Washed, natural, natural pulping, semi-washed, honey coffee producers around the world process their beans in different ways. In recent years, with the rise of specialty coffees, variations of these techniques have begun to appear, often taking advantage of the fermentation that takes place during processing. These methods are usually grouped under the label of "experimental processing".
Some of these techniques have been inspired by movements in other unrelated industries. Others have emerged as coffee growers try to reach new markets.
In our case, mosto is a process used for sweet wines that are transferred to coffee processes, so when we talk about mosto the first thing that comes to mind is probably a wine making process; however, here we explore the role of mosto in coffee production.
In the wine industry, "mosto is defined as the natural juice of the grapes, which is extracted during the first steps of winemaking and is a key starting point for determining the quality of the final product".
In the coffee world, mosto is the result of the fermentation of ripe fruit, known in some places as leachate. This product is widely known but very few use it. The mosto is the fermentation of clean, freshly picked cherries in a medium with a low incidence of oxygen.
This process to extract the leachate is equivalent to 10% of the total weight of the initial cherries which can then be used in a new fermentation process. These observations relate to the production of mosto, which does not need any additives or water because, naturally, cherry mucilage contains more than 80% water and beneficial bacteria, which change in quantity among some varieties.
It should also be mentioned that through the mosto, it is possible to obtain more fruity notes, body, more complex acidity, and hints of spices thanks to the presence of bacteria and yeasts. Likewise, we found many bacteria that provide body, cleanliness, and sweetness in the cup, depending on some variables in the process.
In particular, it was found that the production does not require high technology and that it works very well to obtain coffees with exotic flavors. It is considered that these practices have always been available but should now be taken up and applied in the processes.
To produce a quality mosto, first of all, it is necessary to take into account the harvesting of coffee cherries at a good point of ripeness, which is the most important part of the whole process. Subsequently, they mosto be free of foreign materials and well washed, but not with chemical products that can reduce the positive bacterial load that the cherries bring from the field. The appropriate method is to pass clean water through the coffee.
Then, they should be placed in containers that allow low oxygen presence, pH, and temperature monitoring. For this, use containers that allow a part of the leachate to be drained to check these conditions. Another feature of pH for a good mosto is to reach 3.7 or higher, since below is not recommended and indicates an inadequate process, the proper pH is above four when you want to introduce new microorganisms in the mosto.
Temperature is an important factor for the mosto, considering that different temperatures also generate different flavors, so it must be homogeneous. To improve temperature control, it is necessary to reduce the presence of oxygen as much as possible.
From another point of view, since it is a product of bacteria, some of them may be harmful to health. For this reason, to ensure quality, it is essential to carry out microbiological analyses at the beginning of the processes on each farm and rule out the presence of those that are not beneficial.
As each coffee and place behaves differently, each producer can experiment on his farm at different times and concentrations. The best moment is 72 hours after the fermentation process has started and that is when the leachate known as mosto will be obtained due to the pH and temperature, but this does not mean that it is the only way, the time could vary, depending on the region, the altitude, and the coffee. Considering that it is important to make systematic tests with different harvest times, varieties, and farms to find the best results.
Finally, this translates into the fact that the mosto is a supremely useful substance to develop more yeasts or bacteria by having an optimal substrate for them to feed on. In other words, it is an activator that accelerates the fermentation process of a new batch of coffee, the results of the mosto are good but added to other actions, such as slow drying or slow fermentation, they will be better. For example, a process with mosto, added to controlled drying, can improve the quality and score of a coffee by up to four points. The mosto as a fermentation method generates very good results, but also poses some challenges such as the presence of bacteria and yeasts.