High Hydrostatic Pressure: A Tool for Functional Modification of Lupin Protein Isolates

This study aimed to evaluate high hydrostatic pressure (HHP) processing as a modification method for protein functionalization. Lupin protein isolates (LPI), derived from the species Lupinus luteus , were subjected to pressures of 200, 350, and 500 MPa for 10 min at 20 °C, and the impact of HHP on protein structure and techno-functional properties was studied. HHP treatments induced changes in both secondary and tertiary structures, resulting in partial protein unfolding. A decrease in fluorescence intensity along with increased surface hydrophobicity indicated partial unfolding and exposure of hydrophobic groups to the aqueous environment. Conformational changes also promoted the exposure of sulfhydryl groups, suggesting that the formation and/or rearrangement of intermolecular disulfide bonds may have contributed to protein aggregation, as supported by gel electrophoresis and reduced free sulfhydryl content at 500 MPa. However, particle size distribution indicated coexistence of dissociated/smaller species and larger aggregates rather than a uniform increase in particle size. These structural alterations were associated with increase in solubility and reduction in emulsifying activity. Pressures of 200 and 350 MPa decreased the least gelation concentration of LPI from 13 to 11%, indicating improved gelling capacity, and the viscoelastic results evidenced the formation of stronger gel networks, particularly at 350 MPa. HHP treatment at 500 MPa caused a less favorable effect in the gelling capacity compared to 350 MPa, likely due to further protein aggregation. Overall, the results demonstrated that HHP can be applied to modify the lupin protein structure and tailor its techno-functionality, promoting the use of lupin protein as a gelling agent in food matrices.