Bean Fermentation

In the wet method, as practiced in Colombia, freshly picked ripe coffee cherries are fed into a tank for initial washing. Stones and other foreign material are removed. The cherries are then transferred to depulping machines which remove the outer skin and most of the pulp. However, some pulp mucilage clings to the parchment shells that encase the coffee beans. Fermentation tanks, usually containing water, remove the last portions of the pulp. Fermentation may last from twelve hours to several days. Because prolonged fermentation may cause development of undesirable flavors and odors in the beans, some operators use enzymes to accelerate the process. 

Chou, S.-T., Chung, Y.-C., Peng, H.-Y, Hsu, C.-K. (2013). Improving antioxidant status in aged mice by 50% ethanol extract from red bean fermented by Bacillus subtilis. Journal of the Science of Food and Agriculture, 93, 2562-2567. http //dx.doi.org/10.1002/jsfa.6077. 

Chou, S. T., Chang, C. T., Chao, W. W., Chung, Y. C. (2002). Evaluation of antioxidahve and mutagenic properties of 50% ethanolic extract from red beans fermented by Aspergillus oryzae. Journal of Food Protection, 65,1463-1469. 

Specifically on soya bean fermentations, reviews on Thua Nao (Chukeatirote, Dajanta, Apichartsrangkoon, 2010), the use of okara (soya milk residue) (O Toole, 1999) and the functionality of soya oligosaccharides (Choct, Dersjant-Li, McLeish, Peisker, 2010) are reconunended. 

Snauwaert I, Papalexandratou Z, De Vuyst L, Vandamme P. Characterization of strains of Weis-sellafabalis sp. nov. and Fructobacillus tropaeoli from spontaneous cocoa bean fermentations. Int J Syst Evol Microbiol. 2013 63(Pt 5) 1709-16. doi 10.1099/ijs.0.040311-0. 

The predominant bacteria were A. pasteurianus, and a novel species was found and named A. ghanensis (Cleenwerck et al. 2007), A. senegalensis (Camu et al. 2007 Ndoye et al. 2007), and A. fabarum (Cleenwerck et al. 2008). Acetic acid can penetrate the cocoa beans, kill the embryo, and decompose their internal structure to form flavor and color development. Thus, acetic acid bacteria have an important function during cocoa bean fermentation that contributes to the formation of cocoa flavor precursors and the control of the cocoa bean fermentation process. 

Fig. 3.2 Microbial succession (a) and metabolic activities (b) of the key factors in the cocoa bean fermentation ecosystem. Dashed lines (b) represent the substrates present in the cocoa pulp-bean mass full lines represent metabolites produced by the microorganisms present...

Microbial Ecosystem of the Cocoa Bean Fermentation Process... 

Although the cocoa bean fermentation process is a spontaneous process, it is characterised by a fairly strict microbial ecosystem (De Vuyst et al. 2010 Schwan and Wheals 2004), which dominates this fermentation process at different stages (Fig. 3.2). In general, a specific succession of yeasts, LAB, and AAB results in well-fermented, high-quality cocoa beans, albeit other bacteria might also be involved (De Vuyst et al. 2010 Papalexandratou et al. 2013 Schwan and Wheals 2004). 

During the later stage of the cocoa bean fermentation process (36-112 h Fig. 3.2), conditions become favourable for the growth of AAB, namely, a temperature increase above 37 °C, aeration caused by further breakdown of the cocoa pulp, and the availability of substrates such as ethanol (produced by the yeasts) and lactic acid, acetic acid, and mannitol (produced by the LAB) (Camu et al. 2007, 2008). The main activity of AAB is the (incomplete) oxidation of ethanol into acetic acid, an enzymatic two-step reaction carried out in the periplasm by membrane-bound pyrroloquinoUne quinone (PQQ)-dependent dehydrogenases, enabling energy... 

The community diversity of AAB associated with the cocoa bean fermentation process is restricted, encompassing species of the genera Acetobacter, Gluconobacter, and Gluconacetobacter (Ardhana and Fleet 2003 Camu... 

Garcia-Armisen T, Papalexandratou Z, Hendryckx H, Camu N, Vrancken G, De Vuyst L, Cornells P (2010) Diversity of the total bacterial community associated with Ghanaian and Brazilian cocoa bean fermentation samples as revealed by a 16S rRNA gene clone library. Appl Microbiol Biotechnol 87 2281-2292... 

Hermann S (1928) Uber die sogenannte Kombucha. . I Biochem Z 192 176-187 Ho VTT, Zhao J, Fleet G (2013) Yeasts are essential for cocoa bean fermentation. Int J Food Microbiol 174 72-87... 

Moens F, Lefeber T, De Vuyst L (2014) Oxidation of metabolites highlights the microbial interactions and role of Acetobacter pasteurianus during cocoa bean fermentation. Appl Environ Microbiol 80 1848-1857... 

Papalexandratou Z, De Vuyst L (2011) Assessment of the yeast species composition of cocoa bean fermentations in differem cocoa-producing legimis using denaturing gradient gel electrophoresis. FEMS Yeast Res 11 564—574... 

Papalexandratou Z, Camu N, Falony G, De Vuyst L (201 la) Cmnparison of the bacterial species diversity of spontaneous cocoa bean fermentations carried out at selected farms in Ivory Coast and Brazil. Food Microbiol 28 964—973... 

Papalexandratou Z, Lefeber T, Bahrim B, Lee OS, Daniel H-M, De Vuyst L (2013) Hanseniaspora opuntiae, Saccharomyces cerevisiae, Lactobacillus fermenlum, and Acetobacter pasieurianus predominate during well-performed Malaysian cocoa bean box fermentations, imderlining the importance of these microbial species for a successful cocoa bean fermentation process. Food Microbiol 35 73-85... 

Cocoa bean fermentation is a mixed-culture process, consisting initially of fermentations by yeast and lactic acid bacteria followed by oxidation of the fermentation products ethanol and lactic acid into acetic acid and acetoin by several Acetohacter strains, of which /I. pasteurianus is the prominent one (Moens et al. 2014). A C-based carbon flux analysis of Acetohacter during cocoa pulp fermentation-simulating conditions revealed a functionally separated metabolism during co-consumption of ethanol and lactate. Acetate was almost exclusively derived from ethanol, whereas lactate served for formation of acetoin and biomass building blocks. This switch was attributed to the lack of phosphoenolpyruvate carboxykinase and malic enzyme activities, which prevents conversion of oxalo-acetate and malate formed by acetate metabolism in the TCA cycle to PEP and pyruvate and subsequently to acetoin (Adler et al. 2014). Lactate, on the other hand, can be converted to pyruvate, which is then used for acetoin formation or, after conversion to PEP by pymvate phosphate dikinase, for gluconeogenesis. The inability of conversion of TCA cycle intermediates to PEP resembles the situation in G. oxydans, where in addition no enzyme for conversion of pyruvate to PEP is present. 

The Functional Role of Lactic Acid Bacteria in Cocoa Bean Fermentation... 

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