Volatile compounds of traditional sorghum beer (tchapalo) produced in Côte d'Ivoire: comparison between wild yeasts and pure culture of Saccharomyces cerevisiae.

In recent years, there had been growing demand for distinctive high quality beer. Fermentation management has a fundamental role in beer quality and the levels of aroma compounds. Use of non-conventional yeast has been proposed to enhance beer flavor. In this study, the bioflavor of traditional sorghum beer from Côte d'Ivoire was investigated. The flavor profile of two beers fermented with wild yeasts and with pure culture of Saccharomyces cerevisiae respectively were studied. The main flavor components of the beer fermented by pure culture of Saccharomyces cerevisiae were different from those of the beer fermented with wild yeasts. The total level of esters and higher alcohols were (173.51 and 128.85 mg/L) respectively in the beer fermented with wild yeasts. These levels were significantly higher than those in the beer fermented with pure culture of Saccharomyces cerevisiae which were 13.08 and 78.26 mg/L for higher alcohols and esters respectively. On the other hand, the beer fermented with pure culture of Saccharomyces cerevisiae had an acid content higher than beer fermented with wild yeasts, i.e. 9.3 mg/L and 7.53 mg/L respectively.

Dynamics and species diversity of lactic acid bacteria involved in the spontaneous fermentation of various palm tree saps during palm wine tapping in Côte d'Ivoire.

To document and speed up research on the usefulness and selection of potential health-promoting bacterial starter cultures from unexplored fermented saps of various palm species in Côte d'Ivoire, benchmark tapping processes were successfully developed and implemented at field level. Therefore, spontaneously fermented saps of three palm species (Elaeis guineensis, Raphia hookeri, Borassus aethiopum) were collected throughout tapping process and lactic acid bacteria (LAB) diversity and dynamics were studied through a multiphasic approach. Overall microbiological analysis revealed a LAB species diversity throughout tapping process. LAB isolates belonged to two main (GTG)5-PCR clusters, namely Fructobacillus durionis (40.33%) and Leuconostoc mesenteroides (45.66%), with Leuconostoc pseudomesenteroides, Lactobacillus paracasei, Lactobacillus fermentum Weissella cibaria, Enterococcus casseliflavus and Lactococcus lactis occurring occasionally. LAB diversity was higher in fermented saps from E. guineensis (8 species) than those of R. hookeri (5 species) and B. aethiopum (3 species). Dynamic study revealed that F. durionis and L. mesenteroides dominated the fermentations from the beginning until the end of tapping process in all palm wine types. But the earlier stages of the process were also populated by some species like W. cibaria, L. pseudomesenteroides and L. fermentum, which population decreased or disappeared after some days. Also, species of Enterococcus and Lactococcus genera were sporadically detected uniquely in sap from E. guineensis. This study is the first to investigate extensively the LAB diversity and dynamics throughout palm trees tapping process in Côte d'Ivoire and is relevant for future selection of health promoting bacteria.