there are risks of defects. So they're not sure how to thread this needle.

James Harper: Okay, so to understand how fermentation can create beautiful specialty coffee flavours and, at the same time, lots of defects — but the same process — let's get some basics out of the way. What is actually happening inside the fermentation tank?

Lucia Solis: When you depulp your coffee and put it into a tank or barrel, you're creating the conditions for microbes. And when I say microbes, I mean yeast and bacteria, to start feeding on the sugars in the mucilage.

And as they eat, these microbes produce byproducts. Just like when we eat something, we have byproducts. Their byproducts are organic acids, alcohols, enzymes, and flavour precursors like esters and thiols, which are just flavour compounds. So this means that the fermentation can impact the perceived acidity of the cup, it can impact the texture, and the flavours that we can taste. And all of those byproducts have a direct effect on the flavour of the final cup.

James Harper: Now, where do these microbes come from?

Lucia Solis: All of these microbes are existing on the skins of the cherry, they're in the water, they're on the equipment, all of the surfaces surrounding the mill. And it's not just the equipment. Us humans, we are a big source, We're a big carrier of these microbes.

And so, under the right conditions — where you have warmth, so, you know, a warm tropical climate; we have a lot of sugar from the fruit; we have a lot of moisture — all of these things combined help these microbes multiply really, really fast. And we're talking about doubling every 20 minutes, depending on the species. So very quickly, a small population could reach billions of cells in a matter of hours.

James Harper: Right, so basically, as soon as coffee cherries go into a tank, they're gonna ferment. Tiny microbes are going to multiply into billions, without you doing anything. It's gonna happen naturally.

Lucia Solis: Exactly. Your fermentation is going to take off whether you want it to or not. And the question is whether we're going to play nature's lottery, or be the ones in control of the outcome.

James Harper: Right, so you mentioned there's yeast and bacteria on the coffee cherries, on the workers’ hands, on the sides of the tank itself, in the air. Are all these microbes the same microbes? Do they all do the same thing?

Lucia Solis: Oh, absolutely there are many, many different types of microbes. And some produce the flavours that we want. Some produce really great fruit flavours, acidity and complexity. And others produce the flavours that we don't want. So, the vinegar, the off notes and potato defects. So this is how we can have the opposite results when you're doing the same thing. How a fermentation can create incredible quality and really complex coffees, and it can also create defects.

James Harper: It's kind of like random chance. You do a fermentation that has the right microbes that produce great flavours, but the next batch of coffee could have the wrong microbes that produce bad tastes in coffee.

Lucia Solis: Yep, that's what I mean by nature's lottery.

James Harper: Right, and so that is why, 20, 30 years ago, producers were advised to have short fermentations — that would reduce the risk of instances where the wrong microbes would come along and ruin a batch of coffee.

Lucia Solis: And that's what made mechanical washing such a popular choice, Because by mechanically washing the coffee, you could remove the source that the microbes were feeding on. So even if the microbes were there, they had nothing to eat. And therefore, there was not an opportunity to createa defect.

James Harper: But the specialty industry later discovers that fermentations can introduce lots of wonderful flavours to coffee, when you have the right microbes present. And if you have your coffee only mechanically washed, then you're totally skipping that fermentation step in the tank and you don't have the potential to create those extra beautiful flavours.

Lucia Solis: That's right. And it works the other way too. Where those microbes were doing really useful work — those microbes are able to build complexity and develop the cup profile. And so when they were removed, the coffee lost that extra layer of complexity.

James Harper: So great coffee flavours all come down to carefully controlling your fermentations, right? Controlling which microbes are the ones actually proliferating. The challenge is on the farm: if you leave it to chance, you have no idea what microbes are going to be in your fermentation.

Lucia Solis: That's why I recommend working with commercial microbes. These are microbes that have been grown in laboratories under carefully controlled conditions. When you add these microbes to your fermentation, not only will you avoid defects, but you're ensuring a positive result. And because these microbes are always the same, you can stop playing the lottery and get reproducible results the entire harvest.

James Harper: Right, and just to clarify something. We are specifically talking about commercial microbes made for coffee, nothing else. Not bread, not wine, only coffee. And these are commercial microbes made, for example, by one of our partner sponsors for this series, Novonesis.

Novonesis staff member: First of all, welcome to the site in Copenhagen.

James Harper: And Lucia, you and I and your partner Nick, we all went to Copenhagen, Denmark, to see the Novonesis facilities ourselves.

Novonesis staff member: It's the largest dairy culture production plant in the world. It has the capacity of 7,500 tonnes per year in fermentation, and that can cover a bit over 50% of the entire world's need of food cultures.

Lucia Solis: And James, something that's really surprising. While commercial microbes are new for coffee, you've already enjoyed foods made by Novonesis cultures.

James Harper: Yeah, Helen Riley, one of Novonesis's business development managers for coffee, gave us this crazy statistic,

Helen Riley (Novonesis): So if you're eating a yoghurt or a cheese, or if you ever have in your life, then it is very likely that you've had one of our cultures before. We're about in every second dairy product in the world.

James Harper: In every second dairy product?

Helen Riley (Novonesis): Yes. So you don't know us, but you know us.

James Harper: And what was super interesting is that to create a single strain of microbe that you could use, for example, in a coffee fermentation — one that's gonna perform as you expect it to — Novonesis had to build these incredible facilities.

Lucia Solis: I'm seeing a very — yeah, a facility with a lot of stainless steel, lots of tubes.

James Harper: They had these hermetically sealed rooms where, you know, the pipes transporting the microbes around —

Novonesis staff member: — but we are very aware of any contaminants. And even a few grams would contaminate 1,000 kilos.

James Harper: And it was almost entirely automated.

Lucia Solis: So, James, something I'm not seeing in any of these rooms — people.

James Harper: Lucia, remember the robot forklift we saw?

Lucia Solis: Yeah. It reminded me of being in San Francisco and seeing the self-driving cars. We saw some self-driving forklifts.

James Harper: They also have to store them, ship them around.

Novonesis staff member: So we have two minus-55 freezers. One —

James Harper: They freeze them down to minus 55 degrees Celsius. And so, of course, in the interests of science, we went inside those freezers for about 30 seconds.

Oh my God. Oh my God. This is crazy.

Lucia Solis: Breathing is a little difficult.

James Harper: We were only in that room for 30 seconds, enough time just to get that photograph of us blowing out steam.

Should I take a picture of the group?

Novonesis staff member: Yes, it will be fine.

James Harper: You were sick for the rest of the day after that.

Lucia Solis: Oh, that's true too, I think. I think also being, like, a little person — like, I think compared to these very large Danes that have more, like, thermal mass. Being a tiny person, I lost heat very quickly.

James Harper: Absolutely.

Lucia Solis: And yeah, I did get sick for the rest of that trip. I felt like my nostrils were sticking together. I felt like my hair was kind of cold. Like the hairs in your nose freezing.

James Harper: Right, so these are the facilities it takes. Hundreds and hundreds of millions of euros to reproduce a microbial strain precisely, to use in a fermentation. This could not be more different from my coffee farm, where there's just loads of different random microbes everywhere.

Lucia Solis: Having those facilities, you know, it's not just a nice to have. It's really important for that level of sterilisation and sanitisation, because they need to keep all of these strains separate. They need to be pure strains and not mixed with others, because again, that's what you're paying for, versus what you get in nature, which is a big old blend of who knows what.

James Harper: Now, Novonesis also make microbes for many other industries — wine, cheese. It's funny, Lucia, that, you know, these other industries all use commercial microbes, but in coffee, very few farmers do. Oftentimes the microbes are just left to chance, whatever nature provides that day.

Lucia Solis: Really, coffee is lagging behind a lot of other industries. Almost all other fermented industries. And all of those other industries started with a wild fermentation. And they had to go through this phase of having inconsistency. Having occasional really great lots. Occasional brilliance. And frequent disaster. And what changed those industries was understanding the microbiology, and selecting the strains that produce the outcomes that those producers wanted, and introducing those strains in a controlled way. So all of those other industries have been using commercial starter cultures, and that's what was able to transform them from, you know, artisanal kind of handmade things into proper businesses. And coffee is one of the last major fermented foods to go through this, and we're still in the early stages of that transition.

James Harper: So, looking at this as a coffee producer —

Lucia Solis: Exactly. I think fermentations are great, and we're not here to say that everybody always has to use commercial microbes. But understanding how to control the fermentation with whatever tools are available to you is what's going to take your business to that next level.

James Harper: And so, coming up: five ways you can use commercial microbes to ensure your production, to get reproducible results, to ultimately have a more profitable coffee farm.

James Harper (Filter Stories narration): Pressing pause. Coming up

in the next episode, we get practical with fermentations. We look at

the five ways Lucia suggests our producers use commercial

microbes, and step-by-step guides on how to actually do a

fermentation on a coffee farm. We're going to take a break, so I'll

see you in the next episode.