Increased stability and protease resistance of the β-lactoglobulin/vitamin D3 complex

The stability of the β-lactoglobulin (βlg)/vitamin D3 (D3) complex at 4 °C and upon exposure to UV-C light, and in simulated intestinal fluid, were studied in vitro. Caco-2 cells were used to demonstrate the passage of the βlg/D3 complex across the monolayers. Furthermore, an in vivo experiment was conducted by force-feeding rats with the free D3 and βlg/D3 complex, with subsequent determination of the plasma concentration of 25-hydroxy-D3. The βlg/D3 complex significantly improved the stability of the vitamin at 4 °C and when exposed to UV-C light. The resistance of βlg to proteases was increased, indicating a mutual protective effect. The βlg/D3 complex crossed the monolayers, which was confirmed by the significant increase in the concentration of 25-hydroxy-D3 in rats fed the βlg/D3 complex compared to the ones fed the free D3. Therefore, the current study suggests that the βlg/D3 complex can effectively be used for the fortification of milk products and low-fat content foods to improve the intake and bioavailability of D3.