Characterization of catechin-α-lactalbumin conjugates and the improvement in β-carotene retention in an oil-in-water nanoemulsion

Abstract

The goal of this study was to prepare and characterize α-lactalbumin (ALA)-catechin conjugates as a novel emulsifier in improving the retention of β-carotene (BC) in nanoemulsions via a free radical method. Covalent modification was observed and at least one catechin molecule was binding with ALA according to ESI-MS results. Far-UV CD indicated that the secondary structure of ALA was changed after conjugation. The Z-average particle diameters of nanoemulsions stabilized with ALA and ALA-catechin conjugates were 158.8 and 162.7 nm, respectively. The increase of mean particle size and the degradation of BC at 50°C were both larger than at 25°C during 30 days storage. BC retention stabilized with ALA-catechin conjugates was appreciably greater than ALA (control), which was attributed to the increase of ALA's radicals-scavenging and free metal ion binding ability after grafting with catechin. The chemical antioxidant activities of ALA-catechin conjugates were increased with increasing concentrations from 0.1 to 1.0mg/ml. In general, labile phytochemicals, like BC, can be protected against oxidation during storage by proteins-polyphenols conjugates without any side effects.

Keywords: Chemical stability; Nano-encapsulation; SDS–PAGE; α-Lactalbumin; β-Carotene.