Improving pea protein functionality by combining high-pressure homogenization with an ultrasound-assisted Maillard reaction

The functionality of many plant proteins is limited by their poor solubility characteristics. In this study, a combination of high-pressure homogenization and an ultrasound-assisted Maillard reaction were used to improve the functionality of pea protein isolate (PPI) by conjugating it with xylo-oligosaccharides (XOS). The reaction conditions with high grafting degree of PPI for producing these conjugates were established: XOS:PPI=3:1, wt%; ultrasound power = 400 W; reaction time = 20 min; and treatment temperature = 70°C. Homogenization of the PPI solution (three times, 80 MPa) prior to the ultrasound-assisted Maillard reaction increased the grafting degree of the conjugates. In addition, the combined treatment promoted the partial unfolding of the pea proteins, increased their thermal stability, and enhanced their in vitro antioxidant activity. It also improved the solubility of PPI from pH 3 to 10, as well as its emulsifying and foaming properties. Moreover, the conjugates fabricated using the combined treatment produced emulsions containing smaller and more dispersive oil droplets that were more resistant to oxidation. This research shows that a combination of high-pressure homogenization and an ultrasound-assisted Maillard reaction can improve a variety of functional properties of pea proteins, which will be beneficial for the development of various kinds of plant-based foods in the food industry.