Optimization of Microencapsulation of β-Lactoglobulin-Vitamin A

Abstract

As one of essential nutrients, vitamin A is important for growth, development, immune and vision system. It is widely used in various types of foods as a nutritional supplement. However, the functional properties of vitamin A are not fully exhibited by its great reactivity and low stability. Microencapsulation of vitamin A could increase the stability of vitamin A, prevent light-induced degradation and oxidation, and disperse vitamin A in water-soluble compounds. β-Lactoglobulin (β-Lg) is the major whey protein in cow's milk and has a central cavity able to bind hydrophobic ligands such as vitamin A. Furthermore, using ultra-high pressure (UHP) treatment, which changes the conformation of β-Lg, could increase the binding ability of β-Lg to vitamin A. In this study, microencapsulation condition for vitamin A using β-Lg as a wall material was optimized using response surface methodology (RSM). In order to achieve a higher microencapsulation efficiency (MEE), β-Lg was treated by UHP before encapsulating vitamin A. The UHP treatment condition of β-Lg was optimized using orthogonal array design (OAD). The microstructures of the microcapsules of β-Lg-vitamin A and microcapsules of UHP treated β-Lg-vitamin A were observed by transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. Optimal conditions for microencapsulation of β-Lg-vitamin A were 4.74:1 of the molar ratio, 1.43 h, pH 6.87, and 48.68℃ determined by RSM. The MEE under the optimized condition was calculated as 82.2% and the experimental value was 81.5%. Optimal conditions for UHP treatment of β-Lg were 300 MPa, 20 min, and 20℃ determined by OAD. The experimental MEE under the optimized condition was 94.8%. The optimized microcapsules of β-Lg-vitamin A and microcapsules of UHP treated β-Lg-vitamin A observed by TEM were sphere-shaped in a regular order. Vitamin A was observed by FT-IR to be inserted in the central cavity of β-Lg. These results indicate that the microencapsulation conditions forβ-Lg and vitamin A were optimized by RSM, the UHP treatment conditions forβ-Lg were optimized by OAD, and the microcapsules were successfully formed.