Arabica (C. arabica) and Robusta (C. canephora) varieties differ in many aspects: firstly, in their caffeine content (Arabica approx. 1%, Robusta approx. 2%), and secondly, in their chlorogenic acid content (Arabica approx. up to 8%, Robusta approx. up to 12%). Fat content is another key distinguishing feature: while Arabica varieties have a fat content between 15 and 18%, Robusta varieties only reach up to 10%. But why should this matter to us?
When it comes to crema, a high fat content negatively impacts foam stability. This means that an espresso with a high Robusta content generally has a more stable crema than a pure Arabica espresso with a high fat content. However, conversely, most of the coffee's aromas are located in the coffee oils. The advantages and disadvantages of fat content, therefore, depend on the perspective. Wonderful aromatic experiences can be found in the same cup with a "thinner" crema. Certainly, the foam intensity also depends on the age of the coffee bean: the carbon dioxide necessary for crema diffuses out of the bean over time, and the same is true for the aromas.
Arabica and Robusta varieties have a comparable protein content of up to 12%. However, Robusta varieties have a slight edge in free amino acids, which are not incorporated into proteins, at approximately 0.8% (compared to Arabica's approximately 0.5%). One might think this small difference in concentration would have little noticeable effect. However, these free amino acids should not be underestimated. This very small difference contributes significantly to the different taste and aroma experiences. The classic "roasted" aromas (e.g., pyrazines), which are also found in bread or meat crusts, are largely formed from amino acids during the roasting process. The concentrations of these roasting products can be ten times higher in Robusta coffees than in Arabica beans. Therefore, Robusta varieties, unlike Arabica, often exhibit the classic "roasted," nutty, and spicy aromas. In Arabica varieties, however, the higher aliphatic acid and sucrose content (especially during caramelization) is a significant factor… But more on that in the August issue of PRESSE.