Study on the physicochemical properties and gelation characteristics of pea protein isolate modified by ultrasonic-assisted succinylation.

Ultrasound could facilitate the succinylation of protein and improve the function of succinylated protein. However, the effects of ultrasound-assisted succinylation on the physicochemical property and gelation characteristics of PPI were scarely reported. Therefore, this research studied the effect of succinylation with different ultrasonic power on the physicochemical properties and gelation characteristics of succinylated pea protein isolate (PPI). Results displayed that the succinylation degree of PPI increased with the increasing ultrasonic power. The succinylated PPI treated with 318 W/cm² of ultrasound power had the lowest turbidity (0.247), and had the smallest particle size (171.3 nm). Excessive ultrasonic power led to the conversion of random coils in succinylated PPI into α-helix structures. Moreover, ultrasound reduced the crystallinity of succinylated PPI. The gel strength of succinylated PPI decreased with the increasing ultrasonic power. The gel strength (65.66 g∙mm) of SPPI treated with ultrasonic power of 636 W/cm² was 20.89 % lower than that of SPPI without ultrasonic treatment. Succinylation promoted bound water content in PPI. The content of bound water in the SPPI gel at 636-1273 W/cm² ranged from 96.95 % to 98.52 %, which was 2.1 %-3.7 % higher than that in the SPPI without ultrasound treatment. As the ultrasonic power increased, the storage modulus (G') and loss modulus (G″) of the SPPI gel decreased. Compared to SPPI without ultrasound treatment, the mass loss rate of ultrasonic-treated SPPI at the second stage was significantly reduced by 57.4 %-63.3 %, indicating that ultrasound treatment enhanced the thermal stability of SPPI. This study could offer more evidences for the modification of PPI and develop succinylated PPI gel-based products.