Model-based kinetic espresso brewing control chart for representative taste components

Influencing espresso coffee quality by adjusting the extraction process parameters is a current issue in coffee research. In previous literature, significant effects of the brewing parameters on taste have been demonstrated for espresso, and mathematical models were developed describing extraction kinetics. However, an attempt to include the effects of process parameters in a model for predicting the extraction kinetics of taste-relevant solutes had been lacking. In this study, the two-grain model, originating from the work of Melrose and Corrochano et al. (2012, 2015, 2018), and adopted by Moroney et al. (2019), was extended by equations describing the influence of water flow rate and temperature on mass transfer. The model parameters were estimated using experimental extraction kinetics data for total dissolved solids, caffeine, trigonelline, and chlorogenic acid from our previous study. Model predictions were compared with experimental data, including time-varying temperature and flow rate. The results are summarized in a control chart and a publicly available app visualizing the importance of extraction kinetics on espresso composition.