A preliminary model to establish a digital twin for coffee roasting

The coffee industry has an economic impact of over 100 billion dollars per year, making it one of the most valuable markets in the world. Coffee roasting is a crucial step that occurs before the extraction process and is essential to the final quality of the coffee. The roasting of green coffee beans is a complex process involving various chemical reactions that play a crucial role in determining the taste, colour and aroma of the coffee. It consists of three steps: drying, roasting and cooling. All of them are characterised by heat and mass transfer. Heat transfer during the roasting process significantly influences the flavour profile of a coffee cup. The main chemical reaction that occurs during roasting is known as the "Maillard reaction", which is fundamental for the sensory profile of roasted coffee. In this study, we first introduce a mathematical model for coffee roasting based on the chemical dynamics of key compounds. The kinetic model is used to determine the variation in concentration of the main chemical substances that characterise the taste and aroma of coffee. The calibration of the model is obtained through an optimisation procedure, capable of estimating the kinetic rate constants. Real data from chemical analyses carried out on coffee samples at the end of the roasting process were used to support the calibration phase, while the initial chemical composition of green coffee was obtained from the ranges available in the literature.