What question did this study set out to answer?

The research aims to evaluate the effects of different extraction methods on the yield and functional characteristics of Solanum scabrum protein concentrates.

February 26, 2026Open Access

Physicochemical, Structural, and Techno-functional Characterization of Solanum scabrum Leaf Protein Concentrates Obtained by Alkaline Extraction, Ultrasound-assisted Extraction, and Ultrafiltration

Key Points

The research aims to evaluate the effects of different extraction methods on the yield and functional characteristics of Solanum scabrum protein concentrates.
Investigated three extraction methods: alkaline extraction with isoelectric precipitation, ultrasound-assisted extraction, and ultrafiltration.
Measured protein yield, structural characteristics, and functional properties of the resulting protein concentrates.
Conducted spectroscopic analysis and scanning electron microscopy to understand protein conformation and structure.
Ultrasound-assisted extraction yielded the highest protein concentration at 48.71%, while ultrafiltration had the lowest yield at 26.45% but the highest protein content at 71.43%.
Ultrafiltration protein concentrates exhibited superior colloidal stability with higher zeta potential values at both acidic and alkaline conditions.
Functional tests showed ultrasound-assisted and ultrafiltration concentrates had improved solubility, emulsifying, and foaming properties.

Abstract

Abstract Global demand for plant-based proteins is rapidly increasing, driven by sustainability concerns and health-conscious consumer preferences. In this context, African nightshade (Solanum scabrum), an underutilized leafy biomass rich in protein, represents a promising alternative protein source. This study investigated the influence of alkaline extraction followed by isoelectric precipitation (AE-IP), ultrasound-assisted extraction (UAE), and ultrafiltration (UF), on the yield, composition, structural and functional characteristics of Solanum scabrum protein concentrates (AE‑IPSPC, UAESPC, UFSPC). UAE significantly enhanced protein yield (48. 71%) compared to AE-IP (34. 02%), while UF produced concentrates with lowest yield (26. 45%) but highest protein content (71. 43%). UFSPC exhibited a lighter color (L* = 71. 53 ± 0. 22) and lower browning index (20. 76 ± 0. 11%) than AE-IPSPC (L* = 57. 89 ± 0. 17; browning index = 42. 90 ± 0. 54%), indicating reduced pigment co-extraction. Scanning electron microscopy revealed dense, fibrous structures with irregular cracks in AE-IPSPC, smooth, layered structures with interconnected channels and cavities in UAESPC, and irregular wavy patterns and shallow depressions in UFSPC. UFSPC displayed the highest absolute zeta potential values at both acidic (36 mV at pH 2) and alkaline pH (-39 mV at pH 10), indicating enhanced electrostatic repulsion and improved colloidal stability. Functionally, UFSPC and UAESPC exhibited superior solubility at alkaline pH, along with enhanced emulsifying and foaming properties. Spectroscopic analysis suggested extraction-dependent alterations in protein conformation associated with improved hydration behavior. Overall, ultrasound-assisted and ultrafiltration approaches effectively improved the functional and nutritional performance of Solanum scabrum protein concentrates, supporting their potential application as sustainable plant-based protein ingredients and establishing clear process-structure–function relationships.

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Physicochemical, Structural, and Techno-functional Characterization of Solanum scabrum Leaf Protein Concentrates Obtained by Alkaline Extraction, Ultrasound-assisted Extraction, and Ultrafiltration

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