Kinetic Analysis of Strains of Lactic Acid Bacteria and Acetic Acid Bacteria in Cocoa Pulp Simulation Media toward Development of a Starter Culture for Cocoa Bean Fermentation

Abstract

The composition of cocoa pulp simulation media (PSM) was optimized with species-specific strains of lactic acid bacteria (PSM-LAB) and acetic acid bacteria (PSM-AAB). Also, laboratory fermentations were carried out in PSM to investigate growth and metabolite production of strains of Lactobacillus plantarum and Lactobacillus fermentum and of Acetobacter pasteurianus isolated from Ghanaian cocoa bean heap fermentations, in view of the development of a defined starter culture. In a first step, a selection of strains was made out of a pool of strains of these LAB and AAB species, obtained from previous studies, based on their fermentation kinetics in PSM. Also, various concentrations of citric acid in the presence of glucose and/or fructose (PSM-LAB) and of lactic acid in the presence of ethanol (PSM-AAB) were tested. These data could explain the competitiveness of particular cocoa-specific strains, namely, L. plantarum 80 (homolactic and acid tolerant), L. fermentum 222 (heterolactic, citric acid fermenting, mannitol producing, and less acid tolerant), and A. pasteurianus 386B (ethanol and lactic acid oxidizing, acetic acid overoxidizing, acid tolerant, and moderately heat tolerant), during the natural cocoa bean fermentation process. For instance, it turned out that the capacity to use citric acid, which was exhibited by L. fermentum 222, is of the utmost importance. Also, the formation of mannitol was dependent not only on the LAB strain but also on environmental conditions. A mixture of L. plantarum 80, L. fermentum 222, and A. pasteurianus 386B can now be considered a mixed-strain starter culture for better controlled and more reliable cocoa bean fermentation processes.

The impact of yeast starter cultures on the microbial communities and volatile compounds in cocoa fermentation and the resulting sensory attributes of chocolate

“…was later found in the inoculated fermentation than in the spontaneous fermentation. LAB convert carbohydrates and citric acid into lactic acid from the second day of cocoa fermentation (Camu et al 2007;Lefeber et al 2010Lefeber et al , 2012. However, recent research suggests that LAB may not be necessary for successful cocoa fermentation due beans fermented in the presence or absence of lactic acid bacteria are fully fermented, have similar shell weights and produce acceptable chocolates with no differences in sensory rankings (Ho et al 2015).…”

Interesting Starter Culture Strains for Controlled Cocoa Bean Fermentation Revealed by Simulated Cocoa Pulp Fermentations of Cocoa-Specific Lactic Acid Bacteria

“…These substrates are used for the oxidation of NADH ϩ H ϩ to bypass the energy-limiting ethanol pathway and, so, to maximize their growth rate on glucose, thereby producing mannitol and lactic acid plus acetic acid, respectively (16). They are to be consumed under low-pH and anaerobic conditions in the beginning of the cocoa bean fermentation.…”

“…During fermentation, bacterial growth (CFU per ml) was quantified through plating of 10-fold serial dilutions of the samples in saline (0.85% [wt/vol] NaCl solution) on CPSM agar (CPSM containing 1.5% [wt/vol] agar, pH 5.5) that was incubated at the appropriate fermentation temperature for 24 h. Metabolite concentrations were determined through high-performance anion-exchange chromatography using a standard addition protocol (glucose, fructose, mannitol, and citric acid) (15,23) and high-performance liquid chromatography using external standards (lactic acid, acetic acid, and ethanol) (16). Cell count and metabolite (with external standards) measurements were performed on three independent samples.…”

“…Monoculture fermentations were performed in 1.5 liters of a cocoa pulp simulation medium (CPSM) for LAB (16) in Biostat B-DCU fermentors (Sartorius AG/B. Braun Biotech International, Melsungen, Germany) anaerobically for 48 h. Inoculum build-up, fermentor setup, online control of temperature (Table 2), pH profile, agitation, and sampling were as described previously (13,16).…”

Cocoa Fermentation from Agnéby-Tiassa: Biochemical Study of Microflora

“…This observation was not the same for Gluconobacter genera. The same observation has been regularly recorded in cocoa beans fermentation According to these authors, from the 10 existing genera of AAB, only the Acetobacter and Gluconobacter reported to colonize cocoa beans fermenting mass the Acetobacter genus dominant [51,52 genus is known to oxidize ethanol to acetic acid and species from the genus Acetobacter have the additional capacity to oxidize acetic acid to carbon dioxide and water known that production of acetic acid during cocoa fermentation is desirable for development of precursors chocolate aroma [54,55]. At date, the possible impact of the balance between both types of AAB, on the quality of bean is not established.…”