Stability and Digestibility of Lotus Seed Protein Isolate Emulsion Loaded with β-Carotene

Lotus seed protein isolate (LSPI) was used as emulsifier to prepare high internal phase (high load) β-carotene-loaded emulsion (LSPI-BC). The stability and β-carotene retention rate of LSPI-BC were measured, and the mechanism of the changes in LSPI-BC at different stages of in vitro digestion was investigated. The results showed that LSPI-BC had long-term stability at low temperature (4 ℃), and the retention rate of β-carotene was over 85%. However, the stability and β-carotene retention rate of LSPI-BC decreased significantly when the temperature was above 25 ℃. High temperature treatment caused LSPI to unfold and expose hydrophobic groups, forming a spatial network structure that imparts LSPI-BC with good thermal stability and protects the β-carotene from further degradation. In the in vitro digestion experiment, salivary mucin and high concentrations of ions in the oral digestive fluid decreased the magnitude of surface charge on the droplets and then affected the stability of the emulsion. In the gastric phase, flocculation or fusion occurred due to the effect of pH, the potential changed from negative to positive, and the protein aggregates dispersed. In the intestinal phase, the droplet size decreased obviously and the absolute value of potential increased. After hydrolysis, the 1,1-diphenyl-2-picylhydrazyl (DPPH) radical scavenging ability increased significantly. In addition, free fatty acids were released gradually during simulated digestion, and the amount of free fatty acids released increased obviously in the first 30 min of digestion, and then reached 61.94% at 60 min, indicating that LSPI was more suitable for encapsulating active substances. The encapsulated active substance remained stable in acidic medium, its release was delayed during in vitro digestion and its bioavailability was increased to 58.51%. This study may provide a theoretical basis for the development and utilization of LSPI for high loading and sustained release of lipid-soluble active substances.