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Updated: Jun 16, 2025

Mechanical Separation and Protein Solubilization of the Outer and Inner Perivitelline Sublayers from Hen's Eggs
Published on: January 27, 2021
Structural and techno-functional properties of pH-shifted protein isolates from unhatched hen eggs
Supalak Ruangprom1, Manat Chaijan1, Chantira Wongnen1
1Food Technology and Innovation Research Center of Excellence, School of Agricultural Technology and Food Industry, Walailak University, Nakhon Si Thammarat 80160, Thailand.
Abstract:
This study explores the effects of pH-shift processing (acid and alkaline) on the physicochemical and techno-functional properties of protein isolates (PPI) from unhatched hen eggs-infertile (INF) and dead-in-shell (DIS)-compared to commercial whole hen egg powder (CEP). Structural changes were evident in PPI, with reduced reactive SH content and surface hydrophobicity relative to CEP (p < 0.05). Thermal denaturation temperature (Td) varied by egg type and pH treatment, with DIS alkaline-PPI exhibiting the highest Td (p < 0.05). While CEP demonstrated superior solubility, DIS alkaline-PPI exhibited higher viscosity (p < 0.05). Foamability was highest in CEP (p < 0.05), yet PPI, particularly acid-INF-PPI, showed enhanced foam stability. CEP had the highest emulsifying activity index (EAI), whereas DIS alkaline-PPI displayed superior emulsion stability index (ESI) (p < 0.05). Gel formation was concentration-dependent; CEP formed a soft gel at 20% protein, whereas all samples gelled at 30%. CEP gels demonstrated significantly greater breaking force, deformation, gel strength, and water-holding capacity (WHC) than PPI gels (p < 0.05), which exhibited a more porous and aggregated microstructure. Rheological analysis revealed that INF alkaline-PPI had the highest storage modulus (G'), indicating strong elasticity; however, CEP exhibited superior mechanical strength, suggesting that a compact protein network enhances resistance to external stress. Acid-extracted PPI displayed lower G', indicating weaker gel formation, while DIS alkaline-PPI showed a delayed gelation process. Loss modulus (G'') and loss tangent (tan δ) further highlighted distinct viscoelastic behaviors across samples. These findings illustrate that the pH-shift process significantly influences the structural and functional properties of unhatched egg PPI, with implications for their application in food formulations.
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