Microwave-assisted extraction drives changes in the proteomic profile, structural, and functional properties of lupin protein isolates

The increasing demand for plant-based protein ingredients highlights the need for efficient extraction methods suitable for food applications. In this context, this study aimed to evaluate the potential of microwave-assisted extraction (MAE) using food-grade and Generally Recognized As Safe (GRAS) reagents for obtaining functional protein isolates from lupin seeds. Semi-defatted lupin flour, obtained by supercritical CO2 extraction (scCO2), was used as the starting material. Proteins were extracted using sodium carbonate and precipitated with citric acid. The effects of microwave (MW) power (50–250 W) and extraction time (1–8 min) on protein yield, composition, structure, and functionality were investigated. MAE increased protein yield by up to 9 % compared to conventional extraction and produced isolates whose proteomic profile more closely resembled that of the semi-defatted flour. Structural analysis using Fourier-transform infrared (FTIR) spectroscopy revealed that MW-induced changes in protein secondary structure, which appeared to enhance solubility (up to 95 % at pH 7) and foaming capacity (up to 112 %). Emulsion stability was also improved, with increase in droplet size during storage being significantly reduced. These results highlight that MAE combined with food-grade reagents not only enables efficient protein recovery, but also enhances functionality, supporting their potential application in food systems.