pH-assisted and heat-induced nanostructures of beta-lactoglobulin for the stabilization of anthocyanins.

Heat-induced protein aggregation can enhance the efficacy of proteins as carriers of bioactive components. This study examined the structural properties of beta-lactoglobulin (BLG) aggregates-fibrils (BLGF), nanoparticles (BLGNP), and worm-like chains (BLGWC)-induced by pH and heat. Cyanidin-3-O-glucoside (C3G), the predominant anthocyanin in natural sources like black rice, was used to investigate the impact of structurally diverse BLG aggregates on binding affinity and protective effects on anthocyanins. Results showed that BLGF, characterized by a cross-β-sheet structure, exhibited the highest surface hydrophobicity (BLGF > BLGWC > BLGNP ≈ BLG). The binding of C3G to the aggregates was driven mainly by hydrophobic forces. The half-life of anthocyanins at 90 °C correlated linearly with the surface hydrophobicity of BLG aggregates (R2 = 0.998). BLGF notably enhanced anthocyanin stability twofold compared to BLG. TEM images indicated that BLGF with anthocyanins after heating formed a densely packed lateral arrangement of fibrils, enhancing their thermal protection.