Dynamics of volatile compounds and flavor precursors during spontaneous fermentation of fine flavor Trinitario cocoa beans

Fine flavor cocoa is worldwide renowned to produce origin chocolates with special aromas, e.g. fruity or floral, in addition to its chocolate aroma. This research aims to elucidate fine flavor dynamics during fermentation by analyzing the sugar, free amino acid (FAA) and volatile profile. Ecuadorian Trinitario beans (Sacha Gold) were sampled after 0, 18, 24, 48 and 66 h of spontaneous fermentation. The unfermented beans contained significant sucrose, glutamic acid and asparagine amounts while the fermented beans (66 h) contained more flavor precursors, e.g. glucose, fructose, hydrophobic and other FAA. Forty-one volatiles were identified, including 13 fruity- and 12 floral-like, derived from various metabolic pathways. Whereas the level of fatty acid-derived fruity volatiles decreased, the amount of amino acid-derived fruity and floral volatiles increased and floral terpenes remained stable. Some fine volatiles were assumed to be pulp-derived (e.g. linalool, β-myrcene, 2-heptyl acetate) or intrinsic to the bean (e.g. 2-heptanol, 2-heptanone, 2-pentanol), while others were generated during fermentation by microbial synthesis (e.g. 2-phenylethanol, isoamyl alcohol). Multivariate analysis clustered samples according to fermentation time and quality. These findings demonstrate that cocoa fermentation is essential for the formation of flavor precursors and the development or preservation of important fine aroma compounds. Trinitario (or hybrids), one of the cocoa varieties with fine flavor potential, is cultivated all over the world and hence, care should be taken during post-harvest to fully exploit this fine flavor character and deliver high-quality cocoa beans with fine sensory characteristics.