Ultrasound-assisted alkaline extraction of wheat germ protein: Effects on extraction yield, functional properties, and secondary structure

Aims: Wheat germ is a valuable source of protein; however, conventional extraction techniques often suffer from limited yields. This study aimed to evaluate the impact of ultrasonic waves as an assisting physical treatment during alkaline solubilization on the extraction yield, functional properties, and secondary structure of wheat germ proteins.

Methods: In this experimental study, defatted wheat germ flour underwent alkaline extraction combined with ultrasonic treatment, followed by protein isolation through isoelectric precipitation. Functional properties—including surface hydrophobicity, emulsifying capacity, and foaming characteristics—were assessed. In addition, changes in the secondary structure of the proteins were examined using Circular Dichroism (CD) spectroscopy.

Findings: Ultrasonic treatment significantly enhanced the extraction yield, increasing it from 24.75% (conventional method) to 42.08%. The ultrasonicated proteins showed improved surface hydrophobicity and emulsifying capacity compared with those obtained by the conventional method. However, reductions were observed in emulsion stability, foaming capacity, and foam stability. CD spectroscopy revealed that ultrasound treatment did not induce significant changes in the secondary structure of the proteins.

Conclusion: The application of ultrasonic waves during alkaline extraction is an effective approach to markedly improve wheat germ protein yield. Although this technique modifies certain functional properties, it maintains the structural integrity of the proteins, indicating strong potential for use in food industry applications.