In western Austria, mountains are generally only recognized as such above the tree line. This phenomenon is unknown around the equator and therefore also within the coffee belt. Here, it's quite possible to find coffee plantations at altitudes of 2200 meters. The term "highland coffee" for C. arabica varieties is indeed fitting. The C. canephora genus, widely known as Robusta, is traditionally found at lower elevations, up to 800 meters. However, even this is no longer a universal rule; this genus has been "migrating" to higher altitudes in recent years. C. canephora plants can now be found at elevations as high as 1500 meters. Does all this have an impact? – Quite a few! – One example can be quickly explained. An Ethiopian-Belgian team of scientists (Worku et al., 2018) described several aspects in a very readable publication. In summary: the sucrose (sugar) content of the green bean correlates positively with the altitude at which it is grown. This means that if the same coffee variety is grown at different altitudes, higher sucrose (and also glucose) content can generally be expected from the coffee beans grown at higher elevations. This phenomenon is currently attributed primarily to a combination of cooler temperatures, a slower ripening process, and simultaneously more intense sunlight. Sucrose undergoes numerous transformations and breakdowns during roasting. Many desirable flavor compounds are produced in the Maillard reaction and through caramelization – processes in which sucrose or its constituent sugars, fructose and glucose, are involved. And believe it or not, various acids are formed in the bean from sucrose and other sugars during roasting: formic acid, acetic acid, and lactic acid, to name the most important. These reach their maximum concentration at a certain point during roasting and are subsequently partially broken down. Additionally, green coffee beans also contain significant amounts of citric and malic acid – like many seeds from other fruits. The natural "green" acidity increases further with altitude, especially when the coffee plants are shaded from direct sunlight by trees. This interesting blend of diverse aromas and acids contributes to the exceptionally complex and rich aroma and flavor profile of coffee extracts.

Arabica und Robusta Sorten unterscheiden sich in vielen Aspekten: unter anderem im Coffein Gehalt, dem Chlorogensäurengehalt und dem Fettgehalt.

Coffee is a genus of plants in the Rubiaceae family. More than 100 species are known to date. The best-known of these are Coffea arabica and Coffea canephora (commonly known as Robusta). These are also the two most important coffee genera on the world market. Looking at both coffee varieties at a chemical level reveals distinct flavor profiles. Significant distinguishing features include caffeine and chlorogenic acid content, fat and free amino acid content, sucrose, and polysaccharide content. As "molecular building blocks," these groups of substances play a major role in the roasting process and thus in the flavor of the cup. Caffeine remains essentially stable during roasting—its levels hardly change. Arabica beans typically contain around 1% caffeine, while Robusta beans contain around 2%. In its pure form, caffeine tastes bitter and contributes between 10% and 30% to the bitterness of the final cup. To date, 72 different chlorogenic acids have been identified in green coffee beans. Their main groups contribute significantly to the characteristics of roasted coffee during roasting: Arabica contains up to 10% and Robusta up to 14% chlorogenic acids. Roasting can transform chlorogenic acids into spicy to smoky aromas like guaiacol, as well as vanillin. Other breakdown products—especially in darker roasts—such as chlorogenic acid lactones or phenylindanes, often cause extreme bitterness for the coffee drinker. These processes are therefore more likely and frequent in Robusta varieties. Here, great care in cultivation and roasting is essential to ensure that the gustatory advantages of this variety outweigh its disadvantages. Besides their sensory effects, chlorogenic acids also make important physiological contributions – as antioxidants in the body. Coffee is considered one of the main food sources of chlorogenic acids. Caffeine and chlorogenic acids are so-called "defense metabolites" in coffee plants. Caffeine acts as a neurotoxin, primarily against herbivores. Chlorogenic acids have an antioxidant effect against stress reactions in the plant or serve as building blocks for lignin, which is essential for lignification. This means they help the plant defend itself against herbivores, infections, and inflammation. The more coffee varieties are forced to assert themselves in evolution, the more of these substances have been incorporated into the DNA blueprint. The name "Robusta" derives from this ability to withstand adverse conditions. Due to these properties, Robusta is gaining increasing importance in the context of climate change. New developments offer hope that its qualities will improve, and that in addition to its robust nature, we will also find a compelling taste surprise in our cups.

While we can quite expertly distinguish between Grüner Veltliner and Muskateller, between Merlot and Zweigelt when it comes to wine, we are usually still quite naive when it comes to coffee. Just like wine, the world of coffee offers us a great wealth of different varieties. Coffea arabica and Coffea canephora (commonly known as Robusta) are the two most important coffee species on the world market. The varieties derived from them exhibit specific regional characteristics depending on their origin, geographical location, terrain, and processing, similar to the different grape varieties in winemaking. C. arabica and C. canephora share a common history. A historical paradox: C. canephora is the older species and a "parent" of the Arabica genus, even though it was discovered later. C. canephora has been used by humans since the mid-19th century. The history of the use of Arabica plants, on the other hand, begins between 500 and 1000 AD.Ethiopia and Yemen are home to the oldest Arabica varieties. Ethiopia is the cradle of Arabica. Many local varieties arose naturally over millennia in the Ethiopian rainforests (Wolisho, Kudumé, Dega, Yawan, to name just a few). Over time, people selected from this diversity of plants based on specific characteristics to create new varieties (Dilla, Geisha, etc.). Further new varieties arose naturally through the expansion of Arabica cultivation to other regions. Yemen was the first country to which the Arabica coffee plant spread from Ethiopia. And Yemen is the source of three varieties that are the starting point for many of today's hybrids—naturally occurring or cultivated: Typica, Mocha, and Bourbon. These three very old varieties are less productive than newer hybrids. They are highly prized by coffee connoisseurs for their rich aromas, which is reflected in the price of these green coffees. New varieties – whether naturally mutated or bred by humans – also have a long history. For example, a mutation in the Bourbon plant was observed in 1935 – named Caturra. This plant became the basis for many breeding programs aimed at high yields. While a Typica plant yields no more than 500 kilograms per hectare, Caturra can produce up to 1,500 kilograms.Nature and humanity are constantly striving to produce new varieties. Quality and yield represent the extremes of this pursuit. For a long time, humans focused on yield. However, these varieties have never been able to compete with the three oldest varieties in terms of taste. Generally speaking, Arabica varieties have a higher acidity and more subtle aromas. Robusta varieties tend to be known for their tart, strong, smoky, and bitter-walnutty characteristics. The qualities of both are often combined in blends to create well-rounded, full-bodied flavor profiles. In plant breeding, there are also attempts to cross Arabica and Robusta varieties with the aim of combining the sensory attributes of Arabica with the resilience of Robusta. Looking at both types of coffee at a chemical level reveals distinct flavor profiles. Significant distinguishing features include caffeine and chlorogenic acid content, fat and free amino acid content, sucrose, and polysaccharide content. As "molecular building blocks," these groups of substances play a major role in the roasting process and thus in the taste of the coffee in the cup.

Freshly roasted... and the clock is already ticking! Coffee is a perishable product. From the moment roasting is complete, the aging process of the coffee beans begins. Then the clock starts ticking. The beloved aromas in coffee largely develop during roasting from the building blocks of the green bean. The fact that we smell aromas from coffee means that these are volatile: they travel to our noses in gaseous form. Most of what we think we taste, we actually smell. These volatile aromas are therefore (unfortunately) only a temporary delight within the coffee beans. In addition to the aromas, carbon dioxide (CO2) is produced during the roasting process. This originates from reactions between carbohydrates and amino acids. Carbon dioxide is particularly valued for its foaming effect – in the crema formation of espresso. Carbon dioxide plays an equally important role in the storage of coffee beans. It acts as a protective gas within the coffee packaging, displacing atmospheric oxygen. If a coffee package swells due to CO2, this is a good sign. Oxygen triggers aging processes in roasted beans and can even create so-called "off-flavors." These are aromas that produce undesirable odors. Therefore, if coffee beans are packaged quickly after roasting, the initially high CO2 content in the packaging, which diffuses out from the beans, provides the best possible protection for freshness. Like aromas, carbon dioxide also diffuses gradually out of the bean as a gas and therefore decreases over time. Darker roasted beans have a higher CO2 content than lighter roasts – this also affects crema formation and stability in espresso. Darker roasts also have a lower bean density and higher bean volume and are more porous. This means that carbon dioxide and aromas diffuse more quickly through the larger pores and channels in the bean, thus accelerating the aging process. Whole coffee beans age more slowly than ground coffee. This is due to their surface area: grinding coffee beans "cuts" them into many small particles. This increased surface area is essential for coffee extraction. Storing ground coffee, however, leads to accelerated aging: the small particles release aromas and CO2 into the surrounding air more quickly, and atmospheric oxygen finds numerous binding sites to act upon.All the processes described so far are accelerated by elevated ambient temperatures, while diffusion and oxidation processes are slowed down by cooler temperatures. If you happen to have too much coffee in storage, you can freeze it: thaw it in a closed container for at least 12 hours before use (to protect it from moisture). The key factors affecting the aging of coffee beans are oxygen, warmth/heat, and their own surface area (the finer the grind, the larger the surface area). The optimal window for using coffee beans is 1 to 4 weeks after roasting for darker roasts; lighter roasts can be stored for a few weeks longer if stored properly.One final tip: Carbon dioxide is heavier than the surrounding air. If you scoop coffee beans from the package instead of emptying it, a large portion of the carbon dioxide remains inside. Quality assurance can be this convenient and smart! Yemen was the first country to which the Arabica plant spread from Ethiopia. And Yemen is the source of three varieties that are the starting point for many of today's hybrids—naturally occurring or cultivated: Typica, Mocha, and Bourbon. These three very old varieties are less productive than newer hybrids. They are highly prized by coffee connoisseurs for their rich aromas. This is also reflected in the price of these green coffees.New varieties – whether naturally mutated or bred by humans – also have a long history. For example, a mutation in the Bourbon plant was observed in 1935 – named Caturra. This plant became the basis for many breeding programs aimed at high yields. While a Typica plant yields no more than 500 kilograms per hectare, Caturra can produce up to 1,500 kilograms. Nature and humanity are constantly striving to produce new varieties. Quality and yield represent the extremes of this pursuit. For a long time, humans focused on yield. However, these varieties have never been able to compete with the three oldest varieties in terms of taste.Generally speaking, Arabica varieties have a higher acidity and more subtle aromas. Robusta varieties tend to be known for their astringent, strong, smoky, and bitter-walnutty characteristics. The qualities of both are often combined in blends to create well-rounded, full-bodied flavor profiles. In plant breeding, there are also attempts to cross Arabica and Robusta varieties (image: Coffee Tree) with the aim of combining the sensory attributes of Arabica with the resilience of Robusta. Looking at both types of coffee at a chemical level reveals distinct flavor profiles. Significant distinguishing features include caffeine and chlorogenic acid content, fat and free amino acid content, sucrose, and polysaccharide content. As "molecular building blocks," these groups of substances play a major role in the roasting process and thus in the taste of the coffee in the cup.

Part II