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Sometimes You Just Have to Add Things to Coffee - Lucia Solis on Fermentation and Adulteration

Why we’re probably not using the word “infused” right, what really happens when a farmer adds fruit to coffee and why we should think twice before calling that adulteration. Read about how one of the loudest voices in coffee approaches the subject and learn about other lesser-known benefits of fermentation such as batch consistency, longer shelf-life and why the process doesn’t have to go beyond 36 hours.

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Recent discussions about infusion and adulteration in coffee are leaving industry professionals with a bitter taste in their mouths. There is a simple message behind all the arguments and claims being made that coffee should be “natural” and that interfering with the purity of the terroir is "bad". The message is that producers are lying to us and taking advantage of naive roasters and baristas. This is a much bigger problem than one coffee being infused with cinnamon.  

Lucia Solis, a former winemaker and specialist in coffee fermentation currently based in Colombia, is one of the main voices fighting this narrative. In her podcast, Making Coffee with Lucia Solis, she questions some of the common myths we as an industry believe and repeat without really knowing the science behind them. In her work with mills and farmers, she constantly makes use of inoculation or adding external yeast to fermentation.

In the latest episode of her podcast, Lucia talks about adding fruit to the fermentation tank, chaptalization in wine and why it’s not "wrong" to add foreign microbes to coffee. As she is joining Algrano for a webinar on all things fermented on November 4th, we wanted to ask her what she makes of this whole shebang - and she is not very happy about it.

Fermentation is not a process in which flavours of foreign materials simply migrate to the coffee bean. It is rather a metabolic process in which microorganisms such as yeasts and bacteria degrade organic matter to produce energy. The flavour and aroma molecules we prize so much are the residue of this process. These molecules are the ones who migrate from the fermentation solution to the coffee bean and improve (or not) its cup profile. 

As all coffee post-harvest methods involve fermentation, every single coffee on Earth was “improved” by such molecules. Coffee enhanced by fermentation IS natural coffee, though we should probably avoid that word. So where is the problem? The issue might be the word “infusion”, which is used to indicate coffees with the addition of essential oils and fruit as if they were the same. They are not. However, the industry is putting everything in the same bag and we risk discouraging future experimentation. 

Adding things to coffee: “It’s not because it’s sexy”

So what happens when you add fruit to the fermentation tank? Fruit won’t infuse the beans with its flavour/aroma as oil would with beans. It will rather help control the fermentation by providing sugar to the existing microbes. It also enriches the solution’s microbiota or changes its pH and therefore modifies the type of microbes that will be active during the fermentation. The change in flavour we observe in the cup is always an indirect consequence of the metabolic process.

“Adding fruits or other foreign materials can really help your fermentation”, she starts. “If you want to do an extended process or if you have to because you don’t have enough people to wash the coffee at the right time, giving the microbes something else to eat can buy you that time so they don’t degrade the coffee and compromise the bean structure long term. It’s not because it’s sexy. This is where the conversation on adulteration can get dicey because it can be a really good way to preserve the coffee. It’s just a tool producers can use if something goes wrong.” 

Chaptalization: from wine to coffee

On her podcast, Lucia also talks about chaptalization, a common procedure in winemaking (including the traditional champagne) that involves adding sugar to the grapes to further the fermentation process. Disclaimer: this doesn’t result in sweeter wine but in more alcohol as fermentation degrades sugar and ultimately results in less sweetness. Anyway, this is how champagne is made and no one questions the integrity of the winemaker. 

“Sometimes I do it [add sugar to coffee] because I monitor my Brix and I know I want to start with a Brix of 15. Let’s say it rained a lot and my coffee is coming with a Brix of 10. If I’m used to having 15 as a starting point to ferment the coffee for X number of hours, I know that the extra sugar [as in fuel for microbes] is going to have to come out of somewhere else. It might be from my coffee and I don’t want that. So I add that little sugar to get the Brix up to 15 so my coffee tastes exactly as it did before”, Lucia explains.

Foreign yeast: like washing your hands before surgery

Adding bought yeast to coffee is also a great way to achieve consistency. “If you want to produce 10 containers of consistent coffee you should be inoculating. It’s kind of like washing your hands before surgery. It’s a no brainer. It’s what you do for security”, Lucia says.

Also, as acids are one of the residues of the process, fermentation can help prolong a coffee’s shelf-life. “Acid is key in preserving food in general. It brings stability and I also like it because it creates a structure that will withstand for a long period of time. You are creating body and fruity flavours but also more organic acids to preserve those flavours over time.” 

If you, as a buyer, are worried about the processing method of a coffee you bought, please don’t start by accusing the producer of adulteration. Though there might be cases, most producers know they depend on their reputation to sell coffee and making one good sale largely outweighs the risk of ruining one's name. Rather than buying coffee on flavour alone, develop relationships with farmers based on mutual trust and frank conversations. 

Other insights into fermentation

It leads to even drying and roasting

The advantage of washed or fermented coffees over naturals is that when the beans are submerged in water or a solution their moisture content will even out. “You’ll generally have more even drying than you would with a natural or honey. As a result, the roasting should also be a lot more even. Basically, it should be easier to roast. Cherries have a different internal moisture content based on their ripeness. So, with naturals, some cherries will start drying at 45%, some at 30%...”, explains Lucia.

It reduces sugar content but increases perception of sweetness

Strictly speaking, no producer will get sweeter coffees by fermenting them. “Fermentation is a breakdown of sugar. You are always losing it”, Lucia explains. But sweetness is not only about the real sugar content of the brew and our brains perceive sweetness even when it’s not really there. It's a fermentation paradox. “A lot of the time, sweetness gives you body and mouthfeel. Fermentation, especially with yeast, is really good at [replicating] that. It creates large compounds that increase the mouthfeel, so you can approximate sweetness if you have a really syrupy coffee. Fermentation also creates fruity or honey-like compounds so “your brain fills the gap”.

More time is not the same as more flavour

Lucia is very clear about her fermentation style. She is all about efficiency and science. Under typical tropical conditions and a temperature of 25°C, 24 hours is enough for the molecules generated by the process to enter the beans. It’s been tested with dyes and this provides a “really good guess” as to how long it all takes. As Lucia uses other yeasts that need more time to “warm-up”, she extends it to 36 hours. “More is not necessarily better. And the danger is that at some point the microbes run out of fuel, so they have to find something else. If a producer is selling coffee on weight it can also be an issue because you lose density. With less density, the way you roast that coffee will also change.”

Defects? Don't jump to conclusions

When coffee doesn't taste right, it's tempting to blame the fermentation process. It was either too long or not monitored well. But fermentation alone doesn’t offer enough information on quality. You also need to understand the drying process in more detail. “Drying can have more of an impact on quality and longevity than what we do at the fermentation tank”, Lucia starts. “We know that really high temperatures damage the seed's embryo, the structure and long-term viability of the coffee. So if the producers are drying on raised beds, are they covering the beans so they don’t get too hot? If they use a guardiola, are they just trusting the inlet temperature of the machine or are they measuring the temperature of the beans with a thermometer?”

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