Abstract: In order to improve the thermal stability of vitamin E (VE) in ultra-high temperature sterilized (UHT) milk, a complex of β-lactoglobulin (β-LG) with VE was prepared. Turbidity, particle size, zeta potential, scanning electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), infrared spectroscopy and fluorescence spectroscopy were used to explore whether β-LG combined with VE. The degree of binding was further analyzed by bio-layer interferometry. The contents of VE in common fortified milk (with VE) and complex fortified milk (with β-LG/VE complex) before and after ultra-high temperature sterilization were determined by high performance liquid chromatography (HPLC) and the loss rate of VE was calculated to determine the effect of β-LG on the thermal stability of VE. The results showed that β-LG combined with VE to form a complex through hydrogen bonds and hydrophobic interaction, and that binding to β-LG reduced the aggregation of VE in aqueous solution and increased its solubility. Bio-layer interferometry corroborated the binding between β-LG and VE, and the binding constant was 7.493 × 10-2 mol/L. The loss rate of VE in complex fortified milk was significantly lower than that in common fortified milk, (4.01 ± 0.18)% versus (10.90 ± 0.17)% (P < 0.05). The above results showed that β-LG/VE could effectively improve the thermal stability of VE, which provides a theoretical basis for the development of vitamin fortified dairy products.

Key words: β-lactoglobulin; vitamin E; bio-layer interferometry; ultra-high temperature sterilized milk; thermal stability