Distribution and transition of aroma-active compounds in dark chocolate model systems under conching conditions.

Understanding mechanisms inside the conche is inevitable for targeted conching. Therefore, distribution and transition of aroma-active volatiles (acetic acid, benzaldehyde, (R,S)-(±)-linalool, 2,3,5,6-tetramethylpyrazine, 2-phenylethanol, and 2-phenylethyl acetate) between the different components of dark chocolate (cocoa butter, cocoa particles, sugar particles) were studied. Different model systems were designed and aroma-analytically analyzed by stable isotope dilution analysis. Diffusion mechanisms of selected aroma-active compounds within the chocolate mass depended on their physico-chemical properties and the mass composition, such as fat content and crystallization state of the sugar particles. The compound accumulation in the fat phase increased with decreasing compound polarity and increasing fat content. In the presence of cocoa particles, a 1.5-fold fat content resulted in a 1.6-fold higher proportional acetic acid concentration in the fat phase. Further, total acetic acid concentrations raised in all model systems containing crystalline sugar or cocoa particles (by 13.8-56.9 %), indicating the formation of free acetic acid.