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di Alessio Simonetta
ultimo aggiornamento 15/02/2018 08:49:50


When the sun sets, in the coffee plantations the hard work of picking cherries ends, then a first selection is made by separating them by colour, the first index of the maturation state, then they’re divided into bags and transported to the mill. Only for washed and semi-washed (honey) coffees it happens immediately the depulping and so obtein the seeds in parchment covered by the mucilage after that are deposited in tanks, where fermentation begins.
To learn more about this process I had a chat with Lucia Solis, originally from Guatemala but raised in California where she graduated in enology and viticulture at the “U.C. Davis” but from many years she works in the production of quality coffee alongside the producers of Latin American countries, she defines herself as fermentation designer and with her consulting helps to find customised individual solutions based on fermentation control to keep the production process consistent, she’s also licensed Q-grader for quality control in cupping.
Hey Lucia, let’s start from the bases:
A terms used very often in coffee is “anaerobic fermentation” what exactly does it mean?
Mostly of the people in coffee industry don’t use scientific terms, and I like to crìorrect them. Sometime somebody want to be more specific saying “anaerobic fermentation” but is actually less specific and more confusing. Fermentation is always by definition anaerobic, aerobic fermentation does not exist because yeast and bacterials do not “respire”.

What happen during the fermentation process in coffee?
Yeast and bacteria naturally found in the soil, cherry skin, and mill environment metabolize the sugar in the mucilage and convert it to carbon dioxide and alcohol in the case of yeast, and acids in the case of bacteria. Both yeast and bacteria produce enzymes to help break down available food sources like the sugars found in mucilage. The coffee seed itself is not transformed by this process, but there is still a flavour impact from fermentation that can be noticed after roasting. Even though only mucilage is removed in the fermentation, the impact is obvious to anyone who has ever found an “over-fermentation” or “winey” defect in a cupping.

Is it possible control the fermentation in the way that the coffee going to express in cup the flavours that we want?
Yes, I notice that yeast strains have an effect on the flavour profile of coffee, like in wine is.
My job is helping my clients to be consistent in what they want. I can design a fermentation process for their coffee that express the components in more acidity, more body or more fruity and this is also depending from the raw material that we using and to the constant control of time and environmental temperature.
Does the choice of container material in which fermentation takes place affect the final result in the cup?
The material doesn’t matter in so, but the way the material interact with coffee matters.
Concrete is harder to clean for example, I prefer plastic or stain steel because are easy to clean, is all about hygienic and temperature so the heat transfer that the material that we choose act and obviously this factor has to do with the climate.

To produce some wines they use the technique of macerating the grapes with the peel, it is possible apply this technique in coffee?
When we produce wine we are interested in the pulp and peel because there are concentrated phenols and aromatic notes, we try to maximize the composition of these two elements while minimizing that of the seeds.
In coffee you only worry about the seeds, not the peel or the pulp, all the flavors of coffee are in the seeds is there the game, so we have a completely opposite objective and consequently also a process opposite from that of wine.
It is right to exploit my studies regarding chemistry and microbiology but it makes no sense to replicate the techniques used in wine production on coffee, I think it is stupid. I know that someone tries to use this system and if it achieves good results in the cup it's just lucky because they do not know what they're really doing.

Will the new generations of coffee producers be more sensitive about this step in the production chain?
There is a lot of resistance to changes the ways. Coffee, especially in Central America where I’m specialise, it has been produced with the same system for 80 years, a lot of the mill are build ages ago and even the new ones are build with almost the same instructions only with new material, so there is still the same mentality and the production is kind of stock at the same point, but the market demand has really changed a lot in terms of specialty so there is a big gap between what the people want and what the producers are able to provide right now.
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