Mechanistic study on the nanocomplexation between curcumin and protein hydrolysates from Great Northern bean (Phaseolus vulgaris L.) for delivery applications in functional foods

There has been a great interest in utilization of plant protein such as dry edible bean (Phaseolus vulgaris L.) proteins as cost-effective biomaterials to replace animal proteins for delivery of nutrients in foods. The functional properties of bean proteins may be further improved by tuning the degree of enzymatic hydrolysis. In this study, the complexation of Great Northern bean hydrolysates (BPH) with curcumin was investigated. Compared to the micro-sized BPH globulins (1.2–1.5 μm in diameter), self-assembled nanocomplexation took place spontaneously after mixing with curcumin, with size ranging from 244.7 to 344.7 nm. BPH with 5% degree of hydrolysis (DH) showed the highest curcumin loading capacity value (9.97 μg/mg). By investigating the intrinsic fluorescence quenching and curcumin fluorescence enhancement, we found that the binding affinity was increased at low DH but decreased at the DH of 7% or higher, compared to pristine protein. BPH-5 showed the highest loading capacity (9.97 μg/mg), relatively small particle size (286.9 nm) and low PDI value (0.359), and optimal storage stability, which was mainly attributed to its relatively high binding affinity and surface hydrophobicity. The findings in this study provide insight on fabricating, optimizing and selecting plant protein-based delivery systems in functional foods.