The influence of varieties, origin and processing on coffee taste
Taste and aroma of coffee
The research on coffee from coffeeadastra.com, from which my article is based, will give us an insight into what influences the taste of coffee today.
The taste and aroma of coffee are created during roasting. Aromatic compounds are formed by the transformation of chemicals that occur naturally in green coffee beans.
To understand how coffee flavours are created, we need to delve into a little chemistry. Hydroxyamino acids, such as threonine and serine, are converted into volatile compounds called pyrazines and pyrroles, which create the characteristic aroma of roasted coffee.
The breakdown of simple sugars and polysaccharides during roasting produces sweet and caramelised aromas. In contrast, the breakdown of hydroxycinnamic acids produces spicy aromas.
But what does this have to do with processing, coffee variety and origin? All of these components have a big impact on how the coffee tastes.
Coffee from Africa tastes different from American coffee. If you taste Arabica, you will find that it is very different from Robusta, and coffee processed by the washed method is completely different from that processed by the dry method.
Coffee variety
Coffee beans are basically divided into two main types - arabica and robusta. There are a number of subspecies of Robusta beans, each with unique characteristics. The same applies to Arabica beans
The main difference, apart from the fact that they are different species of the same plant family, lies in thetaste and characteristics of the beans themselves. Although Arabica beans contain less caffeine than robusta, they are oftenconsidered better tasting.
Arabica usually has asmoother and sweeter taste withnotes of chocolate and sugar. They also often have hints of fruit or berries. Robusta, on the other hand, has astronger, harsher and more bitter taste with grainy or rubbery undertones.
Origin of coffee
How do coffee beans change depending on their origin? It is not only the variety and processing that contribute to the taste of coffee. The story is also based on origin-specific factors, such as soil, altitude, sun, wind or rainfall.
For any plant, soil has abig impact on its overall health and ability to deliver nutrients where they are needed. When it comes to coffee, the plant needs the right amount of nutrients to deliver them to the cherries.
A nutrient deficient coffee plant will show up with underdeveloped fruit and uneven size and ripening of the cherries. In bad cases, the coffee beans will simply break down and can have really serious deformities.
Extraction
Depending on the country of origin, extraction yields of coffee vary. Varieties typically grown in Kenya and Ethiopia gave the highest extraction yields, while varieties often grown in South America tended to give lower yields.
Of particular interest is the case of the Geisha variety, which originated in Ethiopia, where more soluble matter can be observed. The Ethiopian Geisha yields on average 0.4% more than the South American Geisha.
Why such differences occur is unclear. It may be due todifferences in coffee genetics, in how these genes are expressed in different environments, or it may also be due todifferent agricultural or processing practices.
It is believed that the different extraction yields are due to the higher soluble matter content of African coffee beans.
However, there could be another explanation; the different chemical profiles corresponding to different varieties may also bias thecalibrations of the VST refractometer, which uses the refractive index of the coffee and converts it to concentration using its own calibrations.
There may be some differences in the sense that obtaining extremely accurate extraction yields would require using a different calibration for, for example, Ethiopian, Kenyan or Colombian coffee.
The graph shows that coffees grown at higher altitudes give higher average extraction yields. This means that the differences are real and are at least partly due to growing conditions.
Specifically, some research by Vaast et al. (2006) and by Worku et al. (2018) has shown that coffees with higher growing requirements tend to concentrate more nutrients in their seeds in harshergrowing conditions, such as high-altitude farms.
Coffee processing
Another aspect that is widely known to affect the flavour profile of a cup of coffee is the process by which the pulp is removed and the beans are dried, generally referred to by the collective term coffee processing.
The choice of coffee processingmethod can affecthow many chemical components are present in the bean when it reaches the roaster and therefore influences which flavours are produced and in what quantities.
Keep in mind that even one type of coffee bean or variety can vary in quality and taste. Try out the differences in different varieties and types of coffee processing and find your favourite.