Sustainable Extraction of Bioactive Compounds from Cocoa Shells Waste and Brewer’s Spent Grain Using a Novel Two-Stage System Integrating Ohmic-Accelerated Steam Distillation (OASD) and Supercritical CO 2 Extraction (SSCO 2 )

Hao-Yu Ivory Chu, Xinyu Zhang, Yuxin Wang, Taghi Miri () and Helen Onyeaka
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Hao-Yu Ivory Chu: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Xinyu Zhang: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Yuxin Wang: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Taghi Miri: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Helen Onyeaka: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

Sustainability, 2025, vol. 17, issue 16, 1-18

Abstract: This study introduces a novel, two-stage extraction system that combines Ohmic-Accelerated Steam Distillation (OASD) with Supercritical CO 2 Extraction (SSCO 2 ) to efficiently recover bioactive compounds from plant-based wastes with varying cell wall complexities. Brewer’s spent grain (BSG) and cocoa shell were selected as representative models for soft and rigid cell wall structures, respectively. The optimized extraction process demonstrated significantly enhanced efficiency compared to traditional methods, achieving recovery rates in BSG of 89% for antioxidants, 91% for phenolic acids, and 90% for polyphenolic compounds. Notably, high yields of p-coumaric acid (95%), gallic acid (94%), ferulic acid (82%), quercetin (87%), and resveratrol (82%) were obtained with minimal cellular structural damage. For cocoa shells, despite their lignin-rich, rigid cell walls, recovery rates reached 73% for antioxidants, 79% for phenolic acids, and 74% for polyphenolic compounds, including chlorogenic acid (94%), catechin (83%), vanillin (81%), and gallic acid (94%). Overall, this hybrid technique significantly improved extraction efficiency by approximately 60% for BSG and 50% for cocoa shell relative to conventional approaches, highlighting its novelty, scalability, and potential for broad application in the sustainable valorization of diverse plant-based waste streams. This research presents a green and efficient platform suitable for valorizing agri-food by-products, supporting circular economy goals. Further studies may explore scale-up strategies and economic feasibility for industrial adoption.

Keywords: two-stage extraction system; bioactive compounds; Ohmic-Accelerated Steam Distillation (OASD); supercritical CO 2 (SSCO 2 ); Brewer’s Spent Grain (BSG) and Cocoa shell (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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