Unraveling the mechanism by which high intensity ultrasound improves the solubility of commercial pea protein isolates

Abstract: Although plant-based proteins potentially provide merits for long-term global food security, their poor functionality particularly solubility has hampered the utilization as functional biopolymers in the industry. High intensity ultrasound (HIUS, 20 kHz) has been researched extensively for its possible application in modifications of protein functionality. Here, we show that the solubility of commercial pea protein isolate (PPI) is drastically improved from 7.2 to 58.4 mg/mL at an intermediate power (150 W) after a sequential HIUS treatment with an elevated power (100, 150, 200, 300, and 400 W). The dynamic changes of protein structure and confirmation over the course of sequential HIUS treatment are comprehensively investigated. This allows us to address the knowledge gap among the extensively studied power of HIUS and the structure changes of pea protein. Quantifying nonproteinaceous constituents (dietary fiber and β-glucan) and observing the morphological changes of the resultant pea protein solution have served as a critical step toward understanding the mechanism of action of HIUS in improving protein solubility. These successive investigation unravels that the formation of soluble aggregates between pea proteins and soluble complex between pea protein and indigenous dietary fiber is the underlying reason that HIUS improves the solubility of poorly soluble pea protein. Our findings offer unprecedented insights into the fundamental role of HIUS on structure modification of plant protein, thus paving the way for their industrial applications as green technique in fabricating plant proteins with improved solubility.