An efficient ultrasound-assisted extraction method of pea protein and its effect on protein functional properties and biological activities

An ultrasound-assisted alkali method was developed to obtain high extraction level of pea protein isolate (PPI). The method parameters of ultrasound-assisted alkali extraction were successfully optimized using response surface methodology. The highest extraction level of PPI reached 82.6% at a solid/liquid ratio of 1:11.5 g:mL, pH 9.6, 13.5 min extraction time and 33.7% ultrasonic amplitude. Ultrasound caused changes to the secondary and tertiary protein structure of PPI, resulting in partial protein unfolding and the exposure of hydrophobic groups. In addition, smaller particle size and better dispersion were obtained in PPI with ultrasound-assisted extraction. The ultrasound-assisted alkali method resulted in significant improvements in the functional properties of PPIs, including increased solubility, water/oil holding capacity, foaming/emulsifying capacity, stability, and gel formation capacity. The biological activities of PPIs were also enhanced. Hydroxyl radical scavenging capacity was doubled, and angiotensin-converting enzyme inhibitory activity was increased by 55.1% compared with those of PPI extracted using traditional method. This study provides a potential strategy for the production of pea protein with high efficiency and high quality.