Naturals: Characteristics in Cup

Post-Harvesting | Part 2 of 4

Naturals: Characteristics in Cup

Coffee beans must be processed into a storable form after harvesting. In the "post-harvest processes," the beans, which may have a moisture content of up to 65%, are dried to a level of 10-12%. The different methods used influence the composition of the ingredients and thus ultimately the cup profile.

In the first part of our press series ( PRESS 01/24 ), we focused on the so-called "natural/dry process," which involves drying the beans along with the pulp of the surrounding cherry.

What does the "dry process" mean for the result in the cup? Generally speaking, beans from this process tend to have more sweetness and body, and less acidity, than beans from the "washed process." Body in the cup is defined as a sensation of greater volume or breadth in the mouth. It is primarily the coffee's fats and larger, water-soluble carbohydrates that contribute to this body. In other words, a higher proportion of these substances also increases the body in the cup. The fat content of coffee is not influenced by the "post-harvest process," but rather by the species, variety, and especially the altitude at which it is grown. As a general rule, the higher the altitude at which a coffee plant is grown, the higher its fat content. The proportion of water-soluble carbohydrates, however, is indeed influenced by the "dry process." Due to the drying of the beans in the pulp of the cherry, remnants of a pectin layer adhere to the outside of the bean, which, unlike in the "washed/wet process," is removed through fermentation and washing. Roasting the dry-processed beans breaks down this large carbohydrate structure of the pectins into smaller, more complex molecules. Water-soluble components are broken down. The more of these components are produced by a longer roasting time, the more body the coffee will have in the cup. The sweetness in the cup that we believe we taste is primarily due to aromas that we perceive through our nose. Many discussions about the sweetness of "naturals" (dry-processed coffees) are based on the misconception that the sugars from the pulp migrate into the bean during drying. This would imply that the sugar molecules, like salmon spawning, move against the current of the water during drying. This misconception has been scientifically disproven. The higher fructose and glucose content in "naturals" compared to "washed coffees" is a result of the dry processing method.

Image: Coffee cherries during natural processing. Source: Meet los Amigos/Belco

Unlike natural coffees, "washed" coffees are in contact with water for an extended period. This moist environment triggers germination processes in washed coffees – meaning the enzymatic breakdown of proteins and carbohydrate units begins. These germination processes do not occur, or occur to a lesser extent, in natural coffees. Therefore, natural coffees have a different starting point for roasting. The resulting aromas contribute to the perception of sweetness.

Graphic: Knopp, S., Bytof, G., Selmar, D. (2006). Influence of processing on the content of sugar in green Arabica coffee beans. European Food Research and Technology 223, 195-201

Dry processing is widespread in Brazil because there is no rain during or after the harvest. However, Brazilian "naturals" differ significantly from those from, for example, Ethiopia. In Brazil, most coffee plants grow at an altitude of approximately 1000 meters above sea level. In Ethiopia, many growing regions are found between 1800 and 2200 meters. Brazilian varieties tend to have a good body and a fine, creamy sweetness in espresso, while Ethiopian "naturals," for example, can be quite fruity and are therefore better suited for filter brewing.

For a long time, the major drawback of coffee beans processed using the dry method was often the lack of cleanliness in the cup. Cleanliness, or a "clean cup," is defined, in short, by the clear recognition and differentiation of aromas and flavors in the cup, as well as the gradual disappearance of these impressions after a short time. In this category, washed coffees often have the advantage. Producing "natural" coffees, therefore, requires considerable expertise to preserve body and sweetness on the one hand, and to maintain a clean cup on the other. We will learn more about cleanliness in washed coffees in the next issue of PRESSE.

 

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"Naturals: Characteristics in Cup" | Post-harvesting part 2 of 4