Estudio de los compuestos volátiles de Theobroma cacao L., durante el proceso tradicional de fermentación, secado y tostado

Abstract

Fermentation, drying and roasting of cocoa bean are essential steps and they have effect in the aromatic cocoa quality and its products. In this research the effect of these processes on the volatile profile of the cocoa bean Forastero was evaluated. The cocoa bean was from Cunduacán, Tabasco. The dynamics of volatile and nonvolatile compounds was observed during traditional fermentation and drying processes. The principal component analysis (PCA) was used to determinate the relations and importance of these compounds on each day of fermentation and drying. In addition, esterification of 3-methyl-1-butanol to 3-methyl-1-butanol acetate, an increase of volatile acids such as isobutyric, isovaleric and propanoico, were used as fermentation index. These changes suggested that the fermentation process could stop at day 6. The effect of fermentation time and drying temperature on profile of volatile compounds were evaluated with 2, 4, 6, and 8 fermentation days followed by a drying at 60, 70 and 80 °C. Samples of fermented and drying cocoa were compared with dried cocoa in Samoa drier and Sun. In this experiment 58 volatile compounds were found. Furthermore, 6 days of fermentation were enough to produce desirable volatile compounds from cocoa bean quality and also to avoid production of compounds with off-flavor notes. The PCA showed that the volatile profile at 70 and 80 ºC of drying temperature with 6 days of fermentation were associated to sun drying. Therefore, the optimal conditions were 6 days of fermentation followed of a drying process at 70 ºC. Finally, the effect of roasting on the volatile compounds was evaluated at 30, 45 and 60 min with 130, 145 and 160 °C. The treatments were compared with two commercially roasted cocoas. All samples had 70 volatile compounds and esters, aldehydes and pyrazines were affected when temperatures were higher than 160 °C with extended times (45 and 60 min). Consequently, the statistical and PC analysis suggested as best roasting conditions to temperatures below 145 °C with extended times, to avoid degradat ion of the desirable compounds and production of undesirable compounds such as acetamide.