Formation, Stability and In Vitro Digestion of β-carotene in Oil-in-Water Milk Fat Globule Membrane Protein Emulsions

Abstract

The formation, stability and in vitro digestion of milk fat globule membrane (MFGM) proteins stabilized emulsions with 0.2 wt% β-carotene were investigated. The average particle size of β-carotene emulsions stabilized with various MFGM proteins levels (1%, 2%, 3%, 4%, 5% wt%) decreased with the increase of MFGM proteins levels. When MFGM proteins concentration in emulsions is above 2%, the average particle size of β-carotene emulsions is below 1.0 μm. A quite stable emulsion was formed at pH 6.0 and 7.0, but particle size increased with decrease in acidity of the β-carotene emulsion. β-carotene emulsions stabilized with MFGM proteins were stable with a certain salt concentrations (0–500 mMNaCl). β-carotene emulsions were quite stable to aggregation of the particles at elevated temperature and time (85 °C for 90 min). At the same time, β-carotene emulsions were stable against degradation under heat treatment conditions. In vitro digestion of β-carotene emulsion showed the mean particle size of β-carotene emulsions stabilized with MFGM proteins in the simulated stomach conditions and intestinal conditions is larger than that of initial emulsions and simulated mouth conditions. Confocal laser scanning microscopy of β-carotene MFGM proteins emulsions also showed the corresponding results to different vitro digestion model. There was a rapid release of free fatty acid (FFA) during the first 10 min and after this period, an almost constant 70% digestion extent was reached. Approximately 80% of β-carotene was released within 2 h of incubation under the simulated intestinal fluid. These results showed that MFGM protein can be used as a good emulsifier in emulsion stabilization, β-carotene rapid release as well as lipophilic bioactive compounds delivery.