Optimization of espresso coffee extraction through variation of particle sizes, perforated disk height and filter basket aimed at lowering the amount of ground coffee used

Abstract

Espresso machines maintain constant the extraction process of espresso coffee (EC), however, it is difficult to grind roasted coffee in homogeneous way. This research aims to investigate grinded beans at specific particle sizes in three variously designed filter baskets and to compare the concentration of bioactive compounds while decreasing the amount of ground coffee. Analyses on caffeine, trigonelline and chlorogenic acids are carried out with HPLC-VWD, while volatiles with HS-SPME/GC-MS. Extracting with smaller particles escalates the quantity of bioactive compounds. The amount of caffeine/cup increased moving from 500-1000 µm to 200-300 µm particle size, both in Arabica and Robusta for all filter baskets. Keeping constant the volume of EC at various heights of perforated disc, the amount of bioactive compounds at 12 g were only around 9% lower than at 14 g. The outcomes will support further studies on different extraction processes, to develop more sustainable and economically affordable coffee.

Keywords: 3,5-di-O-caffeoylquinic acid (PubChem: CID 6474310); 3-O-caffeoylquinic acid (PubChem: CID 1794427); 5-O-caffeoylquinic acid (PubChem: CID 5280633); Caffeine (PubChem: CID 2519); Espresso coffee extraction; Filter baskets; HPLC-VWD; HS-SPME/GC–MS; Particle size distribution (PSD); Trigonelline (PubChem: CID 5570).