Lipolytic behavior and bioaccessibility of curcumin nanoemulsions stabilized by rice bran protein hydrolysate

This study aimed to use rice bran protein hydrolysate (RBPH)-stabilized curcumin nanoemulsions, compared with rice bran protein (RBP), to investigate digestion in the oral and gastrointestinal tracts and to investigate the effect of each digestion factor (pepsin, bile salts, pancreatic lipase) on the lipolysis rate and curcumin bioaccessibility of oil-in-water emulsions. After the enzymatic hydrolysis with the 3% degree of hydrolysis, the protein molecules tended to be looser and disordered. The droplet size analysis results indicated that during oral digestion the RBPH nanoemulsion showed extensive flocculation from 216 ± 2 nm to 1208 ± 81 nm, while 259 ± 2 nm to 383 ± 4 nm for the RBP nanoemulsion. During gastric digestion, the conformation of the protein emulsifier, especially RBPH, was destroyed by pepsin according to SDS-PAGE. During the simulated small intestine digestion, the RBPH emulsion obtained higher lipolysis rate (107 ± 2%) and bioaccessibility of curcumin (42.4 ± 0.1%). Moreover, the influence degrees of different factors on the in vitro digestion were obtained as follows: pancreatic lipase (oil digestion) > bile salt (micellization) > pepsin (emulsifier digestion). These studies contributed to the construction of an effective delivery system for bioactive compounds based on rice bran protein.