Objectives: Cocoa beans (Theobroma cacao) are a rich source of flavanols. Cocoa undergoes a series of processing steps, including fermentation and roasting, that degrade native flavanols. While it is widely accepted that preservation of native flavanols in cocoa is critical for potential bioactivity, reactions occurring during processing may generate compounds with novel activities- potentially preserving or enhancing bioactivity. Our objective was to evaluate the impact of fermentation and roasting on concentrations of cocoa flavanols and subsequent bioactivity. Methods: Unfermented cocoa beans were processed into cocoa powder through a controlled laboratory fermentation model system and roasting operation. Various fermentation and roasting parameters were selected to develop powders representing the extremes of farm-based fermentation and roasting temperatures. Uniform further processing (winnowing, grinding, pressing) produced cocoa powders for each treatment and extracts were made for analysis. Total polyphenols were quantified by the Folin-Ciocalteu assay. Flavanol polymerization was analyzed through HILIC UPLC-MS/MS and thiolysis. α-glucosidase inhibitory activity was assessed in vitro. Results: Total polyphenols and individual flavanols (monomer-decamer) were reduced 27-90% in hot fermented/hot roasted cocoa and reduced 11-54% in cool fermented/cool roasted cocoa, when compared to unprocessed powder. All treatments dose-dependently inhibited α-glucosidase compared to the acarbose control (IC50 = 133.22 µg/mL), with cool fermentation/cool roasted powder exhibiting the greatest potency (IC50 = 68.09 µg/mL). A significant negative correlation between flavanol polymerization and IC50 was observed (−0.88), indicating polymerization as a marker of enhanced α-glucosidase activity. Strong correlations were not observed for total polyphenols and flavanols. Conclusions: Cocoa powder is potentially a powerful inhibitor of α-glucosidase activity in vivo. Significant flavanol reductions by fermentation and roasting do not necessarily dictate reductions in α-glucosidase inhibition, but rather that processing can enhance cocoa bioactivity.

Mean degree of flavanol polymerization is a superior predictor of α-glucosidase inhibitory activity compared to flavanol or polyphenol concentrations in cocoas produced by controlled fermentation and roasting

ACS Fall 2020 Virtual Meeting

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