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<p>The present study investigates the impact of extraction techniques on the quality and functionality of protein products derived from okra (<i>Abelmoschus esculentus</i>), with the overarching goal of developing natural surface-active ingredients for food applications. Protein mixtures were prepared using five extraction methods, including salt extraction (OPC-SE), ethanol/phosphate (OPC-PE), and ultrasound-assisted extraction (OPC-UAE), the latter affording a protein content of72% and a yield of 2.23%. A conventional aqueous extraction at pH 6.6 (OPC-CE), performed without buffering agents, resulted in the highest protein content (79%) but a lower recovery (186%). In contrast, alkaline extraction at four pH levels (OPC-pH 8, 8.5, 9, 9.5) produced concentrates with lower protein content (44–70%) but higher yields (up to 4.0%) and limited functionality. Each protein extract was subjected to a comprehensive physicochemical characterisation (extraction yield, protein concentration, solubility, ζ-potential and dynamic-light scattering, critical aggregation concentration (CAC), size-exclusion chromatography, and electrophoresis. Technological functionality was evaluated through foaming and emulsification performance. Of the methods employed, OPC-CE and OPC-UAE stood out, displaying high protein content, high solubility (up to 73.2%), strong electrostatic stability (ζ-potential down to − 18.7 mV) and low CAC vales (~ 0.8% w/w), traits that correlated directly with superior foam (FC up to 73%, FS up to 50%) and emulsion stability (d₄,₃ ~11.2&#xa0;μm; CI ~ 20%). By contrast, extracts obtained under alkaline conditions (pH ≥ 8) suffered from protein denaturation and the co-extraction of non-protein macromolecules, leading to diminished functionality. Overall, conventional extraction (OPC-CE) and ultrasound assistance (OPC-UAE) emerged as the most suitable approaches for producing okra protein concentrates with enhanced functional performance, making them promising ingredients for food systems requiring stable foaming or emulsifying properties.</p> Graphical Abstract <p></p>

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Effect of Extraction Methods on the Structural and Functional Properties of Okra Proteins

  • 期刊论文

  • 发表日期：

    2026年5月26日

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  • Theodoros Karakasidis,
  • Christos Ritzoulis,
  • Vassilis Kontogiorgos,
  • Maria Papageorgiou,
  • Eleni P. Kalogianni

摘要

The present study investigates the impact of extraction techniques on the quality and functionality of protein products derived from okra (Abelmoschus esculentus), with the overarching goal of developing natural surface-active ingredients for food applications. Protein mixtures were prepared using five extraction methods, including salt extraction (OPC-SE), ethanol/phosphate (OPC-PE), and ultrasound-assisted extraction (OPC-UAE), the latter affording a protein content of72% and a yield of 2.23%. A conventional aqueous extraction at pH 6.6 (OPC-CE), performed without buffering agents, resulted in the highest protein content (79%) but a lower recovery (186%). In contrast, alkaline extraction at four pH levels (OPC-pH 8, 8.5, 9, 9.5) produced concentrates with lower protein content (44–70%) but higher yields (up to 4.0%) and limited functionality. Each protein extract was subjected to a comprehensive physicochemical characterisation (extraction yield, protein concentration, solubility, ζ-potential and dynamic-light scattering, critical aggregation concentration (CAC), size-exclusion chromatography, and electrophoresis. Technological functionality was evaluated through foaming and emulsification performance. Of the methods employed, OPC-CE and OPC-UAE stood out, displaying high protein content, high solubility (up to 73.2%), strong electrostatic stability (ζ-potential down to − 18.7 mV) and low CAC vales (~ 0.8% w/w), traits that correlated directly with superior foam (FC up to 73%, FS up to 50%) and emulsion stability (d₄,₃ ~11.2 μm; CI ~ 20%). By contrast, extracts obtained under alkaline conditions (pH ≥ 8) suffered from protein denaturation and the co-extraction of non-protein macromolecules, leading to diminished functionality. Overall, conventional extraction (OPC-CE) and ultrasound assistance (OPC-UAE) emerged as the most suitable approaches for producing okra protein concentrates with enhanced functional performance, making them promising ingredients for food systems requiring stable foaming or emulsifying properties.

Graphical Abstract