Volatile compounds in espresso resulting from a refined selection of particle size of coffee powder

Volatile organic compounds (VOCs) influence significantly sensory properties of espresso coffee (EC). However, some of these chemicals, such as furans reported to have a negative impact on human health. This study aimed to monitor 21 key main VOCs of coffee brew and two undesirable compounds such as furan and 2-methylfuran in Robusta and Arabica EC samples as a function of specific particle size fractions (F1 <200, 200 <300, 300 <425, F4 >425 μm). The evolution of the volatile compounds was studied by HS-SPME-GC/MS. The results showed that volatile compounds are released differently in the EC depending on coffee species and the specific particle size. In Robusta ECs the highest concentration of volatile compounds was obtained using 200 < 300 μm except for furan, 2-methylfuran and 2,5-dimethylfuran. Arabica ECs resulted particle size-independent for aldehydes, except for hexanal, phenolic compounds, and some furans and non-monotonic with the highest amount in the 300 < 425 for the nitrogen-containing heterocyclic compounds. With regard to furan and 2-methylfuran monotonic increase was observed along the increasing particle size degree. The HCA analysis separated in four different groups the coffees particle size; Arabica-F1, Arabica-F3 and Robusta-F3 formed the first group, the second included Arabica-F2 and Arabica-F4, the third group consisted of Robusta-F1 and Robusta-F4 and the last one included only Robusta-F2. These results can help to design a-priori unique blends based on appropriate combinations of particle sizes and coffee species to produce an EC with higher aromatic levels while simultaneously lowering levels of furan and 2-methylfuran.