Espresso Coffee Machine Research Articles

How Does Roasting Process Influence the Retention of Coffee Aroma Compounds by Lyophilized Coffee Extract?

The aims of this study were (1) to study the effect of lyophilized coffee extract on the retention of aroma compounds and (2) to study if aroma compounds selected are differently affected by the lyophilized coffee extracts obtained from conventional and Torrefacto coffee brews prepared by filter coffeemaker and by espresso coffee machine. Variable amounts of lyophilized coffee extracts, relative to coffee powder, containing different percentages of high molecular weight compounds, mainly melanoidins (value given in parentheses), were obtained: 20.9% (14.8) and 24.9% (23.3), respectively, for conventional and Torrefacto coffee brew prepared by filter coffeemaker and 18.1% (18.8) and 20.7% (57.5), respectively, for conventional and Torrefacto coffee brew prepared by espresso coffee machine. The retention of aroma compounds increased by increasing the lyophilized coffee extract concentration and was found to be dependent on the aroma compounds. The retention of aroma compounds was found to be slightly different depending on the brewing procedure employed, showing lyophilized coffee extracts obtained with espresso coffee machine had higher retention values that those extracted by filter coffeemaker. Retention capacity of lyophilized coffee extracts obtained from the conventional and the Torrefacto roasted coffee did not show differences except in the case of ethyl nonanoate.

High-resolution1H NMR investigation of coffee

Recent successful applications of NMR spectroscopy and imaging in food science prompted the authors to use these new techniques for the analysis of espresso coffee. The target of this work was to identify an experimental procedure to obtain maximum information from high-resolution 1H spectra. Only the espresso coffee was considered as the true food, since it includes all aromatic substances responsible for the coffee aroma and taste. A big effort was made in order to select an easy, quick and non-degrading procedure to analyse the espresso cup content, preventing artificial or natural degradation effects with a particular care in the measurement of labile and volatile components. The procedure was tested on two arabica and one robusta samples; each sample was prepared with three roasting degrees to follow the chemical changes due to the roasting process. Moreover, one water extract was prepared also from ground green coffees. As a comparison, each coffee extract was prepared both with a standard ‘espresso coffee machine’ and with a ‘mocha’ as used in the domestic setting. Significant differences among the three samples were observed. Moreover, for all samples, as a function of the roasting degree, a clear trend in the chemical composition was observed. © 1999 Society of Chemical Industry