Effect of Fermentation on Bacteria Isolates and Phytochemical Properties of Cocoa (Theobroma cacao) Beans

Abstract

This investigation was carried out to assess the bacteria associated with cocoa beans at different stages of fermentation and determine the changes in the phytochemical constituents of the fermenting beans. The pour plate technique was used for bacterial isolation while phytochemicals were assessed based on standard qualitative chemical reactions. The total bacterial count on the cocoa beans reduced during fermentation from the initial 86.2±0.02 x 105 CFU/g (day 0) to 1.00±0.00 x 105 CFU/g on day 5. However, there was an increase in the lactic acid bacteria count from 48.7±0.03 x 105 CFU/g (day 0) to 111.7±0.03 x 105 CFU/g on day 3, then reduced to 51.4±0.01 x 105 CFU/g on day 5. Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Lactobacillus fermentum, Lactobacillus plantarum and Lactobacillus acidophilus were isolated from the cocoa beans at different stages of the fermentation. There was a gradual increase in the temperature of the fermenting cocoa mass from the initial 25.6°C recorded at the beginning of the fermentation to 42.8°C recorded on day 5. Also, the pH of the fermenting cocoa beans reduced significantly from 6.1 at the commencement of the fermentation to 3.2 on day 5. In the total titratable acidity assay, the acidity of the cocoa beans increased from 3.12% at the beginning of the fermentation to 7.12% on day 5. Further, in the phytochemical screening, only alkaloids, phenols, steroids and flavonoids were detected in the beans throughout fermentation period whereas tannin and saponin were not found in the beans at any stage of fermentation. The preset phytochemicals got reduced in intensity as fermentation advanced. From these results, it can therefore be concluded that fermentation helps to improve the taste quality and phytochemical properties of Nigerian cocoa beans.

Reduction in the Cocoa Spontaneous and Starter Culture Fermentation Time Based on the Antioxidant Profile Characterization

“…In addition, the pH tended to decrease at the end of the fermentation process (in SF, it reached 4.48, and in SC, it reached 4.34; see Table S2). The results are similar to those obtained by De Vuyst and Weckx [47], where the decrease was in the range of 4.5-5 (well-fermented beans), and in the study of Calvo et al [39], who recorded pH values from 4.5 to 4.8, which can be explained by the activity of the fermenting bacteria (lactic and acetobacter) that promote the incorporation of organic acids [36,[48][49][50]. Following the behavior of internal pH, Afoakwa et al [51] and Dewandari et al [49] consider that a pH close to 5.0 is related to cocoa with better aromatic and sensory profiles; in our study, a pH of 4.9 and 5.5 (Figure 3) was observed in SF between 48 and 96 h, while in SC, it was between 48 and 72 h, indicating a difference in the final cocoa quality [39]; the data are presented in the Supplementary Material (Table S2).…”

“…In the first hours (0 to 72 h), the temperature of the fermenting cocoa pulp-bean mass was below 40 • C, with a relatively constant pH, similar to that reported by Melo et al [29]. The temperature also increased from 25 • C to about 48 • C in both types of fermentation (Table S1), similar to the range reported by Racine et al (2019), which was between 25 and 55 • C, associated with the release of heat trapped by CO 2 in the fermentation box [11,36] due to ethanol metabolism by BAA and the conversion of the available substrate (sugar) [4,29], leading to phenolic degradation (Tables 1 and 2), as proposed by Racine et al [37]. Likewise, temperatures remained within the expected range and with very similar values, demonstrating that the use of S. cerevisiae does not affect the temperature of the fermentative cocoa pulp-bean mass with and without starter culture [38].…”