Great intraspecies diversity of Pichia kudriavzevii in cocoa fermentation highlights the importance of yeast strain selection for flavor modulation of cocoa beans

The use of selected yeasts has recently been proposed as an interesting strategy to improve cocoa bean fermentation and chocolate quality. In this study, a total of 39 cocoa-derived yeast isolates were screened for their capacity to produce volatile aroma compounds in a cocoa pulp simulation medium. The seven highest aroma-producing yeasts were identified by ITS-rRNA gene sequencing as belonging to Pichia kudriavzevii, in spite of exhibiting different metabolic profiles. Repetitive extragenic palindromic (Rep)-PCR genomic fingerprinting approach confirmed this high intraspecies diversity of P. kudriavzevii in cocoa fermentation. Two strains with superior aroma production, namely P. kudriavzevii LPB06 and P. kudriavzevii LPB07, were used in cocoa beans fermentation at laboratory scale. They were able to establish an accelerated fermentation process with efficient yeast growth, sugars consumption and ethanol formation compared to the spontaneous process. The resulting cocoa beans were analyzed by diverse chemical analysis methods, including gas chromatography coupled to mass spectrophotometry (GC-MS), fermentation index and metal and colorimetric analysis. All together, the results indicated that inoculated fermentations generated cocoa beans with better color development and richer aroma composition, suggesting that cocoa-associated yeast diversity at strain level can be exploited for flavor modulation of cocoa beans. (C) 2017 Elsevier Ltd. All rights reserved.