Effect of microwave irradiation on the functional properties, digestion behavior, and structural characteristics of protein isolate from black beans (Phaseolus vulgaris L.)

Abstract

Inspired by the potential of underutilized legumes for addressing present and future food security challenges, this study aimed to explore the effects of microwave irradiation (MI) (100, 300, 450, 600, and 800 W) for 2 min on the functional, structural, and rheological characteristics of black bean protein isolates (BBPIs). Scanning electron microscopy of the microwave-irradiated BBPIs revealed a distinct microstructure characterized by larger aggregates than the control BBPIs. Moreover, BBPIs treated with MI presented excellent emulsion activity index (0.55–0.98) and stability index (0.35–0.71 min), with the lowest turbidity index (0.09–0.12). SDS-PAGE analysis revealed that the profiles of the microwave-irradiated BBPI samples were similar to those of the control BBPIs. Differential scanning calorimetry and thermogravimetric analysis revealed that all the MI-treated BBPIs had variations in denaturation temperature and weight loss. Rheological analysis indicated that the gelation temperature for all BBPI samples was approximately 90 °C. The optimal MI condition (450 W for 2 min) had the highest free sulfhydryl content, surface hydrophobicity, and improved the protein digestibility of BBPI dispersions among all the samples. Microwave treatment at 450 W improved the hydrophobic amino acid content, leading to an overall increase in the total amino acid content of BBPIs compared to the control sample. The present study details how varying microwave irradiation results in distinct final properties of BBPIs, enabling their use and customization for various food systems.