Bioprospecting of indigenous yeasts involved in cocoa fermentation using sensory and chemical strategies for selecting a starter inoculum.

Cocoa fermentation is the key and most relevant process in the synthesis of aroma and flavor precursor molecules in dry beans or raw material for producing chocolate. Because this process occurs in an uncontrolled manner, the chemical and sensory quality of beans can vary and be negatively affected. One of the strategies for the standardization and improvement of the sensory quality of chocolate is the introduction of microbial starter cultures. Among these, yeasts involved in fermentation have been studied because of their pectinolytic and metabolic potential in the production of volatile compounds. This study was aimed at isolating and characterizing, both sensory and chemically, yeasts involved in cocoa fermentation that could be used as starter cultures from two agro-ecological regions for the cultivation of cocoa in Colombia. The microbiological analyses identified 22 species represented mostly by Saccharomyces cerevisiae, Wickerhamomyces anomalus and Pichia sp. The preliminary sensory analysis of eight of these species showed that Hanseniaspora thailandica and Pichia kluyveri presented sensory profiles characterized by high intensity levels of fruity notes, which could be ascribed to the production of ethyl acetate, isoamyl acetate, and 2-phenylethyl acetate.

Assessment of the fungal community associated with cocoa bean fermentation from two regions in Colombia.

The quality of the cocoa seeds depends on various factors. Fermentation is among them because during this process flavor precursors are synthesized through the action of fungi and bacteria, whose diversity can change depending on the geographic location and the agricultural practices. This research aimed to characterize and compare the fungal community involved in spontaneous fermentations carried out under the same post-harvest agricultural practices in two farms located at completely different agro­ecological zones by application of a high-throughput amplicon sequencing method. The results showed that the diversity of biological variants is different between regions. In the Magdalena Medio region, the fermentations were dominated by Hanseniaspora opuntiae, and Saccharomyces sp., while in Urabá region all the fermentation was characterized by an almost constant diversity and high abundance of H. opuntiae. In each site, unique biological variants of these two genera were detected. Additionally, differences were observed in the physicochemical parameters such as the pH and temperature of the fermentation mass, and the duration of the process. The analyses of these results allow concluding that the environmental conditions and indigenous microbiota of each cocoa-cultivation zone explained the differences found in this study.