Pea Protein–Curcumin Interactions and Their Effects on In Vitro Protein Digestibility

This study examined the effect of the interaction between pea protein isolate (PPI) and curcumin on in vitro protein digestibility. PPI (0.125 mg/mL) was mixed with different amounts (2–100 μM) of curcumin. UV–vis spectral analysis showed that PPI formed complexes with curcumin, which reduced the transmittance and surface hydrophobicity and increased the average particle size. Fluorescence and transmission electron microscopy imaging revealed the formation of amorphous aggregates after complexation. Nonreducing sodium dodecyl–sulfate polyacrylamide gel electrophoresis showed that curcumin interaction did not affect the pea protein profile. However, curcumin reduced the in vitro protein digestibility-corrected amino acid score of PPI by up to 30.5%. The findings offer valuable insights into the food-matrix interactions that affect protein quality in formulated food products and protein-based nutraceutical delivery systems.