Modification of black bean proteins using pulsed light and ultrasound treatment

Abstract

Black beans have been raising interest as a source of protein concentrates and isolates with high nutritional and functional properties. This study aimed to evaluate the effect of pulsed light (PL) on black bean protein (BBP) extracts for the first time and compare it with ultrasound (US) treatments, to expand the application potential of this protein. For this, an aqueous extract (TE = total extract) and an extract obtained by isoelectric precipitation (PE = precipitated extract) at a protein concentration of approximately 1 mg/mL were exposed to up to 30 pulses for PL treatment or ultrasonication at different levels (30% to 70%). The samples were characterized by techno-functional and structural properties. As expected, PE presented higher protein content (76 mg/100 g) than TE (48 mg/100 g). The differences in protein composition of PE and TE changed their techno-functional and structural characteristics. PL treatment improved emulsification capacity (EC) and foaming stability (FS), primarily in the more intense assay (30 pulses). In contrast, US treatment increased EC and foaming capacity (FC), primarily in the moderate intensity (50% amplitude). Furthermore, PL and US improved the surface hydrophobicity (H₀) of PE while generally decreasing the free sulfhydryl groups (SH) of PE and TE. The observed changes were accompanied by alterations in the secondary structure of BBP extracts with increasing PL and US intensities. These results contribute to the current knowledge on non-thermal treatments, PL and US, and support their roles as promising tools to improve the application of black bean and other pulse proteins.