Physical and chemical effects of different working gases in coffee brewing: A case study of Caffè Firenze

(1) Background: Recently, a new espresso extraction method, Caffè Firenze, has been developed, which uses gas at operating pressures of 20 bar to obtain abundant, persistent foam. The experiment aimed to evaluate the effect of using six gases (air, argon, nitrogen, carbon dioxide, carbon/nitrogen mix, and nitrous oxide) on the foam and liquid coffee. (2) Methods: Foam volume, persistence, sugar retention time, color, and rheological properties were measured. Volatile organic compounds were also evaluated. Analyses were also carried out on the liquid coffee to determine caffeine and chlorogenic acid concentrations. (3) Results: The analysis of variance revealed significant differences between the gases for all parameters. Multivariate analysis identified three groups of gases: the first comprised air, N2, and Ar; the second CO2 and N2O; and the third comprised samples extracted with CO2/N2 mix. (4) Conclusions: The choice of gas significantly influences the drink's chemical-physical characteristics and is fundamental for product diversification.