Characterization of walnut protein isolate-polyphenol nanoconjugates for the developing a food-grade delivery system

Area of Science:

• Food Science
• Protein Chemistry
• Nutraceuticals

Background:

• Polyphenols are known for their antioxidant properties.
• Protein isolates are versatile biopolymers with potential for modification.
• Developing effective delivery systems for bioactive compounds is crucial in food and pharmaceutical industries.

Purpose of the Study:

• To investigate the covalent interactions between walnut protein isolate (WPI) and various polyphenols.
• To characterize the structural and functional changes in WPI upon polyphenol conjugation.
• To evaluate the potential of WPI-polyphenol conjugates as delivery systems for lipophilic compounds.

Main Methods:

• Sodium dodecyl sulfate‒polyacrylamide gel electrophoresis (SDS-PAGE) to confirm covalent interactions.
• Fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy to analyze structural changes.
• Assays for binding capacity, antioxidant properties, and surface hydrophobicity.

Main Results:

• Covalent interactions were confirmed between WPI and EGCG, CLA, CA, and EA.
• Binding capacity followed the order: WPI-EGCG > WPI-CLA > WPI-CA > WPI-EA.
• Conjugation enhanced antioxidant properties, reduced surface hydrophobicity, and improved functional properties, with WPI-EGCG showing the best performance.

Conclusions:

• WPI-polyphenol conjugates exhibit significantly improved functional and antioxidant properties.
• WPI-EGCG conjugates demonstrated superior characteristics and were successfully used for lycopene (LYC) encapsulation.
• These conjugates represent promising food-grade delivery systems for lipophilic bioactive compounds.