Lentil protein-lentil starch interactions modulate starch gelatinization, rheological behavior, and retrogradation

This study investigated how lentil protein isolate (LPI) modulates the gelatinization and retrogradation of lentil starch (LS) during refrigerated storage (1, 7, and 14 days). Results suggest that LPI modulates starch retrogradation through non-covalent starch–protein interactions that restrict starch chain mobility and reassociation. LPI affected LS behavior in a concentration-dependent manner. Dynamic rheological measurements revealed lower normalized storage modulus (G′) values in LS-LPI systems than in native LS, indicating reduced gel strengthening during short-term retrogradation. Pasting analysis showed a progressive increase, which may be related to water competition and heat-induced protein aggregation that influenced starch network development. LPI also reduced starch swelling and amylose leaching, with a maximum decrease of approximately 31% at 20% LPI. Textural analysis demonstrated lower hardness, gumminess, and cohesiveness in LS-LPI gels, indicating reduced formation of rigid starch networks during storage. Long-term retrogradation was similarly inhibited, with the degree of retrogradation decreasing from ∼39% (0% LPI) to ∼25% (20% LPI) after 14 days. FTIR spectra showed no evidence of new covalent bonds, suggesting that the observed effects were governed primarily by non-covalent interactions, likely involving hydrogen bonding. Consistent with this interpretation, DSC measurements revealed lower retrogradation enthalpy (ΔH r ) and reduced increases in peak temperature (Tp) in LPI-containing systems. CLSM observations suggested protein accumulation within protein-rich regions located at or near swollen starch granules, potentially limiting starch chain reassociation. Collectively, these findings suggest that LPI suppresses starch retrogradation by restricting molecular reorganization and network consolidation, thereby improving the textural stability of lentil-based starch systems during storage.