Effect of high-intensity ultrasound on the physicochemical, nutritional, rheological, microstructural, and techno-functional properties of a groundnut (Arachis hypogaea L.) paste protein isolate

With the continuous growth of the global population, obtaining new sources of protein is a priority to meet the nutritional needs of society. In this sense, the recovery of proteins from plant sources such as de-oiled oilseed pastes such as groundnut has gained relevance. In this study, a groundnut paste protein isolate (GPPI) was obtained via alkaline extraction followed by isoelectric precipitation. The GPPI was then treated with high-intensity ultrasound (HI-U) at 200, 400 and 600 W for 15 and 30 min to evaluate the effect on its physicochemical, nutritional, rheological, microstructural and techno-functional properties. Results showed that HI-U increased the GPPI's turbidity by up to 8.85%, antioxidant capacity by 163.71%, protein digestibility by 3.54%, apparent viscosity by 409%, emulsifying activity index by 147% and foaming capacity by 116.17%, while its water activity decreased by up to 18.48%, compared with the control treatment (GPPI without HI-U). The flow and cohesion properties of the GPPI measured as the Carr index and Hausner ratio, respectively, showed enhancements of up to 19.74% and 4.92%, respectively, because of HI-U. According to their fluid behavior, GPPI suspensions showed pseudoplastic characteristics. Furthermore, the apparent viscosity results of the GPPIs were adequately fitted to the power law model (r² = 0.929–0.966), showing low values in the consistency (0.024–0.085 Pa s) and fluidity (0.945–0.891) indices, confirming their behavior as a pseudoplastic fluid. Moreover, microphotographs revealed larger microstructures by the HI-U impact. The findings of this study can facilitate the use of GPPIs as an important protein ingredient for food production.