Cocoa Bean Shells as a Source of Bioactive Compounds: Extraction, Stabilisation and Application Potential

Cocoa bean shell, the testa separated from the seed of Theobroma cacao L. during post-harvest and chocolate manufacture, is increasingly investigated as a feedstock for polyphenols, methylxanthines, dietary fibre and functional polysaccharides. Yet the apparent abundance of these constituents does not by itself establish their recoverability, stability, safety or effectiveness in a finished product. This critical narrative review integrates evidence on shell composition, the effects of upstream processing, extraction technology, compound identification, stabilisation, food and non-food applications, and regulatory and environmental constraints. Peer-reviewed experimental studies and relevant reviews available to 27 August 2026 were assessed thematically, with explicit attention to extraction denominators, process controls, analytical selectivity, scalability and the distinction between chemical activity and physiological benefit. The evidence supports recovery of theobromine, flavanols and fibre fractions using aqueous or ethanol-based extraction, pressurised liquids, assisted processes and hydrothermal or enzymatic treatments. Nevertheless, greater measured phenolic concentration may reflect matrix disruption or assay reactivity rather than higher recovery of intact target molecules. Encapsulation, liposomal systems and protein carriers show encouraging formulation-specific improvements, but storage stability, digestive release and real-product performance are seldom measured together. Bakery, beverage and chocolate studies establish technological feasibility at selected incorporation levels, whereas human efficacy, population-level exposure and industrial-scale safety remain inadequately characterised. Contaminant testing, methylxanthine exposure, solvent management and the resource demands of extraction and drying materially affect the value proposition. A process-linked evidence framework is proposed in which defined shell batches, selective recovery, molecular verification, stabilisation, delivered dose and fitness-for-purpose safety constitute sequential decision gates. The most defensible near-term applications are controlled ingredient substitutions and well-characterised extracts; claims of therapeutic benefit or universal environmental superiority require substantially stronger evidence.