Bioconversão de polifenóis e liberação de catequinas em uma bebida tipo kombucha à base de casca de amêndoa de cacau

The search for functional foods and agro-industrial waste valorization drives the use of cocoa (Theobroma cacao L.) bean husk as a novel fermentative matrix. This study evaluated the physicochemical kinetics and the evolution of bioactive compounds, focusing on enzymatic polyphenol bioconversion and catechin release, in a kombucha-like beverage. Four formulations were monitored over 12 days at 26 °C: a green tea control (F0) and cocoa husk infusions at 0.7% (F1), 1.5% (F2), and 2.3% w/v (F3). The physicochemical kinetics revealed a biphasic pH profile, with a lag phase buffering at ~3.78 between days 0 and 6. This was followed by a sharp decline, stabilizing between 3.13 and 3.44 on day 12, ensuring microbiological safety and compliance with Brazilian regulations (MAPA IN No. 41/2019). Total titratable acidity progressively increased from 0.018 to 0.224 g/100 mL, highlighting formulation F3, which exhibited acidogenic accumulation statistically equivalent to the traditional control (p > 0.05). This acidification reflects Komagataeibacter and Acetobacter strains converting ethanol and hexoses into organic acids. Concurrently, substrate consumption reduced total soluble solids by ~10% (stabilizing between 4.60 and 5.40 °Brix). This confirms the plant matrix's biocompatibility, providing optimal conditions for yeast invertase to cleave sucrose without inhibiting the microbial consortium (SCOBY). The bioactive evaluation by HPLC-DAD revealed a distinct phytochemical signature. While F0 was dominated by caffeine (143.55 mg/L), the cocoa husk treatments exhibited strong dose-dependent initial theobromine concentrations: 57.72 mg/L (F1), 121.86 mg/L (F2), and 162.81 mg/L (F3). During fermentation, the SCOBY assimilated this methylxanthine as a nitrogen source, resulting in an 81.3% degradation in F3. The residual theobromine (30.39 mg/L) beneficially confers mild vasodilation without caffeine-related adrenergic spikes. Crucially, the fermentative bioprocess promoted an expressive enzymatic bioconversion of complex polyphenols in the cocoa matrix. Driven by microbial extracellular enzymes, such as tannases, β-glucosidases, and esterases, structures like procyanidins and condensed tannins were hydrolyzed into more bioavailable monomeric forms. Consequently, free (+)-catechin levels in formulation F3 more than tripled, surging from 7.62 mg/L (day 3) to an exceptional peak of 24.21 mg/L on day 12 (+217%). This final concentration statistically surpassed the traditional tea control (18.72 mg/L), while epicatechin remained stable across all supplemented matrices (10.53 to 33.30 mg/L). The interval between the 6th and 9th day established the optimal operational window. Formulation F3 acts as an excellent biotechnological upcycling platform, synthesizing a nutritionally enriched beverage with superior catechin bioavailability. Acknowledgments: The authors thank CAPES for their financial and institutional support.