Effect of Ultrasound on the Glycosylation Reaction of Pea Protein Isolate–arabinose: Structure and Emulsifying Properties

This study investigated the effects of different ultrasonic power and ultrasonic time on the structure and emulsifying properties of pea protein isolate (PPI)-arabinose conjugates. An examination of the absorbance and color development of PPI-D-arabinose (Ara) conjugates found that compared with traditional heating, the degree of glycosylation of protein reached the maximum when the ultrasonic treatment power was 150 and the treat-ment time was 30 min. Structural analysis revealed that the content of disordered structures (beta-turn and random coil) of the protein conjugates increased, the maximum emission wavelength of the fluorescence spectrum was red-shifted, and the UV second-order derivative values decreased. The protein structure unfolded, exposing more hydrophobic groups on the molecular surface. Ultrasonic treatment improved the emulsification of protein conjugates. The emulsifying activity index (EAI) increased to 19.7 and 19.3 m(2)/g, and the emulsifying stability index (ESI) also increased. The contact angle and zeta potential also demonstrate that ultrasonic power has a positive effect on emulsion stability. Based on examining the thermal stability of the emulsion, the ultrasonic treatment increased the thermal denaturation resistance of the protein. This result confirms that mild sonication can increase the degree of glycosylation reaction and improve the emulsification properties of protein-Ara conjugates, providing a theoretical basis for developing foods with excellent emulsification properties.