Heat-induced changes in secondary structure, gelation and viscoelastic properties of potato protein and precision fermentation-derived β-lactoglobulin

This study investigates the influence of pH and protein blending on the denaturation, secondary structure transitions, gelation, and rheological properties of heat-set gels formed from patatin rich potato protein isolate (PPI) and precision fermentation-derived β-lactoglobulin (BLG). Using ATR-FTIR spectroscopy and rheological analysis, we demonstrate that heat-induced gelation in both PPI and BLG is associated with the formation of intermolecular β-sheets and β-turns. PPI and BLG blends (PPI/BLG) show two distinct gelation pathways: At pH 4.5, non-interactive denaturation and gelation of the protein fractions occur, resulting in a firm but brittle gel dominated by PPI, with limited strain stiffening and energy dissipation onset. In contrast, at pH 6.0, interactive denaturation and network formation are observed. This is accompanied by a minor increase in β-turns, likely from the PPI fraction, which facilitates the formation of intermolecular β-sheets between PPI and BLG. Confocal microscopy indicated that this interaction leads to an interconnected dual network gel structure, exhibiting enhanced gel firmness, pronounced strain stiffening, and delayed energy dissipation. The rheological behavior of these dual network gels is dominated by BLG at low strains and by PPI at high strains, indicating effective stress-sharing between the networks. These findings highlight the potential of PPI/BLG blends to generate heat-set gels with tuneable texture and mechanical properties, inspiring their application as alternatives to animal-derived proteins in various food systems.