The world of coffee is extremely complex. I never realized that till I ran into a few scientific papers on the preparation and extraction of coffee. I so discovered that there is an entire community dedicated to the science of coffee. Considering that it is one of the top beverage in the world, that’s not surprising at all.

I also learnt that there are more than 800 volatile compounds responsible for the aroma of coffee. The list I found is not exhaustive given that researchers are still busy characterizing new molecules.

All the studies have one final goal: obtaining the perfect cup of coffee. There are a few factors determining the quality of coffee that you are about to taste.

The type of coffee

The type of coffee blend as a crucial role in the final outcome. Do you think that’s common sense? Well, follow me… :)

Although there are a few varieties of coffee, the most popular are Arabica and Robusta. Arabica has a smooth and delicate flavour, while Robusta is stronger and slightly more sour. Among all the blends commercially available, my favorite is 100% Arabica. Although Arabica is considered the top quality, I met people swearing to have tasted excellent coffees made with Robusta. When it comes to coffee, people might have their preferences. Generally speaking, Arabica has a more “gentle” flavour and you might appreciate that if you like delicate tastes.

The type of roasting

Roasting is a crucial step that allow to enrich coffee beans of flavours not present in the raw product. We can have different degrees of roasting, from a light to a strong level.

Why roasting?

Roasting has a two scopes. First of all developing flavours that are not present in the raw coffee bean. During roasting, a process occurring at 200-220 C, sugars caramelize, a part of cellulose and caffeine are lost. The molecules developing during the process are mostly aldehydes and ketons. Those volatile compounds are responsible of the aroma of coffee, which is firstly perceived in the nose rather than in the mouth. Listing all this molecules is extremely hard. Scientists are still working on that and I have the feeling that is going to be work in progress, at least for a while.

One of the most interesting compound from the aromatic point of view is the ethyl ciclotene. This molecule determines the flavour of burnt sugar/caramel. It is a strong flavour enhancer, along with cyclotene, present in maple syrup.

Other scope of roasting is making the beans crunchy and suitable for grinding. This is very important when we extract our coffee! Coffee powder has a much higher surface of extraction, compared to the bean.

Do you feel in a mood for coffee now? :)

Coffee references

1.    Borrelli R.C., Visconti A., Mennella C., Anese M., Fogliano V. (2002) Chemical characterization and antioxidant properties of coffee melanoidins. J. Agric. Food Chem. 50:6527–6533
2.    Akiyama M., Murakami K., Ohtani N., Iwatsuki K., Sotoyama K., Wada A., Tokuno K., Iwabuchi H., Tanaka K. (2003). Analysis of volatile compounds released during the grinding of roasted coffee beans using solid-phase microextraction. J. Agric. Food Chem. 51:1961-1969
3.    Baggenstoss J., Perren R., Escher F. (2008). Water content of roasted coffee: impact on grinding behaviour, extraction, and aroma retention. Eur. Food Res. Technol. 227:1357-1365
4.    Baggenstoss J., Thormann D., Perren R., Escher F. (2010). Aroma recovery from roasted coffee by wet grinding. J. Food Sci. 75(9):C697-C702
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8.    Yeretzian C., Pascual E.C., Goodman B.A. (2012). Effect of roasting conditions and grinding on free radical contents of coffee beans stored in air. Food Chem. 131:811-816
9.    Sievetz M. e Desrosier N.W. (1979). Coffee technology. The AVI Publishing Company, Westport
10.    Illy A. e Viani R. (1995). Espresso coffee: the chemistry of quality. London:Academic Press Limited
11.    Andueza S, De Pena MP & Cid C (2003) Chemical and sensorial characteristics of espresso coffee as affected by grinding and torrefacto roast. J Agric Food Chem 51:7034–7039.
12.    Cappuccio R., Suggi-Liverani F., (1999).18th International scientific colloquium on coffee, Helsinki. ASIC, Paris, France, pp. 173-178.
13.    Manara Elena, (2011). Studio tecnico-sperimentale dei processi ossidativi del caffè. Tesi di Laurea Magistrale in Scienze e Tecnologie Alimentari, Università Cattolica del Sacro Cuore.
14.    Manara E., Lambri M., Girasoli A., (2008). Impact of toasting parameters on the color of coffee, Italian Food Materials & Machinery, November, 52-55.
15. F. Chartier in Taste Buds and Molecules.