Modulation of acid-induced pea protein gels by gellan gum and glucono-δ-lactone: Rheological and microstructural insights

This study investigated the effect of gellan gum (GG) and glucono-delta-lactone (GDL) on the acid-induced gel properties of pea protein isolate (PPI) pretreated with media milling. The inclusion of GG substantially enhanced the gel hardness of PPI gel from 18.69 g to 792.47 g though slightly reduced its water holding capacity (WHC). Rheological analysis showed that GG increased storage modulus (G') and decreased damping factor of gels in the small amplitude oscillatory shear region and transformed its strain thinning behavior into weak strain overshoot behavior in the large amplitude oscillatory shear region. SEM revealed that GG transformed the microstructure of gel from a uniform particle aggregate structure to a chain-like architecture composed of filaments with small protein particles attached. Turbidity and zeta potential analysis showed that GG promoted the transformation of PPI from a soluble polymer system to an insoluble coagulant during acidification. When GG content was relatively high (0.2 %-0.3 %), high GDL content increased the electrostatic interaction between PPI and GG molecules, causing their rapid aggregation into a dense irregular aggregate structure, further enhancing gel strength and WHC. Overall, GG and GDL can offer the opportunity to modulate the microstructure and gel properties of acid-induced PPI gels, presenting potential for diversifying food gel design strategies through PPI-GG hybrid systems.