The interplay between ultrasound-induced Maillard conjugates of soy protein isolate–gellan gum and corresponding emulsion-templated oleogels

The structured oils have emerged as a recent development to substitute solid fats for health concerns. The current research used the ultrasound-assisted wet-heating Maillard reaction to accelerate soy protein isolate (SPI) conformational changes. The conjugates were characterized as a function of SPI/gellan gum ratio (1:3, 1:1, and 3:1) and reaction time (0, 10, 20, and 30 min). Afterward, the conjugates stabilized O/W emulsions with different oil fraction (40 or 60%), finally producing emulsion-templated oleogels. More hydrogen bonds formed upon conjugation as evidenced by FTIR. The samples with 1:1 ratio remained in the injection wells of SDS-PAGE, which possessed the maximum glycation degree, intermediate and final products of Maillard, surface hydrophobicity, EAI and ESI, and interfacial adsorption [1:1>1:3>3:1]. The cavitation effect originated from ultrasound increased the local temperature, accelerating SPI unfolding and exposure of amines which enhanced the collision with gum. Although ultrasonication facilitated the emulsifying properties, excessive SPI concentration reduced EAI and ESI as the thermodynamic barrier for emulsifier migration increased. Afterward, ultrasonication reduced the emulsion droplet size and zeta potential since ionic repulsions increased. The oleogels could be classified in 2 groups: I) strong gels: all oleogels containing 40% oil with reaction time of 10 or 30 min, exhibiting solid-elastic behavior, and II) other oleogels displaying a weak physical gel-like properties, dominated by H-bonds confirmed by FTIR. The oleogels can be further functionalized as fat replacer in meat or bakery products, or produce spreads and vegan butter.