1. Prof. Emmanuel Ohene Afoakwa Department of Nutrition and Food Science
Effects of Pod Storage and Fermentation Duration on Total polyphenol, O-diphenol and Anthocyanin concentrations in Cocoa (Theobroma cacao) Beans
Prof. Emmanuel Ohene Afoakwa
Department of Nutrition and Food Science
University of Ghana
Legon-Accra
Ghana

2. Introduction
Generally, post-harvest handling is known to influence the quality characteristics of agricultural produce
In cocoa production, post-harvest activities include pod storage, pulp fermentation and bean drying
These activities affect the biochemical characteristics of the beans

3. Introduction Ripe Pods Harvesting Pod breaking after storage Open Pod
Fermentation
Sun-drying

4. Introduction
Studies have shown that fermentation reduces the concentration of polyphenols in cocoa by 70%
Mainly through the activity of polyphenol oxidase (PPO)
Polyphenols are naturally occurring compounds in cocoa beans. They are stored in the pigment cells of the cotyledons

5. Introduction
They are responsible for the astringency of cocoa beans and contribute to bitter and green flavours
Three groups of polyphenols can be distinguished
catechins or flavan-3-ols (ca. 37%),
anthocyanins (ca. 4%)
proanthocyanidins (ca. 58%)

6. Introduction
Unfermented Forastero cocoa beans are reported to contain 120–180g/kg of polyphenolic compounds
Studies have reported total polyphenols content of
45 to 52 mg/g in cocoa liquor
34 to 60 mg/g in cocoa beans, and
20 to 62 mg/g in cocoa powder
These reflect losses during post-harvest treatments

7. Introduction
During fermentation, polyphenols, originally compacted into vacuoles of specific cells, diffuse through the cotyledon of cocoa beans
They are then subjected to biochemical modification through polymerization and complexing with proteins, thus decreasing solubility and astringency

8. Introduction
Pod storage is expected to influence the activity of polyphenol oxidase during fermentation and drying
This will in turn cause modifications in the polyphenol concentrations in cocoa beans

9. Introduction
This work was therefore aimed at investigating the effect of pod storage as a means of pulp preconditioning on total polyphenols, o-diphenols and anthocyanin concentrations during fermentation and drying of cocoa beans

10. Materials and Methods
Materials: Ripe cocoa pods (mixed hybrids) were obtained from the Cocoa Research Institute of Ghana (CRIG), Tafo-Akim, Eastern Region
Pre-conditioning: Pods were stored at ambient temperature (28-30oC) and RH of % for 0, 3, 7 and 10 days

11. Materials and Methods
Fermentation: Pulp from pre-conditioned pods were fermented using the traditional basket fermentation method for 0, 3 and 6 days
Drying for analyses: Samples were taken at 0, 3, and 6 days and oven-dried at a temperature of 45–50oC until moisture content was between 7–8% (up to 48h)
Dried beans were packed in airtight black plastic bags and stored at ambient temperature (25–28oC) in a dark room free from strong odours and used for analyses

12. Materials and Methods Drying of fermented cocoa beans
The fermented cocoa beans were dried in the open on raised platforms using the traditional sun-drying process

13. Materials and Methods Experimental Design Changes during fermentation
Total polyphenol, o-diphenol and anthocyanin concentrations were measured during fermentation and drying
Changes during fermentation
4 x 3 full factorial design was used
Pod storage = 0, 3, 7, 10 days
Fermentation time = 0, 3, 6 days

14. Materials and Methods Changes during drying
4 x 3 full factorial design
Pod storage = 0, 3, 7 and 10 days
drying time = 0, 3 and 7 days

15. Materials and Methods Analytical Methods
Extraction of phenolic compounds: Method described by Othman et al., (2007)
Total polyphenol content: Measured using the Folin-Ciocalteu’s assay as described by Othman et al. [2007] with slight modifications.

16. Materials and Methods Analytical Methods
O-diphenols: was determined with Arrow’s reagent (10 g NaNO2 and 10 g Na2MoO4 in 100 ml distilled water). A working standard cathecol solution of 20, 40, 60, 80, and 100 ppm was prepared and the absorbance read at 520 nm and a standard curve drawn to determine o-diphenols levels

17. Materials and Methods Analytical Methods
Anthocyanins: method described by Misnawi et al (2002).
Statistical Analyses
Statgraphics® software version 3.0 (STSC, Inc., Rockville, MD, USA) for analysis of variance (ANOVA). Significance was accepted at 5% level (p<0.05)

18. Materials and Methods Statistical Analyses
The combined effects of pulp preconditioning and fermentation time and drying time on the studied parameters were assessed using the response surface methodology

19. Results & Discussion

20. Changes in total polyphenols
Total polyphenols decreased with increasing fermentation for all pod storage treatments

21. Fermentation: Changes in total polyphenols
Concentration decreased from mg/g at the start of fermentation to mg/g at the end of the fermentation process for the unstored pods.

22. Fermentation: Changes in o-diphenols
O-diphenols content decreased significantly (p<0.05) with
increasing fermentation time for all pod storage periods
Increasing pod storage time at all fermentation periods

23. Fermentation: Changes in Anthocyanins
Anthocyanin content decreased significantly (p<0.05) with
increasing fermentation time for all pod storage periods
Increasing pod storage period for all fermentation times

24. Drying: Changes in total polyphenols
Generally, polyphenol content of fermented beans decreased during drying

25. Drying: Changes in o-diphenol levels
O-diphenols content in the beans decreased significantly (p<0.05) with increasing drying time for all pod storage periods

26. Drying: Changes in anthocyanin levels
Levels decreased significantly (p<0.05) with increasing drying time for all pod storage periods

27. Conclusions

28. Conclusions
Pod storage, fermentation and drying caused variable reductions in total polyphenols, o-diphenols and anthocyanins content of the cocoa beans
The rates of decreases were more pronounced during fermentation than pod storage with only marginal reductions observed during drying

29. Conclusions
The reductions in total polyphenols and o-diphenols might be due to polyphenol oxidase activities during pod storage and fermentation
The results suggest that the post-harvest treatments of pod storage, fermentation and drying result in variable reductions in polyphenolic content and anthocyanin content of cocoa beans

30. Thank You