Abstract: The effect of electron beam irradiation (EBI) on the microstructure and hydrolysis characteristics of sunflower seed protein was investigated in this study. Defatted sunflower seed powder was treated by different doses (0, 2.5, 5.0, 7.5 and 10.0 kGy) of EBI. Variations in the microstructure, moisture content, and hydrolysis characteristics of sunflower seed protein after the irradiation treatment were analyzed by using scanning electron microscopy, low field nuclear magnetic resonance (LF-NMR), and a laser particle size analyzer. Results revealed that EBI could change the microstructure of sunflower seed protein, and damaged the integrity of the surface structure, giving rise to pores in it and ultimately breaking it; this effect was positively related to the irradiation dose. After treatment with 2.5 kGy radiation, the surface of sunflower seed protein powder displayed many gaps and became rough; nevertheless, it still maintained an intact granular structure. When the radiation dose increased to 7.5 kGy, the surface integrity was damaged, showing fragmented morphology. Moreover, EBI above 7.5 kGy induced an increase of the hydrolysis degree of sunflower seed protein and facilitated the production of smaller peptides, which indicated that EBI improved the hydrolysis characteristics of sunflower seed protein. This study provides a theoretical basis for the application of electron beam irradiation in improving protein properties.

Key words: sunflower seed protein, electron beam irradiation, microstructure, hydrolysis characteristics, modification