Core‐Shell Biopolymer Nanoparticles Produced by Electrostatic Deposition of Beet Pectin onto Heat‐Denatured β‐Lactoglobulin Aggregates

  The purpose of this study was to produce and characterize core‐shell biopolymer particles based on electrostatic deposition of an anionic polysaccharide (beet pectin) onto amphoteric protein aggregates (heat‐denatured β‐lactoglobulin [β‐lg]). Initially, the optimum conditions for forming stable protein particles were established by thermal treatment (80 °C for 15 min) of 0.5 wt%β‐lg solutions at different pH values (3 to 7). After heating, stable submicron‐sized ( d = 100 to 300 nm) protein aggregates could be formed in the pH range from 5.6 to 6. Core‐shell biopolymer particles were formed by mixing a suspension of protein aggregates (formed by heating at pH 5.8) with a beet pectin solution at pH 7 and then adjusting the pH to values where the beet pectin is adsorbed (< pH 6). The impact of pH (3 to 7) and salt concentration (0 to 250 mM NaCl) on the properties of the core‐shell biopolymer particles formed was then established. The biopolymer particles were stable to aggregation from pH 4 to 6, but aggregated at lower pH values because they had a relatively small ζ‐potential. The biopolymer particles remained intact and stable to aggregation up to 250 mM NaCl at pH 4, indicating that they had good salt stability. The core‐shell biopolymer particles prepared in this study may be useful for encapsulation and delivery of bioactive food components or as substitutes for lipid droplets.