On-farm implementation of a starter culture for improved cocoa bean fermentation and its influence on the flavour of chocolates produced thereof.

Cocoa bean fermentations controlled by means of starter cultures were introduced on several farms in two different cocoa-producing regions (West Africa and Southeast Asia). Two starter culture mixtures were tested, namely one composed of Saccharomyces cerevisiae H5S5K23, Lactobacillus fermentum 222, and Acetobacter pasteurianus 386B (three heaps and one box), and another composed of L. fermentum 222 and A. pasteurianus 386B (seven heaps and one box). In all starter culture-added cocoa bean fermentation processes, the inoculated starter culture species were able to outgrow the natural contamination of the cocoa pulp-bean mass and they prevailed during cocoa bean fermentation. The application of both added starter cultures resulted in fermented dry cocoa beans that gave concomitant milk and dark chocolates with a reliable flavour, independent of cocoa-producing region or fermentation method. The addition of the lactic acid bacterium (LAB)/acetic acid bacterium (AAB) starter culture to the fermenting cocoa pulp-bean mass accelerated the cocoa bean fermentation process regarding citric acid conversion and lactic acid production through carbohydrate fermentation. For the production of a standard bulk chocolate, the addition of a yeast/LAB/AAB starter culture was necessary. This enabled an enhanced and consistent ethanol production by yeasts for a successful starter culture-added cocoa bean fermentation process. This study showed possibilities for the use of starter cultures in cocoa bean fermentation processing to achieve a reliably improved fermentation of cocoa pulp-bean mass that can consistently produce high-quality fermented dry cocoa beans and flavourful chocolates produced thereof.

Interesting starter culture strains for controlled cocoa bean fermentation revealed by simulated cocoa pulp fermentations of cocoa-specific lactic acid bacteria.

Among various lactic acid bacterial strains tested, cocoa-specific strains of Lactobacillus fermentum were best adapted to the cocoa pulp ecosystem. They fermented glucose to lactic acid and acetic acid, reduced fructose to mannitol, and converted citric acid into lactic acid and 2,3-butanediol.

Dynamics and species diversity of communities of lactic acid bacteria and acetic acid bacteria during spontaneous cocoa bean fermentation in vessels.

To speed up research on the usefulness and selection of bacterial starter cultures for cocoa bean fermentation, a benchmark cocoa bean fermentation process under natural fermentation conditions was developed successfully. Therefore, spontaneous fermentations of cocoa pulp-bean mass in vessels on a 20 kg scale were tried out in triplicate. The community dynamics and kinetics of these fermentations were studied through a multiphasic approach. Microbiological analysis revealed a limited bacterial species diversity and targeted community dynamics of both lactic acid bacteria (LAB) and acetic acid bacteria (AAB) during fermentation, as was the case during cocoa bean fermentations processes carried out in the field. LAB isolates belonged to two main (GTG)(5)-PCR clusters, namely Lactobacillus plantarum and Lactobacillus fermentum, with Fructobacillus pseudofilculneus occurring occasionally; one main (GTG)(5)-PCR cluster, composed of Acetobacter pasteurianus, was found among the AAB isolates, besides minor clusters of Acetobacter ghanensis and Acetobacter senegalensis. 16S rRNA-PCR-DGGE revealed that L. plantarum and L. fermentum dominated the fermentations from day two until the end and Acetobacter was the only AAB species present at the end of the fermentations. Also, species of Tatumella and Pantoea were detected culture-independently at the beginning of the fermentations. Further, it was shown through metabolite target analyses that similar substrate consumption and metabolite production kinetics occurred in the vessels compared to spontaneous cocoa bean fermentation processes. Current drawbacks of the vessel fermentations encompassed an insufficient mixing of the cocoa pulp-bean mass and retarded yeast growth.