Fermentation, Pt 2 — The case for avoiding exciting fermentations

James Harper (Filter Stories narration): This is Filter Stories. I'm James Harper, and this is an episode from the Coffee Producer Toolkit podcast, made in collaboration with Lucia Solis. If you haven't heard the previous episode, I highly recommend you listen to that first.

To remind you, the goal here is to help coffee farmers have more profitable businesses. And I think this is going to be really valuable for you, because hopefully it's already changing how you see the coffee industry. And this knowledge will help shape the rest of your coffee journey, and hopefully you change the industry for the better.

To remind you: in the last episode we looked at the basics of fermentation. What's actually happening in a fermentation tank? Now we get practical. So in this next section we give advice on how a producer should use commercial microbes to do their fermentations.

And here's the funny thing. A lot of roasters who are going to be hearing this next section, I think, are going to be a little bit disappointed. Because in the specialty coffee world, interesting, unusual flavours are highly prized. There has been an obsession these last 15 years over very interestingly processed coffees: 120-hour fermentations on a black honey, anaerobic fermentations, whatever it is. Roasters pay higher prices for these coffees, champion these coffees with their consumers, being like, look at these extraordinary flavours you're able to taste in a coffee. And when they hear fermentation advice from Lucia Solis, somebody who is a microbial fermentation expert, they expect her to give recommendations that produce really amazing, unusual flavours.

But that is not what we do here. What we do here is offer very practical, grounded advice on how producers can produce the same coffees consistently, reliably. Because here's the thing. The recipe for long-term success as a coffee farmer, it's not winning competitions, creating these unusual lots of coffee that roasters buy, maybe for a high price. No. That's all flash-in-the-pan stuff. What actually pays the bills and keeps the farm running are good relationships with trusted coffee buyers. Built over the long term. Built on the producer creating a coffee that's dependably good. Something that a buyer can come back to year on year, reliably. This is what the most successful coffee farms actually do.

And Lucia and I think that this chasing of very exotic flavour varieties through really experimental fermentations — this has been a dangerous signal for many coffee farmers. Because what happens is that, you know, coffee farmers, they see the prices that these experimental fermentations fetch, not to mention the excitement it generates. And naturally, they all want in. And they start doing it themselves. And look, this is a universal pattern. It's even happened in podcasting. From around 2016 podcasting got bigger and bigger. A lot of money came in. Some people got very successful, very wealthy. And then all of a sudden, every company decides it needs to have a podcast, too. But then the whole thing faded, as the commercial realities hit home. Look, podcasting — it's good in some specific circumstances. But it's not the money-making machine that everyone thought it would be.

And it's the same thing in coffee farming. Producers see this handful of cases where some farmers have earned very high prices for these very experimental fermented coffees. And they think to themselves: maybe I should try this experimental fermentation thing myself. Maybe I can make good money, too. But as we said last episode, we have to bear in mind the historical context. The farmers who are able to run those experimental lots of coffee and earn good prices from them — we call them rock star producers — and they can do it because they are, for the most part, historically wealthy. They were the privileged minority in history, where their predecessors owned most of the land. They can take this sort of experimental risk because they have fallback plans. There are other businesses in the wider family. You know, a failed experiment on a lot of coffee is not going to sink their farm.

Now for everybody else, this is not the reality. Their farm is their livelinood. It's their one and only claim on land. It's not much land, but it's what they have. And it's very hard to make good money in coffee. They put money in coffee, and in these last decades coffee farming has been a brutal business to be in. Many are in debt.

Lucia believes strongly that the last thing any producer should be doing is experimenting with risky fermentations. You know, for example, long fermentations take a lot of time. And that creates bottlenecks in the mill, and there is only so much wet milling capacity. And so if coffee is sitting there for a long time fermenting, there are fresh cherries that need to get fermented now that are not. And they can get ruined sitting around. That hits the bottom line. Or maybe the entire fermentation just goes wrong — and, you know, we're talking about a quarter container of the farmer's best coffee being ruined. And so what Lucia proposes in this next section is incredibly boring. Use commercial microbes to produce higher quality coffees consistently. We think that's the route to make more money. And so, all that out of the way. Pressing play.

James Harper: Okay Lucia, now we're gonna cover five ways you can use commercial microbes to improve the profitability of your coffee farm. And I'm sure the first thought on many people's minds right now is: all you have to do is add these microbes and you'll achieve phenomenal quality.

Lucia Solis: We often hear stories about famous producers who added specific yeast strains to their fermentations and sold their coffees for record prices. And the message here is usually, if you use the same microbes, you will also get the same results, But I'm sorry to say, just adding microbes will not make your coffee award-winning.

To prove this point, we spoke to Lester Lerner.

Lester Lerner: Le hicimos una catación en la finca con los nuevos procesos de la nueva cosecha... [We did a cupping at the farm with the new processes from the new harvest...]

James Harper: A second-generation Colombian coffee producer, Lester actually came back to manage the family farm back in 2019. Now, up until that point, the family farm was very commodity focused. He wanted to break into specialty and so he planted many Geisha trees. After a couple of years, they finally start producing, he gets the cherries, and now he's at the fermentation step.

He thought this harvest was going to taste amazing. And he wanted to make it taste even better. So he added a commercial yeast — the same yeast that you would use for making bread. Bread yeast and yeast made for coffee fermentations are completely separate yeasts. You can't use one for the other. We'll explain why later in the episode. So, last year, he added yeast made specifically for coffee fermentations.

Lester Lerner: Y sacamos unos geishas que hicimos más o menos con... compré Saccharomyces cerevisiae.

[And we pulled out some Geishas that we'd made more or less with — I bought Saccharomyces cerevisiae.]

James Harper: And the coffee tasted terrible.

Lester Lerner: Lo mandé a catar y me dicen: “¿Sabía a papa?” Yo casi me siento a llorar. A papa, hermano. Nos llegaba como...

[I sent it off to be cupped and they tell me: "It tasted like potato?" I almost sat down and cried. Like potato, brother. It came to us like...)

Lucia Solis: In my experience, you can't just add a single strain of yeast and expect incredible results. The fundamentals, your baseline, has to be there first.

James Harper: See what Lester discovered. He had it on the farm.

Lester Lerner: Sí, sí, sí. Habíamos tenido, yo creo, problemas fitosanitarios; no nos había ayudado el clima. Eran los primeros graneos, y yo, triste con eso.

[Yes, yes, yes. We'd had, 1 think, phytosanitary problems; the weather hadn't helped us. It was the first fruit set, and I was sad about that.]

James Harper: He did eventually get covered.

Lester Lerner: Y encima, bah, lo peor. Pero es definitivamente el mejor café que me he probado en la finca. Era muy rico, perfil balanceado en todo. Nuestro catador le puso 89 puntos, pero yo espero que no sea porque haya sido mi cumpleaños,

[And on top of that — well, the worst. But it's definitely the best coffee I've tasted on the farm. It was delicious, a balanced profile all round. Our cupper gave it 89 points — but I hope that wasn't because it was my birthday.]

James Harper: A professional cupper graded it 89, just because it was his birthday and the cupper was being nice.

Lucia Solis: So the moral of the story is: have your coffees evaluated when it's your birthday. No, just kidding.

Commercial microbes won't increase coffee quality if you're not already doing a lot of other things well. They are not a quality shortcut for your micro lots.

James Harper: Microbes are not some magical dust that you can just sprinkle into a coffee fermentation to transform it into amazing flavours. You use microbes to improve your coffee processing. Lucia, you've identified five practical things that producers can do to improve their consistency and profitability right now with commercial microbes. The first use case is consistency.

Lucia Solis: Use commercial microbes to improve the consistency of your fermentations across the entire season.

James Harper: And to show you what that looks like, we spoke to a producer who is using commercial microbes.

Fridolin Stocker: I'm Fridolin. I started my career in coffee as an agronomist working on different farms, different parts of the world. And I finally found, uh —

James Harper: Fridolin is an agronomist from Switzerland and he's now based in northern Zambia, managing a large farm called Mount Sunzu. 800 hectares of land, 150 of which is coffee. Today he's exporting seven, eight containers a year and it's growing. So the stakes are very high for him, and he's very concerned about things going wrong.

Fridolin Stocker: These are very long-term investments. If you suddenly end up in a year getting much lower prices than expected, it can bring you into huge problems.

James Harper: And one of those problems could be inconsistent coffee flavours.

Fridolin Stocker: Working as an employee for other companies, I saw having inconsistencies just leads to huge difficulty in selling.

James Harper: And so his priority is consistency of flavours.

Fridolin Stocker: The target was: how do we produce good specialty coffee which is very consistent season on season, so that we can establish long-term relationships?

James Harper: And just like we covered earlier in the episode, Fridolin could see the risks of relying on wild yeasts during fermentations.

Fridolin Stocker: Um, wild yeast would be a potential hazard, in that we are inconsistent.

James Harper: And so Fridolin, he uses commercial yeast as a form of insurance, He can guarantee what the microbes are gonna be in the fermentations every single time.

Fridolin Stocker: We tried commercial yeast strains to see if we could produce good coffee, with the assumption that that would be then repeatable over years, as we could buy the same yeast strains again over and over.

James Harper: So, long story short: Fridolin uses commercial microbes as a form of insurance.

Lucia Solis: And that's the word. Insurance. Use commercial microbes to get consistent coffee flavours batch to batch. That helps you offer the same coffee flavours to your buyers season after season.

James Harper: All right, let's see. Now, use case number two for commercial microbes.

Lucia Solis: Commercial microbes can help you do long fermentations safely.

James Harper: But Lucia, please explain: what is the benefit of alonger fermentation?

Lucia Solis: Because extended fermentations are appealing — because if you have more time in the tank, you can add more complexity and more flavour.

James Harper: And just to prove this point: when I was in Copenhagen, after visiting Novonesis, I did a cupping with the team at La Cabra, a specialty coffee roaster. And they told me about a fermentation trial they'd done in collaboration with a Rwandan washing station called Shyira.

Basically, they tasted the same coffee — one lot which was fermented like normal, for 12 hours, with whatever wild yeasts happened to get into the fermentation. And then the second, which was that same coffee, but the fermentation was extended all the way to 48 hours, using Novonesis's yeasts. Roaster Evangelos Filippatos explained how the coffee with a longer fermentation had more intense flavours.

Evangelos Filippatos (La Cabra): So the flavour intensity that the yeasted Shyira had was much, much higher, and it was also a little bit cleaner. It had a little bit more acidity. I think the flavour notes — maybe they are sharing the flavour notes. They have very, very similar notes. But everything that was going onin this cup, it was just a little bit higher in intensity.

James Harper: And that increase in the coffee's complexity was positively reflected in a higher cup score. So can you explain why that works? Why does having more time in the tank lead to coffees having more complex flavours?

Lucia Solis: Well, it's because when the coffee is fermenting, it's unlike other foods like dairy, where you have microbes transforming the milk into cheese, and then you eat that actual fermented product. With coffee, the fermentation is adjacent. So in coffee, we're not fermenting the coffee seed. We are fermenting the mucilage around the seed. And as that mucilage layer is decomposing, the microbes are creating flavours. They're creating acids. They're creating polysaccharides, which give us texture. And those molecules need to get into the seed for us to be able to perceive them.

James Harper: I see. So the longer the coffee stays in the fermentation tub, the more time it has to soak up these flavours that are being produced in the slush all around it.

Lucia Solis: That's exactly right.

James Harper: But if you don't control the microbial population during these very long fermentations, then you could get the wrong microbes proliferating and getting the wrong flavours into your coffee.

Lucia Solis: This is exactly the point. If that washing station had just tried a long fermentation, eventually a wild yeast would have contaminated the tank and introduced negative flavours, or maybe even a defect. Because they used a Novonesis microbe, they were able to extend the number of hours of the fermentation to increase the intensity of the desired flavours without risking getting derailed by wild yeasts. Commercial microbes, they can crowd out the wild yeast. And because they can grow quickly, they can use up all of the available sugars before the wild microbes do. The commercial ones are not killing the wild yeast to eliminate them. It's just that the commercial strains are more abundant.

James Harper: By using commercial microbes, you are stopping wild microbes coming in and ruining the fermentation halfway through. So that is the second way that using commercial microbes can increase your profitability. You are able to get those higher quality flavours through extended fermentations that are safe.

Lucia Solis: Okay, now we're going to look at the third way you can use commercial microbes to increase your profitability. And that is by increasing the quality of your imperfect coffee cherries. I recommend using commercial microbes to increase the quality of your lowest quality coffee cherries first.

James Harper: Okay, say more. How does that work?

Lucia Solis: Most producers think that commercial microbes should only be used for their top cherries. In fact, many wait until the peak of harvest to even begin using them. But I recommend a different strategy. I recommend using commercial microbes to target those less-than-ideal coffee cherries. And the ones that I'm talking about, for example, are the cherries at the very beginning of harvest, which are more likely to be underripe and not have as much sugar. And the cherries towards the end of the harvest, which are more likely to be dry and overripe and more susceptible to defects. Those two will be of lower quality compared to the cherries that you pick in the middle of the harvest, when everything is at its peak ripeness, So these early and late cherries have more opportunity to improve, and are really great candidates for commercial microbes.

James Harper: And Helen Riley from the Novonesis team told us about some of the results she had seen with producers she had worked with.

Helen Riley (Novonesis): So we have a case that's coming to mind where it was an 82 to an 85.

Lucia Solis: You're able to see a much bigger increase in the cup profile towards the lower end of the quality range compared to the top end. In Helen's example, commercial microbes helped an 82-point coffee improve 3 points to an 85, That's a much bigger jump than if you use those microbes for your best coffees.

In fact, if you have an 89-point coffee, it's unlikely commercial microbes will help you get to a 92, In my experience, commercial microbes on an 89 or a 90-point coffee don't tend to increase in points at all. Now, there are still cases where you might want to use them on high-scoring coffees, but I believe this is the most effective use of your investment. By targeting your lower quality coffees first, you can be more profitable, because there's more room to improve and usually larger volumes too. If that increase in quality can get you 50 cents or a dollar more per pound, and that increase applies to about 40% of your entire harvest or more, that will have a much bigger impact than trying to find a buyer for a top scoring micro lot where maybe you only have a handful of bags of that.

James Harper: You can noticeably increase their scores, and now you have more coffee at a higher score that sells for a higher price.

Lucia Solis: Okay, James. And now we're going to talk about use case number four for commercial microbes.

James Harper: Yes, we heard many stories from producers where different parts of their wet mill became a bottleneck, where they weren't able to move coffees as fast as they would have liked through the wet mill, and so not all their coffees could reach the quality that they were hoping for. And the fermentation stage is one of those bottlenecks. Producers only have so many tanks to work with.

Lucia Solis: You know, James, I have clients whose fermentations just take too long.

And when a tank is occupied for 100 hours, that means they can't process more coffee. So, you know, I had this client who wanted to process more coffee. He had the patio space, but he didn't have the tank space. Because it was so cold in his area of the mountain, he got very little sunlight, and the water was incredibly cold, so it would take, you know, at least 100 hours for a lot of the mucilage to be off of the cherries. So what we can do is use these commercial microbes that are selected to have a, you know, really fast metabolism, and that can break down that layer from the seed very quickly. And so he was able to dramatically reduce his fermentations from 100 hours to 24 hours, and to turn over his tanks and process a lot more cherry.

James Harper: Right, and the value of a commercial microbe here is that they have been selected and bred because they can perform very well at colder temperatures, The wild microbes just weren't able to do that.

Lucia Solis: Exactly.

By using commercial microbes, his coffee moves through the wet mill much faster. Because his cherries aren't sitting in sacks fermenting uncontrollably and decomposing on their own, potentially picking up defects that could drag down his quality. And that alone is insurance for his quality and good for his bottom line.

But it goes further than that, because now his wet mill is faster. He can process coffee that he's bought from neighbouring farms in his own wet mill. Something that he couldn't do before, because the fermentation step was a bottleneck. So this increases his revenue and profitability, because he has more coffee to sell.

James Harper: Okay. And now let's turn to the fifth and final way you can use commercial microbes to increase your profitability. Commercial microbes can help increase the storage life of your coffee.

Lucia Solis: So James, even though I haven't seen any official research on this yet — even though I do think some should be forthcoming soon — it's my 12 years of experience that these types of fermentation can actually extend coffee's shelf life. That coffees that I ferment with certain microbes last longer. They stay fresher in green bean.

James Harper: Explain how that works.

Lucia Solis: The original goal of fermentation for humans has been food preservation. So fermentation has always been tied to keeping food longer. If you had a fresh cabbage, you had to get rid of that cabbage and sell it very quickly, because that cabbage was going to spoil. But if you could ferment it and create sauerkraut, you could keep it in your storage and feed your family for a whole year in that preserved state. So what fermentation does is lower the acidity so that you have less spoilage, and it creates a more stable product on the other side.

Coffees that have undergone a controlled fermentation with selected microbes, I have found, can last much, much longer than ones that are fermented wild, or without control.

So that's the first mechanism. But the second mechanism, I think, is intensity. Because coffees that go through a longer fermentation tend to have more intense flavours, which means a greater concentration of flavour molecules to begin with.

Think of coffee like money sitting in a bank account, right? As coffee ages, due to reactions like oxidation, you get a slow, steady withdrawal of flavours. Every month in storage, the coffee is fading a little bit. And if you started with $100 and are constantly withdrawing funds, you can go broke really fast — the coffee is faded within a couple of months. But if you have loaded up that account with $10,000 worth of flavour compounds, you can withdraw for several months and still feel rich a year later.

One of the ways controlled fermentations help coffee last longer is that you have more flavour molecules to work with. You are depositing more in the bank account.

James Harper: All right, and now to bring this back to profitability. A longer shelf life for your coffee can improve your profitability. The longer it lasts, the more time you have to find the right buyer at a good price. It can sit in the warehouse without losing value. You want to avoid being forced to sell under pressure for alow price because the clock is running out on your coffee's freshness.

Lucia Solis: And also this allows a customer to buy more coffee from you at once, because they know that your coffee is going to last longer and not go stale in their warehouse.

James Harper: It also, by the way, opens up more distant markets. You know, maybe a buyer who has a very, very long shipping time. You can now ship your coffee further. And so that also opens up the pool of available buyers for you.

Lucia Solis: These are the five use cases for using commercial microbes, but this is by no means an exhaustive list, because we don't have time to go through all of the possible benefits.

James Harper: And so, the ones we've covered today are: you get more consistency batch to batch.

Lucia Solis: Extend your fermentation safely to guarantee good flavours.

James Harper: It can bring up the scores of your lower quality coffee, so you can get better prices.

Lucia Solis: And you can free up your processing capacity in your wet mill, avoiding spoilage and increasing your revenue.

James Harper: It can also help extend the shelf life of your coffee, so you can sell more coffee to the same buyer or to more distant markets.

But to get these benefits, it really matters how you use commercial microbes, how you control your fermentations. As Lester Lerner said to us:

Lester Lerner: No era la primera vez que utilizamos levadura, pero creo que era la primera vez que utilizamos la levadura bien.

[It wasn't the first time we used yeast, but I think it was the first time we used the yeast properly.)

James Harper: And so, coming up next: how to run a good fermentation.

James Harper (Filter Stories narration): Pressing pause. In this next section, we go through the basics of what a good fermentation protocol looks like. And it's fairly self-explanatory, so there isn't much for me to add. Except for one thing. Coffee farms are a very difficult place to do controlled fermentations. Let me give you the contrast. In the wine world, fermentations happen inside fermentation cylinders that are closed off to the environment. The environment in which they sit is closed off, and it is very carefully controlled. Winemakers are petrified of the wrong yeast or bacteria getting in and changing the fermentation. That's why they scrub their facilities to death! They sanitise their instruments over and over. They sometimes even put sulphur dioxide on the grapes to lower the wild microbial population. All of this is done so that when they add their microbes — maybe it's like a Saccharomyces strain — that is the one that's gonna proliferate and nothing else.

Now, in the coffee world, wet mills couldn't be more different from wine facilities. Instead of being in these hermetically sealed rooms, a coffee wet mill is out in the open. You have people coming in from the fields with microbes and bacteria on their hands, on their boots, on their clothes. You have microbes floating in the air. The fermentation tanks are just these big vats that are just open to anything coming in. There are countless opportunities for the wrong kind of microbe to come along and ruin a fermentation. So that's the context for why Lucia recommends what she does. Cleaning the facilities very carefully. Cleaning the tools. And as we'll hear later on, we have examples of producers using sealed blue barrels, which are also good because by sealing the barrels — where, you know, the fermentation takes place inside those barrels — you are not letting bacteria that's floating in the air come inside. And now, pressing play.

James Harper: Let's turn to practical ways to run a fermentation, so you can get the results you want every time. And achieving a successful fermentation is so much more than just using the right microbes.

Lucia Solis: You don't only need good microbes, yes. And the first thing I'd say is that while commercial microbes are a powerful tool, they're not a substitute for good process. And a controlled culture will help you, but it won't compensate for dirty equipment, or poor monitoring, or not taking any records. So at a minimum you need three things. The first is a clean environment. And that means anything that the microbes will come in contact with. So that's the tanks or barrels. Um, and tools that you have for mixing. And then also your water. One of the things to keep in mind is that these organisms are alive. And if you have chlorinated water, then the chlorine will act as an antimicrobial. So if you're getting your water from a city source and trying to do yeast, that's something that will, uh, antagonise them. So make sure you don't have chlorinated water.

And another important thing is close monitoring. So I really recommend having a pH meter anda thermometer, because they're — they're your eyes inside of the fermentation. So you are going to want to take data.

The last thing is cupping. You have to taste the coffees to make the connection between the tank and the cup, what flavours you're tasting in the cup. So without that feedback loop, you really can't improve.

James Harper: Now, when it comes to collecting data, are we talking notebooks, spreadsheets?

Lucia Solis: For me, you know, a notebook is enough. The discipline is what matters. Taking good notes, um, using your phone for videos and pictures. That's a really underutilised tool, because the video and the pictures will automatically give you date and time and more context. Like, what was the weather around that date?

Things that I would love for you to take notes on are not just what is the pH and what is the temperature, but other things like how was the weather during that time? What did the tank smell like? What was the condition or the quality of the cherry before you started your fermentation? And taste your coffee.

James Harper: Now, what we'd like to show you here is what a fermentation protocol looks like for smaller producers. And our partner sponsor for the series, The Coffee Quest, is trialling this barrel-based method with many of the producers they work with.

Now, to be clear, The Coffee Quest understands that these smaller producers, they can't absorb big losses, right? A failed fermentation can be economically devastating for a smaller producer. So what they do first is experiment in very small batches. They work very closely with the professional cuppers at The Coffee Quest buying stations. And then only once they develop these repeatable protocols that deliver consistent, high-quality flavours, do they then scale up.

So let's now hear from Victor Chala, a producer in Huila, who worked with The Coffee Quest, to hear what kind of fermentation protocols they developed together.

Victor Chala: En este momento se le estan aplicando levaduras practicamente a todos los lotes, porque no son cafés especiales, ¿sí?

[Right now we're applying yeast to practically all the lots, because they're not specialty coffees, you see?]

James Harper: Victor only uses commercial yeasts on his conventional coffees. He doesn't put it on his exotic varieties, because they've already reached a very high quality. Instead, he uses commercial microbes on lower quality coffees, to noticeably improve their flavour profile.

Victor Chala: Cafés que dan 86, 87, 88 — entonces no necesitan la levadura.

[Coffees that come in at 86, 87, 88 — those don't need the yeast.]

James Harper: For fermentations, Victor uses these large plastic blue tubs with lids. In Colombia, they call them canecas. Okay, so here's his protocol. For a batch of depulped coffee, he heats 14 litres of water to about 30 degrees Celsius, then he mixes in 500 grams of dry commercial yeast, and he lets it activate for about 10 minutes. Again, to be clear, this is not baker's yeast, this is yeast for coffee fermentations, very different.

Victor Chala: ...pa' activar los microorganismos que tiene la levadura, y luego la llevamos ala caneca. [...to activate the microorganisms in the yeast, and then we take it to the barrel.]

James Harper: Then he turns to his barrels. There's about 14 big blue barrels all lined up, and into each one, he puts 40 to 45 kilos of demucilaged coffee.

Victor Chala: Y ahí mismo le agregamos azúcar.

[And right then we add sugar.]

James Harper: He also adds sugar depending on the Brix readings of the cherries. Very high sugar content — they're very mature, you know, 17 on the Brix meter — he adds maybe half a kilo of sugar per barrel. If it's towards the lower end, 12 on the Brix meter, he adds a kilo of sugar to each barrel. This added sugar provides lots of starting energy for the fermentation to get going quickly.

Victor Chala: ...y mañana por la mañanita la destapo, la revuelvo, y vuelvo y la sello.

[...and tomorrow first thing in the morning I take the lid off, stir it, and seal it up again.]

James Harper: Then Victor seals each barrel, turning it into an anaerobic fermentation, and every morning he opens it again, gives it a stir, and seals it back up. At the 50 hour mark, he adds molasses.

Victor Chala: ...trabajando, y ya cuando van 50 horas de fermentación, aplico la melaza. [...working — and once it's 50 hours into the fermentation, I add the molasses.]

James Harper: This was suggested to him by The Coffee Quest, because they found that adding molasses at this step made the coffee cleaner. And then, 24 hours after that — so roughly 70 hours of total fermentation time — the coffees come out of the barrels and into his secadora, his drying tunnel. A few things worth noting. First —

Victor Chala: Se le puede echar un poquito de agua porque muchas veces queda muy seco. [You can add a little water, because it often ends up very dry.]

James Harper: — no extra water is added to this, which keeps his water use remarkably low. For some dry varieties, Victor might add a splash of water to keep things moving, but that's it.

Second, Victor mentioned that these blue barrels have a huge advantage over the more common large concrete tank that many producers use for their fermentations.

Victor Chala: La diferencia es muy grande: él se quema, él completamente se pone caliente. [The difference is huge: it burns, it gets completely hot.]

James Harper: The blue barrels don't overheat. Because in a large fermentation tank, all that microbial activity can drive temperatures dangerously up, and that can ruin a coffee's flavour, But in smaller barrels, there just isn't enough mass for that runaway heating to happen. Temperature stays more stable, and the fermentation stays in control.

So, Lucia, what do you make of that approach?

Lucia Solis: I'd say that one of my philosophies is: if it's not broke, don't fix it. So if this is working for Victor, then that's great.

One thing I would like to caution our audience against is blindly copying somebody's recipe. This reminds me of what we talked about in episode one with Lalo, about, you know, your soil and your conditions are very unique. So if you start applying nitrogen without first taking a soil sample, you really could be wasting a lot of money.

The other thing I wanted to mention was about how Victor rehydrates his yeast. And these steps are really specific to the yeast that he buys. So not all commercial microbes require all of the steps that Victor walked us through. This is one of the reasons I really love working with the Pichia yeast sold by Novonesis. It's because they're able to be applied very easily. You basically just open the bag and apply them directly to coffee cherries or to pulped coffee. There's no need to rehydrate them with warm water. There's no time to, you know, wait for them to wake up. You don't need to add sugar or molasses. The elimination of these steps can save a lot of time. So I would spend maybe an hour to an hour and a half preparing the microbes for my larger fermentations, and when I use the Novonesis microbes, it's 30 seconds.

James Harper: Now, turning back to those blue barrels that Victor is using — do you recommend that a larger producer also use blue barrels? Because I can imagine having lots of these barrels, you know, at some point, once you get beyond 50 barrels, that's a lot to manage.

Lucia Solis: This is not a hard and fast rule, but if you're getting less than 2,000 pounds of cherry per day, then I think the barrels make a lot of sense. But if you have more than 2,000 pounds of cherry in a day, then I think putting all of that coffee in a single tank, or larger tanks, is going to make your process easier.

James Harper: And what are good rules to follow when it comes to cleaning?

Lucia Solis: For any size fermentation, from a five-gallon bucket trial to a plastic barrel to a 10-tonne tank, you are going to want to prioritise cleaning after every fermentation, after every use. Cleaning after every use is going to give your commercial microbes the best chance to succeed.

I also recommend you use a detergent, especially later in the harvest when the dirt and mucilage accumulates. But please avoid any scented soaps. At this stage, the coffee is very vulnerable and it can easily pick up those aromas.

The regular hoses I usually find in coffee wet mills don't do enough for stubborn coffee mucilage and dirt, so a great investment is a pressure washer for your equipment and your tanks. It's also a good idea to have something you can use to sanitise your tools and equipment, something really simple like a spray bottle with 60-70% alcohol or 5% white vinegar.

James Harper: And finally, when it comes to recording data, how often should you be taking readings?

Lucia Solis: How often to take a reading really depends on your personal preference. For example, you could be somebody like Manuel Mata, who has sensors hooked into all parts of the process and he's getting data every 20 seconds.

James Harper: Yeah, listen to the previous episode on post-harvest processing to learn more about Manuel Mata's approach.

Lucia Solis: For me, I'm a little bit more old school. I like the analogue thermometer and the, you know, analogue pH meter, and I take data three times a day: in the morning, middle of the day and the end of the day. So it depends on your comfort level. But at the very least I would recommend at least twice a day, to check on your temperature and your pH measurements of your fermentation. That'll give you an idea of how the fermentation is getting along.

James Harper: So those are our practical tips for how to run a fermentation. But of course, what works on somebody else's farm will probably not work on your farm. So you have to do a lot of trial and error. In the show notes, we have a lot of practical resources to help you master fermentations on your farm.

Lucia Solis: Okay, now, coming up next, we'll cover what it costs to use commercial microbes.

James Harper (Filter Stories narration): Pressing pause. Okay, so

that's it for this episode. Coming up in the next episode, we finish

this three-parter on fermentation, and we look at the economics of

using commercial microbes, and some of the really gnarly questions

that producers have to confront. In a way, we're going to explore

the question: who gets to determine what a high-quality coffee is?

I'll see you in the next episode.