Joy Chinenye Mba, Leda Atílio Pita, Helen Obioma Agu, Chioke Amaefuna Okolo, Carmen Sílvia Fávaro-Trindade
Cocoa bean shells (CBSs), a by-product of cocoa processing, are an underutilized source of bioactive polyphenols with strong potential for functional food applications. Although several studies and reviews have investigated polyphenol extraction techniques, gaps remain in consolidating findings, optimizing extraction conditions, and understanding the synergistic effects of combined green extraction methods under comparable conditions. This systematic review critically evaluates environmentally sustainable approaches for maximizing polyphenol recovery from CBS for food applications. Literature searches were conducted in Web of Science, Scopus, and PubMed, and studies were selected according to the PICOS (population, intervention, comparison, outcomes, and study design) framework and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Thirty-six articles published between 2010 and 2025 across 15 countries were included. The findings showed that green extraction technologies generally demonstrated higher polyphenol recovery, enhanced the stability and antioxidant activity of the recovered polyphenols, reduced extraction time, and lowered solvent consumption under optimized extraction conditions. However, combining green extraction techniques did not significantly increase total phenolic content compared with single-technique approaches, suggesting that process intensification does not always improve extraction efficiency. Considerable variability in reported total phenolic content was observed in the reviewed papers due to differences in extraction conditions, solvent systems, and reporting units. Overall, CBS demonstrated strong potential as a sustainable source of polyphenols, while green extraction technologies provide a promising strategy for valorizing CBS into high-value ingredients for functional foods, nutraceuticals, and natural preservatives.