Stability of β-Carotene in Oil-in-Water Emulsions Prepared by Mixed Layer and Bilayer of Whey Protein Isolate and Beet Pectin

Abstract

The addition order of mixed layers of protein and polysaccharide on oil-water interface has been shown to influence physical stability of the emulsion, but little is known about how it impacts chemical stability. Therefore, this study investigated differences in the chemical stability of oil-in-water (O/W) emulsions containing β-carotene droplets coated by whey protein isolate (WPI)-beet pectin through direct preformed mixture (mixed emulsion) and consecutive layer-after-layer (bilayer emulsion) at pH 4.0 and 7.0. The results clearly indicated that both forms of β-carotene emulsions exhibited nearly identical degradation profiles during storage at 55°C. The stability of β-carotene in O/W emulsions could be significantly improved by the addition of iron chelator desferroxamine for both mixed and bilayer emulsions at pH 4.0, but not at pH 7.0. The addition of α-tocopherol could also significantly inhibit the β-carotene degradation for both emulsions at pH 4.0 and 7.0. However, the difference of the improved β-carotene stability between the mixed and bilayer emulsions was not significant. These results implied that the protein-polysaccharide adsorption approach in the β-carotene droplet surface did not play a major role in the degradation rate of β-carotene in O/W emulsions, and it was possible to produce emulsions through mixed and bilayer methods with the similar chemical stability of active compounds for use in a variety of food products.