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A mechanistic insight into whey protein isolate (WPI) fibrillation driven by divalent cations
Zahra Kazemi-Taskooh1, Mehdi Varidi1
1Department of Food Science and Technology, Faculty of Agriculture, Ferdowsi University of Mashhad, Azadi Sq., Mashhad, Khorasan Razavi P.O. Box 9177948944, Iran.
Food Chemistry
|January 17, 2025
Summary
Divalent cations like iron and calcium influence whey protein isolate (WPI) fibrillation through distinct mechanisms. Understanding these protein fibrillation pathways is key for food science and biomaterials development.
Area of Science:
- Food Science
- Biomaterials Science
- Protein Chemistry
Background:
- Protein fibrillation is a complex process with significant implications in food science and biomaterials.
- The specific mechanisms of whey protein isolate (WPI) fibrillation induced by divalent cations are not fully understood.
- Divalent cations are known to interact with proteins, potentially influencing their structural conformation and aggregation.
Purpose of the Study:
- To elucidate the distinct mechanisms of WPI fibrillation induced by different divalent cations (Ca2+, Fe2+, Mg2+, Zn2+).
- To investigate the role of cation type, ionic strength, and intermolecular forces in WPI fibrillation.
- To characterize the resulting fibril structures and relate them to the underlying fibrillation pathways.
Main Methods:
- Spectroscopic analysis (amide I and II bands) to confirm fibrillation and assess secondary structure changes.
- Microscopy techniques to visualize fibril morphology and measure fibril length.
- Investigation of the role of hydrophobic forces and disulfide bonds in the fibrillation process.
- Varying cation concentrations and ionic strength to study their effects on fibrillation.
Main Results:
- All tested cations (Ca2+, Fe2+, Mg2+, Zn2+) enhanced microenvironment polarity via π-π stacking, confirming fibrillation.
- Fe2+ induced fibrillation via a nucleation-growth mechanism, forming long, β-sheet-rich fibrils.
- Ca2+ and Mg2+ promoted fibrillation through nucleated conformational conversion and electrostatic shielding, leading to multilayer fibrils.
- Zn2+ resulted in worm-like fibrils, suggesting a simple nucleated polymerization due to high binding affinity and stabilization.
- Increased ionic strength accelerated fibril growth by enhancing hydrophobic amino acid exposure and increasing nuclei formation.
Conclusions:
- Divalent cations trigger WPI fibrillation through diverse mechanisms, including nucleation-growth, nucleated conformational conversion, and simple nucleated polymerization.
- The specific cation (Fe2+, Ca2+, Mg2+, Zn2+) dictates the fibrillation pathway and resulting fibril morphology.
- Hydrophobic interactions play a crucial role, while disulfide bonds appear to have a minor role in cation-induced WPI fibrillation.
- Ionic strength significantly impacts the fibrillation process, particularly the growth phase.
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