EFFECT OF FERMENTATION METHOD, ROASTING AND CONCHING CONDITIONS ON THE AROMA VOLATILES OF DARK CHOCOLATE

ABSTRACT The combined effect of two cocoa fermentation methods – heap and tray – and different roasting and conching conditions on aroma compounds of dark chocolate were investigated. Dynamic headspace sampling/gas chromatography-mass spectrometry (GC-MS) was used to isolate and identify aroma volatiles. Odor-active volatiles were detected and identified by gas chromatography-olfactometry/GC-MS. Fermentation method, roasting and conching conditions influenced mostly the levels of aroma volatiles identified. Principal component analysis based on a reduced data set of 16 important odorants resulted in a total variance explained by two principal components of 81% accounting for fermentation method, roasting and conching conditions. The levels of most important odorants were generally higher at high roasting temperature (150C) but decreased significantly (P < 0.05) with increased conching duration from 6–10 h at 80C. Roasting at high temperature (120C or 150C), coupled with short-time conching (6–8 h) or no conching, makes the difference between heap- and tray-fermented samples more pronounced. PRACTICAL APPLICATIONS The method of cocoa bean fermentation as well as roasting and conching conditions are important determinants of chocolate aroma/flavor but their effects are often studied individually. Production of chocolate typically involves a combination of all three processes and not individually so it is important to investigate how they impact together on the levels and type of important chocolate aroma-determining compounds in a bid to optimize them for improved chocolate flavor. This is especially important in chocolate produced from tray cocoa fermentation, which is a relatively new and improved method of fermenting cocoa beans. Long conching durations, for instance, were found to result in the loss of not only undesirable aroma volatiles, but others which contribute desirable aroma characteristics. The choice of an improved cocoa bean fermentation method coupled with optimization of the chocolate processing methods will result in chocolate with improved flavor quality – the choice of many chocolate lovers.