Long Fermentation Q and A with Lucia Solis
March 18, 2022
Long Fermentation Q and A with Lucia Solis

There is some crossover between modern coffee fermentation techniques and winemaking. As part of our research into long fermentation techniques we interviewed Lucia Solis. Lucia, who was once a wine professional, is a graduate of the legendary Department of Viticulture and Enology at the University of California, Davis. These days, Lucia spends the majority of her time as a consultant in coffee fermentation and processing. Lucia confirmed that interest in long fermentation is trending in Colombia, where she is based.

Lucia Solis

Jem Challender: We are doing some investigations into a trend that has been slowly gaining traction in Colombia: long fermentations, well in excess of 100 hours. We have some friends who just finished a 740-hour process. Have any of your producer partners approached you for advice on how to successfully carry out fermentations of longer than 100 hours?

Lucia Solis: Yes, I get this type of request frequently. If a client comes to me looking for extended fermentations of +100 I try to decline because it’s not the type of fermentation I want to work on. I see long fermentations as inefficient in terms of flavour quality. And rewarding inefficiency seems bonkers to me. I think of it like work culture in America vs. Europe. Americans are all about hustle culture and working 24/7. But in Germany they have the 35-hour work week. Why are we rewarding taking 100 hours to complete a task than can be done in 35?

Conversely, I support producers who have a drying bottleneck in doing +100 fermentations. For example, if a lot is not finished drying but they have new cherry coming in, it can be helpful for a producer to extend their processing from 24–36 hours up to +100 hours so that the drying area can be cleared. But again, the coffee is not ‘better’ for having a longer fermentation.

The other reason I stay away from this type of fermentation is because I want to focus on what I’m good at — for example, if I was really good at making croissants but someone was hiring me to make muffins. As a pastry chef, I can figure out how to make muffins, but what I’m good at is croissants. So, I try to match with people who already want what I’m making.


JC: What’s your opinion of the flavour of long-fermentation coffees? 

LS: My experience is limited because I do not seek them out, but I’ve tasted some from Brazil, Fazenda California, that I enjoyed. But most often I find the coffee tastes tired and overworked. I think very few varieties can handle that type of processing. I don’t see enough talk about pairing this type of processing with certain varieties. I have found that the hybrid-disease resistant cultivars tend to pair better with extended processing.

I have tasted tired coffees and I’ve also tasted a +400-hour frozen cherry process here in Colombia that tasted like a regular 48-hour fermentation. In Guatemala, in the Volcafe cupping room, I tasted a 7-day cherry process that cupped like their normal 20-hour pulped fermented process. I guess my point is that there’s nothing inherent in the amount of hours that changes flavour. It’s about the context surrounding those hours. Pulped vs. cherry, hot vs. cool temperature, oxygen-rich vs. anoxic environment, submerged underwater vs. dry, etc. Extended time/hours provides very little information. So maybe it’s better to say that in my experience, long-fermented coffees taste similar to short-fermented coffees. I don’t think ‘long’ is a good qualifier to distinguish a type of fermentation.


JC: What advice would you like to share with producers wishing to mitigate some of the risks involved with long fermentations?

LS: I see this more as an issue about relationships, not microbiology. The best way for a producer to reduce the risk involved in this type of fermentation is to get the buyer to commit to buying the lot, regardless of the result. A producer can best reduce the risk by sharing it with a buyer.


JC: As we discuss in this recent post on the BH blog, Nikolai Fürst’s attempts to transfer the same techniques used on Omar’s farm to another farm were unsuccessful. Do you have any theories about what at Omar’s farm makes this process more viable? Could folks perhaps do some microbiota mapping to work this out, as I discuss in question 8?

LS: This is tough to speculate on, but I think the bottom line is genetic luck. Omar’s farm could be [located] in a specific niche microclimate with favourable microbes. The other often-overlooked reason is cleanliness. I’ve been to some really dirty beneficios where maybe the ‘right’ microbes exist but the culture of cleaning doesn’t exist and there is a lot of cross-contamination from water, equipment, animals, or people.


JC: Have you identified any particular yeast strains that might be compatible with longer fermentations?

LS: No, I don’t do this type of work (strain identification). I think all the yeast strains I currently use are compatible with extended fermentations, but I just don’t let them go that long.


JC: What is your opinion of the practice of adding rapadura sugar to coffee fermentations? 

LS: I actually do recommend adding sugar to the fermentation if the starting levels are low or if a client really wants to do a long fermentation


JC: If a producer in your area wanted to have a coffee tested for mycotoxin levels, what would be the process, and can you estimate the cost and availability of such testing? 

LS: I think for my area (high-grown/cold climate/Colombia/arabica) this is a non-issue. Most of the mycotoxin issues are lower-elevation/hot climate/robusta concerns. This is very unlikely to be a concern for specialty.

If an arabica producer has a mycotoxin issue, it’s unlikely to come from the farm or processing. Most likely the contamination is from transportation. I think in that case it should be the importer/exporter who pays for the analysis. Tests like these are much more available and affordable in importing countries. I’ve heard of some roasters testing their coffee for $75 per sample.


JC: This article discusses an interesting approach to fermentation being employed by Melanie Edwards in Myanmar, involving a style of yeast traditionally used in the production of rice wine. The producers have an interesting safeguard to avoid the growth of unwanted mould species during the 22 days their coffee spends on the drying beds. Have you encountered similar results in Colombia?

LS: The protective effect of yeast against mould is not specific to the rice wine starters. One helpful side effect of the Saccharomyces cerevisiae strains I use is that they have a protective effect against mould. This is a very common effect of all Saccharomyces yeast strains.


JC: Should all producers get microbiota mapping done on their coffee? Have you found this kind of data to be useful for producers you work with? (The producers in the Myanmar article I referenced above describe their desire to carry out microbiota mapping in the future, but this has not been feasible during Covid.)

LS: Many producers want to get their coffee mapped, and I honestly think it’s not the best way to invest their money. It’s not widely available yet, it’s expensive, and it’s a moving target — so I’m not sure it would even be very helpful to most producers. If a producer has infinite money and resources, then sure, why not get their microbiota mapped? But very few producers have so much money they don’t know what else to spend it on. Not being able to map your microbiota is not a barrier to producing good coffee.


About Lucia Solis

Lucia Solis is a coffee processing specialist, she specialises in “microbial demucilagination”, or the use of microbes to process coffee following pulping. Born in Guatemala and raised in San Francisco, Lucia studied Viticulture and Enology at UC Davis prior to working in Napa as an enologist. She started working with yeast and coffee fermentation in 2014.

She has a podcast focused on microbes and coffee fermentation called Making Coffee with Lucia Solis.
Website: www.luxia.coffee