Thin-Layer, Kinetically Controlled Roasting with Aroma Tracking: Modeling Pyrazine/TMP Formation and Volatilisation in Cocoa

Cocoa roasting triggers complex thermochemical reactions that impact the final quality of chocolate products. In this study, a thin-layer experimental setup coupled with solid-phase microextraction (SPME) and GC-MS was employed to investigate the formation and degradation dynamics of total pyrazines and tetramethylpyrazine (TMP) under nonisothermal conditions at different heating rates (280, 340, and 520 °C/min). Kinetic model was developed from a simplified three-step reaction network and fitted to experimental data. Results indicate that higher heating rates minimize pyrazine loss via volatilisation, thereby preserving key aromatic compounds. TMP formation exhibited activation energies of 66–87 kJ/mol, consistent with Maillard intermediates, whereas degradation pathways displayed low energy barriers indicative of volatilisation-dominated losses. The thin-layer system minimized internal temperature gradients, enhancing kinetic resolution. These findings provide fundamental insights into optimizing cocoa roasting conditions to maximize aroma retention and product quality.