The functional modification of legume proteins by ultrasonication: A review

Background: The use of vegetable proteins is one of the key elements of vegetarian diets. Legumes are an alternative protein source with comparable quality as animal derived proteins, and can be more economical. However, nutritional and technological improvement of legume proteins (LPs) is needed to modify their structure and function. Ultrasound is a promising non-thermal system that has attracted considerable interest worldwide in preparing highly functional LPs. Scope and approach: The ultrasonication effect on the improvement of physicochemical (free sulfhydryl content, surface hydrophobicity, surface tension, particle size, turbidity, viscosity and rheology), thermal, microstructure, and techno-functional properties (solubility, water (WHC), and oil (OHC) holding capacity, emulsifying activity index (EAI), emulsion stability index (ESI), foaming capacity (FC) and stability (FS), and gel strength) of pulses and soy protein was comprehensively reviewed. The future research needs, existing challenges, and practical solutions related to the utilization of this green technology in the functionality and enhancement of LPs were also elucidated. Key findings and conclusions: High-intensity ultrasonic treatment, as a result of cavitational forces, can reduce the particle size, surface tension, turbidity, and viscosity of LP-based solutions with a significant increase in free sulfhydryl and hydrophobic groups on LPs surface. The partial unfolding and structural changes along with the break-up and re-formation of inter-molecular bonds resulted in different microstructures from large, irregular aggregates to small, uniform particles. A significantly improved solubility, WHC, OHC, EAI, ESI, FC, FS and gel strength was found for most LPs treated with ultrasonication.