As you saw, each process is different because fermentation occurs differently in each case. In natural coffee, fermentation occurs inside the cherry. So the mucilage is in direct contact with the coffee beans all the time until the bean reaches a humidity between 9% – 10% that allows for the threshing.
The result is sweeter cups, with vinous notes, intense tropical fruit flavours, tart acidity and full body. Honey coffees have pronounced profiles, with sweet and fruity aromas and a balanced malic and tartaric acidity. The flavours are not as intense as in a natural coffee but are clearer and more defined.
However, if in the processing natural and honey coffees, the cherries have not been correctly selected at the time of harvesting, for instance leaving green and dry beans, or in the case that molds have appeared during the drying process, the cup will be really unpleasant with astringent, earthy, vinegar, mold, quaker and stinker flavours.
Washed coffees, on the other hand, present delicate, clean cups, bright citrus acidity, flavours of honey, chocolate, hazelnut, citrus fruits, floral and herbal aromas.
Natural and Honey coffees are sweeter than Washed coffees: Myth or Fact?
At the moment, it is not yet fully clear why the cup profiles of naturals and honey seem to be sweeter than those of washed coffees. Research has found contradictory results. One of the main reasons is that, as we said before, sweetness does not depend only on the process. Rather, it depends very much on the variety, the climate and the way the coffee plants have been cultivated.
Initially, some researchers found that sugar losses occurred in coffee beans subjected to the wet fermentation process of washed coffee (coffee mass immersed in water). In 2005, Knopp, Bytof & Selmar decided to study what happens to the contents of sugars with low molecular weight when coffee beans are subjected to different processes. They found that there are differences as a consequence of the metabolic reactions that occur in the cherries during the fermentation process. And that there are also changes in the free amino acid reserves that are responsible for many of the flavour and colour attributes of coffee in the cup.
Their results showed that although sucrose contents were similar in all three processes, fructose and glucose contents were higher in the natural process coffee, low in the washed coffee and intermediate in the semi-washed (honey) process coffee. They also showed that raffinose and galactose contents were higher in washed coffee.
Do sugar losses occur in coffee cherries during the washed process?
Knopp and colleagues observed that some sugars such as mannose and arabinose, which are found in small amounts in coffee cherries (100 times lower than sucrose contents), may be lost by passive leaching during the fermentation process of the washed coffees.
But in general, they point out that although carbohydrate loss during seed germination processes is a normal metabolic phenomenon, it is unlikely that sugars are lost in high amounts during the fermentation process. This is because the cherries are fully hydrated at the start of any of the processes. Thus, it seems that the fermentation processes do lead to a difference in the sugar and low molecular weight amino acid content of the coffee beans.
As a result, different cups are obtained with greater or lesser sweetness and with differences in the acidity and body of the beverage. So natural and honey coffees are indeed sweeter.