Brewing espresso is considered a craft and even an art by some. Several different rules, recommendations, but also myths exist on influencing espresso bitterness and acidity. An experiment based on the box-behnken design was performed with different temperature (84°C, 89°C, 94°C), flow (1.0 ml/s, 1.5 ml/s, 2.0 ml/s) and coffee grind setting. The extracted espresso was collected in ten fractions and the concentrations of caffeine, trigonelline, chlorogenic acids and chlorogenic acid lactones as well as several organic acids were analysed. Using the resulting extraction kinetics, the influence of the process parameters on the extracted non-volatiles was analysed for ristretto, espresso and double espresso quantities. For each coffee type guiding principles to influence espresso bitterness and acidity are presented.

Espresso bitterness and acidity: Influence of process parameters temperature, flow and coffee grind on non-volatile components

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