Formation of Antioxidant Multilayered Coatings for the Prevention of Lipid and Protein Oxidation in Oil-in-Water Emulsions: <i>Lycium barbarum</i> Polysaccharides and Whey Proteins
Li Tian, Shulin Zhang, Jianhua Yi, Zhenbao Zhu, Meili Li, Eric A. Decker, David Julian McClements
Abstract
polysaccharides (LBPs) on the physical and chemical stability of oil-in-water emulsions coated by a whey protein isolate (WPI) was investigated. At pH 3.0, the anionic LBP (0.2-0.6 wt %) molecules were electrostatically deposited onto the cationic surfaces of the WPI-coated oil droplets, leading to the formation of stable multilayered emulsions containing WPI-/LBP-coated oil droplets. However, increasing the LBP concentration to 0.8 wt % led to oil droplet aggregation, which was attributed to charge neutralization, bridging flocculation, and/or depletion flocculation. For subsequent experiments, a low (0.2%) and an intermediate (0.6%) LBP dose was used to prepare the secondary emulsions, and then their physical and oxidative stability was studied during 8 days of storage at 37 °C. The presence of the multilayer WPI/LBP coatings around the oil droplets inhibited lipid oxidation (reduced levels of lipid hydroperoxides and 2-thiobarbituric acid-reactive substances), as well as protein oxidation (reduced levels of carbonyl formation, sulfhydryl consumption, molecular weight modifications, intrinsic fluorescence loss, and Schiff-base fluorescence gain). The antioxidant effects of the multilayer coatings were greater at the higher LBP concentration. These results suggest that LBP, a natural plant-based polysaccharide isolated from a traditional Chinese medicine, can be used to improve the quality of emulsion-based foods. However, the level used should be optimized to ensure good physical and oxidative stability of the emulsions.