Green Protein Extraction from Hazelnut Press Cake: Yield, Efficiency, and Secondary Structure Analysis

Hazelnut (<i>Corylus avellana</i> L.) oil production generates press cakes, a by-product rich in plant-based proteins. As demand for alternative proteins grows, sustainable extraction methods like deep eutectic solvents (DESs) are essential for reducing the environmental impact. Alkali s...

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Bibliographic Details
Main Authors: Bruna Anzà, Silvia Fraterrigo Garofalo, Alessandro Lapolla, Debora Fino
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Separations
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Online Access:https://www.mdpi.com/2297-8739/12/3/63
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Summary:Hazelnut (<i>Corylus avellana</i> L.) oil production generates press cakes, a by-product rich in plant-based proteins. As demand for alternative proteins grows, sustainable extraction methods like deep eutectic solvents (DESs) are essential for reducing the environmental impact. Alkali solubilization/isoelectric precipitation (ALKIS) is a widely used method for protein extraction due to its simplicity and cost-effectiveness. Despite that, ALKIS extraction has limitations due to the alteration in protein functionality, a reduction in protein stability, and significant wastewater production. This study compares DESs with ALKIS for extracting proteins from hazelnut press cake. ALKIS resulted in higher protein content (42.53 ± 17.45% vs. 8.55 ± 1.68%), while DES extraction showed higher efficiency (56.41 ± 2.4% vs. 45.16 ± 5.32%). FTIR analysis revealed significant structural differences: DES-extracted proteins exhibited higher β-sheet content (α-helix peak: 31.55 ± 6.97% vs. 18.13 ± 1.15%, <i>p</i> = 0.0302), indicating enhanced stability, whereas ALKIS-extracted proteins had more random coil structures (β-sheet peak: 57.92 ± 3.12% vs. 34.07 ± 12.45%, <i>p</i> = 0.0324), suggesting partial denaturation. The preservation of native protein structures in DES extraction is likely due to hydrogen bonding networks that stabilize proteins during processing.
ISSN:2297-8739