For many consumers, its origin is shrouded in mystery, not to mention its potential effects in daily life and in old age. But let's take it one step at a time.
Coffee originally comes from the tropical regions of the African continent, including Madagascar. However, of its estimated 120 species, only 3 are used for coffee cultivation. The evergreen coffee trees, only 5-8m high, grow at different altitudes and thus, from the outset, form a quantitatively and qualitatively different spectrum of ingredients. Coffea arabica, the most commonly cultivated species, grows in the highlands of Ethiopia between 600-1200m ("highland coffee"), while Coffea canephora ("Robusta coffee") prefers altitudes between 300-600m. The third species, Coffea liberica, is only found in the lowlands of West Africa. The occurrence of coffee trees in the equatorial regions of other continents (South America, Asia), also known as the coffee belt, is solely due to the actions of the former colonial masters who used climatically suitable areas for plantation cultivation. The higher the growing area, the slower the coffee plant grows. Its white flowers produce dark red drupes - often referred to as coffee cherries. At higher altitudes, the seeds contained within, the so-called "coffee beans", develop more aromas but less caffeine and taste milder overall than the species growing at lower altitudes, whose taste is described as spicier. The quality of the raw material for green coffee is determined by selective hand-picking (picking method) compared to mechanical harvesting (stripping method).
Traditionally, the coffee cherries are then dried in the sun before the pulp is separated from the green seeds. In the so-called wet processing, machines first remove a large part of the pulp, to subject the remaining residue to a fermentation process before its final removal. This produces aroma acids that give the seeds a fruity taste, while the traditional method tends to produce a sweet taste.
"unfortunately, its effects and taste are all too often reduced to the universally known caffeine"
The green raw coffee thus obtained already exists in various taste variations. In addition to caffeine bound to chlorogenic acid, it contains carbohydrates, proteins, trigonelline, vitamin B3, and coffee oil with kahweol and cafestol. The green, bitter and inedible seeds are then subjected to a roasting process, which is usually not fully disclosed, in the respective destination country. Depending on the intensity, temperature, and duration, the typical coffee aroma, in which up to 600 different aromatic substances can be involved, and so-called melanoidins, which cause the black-brown color of the coffee beans, are formed in a multi-stage reaction (Maillard). At the same time, the caffeine is released from its bond to chlorogenic acid, and trigonelline is converted into N-methylpyridine (NMP). It should be noted that, especially in faster industrial roasting, significantly higher temperatures (up to 550° instead of the usual 250°) are used, which promotes the formation of carcinogenic acrylamides, comparable to deep-frying fat.
Some may now wonder why all these minor details are mentioned here? Well, we want to slowly approach the mystery of coffee enjoyment, and unfortunately, its effects and taste are all too often reduced to the universally known caffeine. This is not sustainable, as a cup of coffee is a hot water extract with, as mentioned above, countless components. And these result in a wide variety of quantities and qualities through the selection of the raw material, its processing, roasting, and even its preparation. Thus, taste and effects can vary widely.
Recent research shows that precisely the many small compounds, unknown to most people, play a decisive role in coffee's many, often contradictory, effects. Its stimulating effect is undoubtedly linked to its caffeine content. Caffeine is almost completely absorbed in the stomach and duodenum and crosses the blood-brain barrier after about 30 minutes to exert its effect in the CNS. However, the potency of the effect is variable, as both habituation effects in regular coffee drinkers and genetically varying caffeine sensitivity are documented. The chlorogenic acid still present in smaller quantities after roasting has antioxidant properties and increases intestinal peristalsis. At the same time, however, it is also held responsible for heartburn in stomach-sensitive individuals. Overall, the roasting process and the compounds and conversion products formed during it seem to have a decisive influence on the positive and negative effects of coffee.
"On average, coffee drinkers appear to have less body fat than non-coffee drinkers"
The acrylamide formed is certainly on the negative side, while melanoidins and NMP are attributed with health-promoting effects of coffee. Melanoidins have antioxidant effects, bind heavy metals and cholesterol. Since they are indigestible for humans, they are metabolized by intestinal bacteria and act like dietary fiber. NMP appears to directly or indirectly reduce oxidative stress in the cell nucleus, thereby reducing possible damage (DNA strand breaks) to genetic material. The vitamin B3 contained in coffee is involved in lowering LDL cholesterol in the blood; its deficiency is associated with dementia and depression.
Then there are the diterpenes kahweol and cafestol, which are contained in the so-called coffee oil. Both increase cholesterol levels in the blood.
Fortunately, they can be filtered out of the brew with the help of coffee filters. Filter coffee contains up to 30 times lower concentrations than unfiltered coffee. Good to know in times of an overflowing supply of the most exclusive coffee machines. Finally, another new research finding. Coffee drinkers appear to have less body fat on average than people who do not drink coffee. This is according to a study from the USA. The effect was significantly higher in women than in men. Caffeine obviously plays no role here either. A precise assignment of the effect to individual groups of ingredients could not yet be made. So everything regarding the effects of coffee remains in flux. It is worth paying attention to the small differences in coffee consumption. Especially or precisely with contradictory and gender-dependent results. Research continues and we remain curious.
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